38~3 UNfVERS1TY OF HAvVAI'1 LIBRARY

THE IMPACT OF REMEDIAL MULCH ON PHOSPHORUS ABSORPTION IN MACADAMIA INTEGRIFOLIA.

A THESIS SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAI'I IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF

MASTER OF SCIENCE

IN

AGRONOMY AND SOIL SCIENCE

May 2004

By

Guy S. Porter

Thesis Committee:

Russell S. Yost, Chairperson Mike A. Nagao James A. Silva TABLE OF CONTENTS

Acknowledgments .iv List ofTables vii List ofFigures .ix Preface xiii Chapter 1 1 Background 1 Origins 1 Description 1 Growth and Production 3 Nutrient Absorption Uptake 6 Soi1. 11 Soil Phosphorus 12 Mulch 14 Objectives and Hypothesis 16 Objectives 16 Hypothesis 17 Chapter 2 18 Materials and Methods 18 Field Experiment. 18 Site Identification 18 Site History 18 Site Soils 22 Weather 23 Management. 24 Experimental Design .24 Experiment Design .24 Plot Construction 25 Mulch 25 Mulch Treatment. 25 Mulch Composting .27 Sample Design 29 Foliar. 29 Soi1. 31 Root Biomass 31 Trunk Circumference 31 Harvesting 31 Nut Quality 32 Statistical analysis 34 Statistics 34 Greenhouse experiment. 35 The Problem 35 Design and Procedure 35 Sample Collection 36

111 Analysis 36 Alternative Diagnostic Tissue Experiment.. 36 The Problem 36 Design and Procedure 37 Ana1ysis 37 Chapter3 38 Result and Discussion 38 Initial Conditions 38 Initial Soil and Foliar Survey 38 Mulch Composition 38 Climatic effects 41 Field Experiment Resu1ts .41 Soil Phosphorus Concentration .41 Proteoid Root Growth 48 Trunk Circumference Growth 55 Foliar P Concentration 57 Yield analysis 66 Nut Quality analysis 69 Greenhouse Experiment. 82 Greenhouse results 82 Moisture loss 82 Temperature change 82 Alternative Diagnostic Tissue Experiment. 85 Results 85 Correlation Analysis 86 Correlation method 86 Soil P vs. Proteoid Root Mass 86 Soil P vs. Trunk Growth 86 Rainfall vs. Foliar P % 89 Autocorre1ations, Spectral Analysis, and Cross-corre1ations 92 Methods 92 Autocorre1ations 93 Spectral analysis 100 Cross-corre1ations l 00 Rainfa1l. 100 Day-length 107 Chapter 4 116 Discussion and Conclusion 116 Response to Mulch 116 Root Growth 117 Reduction in Surface P 118 Trunk Growth 119 Foliar P 120 Bark P Concentrations 121 Nut in shell yields 121

IV Nut quality 122 Mulching options 122 Time series analysis 124 Summary 126 Appendix A: The Modified Truog Method 128 Appendix B: Day-length calculation formulas 129 References 130

v ACKNOWLEDGMENTS:

This project and its completion could not have been fulfilled without the generous contributions and support of the Hawaii

Macadamia Nut-growers Association. And especially Mr.'s Alan

Yamaguchi and Hillary Brown, orchard manager for Mauna Loa

Macadamia and general manager for MacFarms, respectively, whose contributions of in-site, expertise, provision of labor and equipment, and historical orchard data for analytical use, made this project possible.

VI LIST OF TABLES

Table Page

1. Suggested leafconcentrations for macadamia 7

2. Soil P concentrations for selected orchards 13

3. ADSC analysis ofmu1ch 15, 39

4. Keaau husk mean yields 67

5. Keaau yield probability 68

6. Kona husk means yields 70

7. Kona yield probability 71

8. Kona shell mean yields 73

9. Kona shell yield probability 74

10. Keaau nut quality 76

11. Keaau nut quality probability 77

12. Kona husk nut quality 78

13. Kona husk nut quality probability 79

14. Kona shell nut quality 80

15. Kona shell nut quality probability 81

16. Bark Diagnostic Tissue Results 85

17. Rainfall-Foliar P correlations 92

18 Kona husk autocorrelation coefficients 94

19. Keaau husk autocorrelation coefficients 95

20. Keaau husk spectral densities 101

21. Kona husk spectral densities 101

Vll 22. Kona husk rainfall cross-correlations 104

23. Keaau husk rainfall cross-correlations 105

24. Kona husk day-length cross-correlations 110

25. Keaau husk day-length cross-correlations l11

Vlll LIST OF FIGURES

Figure Page

1. Map ofAustralia 2

2. Macadamia pendulant raceme 4

3. Schematic ofproteoid root structure 8

4. Sap solutes for Banksia pronotes 10

5. Iron oxide-phosphate binuclear bridge formation 14

6. Map ofthe Island ofHawaii I9

7. Location map ofKona trial. 20

8. Location map ofKeaau trial.. 21

9. General condition ofA'a land 23

10. Implemented trial photograph .26

11. Plot design 26

12. Forms used for mulch implementation 28

13. Photograph ofimplementation method 28

14. Photograph ofNew Leafdata leaf.. 30

15. Photograph ofOld Leaf data leaf.. 30

16. Photograph ofsoil sample collection template 32

17. Photograph ofsoil sample 32

18. Average soil P concentration from 2000 survey 39

19. Average foliar P for initial survey 39

20. Keaau husk soil P concentration .43

21. Kona husk soil P concentration 44

IX 22. Kona shell soil P concentration .46

23. Comparison ofcumulative soil P reduction .47

24. Comparison of0-5 cm depth soil P concentration .47

25. Proteoid root growth into mulch for a single year. .49

26. Keaau husk root growth at three depths 50

27. Kona husk root growth at three depths 51

28. Kona shell root growth at three depths 53

29. Annual trunk growth difference for Keaau husk. 56

30. Declining growth rate for two-years at Keaau 56

31. Annual trunk growth difference for Kona husk 58

32. Increasing growth rate for two-years at Kona 58

33. Annual trunk growth difference for Kona shel1.. 59

34. Cyclic representation offoliar concentrations at MacFarms 60

35. Keaau foliar Old LeafP concentrations 61

36. Keaau foliar New LeafP concentrations 6l

37. Kona husk foliar Old LeafP concentrations 63

38. Kona husk New LeafP concentrations 63

39. Kona shell Old Leaf P concentrations 65

40. Kona shell New LeafP concentrations 64

41. Kona husk rainfall vs. yields correlation 72

42. Greenhouse pot trial water 10ss 83

43. Greenhouse pot trial average weekly water 10ss 83

x 44. Greenhouse pot trial temperature change with depth 84

45. Cumulative root mass-soil P correlation at Kona 87

46. Cumulative root mass -soil P correlation at Keeau 87

47. Cumulative soil P- trunk growth correlation at Kona 88

48. Cumulative soil P- trunk growth at Keaau 88

49. Correlation ofKona Old Leafwith rainfall.. 90

50. Correlation ofKona New Leafand rainfall.. 90

51. Correlation ofKeaau Old Leafwith rainfall 91

52. Correlation ofKeaau New Leafwith rainfall 91

53. Comparison ofKona and Keaau Old Leafmulch autocorrelations 96

54. Comparison ofKona and Keaau New Leafmulch autocorrelations...... 97

55. Comparison ofKona and Keaau Old Leafnon-mulch autocorrelations...98

56. Comparison ofKona and Keaau New Leafnon-mulch autocorrelations.99

57. Graph ofKona all leaftype spectral densities 102

58. Graph ofKeaau all leaftype spectral densities 102

59. Keaau rainfall- foliar P cross-correlation for all leaftypes 106

60. Kona rainfall- foliar P cross-correlations for allleaftypes .l06

61. Comparison ofKona and Keaau Old Leaf mulch vs. rainfall cross-correlation 108

62. Comparison ofKona and Keaau Old Leaf non-mulch vs. rainfall cross-correlation 108

63. Comparison ofKona and Keaau New Leaf mulch vs. rainfall cross-correlation 109

64. Comparison ofKona and Keaau New Leaf non-mulch vs. rainfall cross-correlation 109

Xl 65. Keaau daylength - foliar P cross-correlation for all leaftypes 112

66. Kona daylength - foliar P cross-correlations for all leaftypes 112

67. Comparison ofKona and Keaau Old Leaf mulch VS, day-length cross-correlations 113

68. Comparison ofKona and Keaau Old Leaf non-mulch vs. day-length cross-correlations l13

69. Comparison ofKona and Keaau New Leaf mulch vs. day-length cross-correlations 114

70. Comparison ofKona and Keaau New Leaf non-mulch vs. day-length cross-correlations 114

XlI PREFACE

The Australian perennial evergreen Macadamia integrifolia was introduced into the Hawaiian Islands in the latter part ofthe nineteenth century. It was a popular ornamental tree amongst islander gardens for many years before gaining attention for its delicious nut. Discovery of macadamia's potential as an addition to local delicacies lead to commercial cultivation in the 1920's.

Commercial development of the macadamia was solely a Hawaiian effort from the 1920's to the 1980's when its commercial growth spread internationally

(Shigeura et aI, 1971).

Originally found in deep, phosphorus and iron poor sedimentary soils along the riversides in the subtropical rainforests ofEastern Australia, macadamia was successfully adapted to Hawaii's volcanic soils as an agricultural crop

(Handreck, 1997). As commercial growth developed, management technique and nutrient requirement in the microclimates and soils of Hawaiian macadamia orchards were researched and formulated to provide optimal health and yields.

Sufficiency indexes for soil and foliar nutrient levels were developed as guidelines for orchard fertilization practice.

The index for Hawaii's soils was divided into heavy soils, light soils, and

A'a land. The soil index was classified based on substantial differences in bulk density, clay mineralogy, and soil characteristics affecting soil fertility. The foliar index, used primarily as a diagnostic tool, was experimentally developed based on nutrient sufficiency of tissue levels for the macro and microelements (Cooil et aI,

1966; Shigeura et aI, 1971; Chia, 1983; Bittenbender and Hirae, 1988; Tamimi et

Xlll aI, 1994). Orchard management strategies based on these indexes are designed to promote cost effective optimal growth and yields.

Where orchard planting practices place macadamia orchards in Hawaiian soils with high adsorbing properties, the alumina and iron sesquioxides, oxides, and amorphous material contained in these soils gives them the ability to fix and retain very large quantities of phosphorus (P) (Fox and Searle, 1978). In some mature orchards where high concentrations of soil P are found in the upper soil layers a disproportionately low foliar tissue P concentration is also found. Even with large additions of inorganic P fertilizer and excessively high soil P levels, foliar tissue P concentration remains low indicating inefficient nutrient absorption. These large applications of P fertilizer that have become adsorbed to surface soils may also be partially transported into waterways by runoff during heavy rain and become environmentally problematic. This condition of mature orchards with foliar tissue P levels below recommended sufficiency levels

(0.07%), with under-canopy soil P above recommended sufficiency levels (>100

1 mg L- ), indicates inefficient nutrient uptake ofP by macadamia as a cause (Fohse et aI, 1988).

XIV CHAPTERl

BACKGROUND:

Origins:

The genus Macadamia was originally found under the forest canopy along riversides fringing the subtropical rainforests ofSoutheast Queensland and

Northeast New South Wales, Australia (Chia, 1983; Hue et al., 1988) (Figure 1).

OfAustralia's five known species ofMacadamia, two are edible, and have been the focus for cultivation and industrial production (Nagao and Hirae, 1992).

Macadamia integrifolia Maiden & Betche (macadamia) or "smooth shell macadamia" was originally found between the 25 th and 28th South latitude (Chia,

1983; Hue et al., 1988), and its hybrids are the primary species used for macadamia production, and are the major focus ofmacadamia research.

Macadamia tetraphylla L. or "rough shell macadamia" is an edible species that has been developed for cultivation at more temperate latitudes. M tetraphylla originated between the 27th and 32nd South latitude (Nagao and Hirae, 1992;

Stephenson and Trochoulias, 1994), and are better suited to near temperate climatic conditions. The major rough shell cultivation is found in New Zealand and California (Stephenson and Trochoulias, 1994), where it is grown on a moderate scale.

Description:

Macadamia integrifolia (macadamia) is ofthe Order Proteales and Family

Proteaceae. It is characterized as a fast growing evergreen, regular shaped,

1 ;;----

INDIAN OCEAN

Australia -- Int.NOOniI boul1Clat} _.- S__ boundllry

* Nollonal capl..1 • SlaI&-IeveICOlliIaI -- RoII_ = EJcpIo5swI)' --Rom INDIAN OCEAN

! I' Ii' ""'-(' •

Figure 1. Map of Australia indicating the City of Maryborough just South of the 25 th parallel. Maryborough is located in the area central to pre­ cultivation Macadamia rainforest growth. Macadamia developed along riversides in thin, nutrient poor soils subject to flooding and periodic fires.

2 medium sized, having heavy, dark green foliage. Macadamia reaches heights of

20 meters with canopy widths of 12 meters and a leaf that is blunt and oblong with fine-toothed edges forming in whorls of two, three, or four (Neal, 1965;

Nagao and Hirae, 1992; Stephenson and Trochoulias, 1994).

Macadamia's fruit is a dehiscent follicle (nut) having a single suture that splits a fibrous husk covering a thick-walled "shell" containing the embryo and cotyledons (kernel). The shell is hard, thick, and tan colored, developing from the integument and protecting a white oily "kernel". Fruit develops on racemes of small, whitish flower tassels, 10 to 15 cm long on interior branches of mature hardened wood (Schaffer et aI., 1994; Figure 2), ripening in the fall, spring, both, or throughout the year depending on the cultivar. The cultivated macadamia of

Hawaii is easily identified by its smooth shell and edible, oily kernel (Neal, 1965;

Nagao and Hirae, 1992; Stephenson and Trochoulias, 1994).

Growth and Production:

The macadamia tree has evolved characteristics that allow it to survive and adapt in marginal to harsh land as an under-forest canopy plant adapted to limited growing conditions. As an agricultural crop, macadamia is strongly conditioned by variations in environmental and growth conditions. Commercially grown macadamia responds to extremes in temperature, light, periods of water stress, and nutrient poor soils.

Optimal temperature for macadamia growth is a narrow 20 to 25°C, with temperature fluctuations outside the general range of 15 to 35°C reducing and limiting tree growth, nut production, quality, yield, and especially floral

3 Figure 2. Macadamia pendulant raceme showing whitish flowering tassel appearance with older racemes in background containing set fruit. Less than 1% ofthe flowers will develop into mature fruit.

Optimal temperature for macadamia growth is a narrow 20 to 25°C, with temperature fluctuations outside the general range of 15 to 35°C reducing and limiting tree growth, nut production, quality, yield, and especially floral development (Trochoulias, 1983; Gallager, 1987; Nagao and Hirae, 1992;

Stephenson and Trochoulias, 1994).

4 development (Trochoulias, 1983; Gallager, 1987; Nagao and Hirae, 1992;

Stephenson and Trochoulias, 1994).

While wild macadamia is an under canopy plant, cultivated trees, when given access to full sunlight, respond with increased production. Low levels of light tend to reduce and inhibit vegetative growth, floral development, nut quality and yield (Nagao and Hirae, 1992; Stephenson and Trochoulias, 1994). Orchard design and pruning management have been developed to maximize light interception for tree growth and production, but are often ignored for other economIC considerations of macadamia production and cultivation (Schaffer,

1994).

Macadamia is generally resistant to drought. However, extended periods of severe water stress will restrict trunk growth, flushing, root and floral development. Macadamia's response to the alleviation of severe water stress can also be delayed by several months, and even short periods of severe water stress during any period of the macadamia reproductive cycle have been detrimental to yield and quality (Stephenson et aI., 1992; Nagao and Hirae, 1992; Stephenson and Trochoulias, 1994; Stephenson et aI., 2003).

In Hawaii optimal macadamia production requires 1500 to 3000 mm of annual rainfall evenly distributed throughout the year. Specific orchard rainfall requirements are dependent on soil type. In areas of cultivation characterized by thin shallow organic soils over volcanic A' a, rainfall requirements are highest.

Rainfall requirements are reduced with deeper mineral soils characterized with

5 higher water holding capacities (Nagao and Hirae, 1992; Stephenson and

Trochoulias, 1994).

Commercial fruit production and optimal yields reqUIre fertilization to

replace nutrient elements removed by the harvested crop, leaching, vegetative

growth, and low retention capacity. Hawaii's macadamia industry researched and

developed methods of nutrient monitoring using a diagnostic foliar tissue.

Tissues element concentrations have been indexed to experimentally derived

element sufficiencies matched to optimal tree growth and yield (Cooil et al.,

1963; Shigeura, 1970; Tamimi et al., 1997 & Table 1). Using leaftissue analysis

to monitor and assess orchard nutritional status is designed to allow managers to

make corrective and maintenance fertilizer application decisions (Cooil et al.,

1957; Cooil et al., 1966; Stephenson and Cull, 1986; Nagao and Hirae, 1992;

Stephenson and Trochoulias, 1994).

In commercial macadamia, seedling trees show poorer kernel quality, higher kernel variability, and lower productivity than rootstock grafted trees. To maintain high productivity, commercial seedlings are grafted onto a rootstock at about 10 to 12 months and transplanted into orchards 8 to 12 months later.

Grafted seedlings begin significant production 5 to 7 years after transplanting and reach maturity and full production at 8 to 10 years (Nagao and Hirae, 1992;

Stephenson and Trochoulias, 1994).

