Land imprinting as an effective way of soil surface manipulation to revegetate arid lands
Item Type Dissertation-Reproduction (electronic); text
Authors Abusuwar, Awad Osman Mohmed,1952-
Publisher The University of Arizona.
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Link to Item http://hdl.handle.net/10150/191107 LAND IMPRINTING AS AN EFFECTIVE
WAY OF SOIL SURFACE MANIPULATION
TO REVEGETATE ARID LANDS
by
Awad Osman Mohmed Abusuwar
A Dissertation Submitted to the Faculty of the
DEPARTMENT OF PLANT SCIENCES
In Partial Fulfillment of the Requirements For the Degree of
DOCTOR OF PHILOSOPHY WITH A MAJOR IN AGRONOMY AND PLANT GENETICS
In the Graduate College
THE UNIVERSITY OF ARIZONA
1986 THE UNIVERSITY OF ARIZONA GRADUATE COLLEGE
As members of the Final Examination Committee, we certify that we have read the dissertation prepared by Awad Osman Mohmed Abusuwar entitled Land imprinting as an effective way of soil surface manipulation
to revegetate arid lands
and recommend that it be accepted as fulfilling the dissertation requirement
Doctor of Philosophy • ItTr; Date
Date
Date
Final approval and acceptance of this dissertation is contingent upon the candidate's submission of the final copy of the dissertation to the Graduate College.
I hereby certify that I have read this dissertation prepared under my direction and recommend that it be accepted as fulfilling the dissertation requirement. A-erti g6: Dis ertation Director Date STATEMENT BY AUTHOR
This dissertation has been submitted in partial fulfillment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to bor- rowers under rules of the Library.
Brief quotations from this dissertation are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or re- production of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his or her judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author.
SIGNED C ACKNOWLEDGMENTS
The author wishes to express sincere thanks to his major ad-
visor, Dr. M. H. Schonhorst, and to his minor advisor, Dr. R. M. Dixon,
for their support, patience, and expert guidance during the course of
this study.
Grateful appreciation is extended to the members of the
committee, which included Dr. R. E. Briggs, Dr. R. E. Dennis, and
Dr. V. Marcarian, for their valuable suggestions during the course of
the study and for reviewing this manuscript. Special thanks are ex-
tended to Dr. P. G. Bartels who served on my committee as a substitute
both during the preliminary examinations and the final oral examination.
Appreciation and respect are due to my family for their encour-
agement and support, and to my loving wife, Samia, for her patience,
sacrifice, and support without which this study could not have been
completed. The presence of my fifteen-month-old daughter, Areij,
encouraged me and gave me the motivation to continue.
The Government of the Sudan paid my expenses for transportation,
tuition, books, food, lodging, and other costs. This assistance made my studies at the University of Arizona possible, and for this I will always be grateful.