Nutrient Absorption Uptake:

Proteoid roots are the main pathway for the uptake ofnutrient P, iron, and moisture by macadamia. These roots were first characterized from the observation

6 that roots of the family Proteaceae often have a root axis with clusters of dense bottlebrush- like rootlets radiating from a large lateral axial root (Figure 3). These roots have become known as "proteoid roots" and are found predominately in the upper surface layers underlying the tree canopy. Proteoid root growth occurs along the extending laterals as intervals ofellipsoid-shaped clusters containing

Table 1. Suggested leaf element concentrations for bearing macadamia trees, based on leaf dry weight. From the Cooperative Extension Service, C/T/A/H/R, University of Hawaii, Nov. 1997 publication on adequate nutrition for Hawaiian crops. Element Initial Unit Concentration Range Nitrogen N g/kg 14.5-16.0 Phosphorus P g/kg 0.8-1.1 Potassium K g/kg 6.0-7.0 Calcium Ca g/kg 7.0-10.0 Magnesium Mg g/kg 0.8-1.0 Sulfur S g/kg 1.5-3.0 Manganese Mn mg/kg 50-1500 Iron Fe mg/kg 30-300 Copper Cu mg/kg 4-10 Zinc Zn mg/kg 15-20 Boron B mg/kg 40-74

numerous short, determinate rootlet fine mats, 2 - 5 em thick. They are found abundant in the soil and within decomposing litter under the canopy (Dinkelaker et aI., 1995; Lamont, 1986; Raghothama, 1999; McCully, 1999). Lamont (1986) reported that proteoid root growth in decomposing litter was greater than in the underlying humus-containing soil layer, and proteoid roots occurred along lateral roots extending from the trunk base to distances often meters.

Proteoid roots are specialized nutrient and moisture uptake root tissues that enhance uptake ofrhizosphere nutrients through root exudates oforganic

7 1st order lateral 2nd order laterals (proteoid rootlets) with root hairs ~ - •. .~

III[IIII-Ini E ~ '''UIIlIlIl e ..... # .-.. 8 ~ N "-" :g ~ j .....0 ~ ... Y_-

Figure 3. Schematic representation ofa proteoid root taken from: McCully M.E. 1999. "Roots in Soil: Unearthing the Complexities of Roots and Their Rhizospheres". Annual Reviews: Plant Physiology Plant Molecular Biology. Vol. 50,696-718. Maximal values are in parenthesis.

8 acids, primarily citric acid, and acid phosphatases (Dinkelaker et aI., 1995;

Neumann et aI., 2000; Gilbert et aI., 2000). They provide strong acidification and chelation of the phosphorus, iron, and manganese ion species bound in the soil

(Lamont, 1986; McCully et aI., 1999). These fine cluster roots have specifically been recognized for facilitating P-acquisition by exuding moisture, hormones

(auxin), and enzymes (acid phosphatase) in White Lupine (Lupinus albus)

(Dinkelaker et aI., 1995; Neumann et aI., 2000; Gilbert et aI., 2000). These processes also contribute binding agents to the soil while accessing the inorganic and organic nutrient phosphorus found in the soil and litter (McCully, 1999,

Gilbert et aI., 2000; Neumann et aI., 2000). The enhanced P uptake and absorption by proteoid roots is a result of increased surface area due to large numbers of rootlets and increased P availability for rootlet absorption through the release of bound nutrients by the secretion of organic acids (Malajczuk and Bowen, 1974).

Jeschke and Pate (1995) found phosphate concentrations ten times higher in proteoid xylem sap than the lateral parent sap in root xylem fluids of Banksia prinotes (Figure 4). Substantially higher solute concentrations in proteoid root xylem fluid than in lateral root xylem fluid were also observed for potassium, malate, and amino acid nitrogen showing a high capacity of proteoid roots for nutrient uptake. Biological mechanisms for proteoid root initiation and signaling ofgrowth and development in macadamia is not well understood.

Root growth tends to be seasonal, developing during heavy rainfall or flooding and senescing during periods of light rainfall or drought, reappearing again with returning heavy rainfall or floods (Jeschke and Pate, 1995). Proteoid

9 t1iU~ 0- ~TEIIoAl. •

....Ell I

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PAOTIlCOOAQ(I' a.' ~ o , • •

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ett»&to8e :=J Na LA.'I1M t 'iI- tINlDl

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2 1'1 Ot 0" 0 0 I-I l I

Figure 4. Mean levels of major inorganic and organic solutes present during the wet winter season in the xylem sap of proteoid roots and in xylem (tracheal) sap obtained by mild vacuum (pressure 25-60 kPa) extraction of lateral roots, sinker roots and trunk bases of 6-year-old trees of Banksia pronotes growing in natural habitat in Banksia woodland at Yanchep, W. Australia. Standard errors of the means of concentrations are given. Taken from Jeschke and Pate, 1995.

10 root growth is considered primarily a response to phosphorus deficient soil and phytohormone stimulation (Gilbert et aI., 2000; Neumann et all, 2000).

Proteoid roots do not support mycorrhizal associations, and research has not found or identified either infecting or non-infecting microorganisms associated with macadamia (Malajczuk and Bowen, 1974; Firth, 1987).

Soil:

Soils in Hawaii develop from basaltic volcanic material deposited in sequential layers and are subject to mechanical and chemical weathering that quickly disintegrates and decomposes the deposited parent material. Pahoehoe and A' a lava, and volcanic ash are three parent materials resulting from volcanic activity, and in moderately to very wet parts ofthe Hawaiian islands, these parent materials form soils where good drainage provides conditions for the leaching of sodium, calcium, and magnesium. This leaching leads to the formation of weathered soils with high concentrations of aluminum, iron oxide, and titanium.

Iron oxide, the least soluble, becomes highly concentrated over time, with accompanying high concentrations of aluminum. These types of soil containing high concentrations of aluminum and iron oxides may have water-holding I capacities of 300 to 600 percent above the volume of clay minerals and other materials present (McDonald and Abbott, 1970).

Dryer microclimatic conditions of Hawaii containing aging depositions of

A' a lava, tend to form soils composed primarily of organic matter resulting from decomposition and mineralization ofplant biomass. These soils have less mineral

11 fines and generally are composed of A' a cobbles and boulders forming the basis of "Rock Culture" cultivation. Hawaiian macadamia orchards have been established on marginal land composed of this aging A' a lava and soils in these orchards normally require higher rates of rainfall and nutrients to be commercially profitable and competitive (Shigeura et aI., 1971; Nagao and Hirae,

1992)

Soil Phosphorus:

Phosphorus moves through the soil solution to plant roots primarily through diffusion, and is taken up by plants from the soil solution as one of two species

(HZP04- or HPO/-) of orthophosphate ions (Villani et aI., 1988). The concentration of P in the soil does not reflect the concentration ofplant available

P in the soil solution since differing soil P fractions are more or less available through soil solution buffering (Guo et aI., 2000; Hedley et aI., 1982). The quantity of available P of a soil P fraction to the soil solution is affected by soil pH and texture. Phosphate ions show high capacity for adsorption to clay micelle surfaces in acid soils composed of significant amounts of iron and aluminum oxide and having high amounts of amorphous clay and andic clay properties.

Soils high in adsorbed P are generally highly buffered and the adsorbed P is difficult for plants to access (Jones et aI., 1997). In Hawaii, soils with this type of high P are often economically attractive for development as macadamia orchards.

Orchards with high P adsorbing soils, after repeated surface applications of inorganic fertilizers, have developed accumulations of adsorbed P well above soil

12 nutrient sufficiency levels (Table 2), and it is desirable to reduce the concentration ofP in these soils.

Table 2. Means of Soil Phosphorus Concentrations in Selected Macadamia Orchards with High P Adsorbing Soils (Shirey et aI., unpublished research)

Soil Phosphorus in mg kg- 1

Location Mean No. ofSamples Standard Deviation

Kau 192 7 54.8

Keaau 468 7 209

MaunaKea 480 7 282

Overall 380 21 205

Orthophosphate ions are adsorbed to iron-oxide soil surfaces in a two-step process of ligand exchange forming a binuclear bridge (Ryden et aI. 1977). An orthophosphate ion in the proximity of a soil surface hydroxyl displaces the hydroxyl and bonds to the iron. A neighboring iron-hydroxyl ion then displaces a proton on the single bonded ortho-phosphate forming a stable "binuclear" bridge

(Figure 5). The binuclear bridge forms tight covalent bonds resisting the release of phosphate into solution. However, citric acid exudates of proteoid roots displace the iron-oxygen bonds of the adsorbed phosphate to form citric acid oxygen bonds with the hydroxide while contributing a proton to the released

13 o

.. ..

Figure 5. Representation of H2P04- penetration into an iron oxide surface and subsequent formation ofa stable binuclear bridge (Ryden et aI., 1977). phosphate making it plant available. This plant available phosphate is then taken up and used for plant nutritional needs (Dinkelaker et aI., 1995; Foshe et aI.,

1988).

Mulch:

Organic and synthetic mulches have been used for weed control, moisture conservation, soil temperature modification, and the reduction of nutrient losses through leaching for thousands of years. Mulch, through its ability to modify the soil hydrothermal regime, increases the density and spread of roots while mitigating the deleterious effects of soil microorganisms (i.e. soil fungi)

(Ashworth and Harrison, 1983; Bumava et aI., 1988).

One important value of an organic mulch is the continuous addition of organic matter to the soil, improving soil cation exchange capacity (CEC), nutrient holding capacity, and providing a favorable medium for root proliferation

(Defrank and Foss, 1989; Firth et aI., 1994; Bittenbender et aI., 1998). Although organic mulches reduce loss by leaching of most macronutrients and sulfur from the soil, they can also immobilize soil nitrogen as they decay (Ashworth and

Harrison, 1983; Wallace and Terry, 1998).

14 In an Australia experiment, macadamia husk mulch applied to Hawaii

Agricultural Experimental Station (HAES) macadamia cultivars 508 and H2 suffering severe conditions of decline, produced improvement in the general tree health, yields, foliar P concentration, soil quality, and generated massive proteoid root growth into the mulch (Firth et aI., 1994). Conversely, in a Hawaiian study, husk mulch effects were inconclusive on the selected HAES cultivar 246, but the husk mulch contributed to soil organic matter, moisture retention, and increased

CEC (DeFrank et aI., 1988).

Laboratory elemental analysis of husk mulch in the Hawaii study indicated nutrient element concentrations in the husk were sufficiently high to act as a nutritional source benefiting tree growth (Table 3). This concentration ofelements found in macadamia husk mulch analysis suggests that applications ofmacadamia

Table 3. ADSC analysis ofMacadamia integrifolia mixed HAES cultivars husk and shell (Spring 2002).

------g kg-1 ------Dlg kg-1 ------

N P K Ca Mg B Mn Fe Cu Zn

M-1* 35.3 0.7 9.0 6.6 6.1 56 269 4425 23 33

M-2* 15.3 1.0 5.1 15.8 10.3 152 882 4385 48 66

M-3* 3.20 .04 1.0 0.40 0.20 56 269 4425 23 33

* M-l for mulch with 30% soil added, M-2 for mulch with no soil added, M-3 for shell.

15 husk mulch may serve as an important source for macadamia nutrient P management. Since applications ofmacadamia husk mulch promote proteoid root growth and development within the mulch proximity, it is expected that P, iron, and moisture uptake by macadamia will increase with increased root growth

(Firth et aI., 1994; DeFrank et aI., 1989).

Macadamia's under canopy origins make it well adapted to nutrient cycling.

Proteoid roots are an adaptation to limited nutrient availability, and form the basis for effective nutrient cycling by allowing macadamia to access both organic and inorganic sources of P. Nutrient cycling in perennial crop nutrition reduces the need for applications of inorganic fertilizers, and increases soil biomass and soil organic carbon (Deenik et aI., 1999). Research verifies that cycled husk litter aids restoration of tree health, and when mineralized and available for plant uptake, contributes sufficient quantities of nutrients to tree health and may contribute to maintaining foliar phosphorus levels (Firth et aI., 1994; DeFrank et aI., 1989;

Bittenbender et aI., 1998).

OBJECTIVES AND HYPOTHESIS:

Objectives:

This research was designed with the following objectives:

1. Quantify the response of aging macadamia trees to applications of

mulch as a means to improving P acquisition while reducing high

surface soil concentrations ofP.

16 2. Develop a means for usmg macadamia husk mulch for reducing

fertilizer costs, P in particular, while maintaining and/or improving

macadamia orchard profitability.

3. Improve knowledge on the effective use of mulch, especially

macadamia husk mulch, for P nutrient management that may later be

used to design or update mulching practice.

4. Quantify macadamia mulch materials characteristics to improve use of

macadamia mulches as mulching materials.

5. Improve knowledge on macadamia's use of a storage tissue for P, and

develop an alternative to foliar tissue as a diagnostic tissue.

Hypothesis:

This research was designed with the following hypotheses:

1. Mulching with a macadamia mulch material can be an efficient and

economic management practice for macadamia growers.

2. Foliar P levels can be maintained or increased through the strategic use of

applications ofmulch under the canopy.

17 CHAPTER 2

MATERIAL AND METHODS:

Field Experiment:

Site Identification:

Two sites were chosen for the mulch experiment (Figure 6); site one located at MacFarms in the Honomolino area, South Kona district, Hawaii Island

(Figure 7). Site two was at Mauna Loa Farms in the Keaau area, Puna district,

Hawaii Island (Figure 8).

MacFarms is a large commercial operation composed of approximately

1600 hectares ofproducing Macadamia orchards. At an approximate elevation of

450 meters, experiments were located 60 meters 'Mauka' ofMamalahoa Highway at 19° 27' N. latitude, 155° 53' W. longitude. The experiment orchards were composed of approximately ten-year-old HAES 344 cultivars of Macadamia integrifolia

Mauna Loa Farms is a large commercial orchard with over 4000 hectares of producing macadamia trees. Experiment trials were located at an approximate elevation of 45 meters and were found along Macadamia Road at 19° 27' N. latitude and 155° 53' W. longitude. Experiment orchards were composed of approximately ten-year-old HAES 344 cultivars ofMacadamia integrifolia.

Site History:

The MacFarms experiment site had been pastureland until approximately twenty-five years ago. This was followed by several years ofintercropped

18 Figure 6. Map ofthe Big Isle ofHawaii, Hawaiian Islands indicating the locations of the two experiment sites at Keaau and South Kona. Isohyet contours are 500 mm for rainfall and 50 calories for solar radiation.

19 5 kJ! orreters

Figure 7. Map of the South Kona area of Hawaii Island showing the location of the MacFarms experiment site. Rainfall contours are in 500 mm increments, and solar radiation contours are in 50 solar calorie increments.

20 Figure 8. Map of the Keaau area of Hawaii Island showing the location of the Mauna Loa Orchards experiment site. Rainfall contours are in 500 mm increments, and solar radiation contours are in 50 solar calorie increments.

21 macadamia and coffee until the coffee was phased out about fifteen years ago leaving the orchard dedicated completely to Macadamia production.

At Mauna Loa Farms in Keaau, the experiment site orchard has been in macadamia cultivation for over forty years, and continues to be used exclusively for macadamia production.

Site Soils:

Soils at the experimental orchards consisted of a fragmented A'a covered by a litter-derived organic layer. Both the South Kona and Keaau soils are classified as Euic, isohyperthermic, Typic Tropofolists, Puna (rPXE) and Papai

(rPAE) series, respectively. These are thin, well-drained soils, requiring higher levels of inorganic fertilizers and rainfall for optimal macadamia tree growth. Dr.

Cooil (Cooil et aI., 1966) in his early macadamia research at the Keaau orchard described macadamia production in these soils as analogous to "rock culture" cultivation (Figure 9).

Soil temperature at 10 cm at South Kona and Keaau ranged from 15 to 21 0

C. The orchard slope at the South Kona experiment site varied with a mean of approximately 20%. The South Kona orchards were composed of a "rolling" geomorphology. This "rolling" geomorphology allowed selected trees at South

Kona orchards located in down-slope geomorphic depressions to have a somewhat deeper accumulation of organic soil. Trees along geomorphic ridges tended to have higher percentage of A' a with less organic soil. Orchard slope of the Keaau experiment site was approximately 5%, and the site had a flat geomorphology with a ratio ofA' a and organic soil being even throughout the

22 Figure 9. General condition ofA'a land used in the orchards ofthe trial.

experiment orchard.

Weather:

Average annual rainfall based for thirty-year WRCC (Western Regional

Climate Center) records of the South Kona experiment area is 152 em with 5 to

17 em per month, and air temperatures ranging between 14 to 27°C (WRCC

Opihihala Station data). The Keaau experiment area average annual rainfall is 325 em (WRCC Hilo Station data) with 18 em to 38 em per month, and air temperatures ranging between 19 to 27°C (WRCC Hilo Station data).

23 Management:

Orchard management at South Kona included regular pruning of trees, leaving an open canopy with ample solar radiation to all levels of leaf within the canopy. Planting density was 175 trees per hectare, and a grass cover strip filled the open areas between tree rows. This grass area was regularly cut and litter tended to accumulate in the strip supporting root growth. Regular fertilization of the experiment orchard was suspended for the duration of the trial, although applications ofpesticides and herbicides continued.

Planting density at the Keaau site was 225 trees per hectare, and the orchard canopy had been allowed to close providing a dense intergrowth of branches reducing solar radiation under-canopy. Regular fertilization was suspended for the duration ofthe trial. There is little under-canopy growth in this orchard due to limited solar radiation. Herbicide application was not performed, however the application ofpesticides was continued as necessary.

Experimental Design:

Experiment Design:

A Completely Randomized Design (CRD) consisting ofsix plots offifteen trees was used in three experiments. Trees were selected and assigned to plots based on an initial soil and foliar P concentration survey ofexperiment trees. Tree foliar concentration was below the optimal 0.08% P recommended levels, and tree under-canopy soil P was in excess of recommended agricultural soil P nutrient levels of 100 mg kg- 1 for A' a agricultural land.

24 Plots were divided into three replications of mulch and non-mulch treatments. A plot received a treatment ofmacadamia husk mulch or shell mulch, dependent upon the experiment, or received no mulch as a treatment control.

Mulch and non-mulch plots were randomly determined and were randomly allocated into replications for each experiment according to the CRD design.

Plot Construction:

Each CRD experimental plot was constructed as a rectangle along orchard planting rows, as three center data trees surrounded by twelve border trees (Figure

10). Where duplicate plots were located beside each other a common border was shared. All trees in a mulched treatment plot received a mulch treatment application, while only the central trees ofa plot (mulch or non-mulch) were used for data collection during sampling and monitoring. Each experiment consisted of three replications of mulch and three replications of a non-mulch treatment for a total ofninety trees arranged in six plot-grids offifteen trees each (Figure 11).

Mulch:

Mulch Treatment:

Each mulch treatment consisted ofapproximately one-third cubic meter of macadamia husk or macadamia shell. The one-third cubic meter (approximately

64 kilograms) of material was concentrated around the trunk and under the canopy of each tree to form flat cylindrical shaped mulch mats (Figure 10) with a one-meter radius by ten-centimeter depth. In an orchard with a 175 tree per hectare density, this quantity of mulch application is equivalent to 12.5 tons of organic compost per hectare by broadcast spreading, the quantity suggested for

25 Figure 10. Photograph ofan implemented trial showing the mulch mat arrangement along a single line oftreatment trees.

@ @ @ @ @ @ @

@ @ @ @ @

Figure 11. Plot design showing treatment data trees in the center oftwelve border trees. Each tree within a plot received the same treatment. Foliar and soil samples were collected from the three central data trees.

26 maintaining tree health by Bittenbender et al. in their 2001 husk mulch and manure experiment.

Mulch was applied around selected trees using a two-part hexagonal form constructed of commercial grade fir 2x4. Form design allowed inclosing the treatment tree trunk (Figure 12).

The addition of treatment mulch consisted of applying 18 full 22-liter buckets ofmulch material into the specially built 2x4 forms (Figure 13). This was followed by the application of 95 liters of water per tree settling the mulch and producing a surface crust preventing rapid dispersion and decomposition of the mulch. Water was also added to non-mulch trees to simulate initial conditions of uniform moisture throughout the experiment.

Annually an additional one-third cubic meter of new mulch was placed directly onto the existing mulch mats leaving developing root growth undisturbed.

Mulch Composting:

Applications of macadamia husk mulch must be fully composted prior to placement to avoid toxic compounds found in green macadamia husk (DeFrank,

1988). These compounds are harmful to macadamia trees when placed in direct contact with the trunk (DeFrank, 1988). Initial application of husk mulch was performed leaving a 15-cm space between the tree trunk and the husk mulch treatment for each tree receiving mulch to prevent any remaining toxic compounds from harming the tree.

27 Figure 12. Fonns comprised of2x41umber for the placement ofhusk or shell mulch around the macadamia trunk.

Figure 13. Implementation ofone-third cubic meter mulch around the trunk base.

28 Sample Design:

Foliar:

Sufficient quantities of leaf available throughout the year for use as a diagnostic tissue was an important consideration in sample leaf determination. The determination of sample leaf for foliar sampling was made based on interviews with orchard management personnel concerning their current practice of diagnostic foliar sampling, and on recommended methods of the University of

Hawaii extension service. A set of "old leaf' and a set of "new leaf' foliar samples were collected from selected data trees within each plot (Figure 14 & 15).

An "old leaf' sample was a fully opened, green leaf from a branch not exhibiting terminal meristem growth or having a surface sheen, and generally found on branches capable of supporting raceme development (>eighteen months old). A

"new leaf' sample was a fully opened, green leaf from a recent flush exhibiting a glossy surface sheen, and generally found on branches not supportive of raceme development «eighteen months old). A leaf sample set consisted often to fifteen leaves, and was collected at approximate ten-week intervals. Samples were dried, ground and submitted to the University ofHawaii Agricultural Diagnostic Service

Center, a certified soils laboratory, for analysis of selected macro and microelements N, P, K, Ca, Mg, Fe, Cu, B, Mn, Na. Results ofthe analysis are to be used in the development ofa diagnostic database.

Soil:

A soil sample was collected annually pnor to implementation or treatment refreshment. Samples were collected from soils found within a one-meter radius

29 Figure 14. Photograph illustrating a New Leafdata leaf. A fully opened green leaf with a surface sheen on the leafand a tan colored bark.

Figure 15. Photograph illustrating an Old Leafdata leaf. A fully opened green leaf with no surface sheen and dark well suberized bark.

30 of the tree trunk, and were collected as grab samples using a ten-centimeter by ten-centimeter surface template to measure and collect a 500 cc volume from three consecutive five-centimeter depths (0 to 5, 5 to 10, 10 to 15 cm) (Figure 16 and 17). Soils were transported to the University of Hawaii at Manoa, Sherman

Lab Room 217 for P using a modified Truog extraction method and a colorimetric analysis by spectrophotometer, developed for the Hawaii Sugar Planters

Association, and summarized in appendix 1.

Root Biomass:

Root biomass was removed and quantified from the soil samples prior to P analysis. Soil samples were sieved through a two mm mesh screen and the root biomass from the soil sample remaining on the screen was collected, weighed and air dry weight recorded as a measure of the root biomass in a 500 cc volume of soil.

Trunk Circumference:

Trunk circumference was measured pnor to implementation and circumference change was monitored at the time of foliar sample collection throughout the duration of the experiment. Measurements were taken at an approximate height of 50 cm from the ground surface or where best suited as determined by specific tree growth. Circumference sampling of recurring measurements were taken at the marked height.

Harvesting:

Experiment orchards in Keaau and Kona were hand-harvested throughout the duration ofthe trial. In South Kona mulch orchards were additionally

31 Figure 16. Sample collection from A'a land orchards was through a ten by ten centimeter template with often-needed tools.

Figure 17. Three 500-cc volume samples collected from three incremental depths beneath a non-mulch tree at the Kona husk trial.

32 harvested during the 2002 harvest using a mechanical shaker harvester after the application ofethelron, followed by the hand harvesting ofremaining crop.

Nuts were harvested at Keaau following blowing of leaf litter from the orchard. Experiment tree harvests at Keaau consisted ofall nuts in a circular area with a three-meter radius surrounding the trunk of each trial tree. Branch intergrowth in the closed canopy ofthe Keaau trial required that a limited harvest area be used to differentiate the harvest of each tree. As a consequence the total production of each tree was not included in the experiment harvest results.

Pruning of Kona trees made it possible to identify yields from each tree and the total production from each tree was collected.

Nut Quality:

Drought conditions caused the complete 2000 crop of the Kona husk experiment to be rejected as unacceptable. An experiment at the Keaau site had not yet been implemented and no harvest collected. For the 2001 and 2002 harvests, a representative sample of in-shell nuts collected from each tree was submitted for quality analysis to the laboratories at MacFarms (Kona) and Mauna

Loa Orchards (Keaau).

For 2001, wet in shell, dry in shell and usable kernel analysis were performed for the Kona husk experiment. For the 2002 harvest, wet in shell, dry in shell, usable kernel with additional analysis for kernel weight, percent stink bug, percent mold, percent immature nut, percent germination, percent crypto, percent TNB, percent KR, and percent rejected kernel were performed by the

MacFarms laboratories for the husk and shell experiment crops.

33 For both 2001 and 2002, the Keaau experiment analysis of nut quality included wet in shell, dry in shell, Fancy kernel, Choice kernel, unusable kernel, usable kernel, moisture percent, moldy grams, stinkbug grams, germination grams, hollow center grams, shrivel grams, brown bottom grams, brown center grams, 0 ring grams, bruised grams, and bacteria grams.

For the purpose ofour study only those nut quality analyses that reported a result for every tree in the experiment were used. Those nut quality analyses that contained empty or missing entries for data trees were excluded.

Statistical Analysis:

Statistics:

The SAS PROC GLM repeated measures procedure (SAS, 1999) was used with nested independent variables in the model and a test statement to specify the error for a CRD with six degrees of freedom (each plot) in the design. Each sample collected was considered independent and foliar nutrient levels were further analyzed for time series auto-correlation, spectral, and cross-correlation with rainfall data provided by orchard mangers and calculated day-length

(Appendix B). ASTSA software developed and distributed by Dr. Robert

Shumway from the University of California at Davis was used for the auto­ correlation analysis, together with the SAS PROC SPECTRA and PROC ARIMA procedures. Dr. Shumway's software was designed to specifically analyze relationships developed from time series data. Additionally, Fisher's least significant difference (LSD) was used to differentiate means for data collected over the two-year period for the SAS analysis.

34 Greenhouse Experiment:

The Problem;

A greenhouse experiment companng soil moisture retention characteristics of macadamia husk and shell mulch was performed to increase knowledge about the application and use of macadamia mulch's as a nutrient source and P management tool. Macadamia husk mulch was hypothesized to have better moisture retention in the soil providing better insulation against soil evaporative loss and temperature change then the shell mulch.

Design and Procedure:

The experiment was composed of two treatments of mulch (husk and shell) in three replications. A locally collected Ultisol (Leileihua) 1.2 kilograms was placed in the bottom of six two-kilogram black plastic planter pots allowing the 10.16 centimeters above the soil to be filled with mulch material. Three pots received husk mulch each, and three pots received shell mulch each. Pots were arranged in a side-by-side configuration under a thick triple layer of black plastic netting simulating a canopy effect. A one-liter volume ofwater was added evenly to each pot and allowed to percolate into the soil. Pots were sealed at the bottom to allow water loss as only evaporative loss through the mulch covering the soil.

A single plastic straw cut to a five-inch length was placed in the center ofeach pot through the mulch to the soil mulch interface, and plugged with a small stopper at the top to allow access to different depths ofmulch.

35 Sample Collection:

Daily measurements were collected at approximately mid-day for four weeks. Time, greenhouse temperature, temperature at four incremental depths of mulch for each pot (2.54, 5.08, 7.62, and 10.16 cm), and change in pot weight were recorded. Pots were weighed using a digital scale and thermal differences at the four depths were recorded using a 25 cm digital soil thermometer marked in

2.54 cm increments. Treatment pots were monitored for mulch temperature differences through the plastic straw channel by removing the stopper, inserting the thermometer at increasing depths, awaiting stabilization and recording temperature.

Analysis:

Collected data was entered into a database and comparative graphs were plotted for daily water loss from soil over the four-week period and mean weekly temperature change at four mulch depths. Student T-tests were applied to identify significant differences in graphs.

Alternative Diagnostic Tissue Experiment:

The Problem:

The lack of a significant foliar P concentration response in the experiment macadamia trees prompted a further investigation ofpossible storage tissue for P.

Based on the development of root growth, especially in the Keaau experiment, that functions as the major pathway for nutrient P uptake it was expected that uptake of P would accompany new roots and be detectable within one (the foliar

36 tissue) or more of the plant tissues. Since nutrients move from the roots to the

shoots through the xylem, a vascular tissue oriented on the outer trunk or branch

beneath the bark, a sampling ofthe trunk and branch woody tissue, and trunk and

branch barks was made to assess the possibility of these tissues as P storage

tissue.

Design and Procedure:

Samples were collected from the two outer of the three data trees in the

Kona husk mulch and Keaau husk mulch experiments. Samples were collected in

August when foliar concentrations are at a cyclic low and a tissue sink for P would probably be at a high concentration. Samples were collected using a one­ halfinch diameter hand turned increment borer. Samples were collected first from the outer bark, and then from the inner bark and wood (xylem) directly beneath the outer bark sample to a depth of about one-half inch. Four samples sites for outer and inner bark were collected from each tree, and composite outer and inner bark samples formed. These composite outer bark and inner bark samples were placed in labeled manila coin envelopes and sealed. They were then transported to a certified laboratory (The Agricultural Diagnostic Service Center, University of

Hawaii at Manoa) and submitted for P analysis.

Analysis:

ADSC analytical results were entered into a database and SAS ANOVA

F-tests were applied to identify significant differences in the bark P concentrations between the mulch and non-mulch treatments and between the

Kona and Keaau experiment sites.

37 CHAPTER 3

RESULTS AND DISCUSSION:

Initial Conditions:

Initial Soil and Foliar Survey:

An initial survey of the soil P concentrations at selected Hawaii macadamia orchards was performed during 2000, sample analysis revealed the mature macadamia orchards had mean under-canopy soil P concentrations above

1000 mg/kg in the 0-5 cm soil depth, and above 500 mg/kg in the 5-10 and 10-15 cm soil depths (Figure 18). These concentrations were well above the recommended agricultural sufficiency of 100 mg kg- 1 for A'a land, the highest level ofextractable nutrients Hawaiian agricultural land requires.

A companion foliar survey ofthe selected orchards during 2000 indicated orchard foliar P lower than the recommended foliar nutrient sufficiency level (0.08%) as determined by the University of Hawaii Agricultural Extension Service and considered optimal for growth and yields (Figure 19).

Mulch Composition:

Husk and shell element analysis of mulching material collected from

MacFarms indicated higher nutrient content ofhusk mulch compared with that of the shell mulch material (Table 3.). The high concentration of nutrient element P in the husk quantity (with no soil added) implemented under the mulched tree canopies was the equivalent of an addition of 64-grams (6.4 kg/ha) ofpotentially available P to each tree.

38 Initial Survey Results of Average Soil P Concentration

1200 1000 ~ 800 m ~ 600- ~ 400 200 a +__------" 0-5 5-10 10-15 Depth in Centimeters

Figure 18. Average Soil P Concentration from the 2000 soil survey of selected orchards on Hawaii at three depths (0-5 em, 5-10 em, 10-15 em).

Initial Survey results of Potential Macadamia Orchard Trial Sites

c. 0.12 ~ 0.1 ~ 0.08 LL 0.06 & 0.04 f! Q) 0.02 ~ 0 KonaHusk KonaShell Keaau Hilo Hamakua Sample Site

Figure 19. Average foliar %P for five orchards surveyed on Hawaii as potential experimental sites. All sites were orchards of mature (>10 year old trees) macadamia with high under canopy soil P concentrations.

39 Table 3. ADSC analysis ofMacadamia integrifolia mixed HAES cultivars husk and shell (Spring 2002).

------g kg-1 ------IIlg kg-1 ------

N PK Ca Mg B Mn Fe Cu Zn

M-1* 35.3 0.7 9.0 6.6 6.1 56 269 4425 23 33

M-2* 15.3 1.0 5.1 15.8 10.3 152 882 4385 48 66

M-3* 3.20 .04 1.0 0.40 0.20 56 269 4425 23 33

* M-l for mulch with 30% soil added, M-2 for mulch with no soil added, M-3 for shell.

Decomposition and mineralization rates of the mulch, and root growth response were expected to be higher at the wetter trial site (Keaau) based on the difference in quantity ofrainfall received.

A serious impediment to root growth at Kona during the first year of the trial was an immature mulch material. Initial material purchased from a commercial supplier had not been adequately composted and when applied to treatment trees created a potential for a toxic response by the trees. Further, as the mulch continued composting, anaerobic zones formed throughout the mats in a response to the dry orchard conditions, inhibiting new proteoid root growth.

Refreshment mulch at the Kona trial was obtained from MacFarms, and was superior in quality to the initial material. It had been completely composted then mixed with 30 percent topsoil. Its application eliminated any further development ofanaerobic zones throughout the mulch mats.

40 Climatic Effects:

Growth responses to mulch treatments by macadamia were observed to be

strongly conditioned by prevailing climatic conditions specific to each location.

Although experimental sites were composed of similar cultivars (HAES 344) and previously similarly classified soils (Euic, isohyperthermic, Typic Tropofolist), continuing drought along the West Coast of the Island of Hawaii and especially severe conditions found at MacFarms hampered tree response to mulch treatments. Experiment trees showed highly reduced vegetative and reproductive growth during periods of highest water stress. Characteristic senescence of proteoid roots during the long periods ofdry conditions between rains reduced the quantity of viable root growth that may have resulted under normal rainfall conditions.

Field Experiment Results:

Soil Phosphorus Concentration:

Baseline soil measurements for the Kona husk and Keaau husk treatments were performed in the fall and winter of 2000-2001. The Kona shell treatment was initially sampled in the winter of 2001-2002 before implementation and then annually sampled with the husk treatments.

Concentrations in soil P showed a declining trend at both husk mulch trial sites for the two years of data collected and reported. No reduction in soil P concentration was found at the Kona shell trial site for the single year of data collected and reported here.

41 Soil P concentrations at both wet (Keaau) and dry (Kona) sites of the mulch husk experiment revealed a reduction in soil P to treatments as an average analysis (0-15 cm) of the three soil depths (Figures 20 & 21). Average reduction at Keaau (wetter) showed a soil P reduction in the mulch treatments at a better than 90% probability level for two years. This resulted in spite ofno apparent soil

P reduction during the second year for the mulch treatment while non-mulch soil

P revealed reduction. This reduction in P in the non-mulch treatment soil may be a result of a random seasonal increase in rainfall (~380 mm). This additional moisture for root growth from the random rainfall increase could stimulate increased root growth in non-mulch treatment trees while the mulch treatment trees would be buffered from the increased rainfall by the husk mulch characteristic of moisture retention. This allows greater moisture to be consistently available for root growth rather than allowing it to runoff or drain as under non-mulch treatment conditions.

The average of soil P at the Kona husk trial showed no reduction during the first year of the trial. All reduction in soil P at the Kona husk site was shown during the second year of the trial reported here when rainfall increased (~ 350 mm). Rainfall ofthe previous year allowed trees to briefly recover from drought­ conditioned dormancy with a burst of vegetative flush and reproductive growth.

Soil P reduction during the second year was shown in the mulch treatment while no reduction was shown in the non-mulch treatment.

Kona shell mulch soil P concentrations showed no significant change during the single year ofmonitoring. Graphs ofthe measured concentrations

42 Trial: Keaau Husk 0-15 em Trial: Keaau Husk 0-5 em

600 600 LSD error bar LSD error bar

400 400 ·0 ·0 '" '" ...... • .,'l5 .,'l5 ~ Cl Cl -'" 200 -'" 200 0- ~ 0- 'l5 'l5 Cl Cl E E 0 0

-200 ..L-_-----,__---r-__--,---_-----.J -200 -'---_-----,__~--~----.J 2000 2001 2002 2000 2001 2002 Sample Year Sample Year ...... Mulch Soil P -e-- Non-mulch Soil P Trial: Keaau Husk 5-10 em Trial: Keaau Husk 10-15 em

600 600-,------, LSD error bar LSD error bar

400 400 ·0 .,'l5'" Cl ...... ~ -'" 200 ~ 200 0- 0- 'l5 'l5 Cl Cl E E 0 o

-200 -200 -'------,------r--...,-----' 2000 2001 2002 Year 2000 2001 2002 Sample Year Sample Year

Figure 20. Keaau Husk Soil P Concentration three annual samplings for three soil depths and an average result. Error bars are LSD for treatments.