Thanks are extended to Mr. Paul Johnson of the Statistical
Consulting Unit, who helped with the analysis of this study, and to
Ms. Anna McKew who typed the thesis. iv
A debt of gratitude is due to all who helped in any way to make this dissertation possible. TABLE OF CONTENTS
Page
LIST OF TABLES vii
LIST OF ILLUSTRATIONS
ABSTRACT xi
1. INTRODUCTION 1
2. LITERATURE REVIEW 7
Land Shaping and Types of Seedbeds 7 Soil Mulching 9 Artificial Revegetation 11 Competition 12 Adapted Species and Suitable Planting Tools 13 Grass-Legume Mixture 16
3. MATERIALS AND METHODS 20
Treatments 21 Parameters Measured 26
4. RESULTS AND DISCUSSION 30
Meteorological Data 30 Soil Moisture 32 Plant Population 46 Physiological Data (Legumes) 52 Transpiration 52 Leaf Diffusive Resistance 55 Plant Height (Grass) 60 Canopy Cover 63 Biomass 66 Individual Harvests 66 Overall Means of the Different Cutting Dates 78
5. SUMMARY AND CONCLUSION 82 vi
TABLE OF CONTENTS--Continued
Page
APPENDIX A: EFFECTS OF TREATMENTS ON PLANT HEIGHT AT THE ORACLE AGRICULTURAL CENTER FOR THE DIFFERENT SAMPLING DATES 85
APPENDIX B: EFFECTS OF TREATMENTS ON PLANT HEIGHT AT THE CAMPUS AGRICULTURAL CENTER FOR THE DIFFERENT SAMPLING DATES 90
APPENDIX C: EFFECTS OF TREATMENTS ON PERCENT CANOPY COVER AT THE ORACLE AGRICULTURAL CENTER FOR THE DIFFERENT SAMPLING DATES 97
APPENDIX D: EFFECTS OF TREATMENTS ON PERCENT CANOPY COVER AT THE CAMPUS AGRICULTURAL CENTER FOR THE DIFFERENT SAMPLING DATES 102
LITERATURE CITED 109 LIST OF TABLES
Table Page
1. Monthly average temperature (C) at the Oracle and Campus Agricultural Centers 33
2. Monthly average relative humidity (%) at the Oracle and Campus Agricultural Centers 34
3. Effects of treatments on percent soil moisture at the Oracle Agricultural Center 37
4. Effects of treatments on the percent soil moisture at the Campus Agricultural Center 38 -2 -1, 5. Effects of treatments on transpiration rates (11.g cm s ) at the Oracle Agricultural Center (Overall means of 8 sampling dates 53 -2 -1, 6. Effects of treatments on transpiration rates (11g cm s ) at the Campus Agricultural Center (overall means of 8 sampling dates) 54
7. Effects of treatments on leaf diffusive resistance (S cm) at the Oracle Agricultural Center (overall means of 8 sampling dates) 56 -1 8. Effects of treatments on leaf diffusive resistance (S cm ) at the Campus Agricultural Center (overall means of 8 sampling dates) .57
9. Effects of treatments on leaf temperature (C) at the Oracle Agricultural Center (overall means of 8 sampling dates) 58
10. Effects of treatments on leaf temperature (C) at the Campus Agricultural Center (overall means of 8 sampling dates) 59
11. Effects of treatments on grass height (cm) at the Oracle Agricultural Center (overall means of 4 sampling dates) . 61
12. Effects of treatments on grass height (cm) at the Campus Agricultural Center (overall means of 6 sampling dates) 62
vii viii
LIST OF TABLES--Continued
Table Page
13. Effects of treatments on percent canopy cover at the Oracle Agricultural Center (overall means of 4 sampling dates) 64
14. Effects of treatments on percent canopy cover at the Campus Agricultural Center (overall means of 6 sampling dates) 65
15. Effects of treatments on forage dry matter production (kg/ ha) at the Oracle Agricultural Center (First harvest on 9/29/84) 67
16. Effects of treatments on forage dry matter production (kg/ha) at the Oracle Agricultural Center (Second harvest on 5/25/85) 68
17. Effects of treatments on forage dry matter production (kg/ha) at the Oracle Agricultural Center (Third harvest on 8/5/85) 69
18. Effects of treatments on forage dry matter production (kg/ha) at the Oracle Agricultural Center (Fourth harvest on 10/12/85) 70
19. Effects of treatments on forage dry matter production (kg/ha) at the Campus Agricultural Center (First harvest on 5/15/84) 71
20. Effects of treatments on forage dry matter production (kg/ha) at the Campus Agricultural Center (Second harvest on 6/28/84) 72
21. Effects of treatments on forage dry matter production (kg/ha) at the Campus Agricultural Center (Third harvest on 8/20/84) 73
22. Effects of treatments on forage dry matter production (kg/ha) at the Campus Agricultural Center (Fourth harvest on 10/24/84) 74
23. Effects of treatments on forage dry matter production (kg/ha) at the Campus Agricultural Center (Fifth harvest on 5/22/85) 75 ix