43 Trial: Kana Husk 0-15 em Trial: Kana Husk 0-5 em

1200 1200 LSD error bar LSD error bar 1000 1000

·0 800 ·0 800 til til '0 '0 600 600 '0) ~ .:.t- 0.. 400 o.. 400 '0 '0 0) 0) E 200 E 200 o o

-200:-.L__~__~__~_-----.J -200 L---r------,-----,------.J 2000 2001 2002 2000 2001 2002 Sample Year Sample Year -+-- Mulch Soil P -e- Nonmulch Soil P Trial: Kana Husk 5-10 em Trial: Kana Husk 10-15 em

1200 1200 LSD error bar 1000 1000

·0 800 ·0 800 til til '0 '0 600 600 '0) .:.t- ~ o.. 400 0.. 400 o o - -0) E 200 E 200 o o

-200 L-__~__~__~_-----.J -200 L---r------,-----r------.J 2000 2001 2002 2000 2001 2002 Sample Year Sample year

Figure 21. Kona Husk Soil P Concentration three annual samplings for three soil depths and an average result. Error bars are LSD for treatments.

44 indicate a slightly higher concentration in 2003 than in 2002 which is considered a result of soil P concentration variability from residual inorganic fertilizer remaining longer in the soil due to the drought conditions (Figure 22).

Average differences between the mulch and non-mulch treatments for

Kona husk were not significant at a 90% probability level as at the Keaau site. For the average two-year period, both the Keaau husk and Kona husk mulch treatment trees showed a mean 24% (53 & 72 mg kg-I, respectively) reduction in soil P concentration under the husk mulch while the non-mulch treatment trees at Keaau showed a mean 16% (40 mg kg-I) reduction and the non-mulch Kona husk treatment trees showed no change at all (Figure 23).

The majority ofsoil P reduction was found in the 0-5 cm depth at both wet and dry sites. Soil P reduction at 0-5 cm at the Keaau (wet) experiment showed the mulch treatment soil P concentrations significantly decreased with time when compared with the non-mulch treatment at a 90% probability level for the two years ofthe experiment (Figure 24). Phosphorus reduction for the Kona husk trial was not significant between treatment soil P concentrations with time, and almost all reduction ofsoil P at the Kona husk trial was found in the 0-5 cm depth. Kona husk (dry) showed a mean reduction of 59.1% (231.7 mg kg-I) in soil P concentration at 0-5 cm for mulch treatment trees and a mean 10.2% (48.9 mg kg­

1) reduction in non-mulch treatment trees for the two-year period reported here.

Keaau husk (wet) showed a mean soil P concentration reduction of 46.9% (116.1 mg kg-I) for mulch treatment trees and a mean 29.9% (79.7 mg kiI) reduction for non-mulch treatment trees for the two-year period (Figure 24).

45 Kana Shell 0-15 em Kana Shell 0-5 em

1400 1400 LSD error bars LSD error bars 1200 1200

"g 1000 0g 1000 '0 -o ~800 '0> 800 .:£ a. a. '0 600 '0 600 0> 0> E 400 E 400

200 200

o-'------'-----1 o-'------'-----1 2002 2003 2002 2003

Sample Year [=:J Mulch Soil P Sal11Jle Year ~ Non-rrulch Soil P Kana Shell 5-10 em Kana Shell 10-15 em

1400 1400 LSD error bars LSD error bars 1200 1200

0g 1000 0g 1000 '0 '0 ~800 ~800 a. a. '0 600 '0 600 0> 0> E 400 E 400

200 200

o-'------'-=- o-'------'- 2002 2003 2002 2003 Sal11Jle Year Sample Year

Figure 22. Kona Shell Soil P Concentration two annual samplings for three soil depths and an average result. Error bars are LSD for treatments.

46 25 I

~--~~ . f 0 15 cm soil P reductIOn as percent difference for two Figure 23. ComparIson 0 - h k and Kona husk trials. years at the Keaau us

'------. 0 5 cm depth soil P reductIOn. .as percent difference for Figure 24. ComparIson of - h k and Kona husk trIals. two years at the Keaau us

47 Change in soil P concentration at the 5-10 cm and 10-15 cm sample depths was generally less than that at the 0-5 cm soil depth. At the wetter (Keaau) site soil P concentration at the 5-10 cm depth in the mulch treatment was significantly lower at the 90% probability level than non-mulch treatment with time, while the

10-15 cm depth showed no significant difference between mulch and non-mulch with time. Mean soil P concentration change at Keaau for the 5-10 cm depth was

6% (13.4 mg kg- 1 reduction) and 0 for mulch and non-mulch treatments, respectively, while 10-15 cm depths were 6% (11.3 mg kg- 1 reduction) and 33.8%

(65.3 mg kg- 1 reduction) for mulch and non-mulch treatments respectively, for two years. For the dryer (Kona husk) site a slight change (2.4% or 6.9 mg kg- 1 reduction) in soil P concentration was observed at the 5-10 cm depth for the mulch treatments, however no significant differences were detected between treatments with time at either the 5-10 and 10-15 depths for the two year period, and no soil P reduction took place for non-mulch treatments

Proteoid Root Growth:

Proteoid root biomass was taken from the collected soil P samples, and used to determine root growth as a mass per unit volume.

Massive root growth in the mulch mats was observed under high rainfall conditions at Keaau within six months ofthe initial mulch application. Mean root biomass growth into the husk mulch material was fifteen grams mean dry weight per one thousand cubic centimeters ofmulch mat during the first year (Figure 25), and new roots were observed after each refreshment ofmulching materials.

In low rainfall and drought conditions at Kona, proteoid root growth

48 40

~

30 If) E ~ r-- C) .!:

1:C) 20 ~ "0 - .------o a:: 10 .--- r--- --

o C1 C2 C3 C11 C12 C13 C14 C15 C16 Treatment Tree 10 Figure 25. A single year of proteoid root growth into treatment mulch at Keaau trial for a 1000 cc volume ofmulch. appeared to be restricted to areas of highest moisture content. When sufficient moisture for growth throughout the mats wasn't available, growth concentrated at the soil-mulch interface where moisture was highest and maintained the longest.

Declining moisture content in the husk mulch produced proteoid root senescence as the mulch dried and moisture availability became restricted at the soil-mulch interface.

Average root biomass varied between the two experiments dependent upon moisture and mulch. In the high rainfall husk experiment at Keaau, husk mulch produced a significant increase in average proteoid root biomass over the non-mulch treatment, while the drier husk trial at Kona showed no change in husk mulch treatments but declining root biomass for the non-mulch treatments

(Figure 26 & 27). The shell mulch treatments at Kona, however, showed an

49 Keaau Trial: 0-15 em Keaau Trial: 0-5 em

14 14

12 12

til 10 til 10 E E ~ ~ G 8 G 8 .!: .!: til 6 til 6 til til C1l C1l ::2: 4 ::2: 4 (5 (5 0 0 0:: 2 ~ 0:: 2 0 0

-2 -2 2000 2001 2002 2000 2001 2002 Sample Year -+- Mulch Proteoid Biomass Sample Year -0- Non-Mulch Proteoid Biomass

Keaau Trial: 5-10 em Keaau Trial: 10-15 em

14 14

12 12

til 10 til 10 E E ~ ~ G 8 G 8 .!: .!: til 6 til 6 til til C1l C1l ::2: 4 ::2: 4 (5 (5 0 0 0:: 2 0:: 2 e 0 ~ 0 r ± -2 -2 2000 2001 2002 2000 2001 2002 Sample Year Sample Year

Figure 26. Keaau husk proteoid root biomass growth showing a 0-15 em average growth, and 0-5 em, 5-10 em, and 10-15 em soil depths growth with LSD for treatments.

50 KonaHusk Trial: 0-15 em KonaHusk Trial: 0-5 em

1.5 1.5 LSD error bar LSD error bar

til 1.0 til 1.0 E E ~ ~ C> C> .!: .!: til 0.5 til 0.5 til til ~ Cll ~ Cll ~ ~ ----' ~ 0 0 0 0 0::: 0.0 0::: 0.0

-0.5 -0.5 2000 2001 2002 2000 2001 2002 --.- Mulch Proteoid Biomass Sample Year Sample Year -0- Non-mulch Proteoid Biomass KonaHusk Trial: 5-10 em KonaHusk Trial: 10-15 em

1.5 1.5

LSD error bar LSD error bar

til 1.0 til 1.0 E E ~ ~ C> C> .!: .!: til 0.5 til 0.5 til til Cll Cll ~ ~ 0 0 0 0 0::: 0.0 0::: 0.0

-0.5 -'------,.---,.----,------' -0.5 -'------=r----,------,------J 2000 2001 2002 2000 2001 2002

Sample Year Sample Year

Figure 27. Kona husk trial proteoid root biomass showing a 0-15 em average growth, and 0-5 em, 5-10 em, and 10-15 em soil depths growth with LSD for treatments.

51 increasing trend in root biomass for the mulch treatments and a decreasing trend in biomass for the non-mulch treatments (Figure 28).

Root biomass collected from 0-5 cm depths in soil beneath the mulch and non­ mulch treatment trees showed the greatest variation in root response to treatments due to moisture and mulch type. Root biomass at Keaau (wet) showed a significant increase in mulch treatments over non-mulch treatment root biomass by the end ofthe second year ofthe trial (Figure 26). At the Kona husk trial (dry) root biomass had been initially higher under the mulch treatments, but biomass declined to an equivalent mass with non-mulch treatments during the first year and remained equivalent for the second year (Figure 27). However, the Kona shell trial (dry) showed a tendency for root biomass under the mulch treatment to increase while non-mulch root biomass tended to decrease during the single year ofroot biomass change monitored (Figure 28).

At the 5-10 cm depth, activity of root biomass change was greatest in the

Kona (dry) trials. Both the Kona husk mulch and shell mulch experiment showed a tendency for the mulch treatment root biomass to increase while non-mulch root biomass decreased. For the Kona husk experiment, mulch treatment biomass increased significantly over time while non-mulch decreased significantly over time at more than a 90% probability level for the two years monitored (Figure

27). Shell mulch, showed mulch treatment root biomass was significantly higher at the 95% probability level than non-mulch biomass at the end of one year of monitoring (Figure 28). Keaau (wet) husk mulch treatments showed a significant increase in root biomass at the 5-10 cm depth for the first year ofmonitoring.

52 KonaSheli Trial: 0-15 em KonaSheli Trial: 0-5 em

8 8,------,

6 LSD error bar 6

(j) 4 (j) 4 E E LSD error bar Cll Cll <'5 2 <'5 2 .!: .!: n ,.+,~ (j) 0 rh " (j) 0 -I------'-+-'--""I"'---....l.d,.L-J (j) (j) Cll Cll ~ ~ o -2 -2 o "8 c::: -4 c::: -4

-6 -6

-8 --'------, ---,------.J -8 2001 2002 2001 2002

c::=:J Non-mulch Proteoid Biomass Sample Year ~ Mulch Proteiod Biomass Sample Year

Kona Shell Trial: 5-10 em KonaSheli Trial: 10-15 em

8 8-,------,

6 LSD error bar 6 LSD error bar

(j) 4 (j) 4 E E ~ Cll -.....;;E---_I..::h -= (j) Cll Cll ~ -2 ~ -2 0 o 0 o c::: -4 c::: -4

-6 -6

-8 -"-- --, ---,- ----.J -8 2001 2002 2001 Sample Y00lD2

Sample Year

Figure 28. Kona shell trial proteoid root showing a 0-15 em average growth, and 0-5 em, 5-10 em, and 10-15 em soil depths growth with LSD for treatments for a single year.

53 However, during the second year root biomass declined to near initial biomass levels, similar to non-mulch biomass (Figure 26).

Root biomass at the 10-15 cm depth generally had a declining trend for all experiment treatments except the Keaau (wet) husk mulch treatment (Figure 26,

27, & 28) where an increase was shown the first year, followed by a decline shown in the second year of monitoring. The Kona husk trial root biomass showed an overall declining trend in both treatments for the two years monitored, as did the shell mulch for one year.

Experiment root biomass graphs indicated that root biomass change for husk treatments at Keaau (wet) had an increasing trend at all soil depths for the first year ofthe trial, but only in the top 0-5 cm during the second year monitored.

Significant root mass differences seen at the 5-10 cm depth the first year, were found at the 0-5 cm depth the second year, suggesting that root growth activity may be moving closer to the treatment where accessible mineralized organic P had become more readily available from decomposed treatment mulch. Kona husk (dry) graphs indicated that root biomass growth took place at the 5-10 cm and 10-15 cm depths, suggesting soil moisture and temperature at these depths were affected by the husk mulch by increasing ofroot growth under the prevailing drought conditions. The Kona shell (dry) graphs indicated root biomass growth was active in the 0-5 cm and 5-10 cm depths, suggesting that the shell conditioned soil moisture and temperature for root growth closer to the soil surface under prevailing drought conditions then did husk mulch. The comparison ofKona husk

54 and shell trials is limited to the single annual monitoring- data ofthe 2001 to 2002 period.

Trunk Circumference Growth:

Experiment trees were considered to be mature macadamia>10 years old

In full fruit production. Vegetative trunk growth was not expected to be significant in these trees as a response to treatments due to the maturity of the trees and the demands on tree resources for fruit production. However significant trunk circumference growth was found in all trees at all experiments. Trunk circumference growth for Kona husk and shell trials were not found to have significant differences between the mulch and non-mulch trial trees, while the

Keaau trial did show a significant difference in mulch over non-mulch mean annual trunk circumference growth.

Mean trunk circumferences for Keaau trial trees increased 0.8 cm and 1.2 cm during the first year for non-mulch and mulch treatment trees, respectively, and 0.5 cm and 1.1 cm during the second year for non-mulch and mulch treatment trees, respectively. Mulch trees showed significant trunk circumference growth greater than non-mulch trees during the second annual growth year (Figure 29).

Although growth was significantly higher during the second year, the mean ofthe annual growth rate for the different treatment trees declined during the second year (Figure 30). An average two-year annual rate for the mean trunk growth was

1.92 percent (1.75 cm) and 1.08 percent (0.65 cm) for mulch and non-mulch trees, respectively (Figure 30).

55 1.8

1.6 c:::=J Nonmulch E ~ Mulch u 1.4 .E Q) u 1.2 c: ~ ~ 1.0 E ::J ~ 0.8 '0 .E Q) 0.6 Ol c: III ..c: 0.4 U 0.2

0.0 Year-1 Year-2 Sample Year

Figure 29. Annual growth of Mulch and Non-mulch Trees at Keaau Husk Trial with Standard Error Bars for 95% Significance Level.

Keaau No-mulch Keaau Mulch

1.8 .s 1.6 ~ ..c: 1.4 ~ 1.2 Cl "iii 1.0 ::J § 0.8 III Q) 0.6 Cl ~ 0.4 ~ 0.2 0.0 -'------'------,-----'---.------'------Year-1 Year-2 Year-1 Year-2

Figure 30. Annual growth rate for Mulch and Non-mulch trees at the Keaau Husk Trial showing declining rates during two years.

56 Kona husk experiment trunk growth showed a significant increase in trunk circumference for both mulch and non-mulch trees during the period of the experiment from 2000 to 2002, but significant trunk growth between the treatments was not found for either year at the Kona husk experiment irrespective of the increased trunk growth (Figure 31). Mean trunk circumference increased

.98 cm and 1.10 cm during the first year, and 2.25 cm and 2.10 cm during the second year for non- mulch and mulch trees, respectively. Average annual rates of mean trunk growth for mulch and non-mulch trees were 2.69 percent (1.62 cm) and 2.65 percent (1.60 cm), respectively (Figure 32). Similar annual rates of growth suggest annual rainfall increase was responsible for the increased trunk growth. The increased growth is considered a response to the reduction of moisture stress, stimulating vegetative growth after prolonged drought.

Trunk circumference at the Kona Shell Trial increased for all trees during the year. Mulch tree growth was less than non-mulch growth with circumference increases of0.8 cm and 1.4 cm, respectively, for the year oftrunk growth (Figure

33). This corresponds to a mean growth rate of 0.9 percent and 1.15 percent for mulch and non-mulch trees, respectively. When rains resumed non-mulch trees responded with greater trunk growth suggesting vegetative response to reduction ofstress by mulch treatment trees may have been delayed.

Foliar P Concentration:

Foliar P concentrations showed a mean P concentration range of 0.04% ­

0.07% in "old leaf' samples and a mean P concentration range of0.07% - 0.12% for "new leaf' samples monitored through 2002. There were no significant

57 3.0

c:=J Nonmulch 2.5 E ~ Mulch (,) .£ Q) (,) 2.0 c: ~ .£!! E ::J 1.5 ~ '(3 .£ Q) 1.0 OJ c:ro ..c: () 0.5

0.0 Year·1 Year·2 Sample Year

Figure 31. Annual growth of Mulch and Non-mulch Trees at Kona Husk Trial with Standard Error Bars for 95% Significance Level.

Kona No-mulch Kona Mulch

3.0 .& ...ro 2.5 ..c:. j e 2.0 OJ 'iii ::J 1.5 c: c: CIl Q) 1.0 OJ ~ Q) 0.5 «> 0.0 Year-1 Year-2 Year-1 Year-2

Figure 32. Annual growth rate for Mulch and Non-mulch trees at the Kona Husk Trial showing increasing rates during two years.

58 1.8

1.6 E c:::::::J Nonmulch u 1.4 ~ Mulch .5 Q) u 1.2 c: ~ .2! 1.0 E ::J ~ 0.8 '0 .5 Q) 0.6 Olc: ro .r: 0.4 ()

0.2

0.0 Year-1 Year-2 Sample year

Figure 33. Annual growth of Mulch and Non-mulch Trees at Kona Shell Trial with Standard Error Bars for 95% Significance Level. differences between mulch and non-mulch foliar P concentrations during the period ending December 2002 for the Kona husk or Keaau husk trials. Monitoring is continuing to assess tree response to the husk mulching treatments. Both "Old

Leaf' and "New Leaf' samples exhibited annual cyclic leaf P concentration increases and decreases as characteristically expressed from the Kona experiment data in Figure 34. LeafP increased during fall and winter and decreased in spring and summer in correlation with tree cycles of major vegetative flushing, raceme development, and nut growth (Figure 34).

There were no significant differences over time between mulch and non- mulch leaf phosphorus concentrations for the two-year period for the Keaau trial

(Figure 35 & 36). Significant increases in "Old Leaf' foliar P levels were observed for the October and December 2001 sampling. These increases were

59 Cyclic Foliar P Concentration in Old and New Leaf

Flush/Flowering Harvest 0.11

0.10

---v- Old Leaf 0.09 -...A- New Leaf

~ 0.08 ~ .~ "0 ~ 0.07

0.06

0.05

0.04 0 0 0 0 0 0 0 ~ ~ ~ ~ N N N 0 0 0 0 ;; ;; 0 ;; ;; ;; ;; ;; 0 0 0 0 9 9 0 .!. .!. , 9 9 Co :; Cl ~ ~ 'Z c: .0 >, Co :; 0, ~ u c: .0 ~ t5 0 Q) III Q) III Cl. III :J :J t5 >0 CIl :J ..., :J CIl 0 ..., ..., ..., CIl 0 ...,III CIl ..., et: (/J Z Cl u. :2 et: :2 et: (/J Z 0 u. :2

Sample Date Figure 34. Foliar P for the period June 2000 to May 2002 illustrating the nature ofthe foliar P concentration annual cycle in macadamia. Results taken from mean P concentrations collected at the Kona husk trial at MacFarms.

60 0.11

0.10

0.09 -0- Mulch ~ 0 ... 0.... Non-mulch a.. L- 0.08 .~ (5 U. 0.07 .. ,0. .0...... t') . 0.06 •......

0. 0.05 ~\:J\:) vS:J\:) 'i"" ;K<::>" dJ ()0 «.~ ~'tf

Sample Month Figure 35. Keaau Old Leaf Foliar P Concentration over the period from

October 2000 to February 2003.

0.12 .------,

0.11

0.10

?f<- a.. .~ 0.09 0 LL. 0.08

0.07 -0- Mulch Foliar P% ....0 .. · Non-mulch Foliar P %

a.a6 ...L..----r---.----,---.----,---.----,r---.--r----.--r-.....-.-----r-.------.---.---'

Figure 36. Keaau New Leaf Foliar P Concentration over the period from October 2000 to February 2003.

61 approximately ten and twelve months after treatment application, were observed in both non-mulch and mulch treatments, and exhibited an uncharacteristic

"spike" in the cyclic pattern of "Old Leaf' P concentrations. Following December

2001, "Old Leaf' P for mulch trees was slightly above that of non-mulch trees although not at a 95% significant probability level. "New leaf' P showed higher foliar concentrations between treatments were alternating between the mulch and non-mulch treatments throughout the experiment period. For the two-year period reported, "Old Leaf' P concentration varied from a mean 0.058% to 0.098%

(0.040% variation) and 0.059% to 0.086% (0.027% variation) for mulch and non­ mulch, respectively. "New Leaf' P concentration varied from 0.078% to 0.116%

(0.038% variation) and 0.084% to 0.116% (0.032% variation) for mulch and non­ mulch, respectively.

Results at the Kona husk trial for mulch and non-mulch leafP revealed no significant difference in leaf P concentrations over time for the two-year period ending December 2002 (Figure 37 and 38). The May and Aug 2001 periods however, did show significant differences at the 95% level. However, a serious pest infestation required removal of the lower branches from trial trees in August

2001. At the same time an inadvertent application ofMacadamia shell mulch was placed between orchard tree rows of the husk trial affecting two plots of non­ mulch trees by producing a mulching effect on those trees. Branch removal and shell mulch application were coincident to foliar concentration connecting lines crossing at the October 2001 sample (Figure 37).

62 0.10

_ Mulch 0.09 ···0·- Non-mulch

0.08 ~ 0 ll. .~ 0.07 0 U. 0.06 o

0.05 .0'- o o.04 -'----,r----r--.-----.--,-,---,----.--r---r-....----,----r--.-----.---,----'

Sample Month

Figure 37. Kona Husk Old Leaf Foliar P Concentration for the period from June 2000 to February 2003.

0.11

0.10

0.09

~ 0 ll. 0.08 .~ 0 0.07 U.

0.06

0.05 _ Mulch ···0·· Non-mulch

0.04 1::>1::> 1::>1::> ';,.§~ ';,~

Sample Month

·f

Figure 38. Kona Husk New Leaf Foliar P Concentration for the Period from October 2000 to February 2003.

63 "Old" and "New Leaf' Kona husk experiment graphs clearly show cyclic phosphorus values for leafP concentration (Figures 34, 37, 38). For the two-year period of data, mean "Old Leaf' P concentration varied between 0.049% to

0.062% (0.013% variation) and 0.044% to 0.06% (0.016% variation) for mulch and non-mulch, respectively, while "New Leaf' P varied from 0.052% to

0.1022% (0.050% variation) and 0.053% to 0.1007% (0.048% variation) for mulch and non-mulch, respectively, indicating similar rates ofP cyclic variation.

Kona Shell foliar results indicated no significant differences between treatments over time in leafP concentrations for a single annual period (Figure 39

& 40). The June 2002 "Old Leaf' sample revealed a statistically higher P concentration ofmulch over non-mulch treatment trees as a drop in foliar P values on the mulch trees. The pest infestation ofAugust 2001 also required the removal of lower branches from Shell experiment trees approximately six months before implementation ofthe experiment site. Trimming ofmacadamia trees is generally followed by a period of reduced yields and increased vegetative growth

(Stephenson et aI., 1986). The trimming of the experiment trees may have affected root to shoot ratios of trees and the response to applied treatments by reducing root growth in favor of vegetative flush. Cyclic uptake of P is clearly shown by the graphs ofthe mean foliar P for both Old Leafand New Leaf. During the one-year mean "Old Leaf' P varied from 0.048% to 0.063% (0.015% variation) and from 0.036% to 0.062% (0.026% variation) for mulch and non­ mulch treatments. New Leaf P varied from 0.062 to 0.09 (0.028% variation) for mulch treatment and 0.061 to 0.087 (0.026% variation) for non-mulch treatment

64 0.10

0.08

.0 ~ 0.06 0a...... !!! (5 u. 0.04

___ Mulch 0.02 ···0·· Non-mulch

0.00 Feb-02 Apr-02 Jun-02 Aug-02 Oct-02 Dec-02 Feb-03 Sample Month

Figure 39. Kona Shell Old Leaf Foliar P Concentration for the period from February 2002 to February 2003.

0.10

0.08

'0·· ......

~ 0.06 0a. .... 'ro (5 u. 0.04

___ Mulch 0.02 .. ·0·· Non-mulch

0.00 Feb-02 Apr-02 Jun-02 Aug-02 Oct-02 Dec-02 Feb-03 Sample Month

Figure 40. Kona Shell New Leaf Foliar P Concentration for the period from February 2002 to February 2003.

65 for the same period.

Generally, the HAES 344 cultivar did not respond to a one-third cubic meter macadamia husk mulch application for the two years reported ofthe study.

In the study by Dr. Cooil (Cooil et aI., 1959) on macadamia P use in the late

1950's, nine year old HAES 344 macadamia cultivars took approximately three years to reach a maximum leaf foliar tissue concentration under increasing applications ofinorganic fertilizer. The work ofFirth et aI., 1986 on the effects of husk mulch on macadamia similarly indicates that a significant response in foliar tissue was not reported for the first three years. It may therefore be too early for foliar concentration levels to respond to the mulch treatments.

Yield Analysis:

Yields from both Keaau and Kona husk mulch and the Kona shell mulch experiments have not shown significant increases over those of the non-mulch treatments during the two years of the experiment reported here. Keaau yield results in Wet in Shell (WIS), WIS per cross sectional area, usable kernel and unusable kernel are presented in Table 4. The results indicate total WIS harvest trended upward for the 2002 season and was slightly larger than that of the 2001 season. This was reflected in the Wet in shell yields calculated for the square centimeter of cross sectional area of trunk. Table 4 also indicates that Usable kernel trended downward in the 2002 season as unusable kernel trended upward, however, none ofthe differences were significant. Repeated measures ANOVA F­

Tests for plots as experimental units are presented in Table 5. Repeated measures

66 Table 4. Mean yields for Wet in Shell (WIS), WIS per cross sectional area oftrunk, usable kernel, unusable kernel with annual rainfall for the Keaau Husk trials.

Keaau (Mauna Loa Orchards) Data

Time Mean WIS WIS/area Usable Kernel Unusable Kernel Annual Rain Year Non-mulch Mulch Non-mulch Mulch Non-mulch Mulch Non-mulch Mulch

gms g/sq. cm gms gms mm

2001 16631 22326 44.9 60.3 3566 4966 178 188 3150

2002 20966 24493 54.7 62.4 4631 5630 386 404 3530

No Significant Difference

67 Table 5. The Probability ofSignificance ofthe Keaau Harvest Results analysis by an ANOVA F-test with six degrees offreedom for plots as experimental units.

Keaau Statistical Probability

ANOVA F-test

2000 2001 2002

WIS 0.2191 0.6102

WIS/area 0.2586 0.5899

Usable Kernel 0.1071 0.2888

Unusable Kernel 0.2572 0.9043

68 Usable Kernel approached significance while all other repeated measures statistics did not (Table 5).

Kona Husk WIS, WIS per cross sectional area, usable kernel and unusable kernel yield results are presented in Table 6. Results indicated larger annual yields in WIS and WIS per cross sectional area for both the mulch and non-mulch treatment trees for the three harvests observed. Usable Kernel increased significantly for 2001 and 2002, while Unusable kernel remained the same.

Repeated measures ANOVA F-tests indicated non-significance differences between tree treatments (Table 7). A strong correlation between the increase in yield and the increase in rainfall indicates that the increasing yields measured for the control and treatment plots at the trial was the result of the better rainfall

(Figure 41).

Kona Shell WIS, WIS per cross-sectional area, usable kernel and unusable kernel yield results are presented in Table 8. An ANOVA F-test indicated no significance differences between mulch and non-mulch treatment trees (Table 9).

Yield results of the Shell trial were limited to a single year, and further data collection and analysis is ongoing.

Nut Quality Analysis:

Both collaborators kindly provided nut quality analysis of nuts from the experiment trees. Mauna Loa Macadamia provided nut quality analysis for the

2001 and 2002 Keaau harvests, and MacFarms provided nut quality analysis for the 2002 Kona Husk and Shell harvests. Analytical emphasis differed between the two labs and only tests that generated enough data for statistical analysis are

69 Table 6. Mean yields for Wet in Shell (WIS), WIS per cross sectional area oftrunk, usable kernel, unusable kernel with annual rainfall for the Kona Husk trials.

Kona (MacFarms Orchards) Data

Time Mean WIS WIS/area Usable Kernel Unusable Kernel Annual Rain

Year Nonmulch Mulch Nonmulch Mulch Nonmulch Mulch Nonmulch Mulch

grns g/sq. cm gms gms rom

2000 1154 904 4.7 3.4 o 0 o 0 305

2001 5108 4797 20.8 18.1 1455 1542 363 265 432

2002 30580 30617 98.9 105.7 4185 4357 1538 1493 787

No Significant Difference

70 Table 7. The Probability ofSignificance ofthe Kona Husk Harvest Results analysis by an ANOVAF-test with six degrees offreedom for plots.

Kona Husk Statistical Probability

ANOVA F-test

2000 2001 2002

WIS 0.6939 0.6439 0.9388

WIS/area 0.5316 0.4609 0.6491

Usable Kernel 0.4239 0.8519

Unusable Kernel 0.7437 0.4253

71 Rainfall vs WIS weight

35000

30000 y =640.33x - 20377 R2 = 0.983 E25000 ~ ~ 20000

..~ C) "a; 15000 ~ en 3E 10000

5000

o +-----,---~--,----~----~-----, o 20 40 60 80 100 Annual Rainfall in em

• Mulch ..••.Nonmulch I

Figure 41. Kona husk trial rainfall versus yields with linear trendline, trendline equation and R2 indicating a strong correlation between rainfall and yields.

72 Table 8. Mean Yields for Wet in Shell (WIS), WIS per cross sectional area oftrunk, usable kernel, and unusable kernel with annual rainfall for the Kona Shell trial.

Kona (MacFanns Orchards) Data

Time Mean WIS WIS/area Usable Kernel Unusable Kernel Annual Rain

Year Nonmulch Mulch Nonmulch Mulch Nonmulch Mulch Nonmulch Mulch

gms g1sq. cm gms gms mm

2000 305

2001 432

2002 20952 23395 89 98 4303 4868 1005 1107 787

No Significant Difference

73 Table 9. The Probability ofSignificance ofthe Kona Shell Harvest Results analysis by an ANOVAF-test with six degrees offreedom for plots.

Kona Shell Statistical Probability

ANOVAF-test

2000 2001 2002

WIS 0.3820

WIS/area 0.5318

Usable Kernel 0.9063

Unusable Kernel 0.7321

-, 74 presented here. Some tests differed between the sites.

Keaau husk trial kernel quality analysis for Mold, Bacteria, Germination,

Hollow Center, and Kernel Shrivel revealed no significant differences at the 95% probability level between treatments in these categories using SAS repeated measures ANOVA F-test with plots as experimental units (Tables 10 and 11).

Results suggest mold tended to be higher in the mulch kernel, and that Hollow

Centers and Shrivel tended to be lower in mulch kernel. Mold, Germination, and

Hollow Center percent ofkernel was higher in 2002 than 2001, but Kernel Shrivel declined while Bacteria results were mixed for the two harvests.

For the Kona Husk kernel quality analysis for Stink Bug, Crypto, Mold and

Immature Kernel, no significant difference between the treatments in these categories was found using the SAS repeated measures ANOVA F-test (Table 12 and 13). Quality analysis of harvest kernel was performed for the single year

2002. The 2000 harvest was completely rejected as unusable by MacFarms while the 200I harvest was insufficient for kernel analysis. Mold, Stink Bug, and

Immature results for 2002 were similar for both treatments, while the Crypto analysis showed mulch kernel tended to be higher than non-mulch kernel.

Kona Shell nut quality analysis for Stink Bug, Crypto, Mold and Immature Kernel revealed no significant differences between the treatments in any category using

SAS (Table 14 and 15). The 2002 shell mulch analysis revealed that Stink Bug and Immature kernel were similar while Mold tended to be slightly higher in non­ mulch, and Crypto tended to be slightly higher where mulch was applied.

75 Table 10. Mean yield percent for Moldy kernel, Bacteria, Germination, Hollow Center and Shrivel for Kernel Quality at the Keaau Husk trials.

Keaau (Mauna Loa Orchards) Data

Time Moldy Bacteria Germination Hollow Center Shrivel Year Non-mulch Mulch Non-mulch Mulch Non-mulch Mulch Non-mulch Mulch Non-mulch Mulch

% % % % %

2001 0.17 0.26 0.19 0.27 0.60 0.39 1.08 0.46 2.41 1.53

2002 0.36 0.46 0.32 0.20 1.55 1.64 3.47 2.65 2.09 1.14

76 Table 11. The Probability ofSignificance ofthe Keaau Harvest Results analysis by an ANOVA F-test with six degrees offreedom for plots.

Keaau Statistical Probability

ANOVA F-test

2001 2002

Mold 0.1434 0.1479

Bacteria 0.3378 0.4526

Germination 0.4809 0.9011

Hollow Center 0.0758 0.4336

Shrivel 0.1071 0.2486

77 Table 12. Mean yield percent for Moldy kernel, Crypto, Stink Bug, and Immature Kernel Quality at the Kona Husk trial.

Kona(MacFanns) Data

Time Moldy Crypto Stink Bug Immature Kernel Year Non-mulch Mulch Non-mulch Mulch Non-mulch Mulch Non-mulch Mulch

% % % %

2002 0.46 0.41 0.56 0.1.12 12.50 12.10 12.53 11.12

78 Table 13. The Probability ofSignificance ofthe Kona Husk Kernel Quality Results analysis by an ANOYAF-test with six degrees of freedom for plots.

Kona Husk Statistical Probability

ANOYAF-test

2002

StinkBug 0.9192

Crypto 0.2508

Mold 0.6675

Immature kernel 0.5968

, 79 Table 14. Mean yield percent for Moldy kernel, Crypto, Stink Bug, and Immature Kernel Quality at the Kona Shell trial.

Kona(MacFarrns) Data

Time Moldy Crypto Stink Bug Immature Kernel Year Non-mulch Mulch Non-mulch Mulch Non-mulch Mulch Non-mulch Mulch

% % % %

2002 0.60 0.37 0.13 0.38 5.97 6.28 12.01 12.09

80 Table 15. The Probability ofSignificance ofthe Kona Shell Kernel Quality Results analysis by an ANOVA F-test with six degrees of freedom for plots.

Kona Shell Statistical Probability

ANOVAF-test

2002

Stink Bug 0.7930

Crypto 0.1950

Mold 0.5835

Immature kernel 0.9826

81 Greenhouse Experiment

Greenhouse Results:

Moisture Loss:

A greenhouse mulch assessment was performed during April and May

2002 to observe moisture-holding characteristics of husk and shell mulches.

Results ofwater loss measurements revealed shell mulch lost 35 percent of500 grams (175 grams) of added water during a 28-day period of observation, while husk mulch lost 95 percent of 500 grams (475 grams) of added water during the same period (Figure 42). Student-T tests of daily moisture loss revealed a significant difference between mulch materials in daily water loss for the four­ week period. Average daily moisture lost for each week revealed the shell mulch was fairly consistent in its daily loss, while husk mulch daily losses were higher at the beginning of observation and declined as moisture loss reduced water content

(Figure 43). Husk mulch lost moisture rapidly, showing over a fifty percent loss in the first ten days of observation, while shell husk showed a fairly evenly distributed water loss over the four-week period. The husk mulch tended to hold a major portion of the added water not allowing it to move down into the soil and allowing rapid evaporation from the mulch to accelerate husk mulch moisture loss.

Temperature Change:

Temperature change through the mulch profile was fairly linear for shell mulch and curvilinear for the husk mulch (Figure 44). The husk mulch showed a major temperature change (-3.0°C) in the 0-5 centimeter depth ofthe mulch

82 600

Shell Mulch 500 0 • ~ ... 0 Husk Mulch o •••••• 400 o ••••• 'E .ill o ••••••••• c 0 ••• () 300 00 ~ Q) 0 -ctl 00 ~ 0 200 00 00 00 00 100 0 000 000 00 0 0 5 10 15 20 25 30 Sample Day Figure 42. Greenhouse experiment water remaining per day in Husk and Shell mulch pots.

30 (J) E ctl ~ --0- Shell Mulch Cl 25 c .. 0·· Husk Mulch ~ Q) Q) ~ 20 ~ Q) 0. 0. (J) (J) .2 15 ~ Q) -ctl ~ 10 .2:- 'iii "'C 0- Q) Cl • ctl 5 ~ Q) ~ 0 0 2 3 4 5 Sample Week Figure 43. Average daily water loss per week for Husk and Shell mulch pots.

83 Temp vs Depth (Husk vs Shell)

Temperature Degrees Celcius 35.5 35.0 34.5 34.0 33.5 33.0 32.5 32.0 _-"-__-'---__L--_---'-__---"--__----'-__-+ -2

0 ...... -...... 2 .• '0 .3"3~1. 4 "0. 32.3 Depth in Cm .. 6 9 32.3 8 -+-Shell Mulch , -- 0 -. Husk Mulch 32.9 032.4 10

12

Figure 44. Graph ofaverage temperature at incremental 2.54 cm depths through husk and shell mulch taken at midday for 28-days. Shell mulch indicates a linear decrease in temperature through the mulch, while husk mulch had its major temperature loss in the top 5 cm. profile, while temperature change at the 5-10 cm depth remained fairly uniform with a small increase at the mulch soil interface (+0.1 °C). Temperature change through the shell mulch profile had an average 0.6°C incremental loss per 2.5 centimeters to a ten- centimeter depth. The average temperature difference for the four-weeks of observation between the husk and shell mulch at the soil/mulch interface was approximately 0.5°C, indicating husk mulch may have a slightly better temperature insulating effect than the shell mulch at the interface.

84 Alternative Diagnostic Tissue Experiment:

Results:

The results (Table 16) the alternative diagnostic tissue experiment for P storage

suggest that no significant difference at the 0.05 probability level between inner or outer branch or trunk bark and wood exists. The Keaau experiment did reveal a significant difference ofgreater then the 0.90 probability level between the inner bark (xylem wood) ofthe mulch and non-mulch treatments, however all other results were non-significant.

Table 16. Results of the inner & outer trunk and branch bark and sap wood P concentration analysis for the Kona and Keaau husk mulch experiment trees with P-values from the SAS ANOVA. P concentrations are in g kg-I. Kana

Mulch Treatment Non-mulch Treatment Probability

Kona-Innerbark P-Mulch Kona-Innerbark P-Non-mulch P-value 0.0209 0.0219 0.7305 Kona-Outerbark P-Mulch Kona-Outerbark P-Non-mulch 0.0253 0.0225 0.1939 Kona-Innertrunk P-Mulch Kona-Innertrunk P-Non-mulch 0.0246 0.0210 0.2960 Kona-Outertrunk P-Mulch Kona-Outertrunk P-Non-mulch 0.0295 0.0269 0.2811

Keaau

Mulch Treatment Non-mulch Treatment Probabilty

Keaau-Innerbark P-Mulch Keaau-Innerbark P-Non-mulch P-value 0.0216 0.0296 0.0925 Keaau-Outerbark P-Mulch Keaau-Outerbark P-Non-mulch 0.0208 0.0211 0.8617 Keaau-Innertrunk P-Mulch Keaau-Innertrunk P-Non-mulch 0.0223 0.0202 0.4009 Keaau-Outtertrunk P-Mulch Keaau-Outertrunk P-Non-mulch 0.0259 0.0239 0.5046

85 Correlation Analysis:

Correlation method:

Correlations of the average measured change of three soil depths between soil P and proteoid root mass and trunk growth were performed using the initial baseline measurements and two years of annual data for soil P, proteoid root mass and annual trunk growth. Correlations were made for husk trials excluding the shell trial that had insufficient data.

Soil P vs. Proteoid Root Mass:

Correlation of the soil P concentration and proteoid root mass indicated strong negative correlations between soil P concentration and root mass (Figure 45 & 46). Keaau non­ mulch treatments showed no correlation of these variables. Both Kona husk and Keaau husk experiment sites exhibited a decreasing trend in soil P concentration over the two­ year period. At Kona, a significant correlation between soil P loss and root mass growth for mulch trees was observed, and with Kona data mulch treatment trees showed with regression equations a slope approximately four and a half times larger then non-mulch trees suggesting mulch treatments were more effective in soil P reduction and promoting root growth than non-mulch treatments. Regression equations of Keaau data showed mulch treatment trees had a regression equation slope approximately five times that of non-mulch treatment tress supporting results revealed at the Kona husk trial.

Soil P vs. Trunk Growth:

Correlation of the soil P concentration and annual trunk growth revealed negative correlations for Keaau mulch, Kona mulch, and Keaau non-mulch trees, and a positive correlation for Kona non-mulch trees (Figures 47 & 48). The negative correlations

86 Kona Husk Average Root Mass vs Average Soil P

y =-166.21x + 563.38 500 o R2 = 0.807 <5 - ~ 400 - - m -- -0 E y = -786.54x + 1101 2 II. 300 R = 0.9991 '0 l/) &200 f! ~ 100

O+------r---,------,----,------.----,------, 0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20 Total Root Mass g/1500cc

• Mulch 0 Nomulch -Linear (Mulch) --- Linear (Nomulch) I

Figure 45. Correlation ofaverage root mass and soil P concentration for a 1500 cc soil 2 sample from Kona with regression equations and R • Kona data were correlated with a probability level ofless than 0.05%.

Keaau Husk Average Root Mass vs Average Soil P

500 450 ~ 400 ~ 350 y = -6.6152x + 289.14 ~ 300 R2 = 0.0069 '0 250 0-. l/) --"..--~--~• j GI 200 Cl f! 150 ~ y = -35.12x + 324.03 100 2 50 R =0.7707 O+------r---,------,------,----,------,------, 0.0000 0.5000 1.0000 1.5000 2.0000 2.5000 3.0000 3.5000 Total Root Mass g/1500cc

• Mulch 0 Nomulch -Linear (Mulch) --- Linear (Nomulch) I

Figure 46. Correlation ofaverage root mass and soil P concentration for a 1500 cc soil 2 sample from Keaau with regression equations and R .

87 Kona Husk Average Trunk Growth vs AverageSoil P

y= 12.114x+ 415.8 2 500 o R =0.1467 Cl 450 ::.. .t---- .• --o a400 O~--.... - __ E 350 ~ 300 y = -27.704x + 413.63.-- '0 250 (I) R2 = 0.3712 Gl 200 g' 150 ~ 100

• Mulch 0 No-mulch -Linear (Mulch)· •• Linear (No-mulch) I

Figure 47. Correlation ofaverage soil P concentration for a 1500 cc soil sample with annual trunk growth for the Kona husk experiment with regression equations and 2 R •

Keaau Husk Average Trunk Growth vs Average Soil P

500 Cl 450 ~ 400 Cl y =-26.395x + 296.48 E 350 2 OR = 0.3926 ~ 300 Q..- '0 250 -0 I/) - -- Gl 200 E150 ~ 100

• Mulch 0 No-mulch -Linear (Mulch)· •• Linear (No-mulch) I

Figure 48. Correlation ofaverage soil P concentration for a 1500 cc soil sample with annual trunk growth for the Keaau husk experiment with regression equations 2 and R .

88 indicate that soil P decreased with increasing trunk growth; while a positive correlation indicates soil P was not decreased with increasing trunk growth. Regression equations indicated similar slopes of change for the negatively correlated results, and that Kona non-mulch positive correlation slope had an absolute value approximately one-half the negative correlations slope, suggesting there was no correlation between soil P reduction for the Kona non-mulch trees and trunk growth (Figures 47 & 48).

Rainfall and Foliar P correlations:

Correlations between monthly rainfall data provided by the orchard managers at the

Keaau and Kona trials and foliar P concentrations from samples collected January 2001 through December 2002, were made with SAS PROC CORR. Use of the PROC CaRR algorithm required that missing foliar P values be filled with a moving average value providing an even pair-wise distribution. Graphs with linear regression best fit line

(Figures 49 to 52) and regression equations revealed little or no correlation between rainfall and Old and New Leaf P mulch and non-mulch treatment at Kona. Keaau Old

Leaf P mulch and non-mulch treatments revealed strong positive correlations with a probability of significance at less than 0.05%. Keaau New Leaf P mulch and non-mulch revealed weaker mixed positive and negative non-significant correlations. The table of

SAS PROC CaRR coefficients and level ofprobability significance (Table 17) revealed that Old LeafP correlations at both Kona and Keaau were significant. Results also reveal that Old Leaf P non-mulch concentrations are more significantly correlated with rainfall than the Old Leaf P mulch concentrations, suggesting that the foliar P uptake may have been modified by the applications ofmulch with its high water holding capacity and source oforganic P.

89 Kona Old Leaf P versus Rainfall Correlation

0.12 ~ .. 0.10 y =1E-05x + 0.0546 8- 2 1I. 0.08 R = 0.0367 Cl E 0.06 0: ett5& d" • • ~ ~ •• ~. g Cia ••• () 'lG 0.04 .e. • Ql ...J y =2E-05x + 0.0521 0.02 2 <5" R = 0.0911 0.00 -5.0 5.0 15.0 25.0 35.0 45.0 55.0 65.0 75.0 Rainfall, mm

• Kona Old Leaf Mulch o Kona Old Leaf Nonmulch -Linear (Kana Old Leaf Mulch) • Linear (Kona Old Leaf Nonmulch)

Figure 49. Correlation ofKona monthly rainfall with Old LeafP concentration collected for the period from January 2001 through December 2002 with added linear regression

Kona New Leaf P versus Rainfall correlation .'

0.12 y =-5E-06x + 0.0812 ~ ~ 0.10 o e t=0.0008 Co ~2. 1I. 0.08 •• . •. ; Cl '0 E. 0.06 1I. m0.04 y = -1 E-05x + 0.0828 ...J 2 ~ 0.02 R = 0.0033 z 0.00 +---,-----,-----,----,----~--_,__--_,_--___, -5 5 15 25 35 45 55 65 75 Rainfall, mm

• Kona New Leaf Mulch o Kana New Leaf non-mulch -Linear (Kona New Leaf Mulch) ••• Linear (Kona New Leaf non-mulch)

Figure 50. Correlation ofKona monthly rainfall with New LeafP concentration collected for the period from January 2001 through December 2002 with added linear regressIOn

90 Keaau Old Leaf P versus Rainfall Correlation

0.14 Cl ~ 0.12 GI y = 3E-05x + 0.0623 Cl. 010 2 Q. . R = 0.1706 ~ 0.08 •o o .t90~ .~. ~ a • • ...a: 0.06 •• e a o o ~ 0.04 ...J y = 3E-05x + 0.0596 5 0.02 R2 = 0.2923 0.00 +-----,------,-----~----~---~ o 100 200 300 400 500 Rainfall, mm

• Keaau Old Leaf mulch o Keaau Old Leaf non-mulch -Linear (Keaau Old Leaf mulch) --- Linear (Keaau Old Leaf non-mulch)

Figure 51. Correlation ofKeaau monthly rainfall with Old LeafP concentration collected for the period from January 2001 through December 2002 with added linear regreSSIOn

Keaau New Leaf P versus Rainfall Correlation

y = 2E-05x + 0.0951 0.14 ­ 2 Cl R = 0.1039 ~ 0.12 ~ ~ ~1"""'I. ~- Q. 0.10 _: __gO b5 'fa Si - tp - i -, ~ 0.08 o • y =-1E-05x + 0.1017 a: 0.06 2 'lO R =0.05 ~ 0.04 ~ 0.02 z 0.00 +-----,------,------,------,------. o 100 200 300 400 500 Rainfall, mm

• Keaau New Leaf mulch o Keaau New Leaf non-mulch -Linear (Keaau New Leaf mulch) - Linear (Keaau New Leaf non-mulch)

Figure 52. Correlation ofKeaau monthly rainfall with New LeafP concentration collected for the period from January 2001 through December 2002 with added linear regression

91 Table 17. Correlation coefficients and probability values for monthly rainfall and 1eafP concentrations for the period from January 2001 through December 2003.

Pearson's Correlation Coefficients and P values for Rainfall and Foliar P

Mulch Non-mulch Mulch Non-mulch Site: Old Leaf P Old Leaf P New Leaf P New Leaf P

Kana Correlation 0.1916 0.3018 -0.0279 -0.0578 P-value 0.3696 0.1518 0.8971 0.7885

Keaau Correlation 0.4131 0.5407 -0.3224 0.2235 P-value 0.0448 0.0064 0.1245 0.2938

Autocorrelations, Spectral Analysis & Cross-correlations:

Methods:

To further examme the annual cyclic uptake of foliar P concentrations, autocorre1ations, frequency domain spectral analysis of foliar P, and cross-correlations between the cyclic patterns of the macadamia leaf P concentrations and those of annual rainfall and day-length were performed.

The autocorrelation analysis of foliar time series data was performed using the

Win ASTSA statistical software. Complementary analysis to autocorre1ations was frequency domain analysis of the cyclic data using the SAS PROC SPECTRA package.

The WinASTSA and PROC SPECTRA programs were applied to identify variations/periodicities in the cyclic data that may reflect plant processes significant to foliar P concentrations. Cyclical foliar data were analyzed for cross-correlations with

92 cyclical rainfall and day-length data using the SAS PROC ARIMA software to identify any correlations over time that might affect tree dynamics.

Autocorrelation:

Results of Win ASTSA auto-correlation analysis ofKona and Keaau leafP (Tables 18 &

19; Figures 53 to 56) show significant positive and negative autocorrelations at near zero lag positions. Large significant coefficients declined in both trials as the lags approach 6, and begin to increase after the lag six to the lag twelve. The increase and decrease of autocorrelation coefficients appears to follow cyclic variation in foliar P concentrations in macadamia. Lag one is aligned with the January (winter) maximal concentration and lag six is aligned with the June (Summer) minimal concentration similar to the data order in the database. Both experiment sites showed significant negative autocorrelation at lag 1 and positive autocorrelation at lag 2 for Old Leaf P and New Leaf P samples. The significant positive autocorrelations at two months may indicate the linear association found in the foliar sampling. Therefore, the value of foliar P in June would be highly correlated with the value of foliar P in Mayor April indicating the association of temporal distance between the samples. Further, the Keaau experiment autocorrelations were significant peaks at lags 9 and 10, and this was reflected by the Kona experiment autocorrelations although not with the same significance. These significant autocorre1ations at the 9 and 10 lag may also be an indication ofsome other plant process or factor that affects foliar P as well as an indication of the increasing cyclic P variation

(Figure 53 to 56).

93 Table 18. Kona husk mulch trial autocorrelation coefficients for n=12. * P = >0.05.

Kona: autocorrelation

Sam~le Leaf Old Leaf P Mulch Old Leaf P Non-mulch New Leaf P Mulch New Leaf P Non-mulch

Lag autocorrelation autocorrelation autocorrelation autocorrelation

1 -0.80040* -0.80210* -0.77810* -0.78570* 2 0.59940* 0.59330* 0.59910* 0.60580* 3 -0.39900 -0.39790 -0.39670 -0.39680 4 0.27080 0.26260 0.27760 0.25840 5 -0.16070 -0.16120 -0.17750 -0.14940 6 0.01950 0.03920 0.01750 0.00310 7 0.02640 0.00990 0.01030 0.02090 8 0.09950 -0.09660 -0.15310 -0.15550 9 0.13240 0.13370 0.16970 0.18250 10 -0.19820 -0.17550 -0.23640 -0.23870 11 0.22830 0.20340 0.25400 0.26670 12 -0.24670 -0.24170 -0.27610 -0.28230

94 Table 19. Keaau husk mulch trial autocorrelation coefficients for n=12. * P = >0.05.

Keaau: autocorrelation

Sample Leaf Old Leaf P Mulch Old Leaf P Non-mulch New Leaf P Mulch New Leaf P Non-mulch

Lag autocorrelation autocorrelation autocorrelation autocorrelation

1 -0.78560* -0.77570* -0.78910* -0.77950* 2 0.56210* 0.56250* 0.54080* 0.55160* 3 -0.36620 -0.37490 -0.34120 -0.34950 4 0.14960 0.16280 0.11390 0.12520 5 0.03420 -0.06520 -0.01300 -0.01320 6 -0.13060 -0.10290 -0.07570 -0.10230 7 0.23670 0.20360 0.18670 0.21070 8 -0.37140 -0.37630 -0.31750 -0.31060 9 0.47550* 0.48520* 0.43130* 0.41590* 10 -0.43880* -0.44140* -0.42440* -0.40470* 11 0.38910 0.42900* 0.33790 0.30690 12 -0.25750 -0.27750 -0.21220 0.21400

95 ACF Old Leaf P Concentration Comparison: Mulch

0.8 0.6 1\ '. 0.4 " ...c , ,.. .0> 0.2 l !~~ , , ' c...> J \ . ~ 0.0 0> 0 .' 8', c...> 2 4 ~ 6 7 , , 9 11 -0.2 . , u. , , 1/ \V/ " ., () -0.4 . « -0.6 -0.8 -1.0 Lag/months 1-Kona: Old Leaf P MUlCh····· Keaau: Old Leaf P MujChJ

Figure 53. Comparison ofautocorrelations for Kona and Keaau Old LeafP mulch foliar concentrations.

96 ACF New Leaf P Concentration Comparison: Mulch

0.8 0.6 0.4 +-' 55 0.2 ·u ~ I ."" " ~ ,. CD.0 0 I IIf 11\ Ii I~" ... - I 7' ~ I ...... '" I ~ ,"" r{! ",,'. o o -0.2 u.. ~ -0.4 -0.6 -0.8 -1.0 Lag/months

EKeaau~ew LeafP~ulch__ -Kona New Leaf P Mulch I

Figure 54. Comparison ofautocorrelations for Kona and Keaau New LeafP mulch foliar concentrations.

97 ACF Old Leaf P Concentration Comparison: Nonmulch

0.8 0.6 ., . ~ . , , ..... 0.4 ~ . , .. , c /\ .~ ., 0.2 1 I \ fA\.. .. ' , ~ 0.0 ", 8.: 8 -0.2 ~ 1 / 2 \3 f 4 5' 6 7 9 'to' .. 11 u. v ' . () -0.4 ---j I ~ « -0.6 -0.8 -1.0 Lag/months

1-Kona: Old Leaf P Nonmulch -_... Keaau: Old Leaf P Nonmulch 1

Figure 55. Comparison ofautocorrelations for Kona and Keaau Old LeafP non-mulch foliar concentrations.

98 New Leaf P Concentration Comparison: Nonmulch

0.8 0.6 . 0.4 / , . -a5 0.2 / . ~ ~ I+-"u I , \/ . ,'\.' . • ~ _ , ..... »,/...... ,. ~ _ h: \. '+-Q) 0. 0 i 1\ II o . / () -0.2 6 7 u.. ~ -0.4 .. -0.6 -0.8 -1.0 Lag/months

E·· Keaau New Leaf P Nonmulch --Kona New Leaf P Nonmulch I

Figure 56. Comparison ofautocorrelations for Kona and Keaau New LeafP non-mulch foliar concentration

99 Spectral Analysis:

The frequency domain analysis of foliar P concentration was performed to further compare results revealed in the time domain analysis. Results of the spectral analysis

(Tables 20 & 21; Figures 57 & 58) show a strong pattern of peaks for the Kona experiment at a frequency of 1.26 with secondary peaks at a frequency of 2.51. Keaau results ofthe frequency domain spectral analysis also showed strong peaks for Old LeafP mulch and New Leaf P non-mulch concentrations at a frequency of 1.26, however, no spectral peak was seen for the New Leaf P mulch or Old Leaf P non-mulch concentrations at this frequency. At a secondary frequency of 2.51, only the New Leaf P mulch concentrations showed a peak (Figures 57 & 58). Conversion of frequencies The frequency domain analysis of the foliar P concentration data were performed into time periods gives nine and one-half months for the 1.26 frequency and four and one-half months for the 2.513 frequency. The 9.5-month period seems to match the 9-month lag of the autocorrelation fairly well, while the 4.5 period matches a clear but not significant peak at the 4-month lag. Spectral analysis did not seem to reflect the significant autocorrelation at the 2 lag due to the limitation of frequency length as 0 to Pi, where the

2 lag would have to be expressed at a frequency higher than Pi.

Cross-correlation Function (CCF):

Rainfall:

Cross-correlations of Kona and Keaau foliar P and rainfall and day-length were analyzed and graphical comparisons of the resulting CCF coefficients plotted. CCF analytical results are presented with negative lags describing the time series relationship

100 Table 20. Spectral densities for the Keaau Foliar concentrations and associated frequencies.

KeaauSpectral Data

Frequency Period Old Leaf P New Leaf P Old Leaf P New Leaf P

Mulch Mulch Non-mulch Non-mulch

0.00000 2.12E-05 3.32E-05 4.03E-05 8.90E-07

0.62832 10.00000 2.12E-05 3.32E-05 4.03E-05 8.90E-07

1.25664 5.00000 5.29E-05 7.84E-06 1.31 E-05 6.19E-05

1.88496 3.33330 1.31 E-05 6.18E-06 2.58E-06 9.46E-06

2.51327 2.50000 1.06E-05 2.97E-05 1.92E-06 7.73E-06

3.14159 2.00000 4.99E-07 1.3757-5 1.89E-06 9.71 E-06

Table 21. Spectral densities for Kona Foliar concentrations and associated frequencies

Kana Spectral Analysis

Obs Frequency Period Old Leaf P New Leaf P Old Leaf P New Leaf P

Mulch Mulch Non-mulch Non-mulch

1 0.00000 3.67E-07 2.34E-05 1.14E-06 7.65E-06

2 0.62832 10.00000 3.69E-07 2.34E-05 1.14E-06 7.65E-06

3 1.25664 5.00000 4.14E-06 4.97E-05 2.84E-06 6.58E-05

4 1.88496 3.33330 1.90E-07 6.67E-06 8.66E-07 3.93E-07

5 2.51327 2.50000 3.39E-06 7.65E-06 5.36E-06 8.92E-06

6 3.14159 2.00000 9.95E-06 5.35E-07 1.29E-06 1.26E-06

101 Keaau Spectral Densities

8.00E-oS ~ 'r! 6.00E-oS • ~ 4.00E-OS -i 2.00E-OS ' A- m O.OOE+OO 0.00000 0.62832 1.25664 1.88496 2.S1327 3.141S9 Freq

- OldMulchFreq - NewMulchFreq - OldNonmulchFreq - NewNonmulchFreq

Figure 57. Keaau Spectral densities versus frequency for Keaau foliar concentrations.

Kona: Spectral Densities

8.00E-OS 1.20E-OS

;; 1.00E-OS "i= 6.00E-OS ' c 8.00E-06 CD c 4.00E-OS ' 6.00E-06 1! + 4.00E-06 i 2.00E-OS I - -I 2.00E-06 mA- O.OOE+OO --l---- O.OOE+OO 0_ 0"'"'" ,-"""" ,..... l.!tJl21 .JUI59 Freq

- NewMulchFreq - NewNonmulchFreq - OldMulchFreq - OldNonmulchFreq

Figure 58. Kona Spectral densities versus frequency for Kona foliar concentrations.

102 ofprevious rain or daylight to foliar P concentration. Each negative lag represents a time period prior to the zero or the present foliar P concentration. A negative lag of five therefore is a time five months prior to the zero value and a significant cross-correlation at a negative five would indicate that a variation in a factor occurring five months before is correlated with and possibly affects foliar P concentration. Additionally, positive coefficients at negative lags indicate that the first variable (rainfall or daylight) precedes the second variable (foliar P) and is positively correlated with the present value of the second variable. A negative coefficient at a negative lag indicates that the foliar (second variable) concentrations follow rainfall or day-length (first variable) and the present foliar concentrations of leaf P are negatively correlated with the past value of rain or day­ length. The negative coefficients are not interpreted here, and alternating positive and negative coefficients of the graphs are considered and indication of the volatility and variability revealed in the small data sets.

Cross-correlations coefficients for foliar P and rainfall are presented in Tables 21 and 22. Results of graphical comparison of all Keaau cross-correlations (Figures 59 &

60) show significant positive correlation peaks for Keaau were focused at the -8, -10, and

-11 lags or at the previous 8, 10, and 11 months, with a significant negative lag at -9 or 9 months. The general impression from the graph (Figure 59) is that CCF coefficients declined to a mid lag near -6 where coefficients began to increase or upturn again. The graph ofKona (Figure 60) results shows a steady increase in coefficient values with two sets of significant or strong positive peaks at the -9 lag or 9 months and -3 lag or 3 months previously.

103 Table 22. Kona husk mulch trial cross-correlation with rainfall coefficients for n=12. * P = >0.05.

Kana: cross-correlation with rainfall

Sample Leaf Old Leaf P Mulch Old Leaf P Non-mulch New Leaf P Mulch New Leaf P Non-mulch

Lag crosscorrelation crosscorrelation crosscorrelation crosscorrelation

-12 -0.85508* -0.31523 -0.09864 -0.21992 -11 -0.42586* -0.38424* -0.13973 -0.05616 -10 -0.42296* -0.09737 -0.28088 -0.29196 -9 0.52876* 0.33746* 0.17065 -0.02533 -8 -0.32452 -0.32326 -0.25993 -0.20131 -7 -0.52045* -0.27447 0.13336 0.15622 -6 -0.32558 -0.31693 0.1238 0.04113 -5 0.19164 -0.52416* 0.39755* 0.25411 -4 0.19103 0.16885 0.3888* 0.22807 -3 0.7008* 0.91196* 1* 0.79075* -2 -0.24415 -0.1925 0.07085 -0.01905 -1 0.06545 0.08128 -0.0763 -0.05291 0 0.18884 0.22319 0.02299 0.03053

104 Table 23. Keaau husk mulch trial cross-correlation with rainfall coefficients for n=12. * P = >0.05.

Keaau: cross-correlation with rainfall

Sample Leaf Old Leaf P Mulch Old Leaf P Non-mulch New Leaf P Mulch New Leaf P Non-mulch

Lag crosscorrelation crosscorrelation crosscorrelation crosscorrelation

-12 -0.15398 0.06589 0.30452 0.90788* -11 -0.35009 -0.39304* 0.89138* 0.09822 -10 0.62995* 0.22948 0.27289 0.84795* -9 -0.20821 -0.80329* 0.25422 0.12135 -8 0.51924* 0.29144 -0.16286 -0.24751 -7 -0.29849 -0.86284* 0.23051 -0.22942 -6 -0.3902* -0.48194* 0.13074 -0.18361 -5 -0.46854* -0.5057* -0.38335* -0.81626* -4 -0.24089 -0.13589 -0.17582 -0.18706 -3 -0.48881* -0.31182 -0.18013 0.12655 -2 0.22973 0.29628 -0.42238* 0.0042 -1 0.11192 0.41881 -0.0491 0.31309 0 0.24254 0.43709 -0.22309 0.18167

105 Keaau: Comparison of Crosscorrelation of All Leaf

,\

..... 0.5 c CD ~ o u.(.,) () () -0.5

-1 Negative lag (months)

--OldLeafPMulch --- OldLeafPNonmulch -.-- NewLeafPMulch -.-.NewLeafPNonmulch

Figure 59. Keaau cross-correlation of Rainfall with foliar P concentration comparing all leafsamples.

Kona: Comparison of Crosscorrelation of All Leaf

1.0

..... 0.5 c CD '(3 lE CD 0 0.0 (.,) u. () () -0.5

-1.0 Negative lag (months)

--OldLeafPMulch --- OldLeafPNonmulch -.-.NewLeafPMulch - .. - NewLeafPNonmulch"

Figure 60. Kona cross-correlation ofrainfall and foliar P concentration comparing all leaf samples.

106 Leaf P compansons with Kona and Keaau rainfall (Figures 61 - 64) show significant or strong positive peaks at -8 and -10 lags for the Keaau Old Leaf mulch and non-mulch with a significant or strong positive peak at -9 lag for Kona Old Leaf mulch and non-mulch with the primary significant peak for Kona at -3 lag. These peaks at larger lags also show a larger positive correlation coefficient for Old Leaf mulch than the Old

Leafnon-mulch (Figures 61 vs. 62).

New Leaf cross-correlation comparisons show significant peaks for Keaau mulch and non-mulch at the lags 10, 11, and 12, while Kona showed a significant peak at lag -3

(Figures 63 & 64). Keaau New Leaf mulch had significant negative cross-correlation peaks at -5 and -2 lags and Keaau New Leaf non-mulch had a significant cross­ correlation at -5 lag. Graphical comparison of the Kona and Keaau New Leaf show strong peaks that are out ofphase with each other, and this difference in cross-correlation with rain may be a result ofthe drought conditions that prevailed at the Kona trial rather than day-length.

Day-length:

The cross-correlation of day-length with foliar P showed significant positive correlations at Kona were focused at a -9 lag or nine months for Old Leaf mulch, New

Leafmulch, and New Leafnon-mulch and that significant positive correlations for Keaau were focused at -6 lag six months for Old Leaf mulch, Old Leaf non-mulch, and New

Leaf non-mulch (Table 23 & 24; Figure 65 & 66). Comparisons of leaf sample type further illustrated the difference in cross-correlation results between Kona and Keaau, with one exception in the results for Old Leaf non-mulch samples (Figures 67 to 70).

Graphs ofOld Leafnon-mulch coefficients show similar plotted curves peaking at

107 Crosscorrelation Comparison of Rain vs Old Leaf Mulch

1.0

0.5 " C " Q) '(3 !E Q) 0 0.0 () -1'2 -1 ~ -~ -3 : 0 LL " . () " , () -0.5

-1.0 Negative Lag (months) --Kona: Rain vs Old Leaf P Mulch .... - Keaau: Rain vs Old Leaf P Mulch

Figure 61. Comparison of Keaau and Kona Old LeafMulch versus rainfall cross­ correlations.

Crosscorrelation Comparison of Rain vs Old Leaf Nonmulch l

1.0

C 0.5 ;gQ) Q) 8 LL () () -0.5 " ',' -1.0 Negative Lag (months)

... -- ,Keaau: Rain vs Old Leaf P Non-mulch --Kona:Rain vs Old Leaf P Non-mulch

Figure 62. Comparison of Keaau and Kona Old Leaf Non-mulch versus rainfall cross-correlations.

108 Crosscorrelation Comparison of Rain vs New Leaf Mulch

r:::: ­.~ 0.5 if oQ) (J u. o o -6 " -5 -4.. r3 -2 ...... 0 , , " , , " ' , , ~ -0.5 Negative Lag (months)

••••• Keaau: Rain vs New Leaf P Mulch --Kona: Rain vs New Leaf P Mulch

Figure 63. Comparison ofKeaau and Kona New LeafMulch versus rainfall cross­ correlation.

Crosscorrelation Comparison of Rain vs New Leaf Nonmulch

0.5 c: -Q) '1:5 lE CLl 0 0 (J , LL -5 i"~ -3 -2 -1 0 () () -0.5 , , '

-1 Negative Lag (months)

---.- Keaau: Rain vs New Leaf P Non-mulch --Kona: Rain vs New Leaf P Non-mulch

Figure 64. Comparison of Keaau and Kona New Leaf Non-mulch versus rainfall cross-correlation.

109 Table 24. Kona husk mulch trial cross-correlation with day-length coefficient for n=12. * P = >0.05.

Kana: Cross-Correlation with Day-Length

Sample Leaf Old Leaf P Mulch Old Leaf P Non-mulch New Leaf P Mulch New Leaf P Non-mulch

Lag crosscorrelation crosscorrelation crosscorrelation crosscorrelation

-12 0.01741 -0.41146* -0.08886 -0.0694 -11 0.19199 -0.21496 0.5006* 0.43835* -10 0.41179* 0.04629 0.70649* 0.64001* -9 0.52987* 0.13124 0.80648* 0.77121* -8 0.43718* 0.32008 0.50884* 0.51132* -7 0.20625 0.35457 0.22288 0.26828 -6 -0.05773 0.32331 -0.27162 0,21334 -5 -0.29423 0.22419 -0.67522* -0.61746* -4 -0.32756 0.24139 -0.77288* -0.83156* -3 -0.35575 -0.00401 -0.77761* -0.80563* -2 -0.46562* -0.32444 -0.58551* -0.66256* -1 -0.27708 -0.4722* -0.22988 -0.21322 0 0.0576 -0.37008 0.1254 0.2794

110 Table 25. Keaau husk mulch trial cross-correlation with day-length coefficient for n=12. * P = >0.05.

Keaau: Cross-Correlation with Day-Length

Sample Leaf Old Leaf P Mulch Old Leaf P Non-mulch New Leaf P Mulch New Leaf p Non-mulch

Lag crosscorrelation crosscorrelation crosscorrelation crosscorrelation

-12 -0.13284 -0.15048 -0.60588* -0.91531* -11 -0.70536* -0.33918 -0.15106 -0.64106* -10 -0.51203* 0.04676 -0.19976 -0.28003 -9 -0.32662 0.13166 -0.23808 0.10611 -8 0.12057 0.51123* -0.1648 0.44015* -7 0.54908* 0.66876* 0.04415 0.70978* -6 0.7357* 0.69* 0.12903 0.68603* -5 0.69936* 0.51896* 0.205 0.47522* -4 0.5096* 0.27146 0.18572 0.27709 -3 0.14033 -0.127 0.13437 -0.14535 -2 -0.1388 -0.33008 -0.12988 -0.64296* -1 -0.48461* -0.58642* -0.09675 -0.78071* o -0.60798* -0.60783* -0.14263 -0.63052*

111 Keaau Cross-correlation Daylength vs Foliar P Concentration

1

ol-Ic 0.5 'uOJ IE OJ 0 0 U lL. u u -0.5

-1 Lag (months)

- Daylength vs Old Leaf P Mulch - Daylength vs Old Leaf P Nonmulch - Daylength vs New Leaf P Mulch - Daylength vs New Leaf P Nonmulch Figure 65. Keaau cross-correlation ofday-length and foliar P concentration comparing all leafsamples.

Kona Cross-Correlation Daylength vs Foliar P Concentration

.... 1 c OJ '0 0.5 IE: Q) 0 8 uu. -0.5 ­ u -1 Lag (months)

- Daylength vs Old Leaf P Mulch - Daylength vs Old Leaf P Nonmulch P

Daylength vs New Leaf P Mulch P - Daylength vs New Leaf P Nonmulch P

Figure 66. Kona cross-correlation ofday-length and foliar P concentration comparing all leafsamples.

112 Crosscorrelation Comparison of Daylength vs Old Leaf P Mulch

-a3 0.5 .. '13 !E ~ O-t-L:.,~----,----,----,---:-----,----T'.....--,---,-----,----'-.--~-'--/----,

() u.. -12, -11 -10 _.,9 o 8 -0.5 "

-1 Lag (months)

--Kona: Daylength vs Old Leaf P Mulch , ,. ,. "Keaau: Daylength vs Old Leaf P Mulch

Figure 67. Comparison of Keaau and Kona Old LeafP Mulch versus Day-length cross-correlation

Crosscorrelation Comparison of Daylength vs Old Leaf P Nonmufch

1 ....c Q) 0.5 'u " it: ~~-, .~~ Q) 0 ,,' -:; I ,, 0 u..u -i.2>.:1t' -10 -9 -8 -7 -6 -5 -4 -3" ~ u -0.5 u -1 Lag (months)

..... Keaau Daylength vs Old Leaf P Nonmulch --Kona Daylength vs Old Leaf P Nonmulch

Figure 68. Comparison of Keaau and Kona Old Leaf P Non-mulch versus Day­ length cross-correlation

113 Crosscorrelation Comparison of Daylength vs New Leaf P Mulch

..... 0.5 c (]) '(3 ...... IE ...... ill (]) 8 LL ,ff . :1-0· -9- - --8' -5 -4 -3 () () -0.5

-1 Lag (months)

.. --. Keaau Daylength vs New Leaf P Mulch --Kona Daylength vs New Leaf P Mulch

Figure 69. Comparison ofKeaau and Kana New LeafP Mulch versus day-length cross-correlation.

Crosscorrelation Comparison of Daylength vs New Leaf P Nonmulch

1

," ...... 'It .j..Jc 0.5 .. (]) 'u .. lE .- OJ 0 0 , U LL -9 -8 -7 -4 -3, u u -0.5

-1 Lag (months)

.. - .. Keaau Daylength vs New Leaf P Nonmulch --Kona Daylength vs New Leaf P Nonmulch Figure 70. Comparison of Keaau and Kona New Leaf P Non-mulch versus day­ length cross-correlation.

114 approximately -6 lag with larger positive cross-correlations for the Keaau results

(Figure 65). The general sinusoidal shape of the graphed curves suggests that the

Kona and Keaau cross-correlation with day-length are out ofphase by about three months. Results of day-length analysis are similar to rainfall analysis such that a positive correlation at negative lags indicates that day-length precedes foliar concentration and is positively correlated with it. The sinusoidal shape of the graphed curves may indicate that data contained fewer large variations, and the significant negative cross-correlation may suggest that other environmental factors may have a greater significance than day-length on foliar concentration at those lags.

115 CHAPTER 4

DISCUSSION AND CONCLUSION:

Response to Mulch:

Experimental results suggest agmg macadamia trees respond to applications of husk or shell mulch, and that elevated soil P concentrations found in macadamia orchards can be effectively reduced by an application of mulch under the canopy. Major reduction in soil P occurs in the 0 to 5 centimeter depth of the soil in both wetter and dryer rainfall regimes. It appears that moisture availability conditions the P reduction as exhibited in the reduction of mulch and non-mulch treatments following increased rainfall during the second year of the trials. Mulch treatments in Keaau, where high rainfall maintained a saturated pad, had little reduction during the second year, however, both Keaau and Kona non­ mulch and Kona mulch had decreases with the additional rainfall. This and the results of the greenhouse trial indicating a high water-holding characteristic for husk mulch, suggests that husk mulch is most effective where the rainfall regime will ensure sufficient water. Although shell mulch did not exhibit a reduction in soil P, treatments had only been in place a single year and under a semi-drought rainfall regime during that period. Continuing monitoring of the shell trial will provide more evidence as to the ability ofshell mulch to promote soil P reduction and proteoid root growth.

Methods of mulch application may also be a factor in effective use of mulch for remedial or preventative tree and soil health. Experiment methods were 116 an application ofa one-meter radius by ten-centimeter deep mulch mat. However, under the conditions of lower rainfall this method of application was unsuitable for husk mulch. Observation indicated that low infrequent rainfall was unable to effectively maintain an adequate level ofmoisture for vigorous root growth at the soil husk mulch interface. An alternative under lower rainfall conditions might include a thinner application of the mulch over a larger area under the canopy allowing more of the rainfall to raise moisture availability at the soil/husk interface and stimulate root growth. A secondary alternative with a more preventative orientation would be applications of thin bands under the canopy along planting rows that could be built up over time by repeated applications. As root growth developed in husk mulch bands forming semi-permanent structures that could act as a block or catch for soil and nutrients that might be lost due to erosion loss by surface water flow from heavy rain. Under orchards with a steeper slope, this may be especially useful when placed normal to the contour of the slope.

Root Growth:

Macadamia husk mulch promoted rapid and vigorous proteoid root growth into overlying mulch under conditions of abundant rainfall, but rainfall availability under semi-drought conditions limited root growth and confined it to the mulch-soil interface where moisture content was highest. Average root growth for a 0-15 centimeter soil profile under husk mulch increased under both the wetter and dryer conditions, with the major root growth in the top five centimeters for wetter conditions, and at the five to ten-centimeter depth for the drier

117 conditions. The Keaau trial showed significant differences in root growth during the first year at the five to ten centimeter depth, followed by significant growth at the zero to five-centimeter depth the next season. But Kona root growth at this depth increased almost linearly for mulch while non-mulch root growth decline steadily for the two-year period. This suggests that the husk mulch insolates and conserves moisture, promoting growth at the five to ten centimeter depth under diverse rainfall conditions.

The vigorous root growth into the applied mulch seen at the Keaau experiment appeared to be similar to that observed by Firth et aI., (1994) during their work on macadamia in decline in Australia. In Australia as in Hawaii, vigorous root growth was seen within a six-month period after application ofhusk mulch suggesting that macadamia trees, when given sufficient moisture, respond relatively quickly to applications ofhusk mulch.

Reduction in Surface P:

A significant correlation of soil P to root mass for mulch treatments over non-mulch further suggests that the mulch additions beneficially contribute to reduction of soil P concentration by improving root mass growth and P uptake.

Differences in regression equation slopes suggest that trees with mulch additions may show an effective reduction of the soil P under the macadamia canopy through increase P uptake by a greater root biomass at a rate approximately five times that oftrees without an addition.

Shell mulch root growth improved quickly as seen in the single year of mpnitoring data. Root growth increased in the shell mulch treatment while root

118 growth in the non-mulch treatment declined for all soil depths sampled. Shell root growth when compared with husk mulch growth during the same 2001-2002 period suggests that the shell mulch may promote root growth more effectively at the zero to five-centimeter depth where conditions of prolonged low rainfall prevail.

The greenhouse experiment results suggested that the shell mulch allowed more added moisture to reach the soil and provided a fairly even rate of evaporative loss over time, while husk mulch acted as a moisture sink with a fairly high rate of evaporative loss over time. The greenhouse experiment results further suggested that under low rainfall, shell mulch might keep higher amounts ofwater at the 0 - 5 centimeter depth promoting root growth more effectively than husk at that depth.

Trunk Growth:

Results of trunk growth monitoring suggest husk mulch may have a significant effect on vegetative trunk growth. At Keaau no significant growth rate differences occurred during the two-years monitored, but mulch treatments did show significant increase in growth over non-mulch during the second year of monitoring, and for both years mulch treatments had a higher circumference growth. Kona results were oriented differently from those at Keaau. They tended to show a trunk growth tied more to the variation in rainfall conditions rather than mulch treatments. This was exhibited by the lack of a significant difference between the treatments for both years while a strong rate of growth change was

119 seen between years for both treatments. Here as in soil P reduction and root growth, water is the most limiting element conditioning tree response.

Correlations of annual trunk growth and annual soil P concentrations for the Keaau mulch and non-mulch, and the Kona mulch trees have similar regression slopes suggesting that the application of husk mulch under dry conditions such as those at the Kona trial may have an effect similar to that at the

Keaau husk trial. Furthermore, the non-mulch trunk growth and soil P correlation at the Kona trial had a slightly positive regression slope ofabout halfthe absolute value, suggesting that for non-mulch treatments under dry conditions there may be no correlation for trunk growth and soil P concentrations.

Foliar P:

The monitoring results indicating a clear foliar P cyclic variation ofhigher leaf P values in winter and lower P values in summer is consistent with the findings of Stephenson and Cull (Stephenson and Cull, 1986) on seasonal variation of nutrients in macadamia in South East Queensland Australia. This consistency of leaf P variation may indicate a characteristic plant mechanism for

P utilization by macadamia.

Periodic foliar P concentration monitoring failed to show, with a few exceptions, significant difference between treatments and over time for a two-year period. Although, both Kona and Keaau trials revealed a reduction in soil P concentration, uptake of P was not seen as a correction for low foliar P concentration. Several factors may have affected the utilization of P by macadamia trees. Root and trunk growth may have had a limiting effect on foliar

120 utilization of P, and the dynamics of P uptake, storage and utilization by macadamia may have larger cyclic periods than at first considered. Correlations of leaf P and rainfall suggest that mulch does modify tree utilization of P on a foliar level in the older leaves, and that there may also be an affect in new leaves under conditions were rainfall is abundant.

The June 2002 drop in the foliar P concentrations of the shell mulch trees during the single year of sampling is most probably a sampling error. The cyclic change in P concentration values found during the experiment indicates that a drop in values followed by a return to more normal values over such a short time would be uncharacteristic ofmacadamia.

Bark P Concentrations:

The results of Table 16 for the comparison of bark P concentration levels suggested no significant differences at the 0.05 probability level between inner and outer branch or trunk bark and wood existed to indicate a P tissue sink or storage in the trunk or branch bark and wood of macadamia. However, for the

Keaau experiment, a significant difference of greater then the 90 percent probability level was found between the inner bark (xylem wood) for the mulch and non-mulch treatments. In this instance the non-mulch trees had a higher P concentration than the mulch trees, suggesting that a further look at these tissues role in P utilization may be worthwhile.

Nut in shell yields:

Nut yields revealed no differences between the treatments based on plot

ANOYA's. Although the Keaau trial had larger WIS (Wet in shell) yields for both

121 years, treatment effects were non-significant. Interestingly, during the 2002 season, all experiments had mulch treatment WIS yields larger than non-mulch.

For the Kona husk trial, the two previous harvests returned WIS yields slightly higher for non-mulch than mulch but mulch was slightly higher during the third season harvest after increased rainfall. No differences were noted for WIS per cross sectional area of trunk, usable kernel, or unusable kernel at any trial.

However, the application of Student T-tests to the treatment trees revealed significant differences between treatments in the yields for the Keaau trial. The comparison of the plot ANOVA with the tree Student t-test suggests that yield differences may exist between the treatments however, our limitations on accuracy design parameters, and experiment size and costs may have reduced the precision ofthe experiment to detect these differences.

Nut quality:

Nut quality analysis revealed only Hollow Center, and Shrivel nut quality measurements neared significance for the single year of 2001. Generally no differences were revealed between treatment nut-quality for the two-year period of study. For other than the two mentioned near significant quality parameters, mulch application did not show either a beneficial or detrimental affect on nut quality. Neither experiment site, with their differing environmental conditions, or mulch type appeared to affect nut quality.

Mulching options:

The greenhouse study of water holding characteristics for the husk and shell mulch when combined with the results for soil P, root growth, and trunk

122 growth suggest that an application of mulch may have potential as a nutrient management tool when combined with inorganic fertilizers. Fertilizer applied prior to a mulch application may be better utilized. Root and trunk growth reveals a vegetative response to the husk treatment. Foliar P response was not observed, but a light top-dressing of inorganic phosphate fertilizer placed on the mulch surface may be sufficient for tree foliar needs since P uptake appears to be taking place within and below the treatment. This could reduce the amount of applied P fertilizer while increasing potential for P uptake by increasing the viable proteoid root system. Further this eliminates the necessary mineralization process required for organic P. This possible use of macadamia mulch with a reduced application offertilizer may be an economic alternative that deserves further investigation.

The greenhouse study further indicated that different types of mulch material might be better suited to different climatic conditions in Hawaii.

Examination of husk and shell suggests that rainfall regime plays a part in determining mulch type and application. Husk mulch loses its moisture relatively quickly and should be applied where sufficient amounts of rainfall or irrigation are available to recharge the mulch and prevent root senescence, especially root growth developed into the mulch. Shell mulch appears to promote root growth in the surface soil layer under the mulch, holding moisture in that layer while insulating against evaporation. Shell mulch may be more effective under conditions where rainfall or irrigation recharge events are more widely spaced in time. Shell mulch also promotes root growth in the underlying soil layer under conditions ofhigher rainfall although it does not provide nutrient value or provide

123 soil conditioning as seen with husk mulch. Either type of mulch may benefit an orchard dependent on orchard need and conditions, a further possibility may be combinations ofthe mulch types in a layering or mixed application, however, this needs further investigation.

Time series analysis:

Investigation attempting to identify possible plant processes related to P uptake and utilization in foliar tissue through time series analysis was performed.

Significant positive and negative autocorrelations were revealed at both Kona and

Keaau. At both experiment sites the autocorrelations revealed significant results at the early lags that declined at the middle lags and increased again at later lags, suggesting the foliar P concentration cycle. Significant coefficients for both Old and New Leaf P were also revealed for Keaau and Kona husk sites at lag 9 and lag 11. The significant coefficient for Keaau at lag 9, and the positive maxima at lag 11 for Kona, suggests a possible foliar P vegetative process. This is further suggested by frequency domain graphs of spectral analysis for foliar P where strong peaks for all types of leaf at Kona are seen at the 1.26 frequency and matched by Old Leaf P mulch and New Leaf P non-mulch strong peaks in the

Keaau analysis. Interestingly, Keaau showed a single peak at a 2.51 frequency by

New LeafP mulch where Kona showed peaks for all leaftypes. These frequencies correspond to periods of approximately 9.5 months and 5 months that compare with autocorrelation at lag 9 and lag 5, roughly maxima and minima for the autocorrelation, suggesting again that these lags reflect some sort ofa tree process or activity.

124 Time series cross-correlation between foliar P concentrations and rainfall revealed a characteristic positive peak in the Keaau analysis at a -10 lag, with the exception of New Leaf P mulch, which peaked at -11. This New Leaf P mulch result may have been an effect of the mulch delaying the cyclic activity. A characteristic positive peak was also seen in the Kona analysis at a -9 lag. The positive peaks indicate that present foliar P is positively correlated with rainfall 9,

10, and 11 months prior. Further, these characteristic peaks in the cross­ correlation coefficients when compared with peaks in the autocorrelation and spectral analysis suggest a plant process concerning P uptake and utilization, that may be occurring nine or ten months prior to the present foliar P concentration.

Interestingly, Kona also had a significant peak in rainfall-foliar P cross­ correlation at a -3 lag. This may have been a response to the relief of prolonged water-stress in macadamia as was experienced at the Kona trial, and is often delayed by several months. Further, the extreme alternation between positive and negative correlation coefficients seen in the rainfall/foliar P cross-correlations are considered to be the results ofthe large variability in the foliar P and rainfall data combined with the relatively small data set. This alternating ofthe coefficient sign was not seen in the day-length and foliar P data where variability in day-length was small.

Keaau cross-correlation between day-length and foliar P revealed a characteristic peak for all Leaf P samples approximately at a -6 lag. This would indicate that the present foliar P is positively correlated with the day-length six­ months prior suggesting that the cyclic foliar minima P at Keaau in the summer is

125 correlated with the shorter days of winter, and that the cyclic maxima in the winter, is correlated with the longer days of summer. This would seem to reflect the macadamia vegetative process. However, for Kona results, a characteristic peak was revealed at a -9 lag, except for Old Leafnon-mulch, which followed the

Keaau results. This -9 lag indicates that present foliar concentrations are positively correlated with day-length of 9 months prior. It is interesting to consider that the three-month lag difference in Kona compared to Keaau is the same period as the 3-month significant peak seen in the rainfall cross-correlation ofKona but not seen in Keaau.

Summary:

In summary, applications of macadamia husk mulch show a tendency to reduce soil P concentrations under the canopy in macadamia orchards. They are beneficial to the growth and development of proteoid roots both under the mulch and within the mulch, and they positively affect trunk growth where sufficient water is available. In a two-year period husk mulch, and shell mulch for a one­ year period, were not able to adjust foliar P upward into a sufficiency range from levels of lower than optimal concentrations. Investigation into mulch material characteristics revealed that applications of mulch material types require consideration on a per site basis to determine an effective and economical use.

Reduced applications of inorganic fertilizers to the mulch surface may be a method that would allow reducing fertilizer cost, but to establish quantitative values offertilizer application and tree responsiveness research is lacking.

126 Investigation into macadamia plant processes using time series, frequency domain, and cross-correlation analysis pointed to a possible active process having a cyclic period ofabout nine or ten months. Rainfall cross-correlated with foliar P concentrations suggests that foliar P uptake may be the process affected by rainfall from the previous nine or ten months. However, the quantity of data and its variability placed limitations on the conclusiveness of the analysis, indicating that the results might best be used as a beginning for further investigation.

127 APPENDIX A:

The modified Truog method:

1. Use an extracting solution ofO.02N HZS04,pH2.02

2. Prepare Molybdate - Antimony Solution - Reagent A

Dissolve 30g Ammonium Molybdate and 0.2 g Antimony Potassium Tartrate in 600ml demineralized water. Dilute to 1 L.

3. Ascorbic Acid Solution, 6% - Reagent B

Dissolve 1.056 g crystaline ascorbic acid with 200 ml Reagent A

4. Extraction

Measure 0.3 g ofsoil into a 30 ml centrifuge tube and add 30 ml of extracting fluid. Shake with a reciprocal shaker for thirty minutes and allow to settle. Filter the extractant through Whatman 40 filter paper and collect the filtrate in a test tube.

5. Colorimetric analysis

Place 1 ml ofthe collected filtrate into a 25 ml test tube, and add 8 ml ofextracting solution and 1 ml ofReagent B. Vortex and allow color to develop for twenty minutes. Set spectrophotometer to absorbance at 880 nm and measure color.

6. Standards

Develop standards by taking 2 ml of50 ppm per ml P stock solution and diluting it to 100 ml in a 100 ml volumetric flask. Add diluted stock to 25 ml test tubes to produce 0, 2, 4, 6, and 8 ppm concentrations of P in a 10 ml volume. Leave enough volume to add 1 ml ofReagent B for color development. Read developed color on set spectrophotometer for standard curve.

128 APPENDIXB:

Equations used for the calculation ofday-length with example:

Dec = 0.4093*sin(O.0172*(JDATE-82.2» DLV=(S1*SIN(Dec)-0.1 047)/(C1 *COS(Dec», HRLT=7.639*ACOS(DLV). Where HRLT is photoperiod in hours calculated for the day of the year at a particular latitude. Example:

Degrees 19.34 radians = 0.337547 Julian 0.523599 Latitude Latitude Date Declination Hours of Sunlight degrees radians Jdate Dec DLV HRLT 19.34 0.337547 1 -0.40311 0.029049 11.77738

19.34 0.337547 180 0.406765 -0.27202 14.10378

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