LIST OF TABLES—Continued
Table Page
24. Effects of treatments on forage dry matter production (kg/ha) at the Campus Agricultural Center (Sixth harvest on 8/5/85) 76
25. Effects of treatments on forage dry matter production (kg/ha) at the Oracle Agricultural Center (overall means of 4 harvesting dates) 80
26. Effects of treatments on forage dry matter production (kg/ha) at the Campus Agricultural Center (overall means of 6 harvesting dates) 81 LIST OF ILLUSTRATIONS
Figure Page
1. The imprintation pattern of land imprinter . . 4
2. The hand imprinter 22
3. The land imprinter 23
4. Precipitation at the Campus and Oracle Agricultural Centers: Long term average vs. study period average . . . 31
5. Neutron probe calibration curves for the Oracle and Campus Agricultural Centers 35
6. Response surface plots showing the effects of surface treatments on soil moisture at the Oracle Agricultural Center 41
7. Response surface plots showing the effects of surface treatments on soil moisture at the Campus Agricultural Center 42
8. Response surface plots showing the effects of cover treatments on soil moisture at the Oracle Agricultural Center 43
9. Response surface plots showing the effects of cover treatments on soil moisture at the Campus Agricultural Center 44
10. Plant population count at the Oracle Agricultural Center (Pilot Study) 47
11. Plant population count at the Oracle Agricultural Center (Second Study) 49
12. Plant population count at the Campus Agricultural Center 51
X ABSTRACT
Research was conducted over a 2-year period at the University of Arizona Campus and Oracle Agricultural Centers to evaluate the ef- fectiveness of surface imprintation in revegetating arid lands.
Introduction of forage leguminous species into arid rangelands through land imprintat ion was another objective of this study.
The soil at the Campus Center is a Brasito, mixed thermic, typic torripsamment with a sandy-loam texture. This was compared with a White House, fine mixed thermic, Ustollic haplargid with a sandy- loam texture at the Oracle Center. Natural rains were the only source of irrigation at Oracle. At the Campus Center, however, a sprinkler irrigation system was installed to match rains with that at the
Oracle Center.
Three cover treatments together with four surface treatments were used at both sites. The cover treatments included a pure stand of grasses, a pure stand of legumes, and a mixture of both grasses and legumes. The surface treatments were imprinted, mulched, imprinted- mulched, and an untreated surface as a check. Surface imprintation was performed by a land imprinter at Oracle and by a hand imprinter at Campus.
The imprinted surface significantly increased soil moisture retention, number of plants per unit area, plant height, plant cover, and biomass compared to the untreated surface. At the Oracle Center, the imprinted surface improved legume germination by 800% over the
x i xii untreated surface, and by 367% over the mulched one. Corresponding percentages at Campus were 48 and 4% over the untreated and the mulched surfaces, respectively. Increases in biomass production achieved through surface imprintation were 102% over the untreated surface and 35% over the mulched surface at the Oracle Center. Corres- ponding increases at Campus were 63 and 33% over the untreated and the mulched surfaces, respectively. Plants grown on imprinted surfaces ex- hibited higher transpiration rates, lower diffusive resistance, and cooler leaf temperature compared to those grown on the untreated sur- faces.
Addition of mulch to the imprinted surface made no significant differences with respect to the parameters measured when compared to the imprinted surface without mulch. When mulch was used as a separate treatment, however, it significantly increased the parameters measured over the untreated surface.
The effect of cover treatments on growth parameters and bio- mass production was masked by seasonality. Grasses tended to be superior over legumes in samples taken during the fall and the opposite was true during the summer. Mixing legumes with grasses, however, resulted in significantly taller grasses compared to grasses grown as a pure stand. CHAPTER 1
INTRODUCTION
Arid lands cover one-third of the earth's land surface and they
support an estimated 1.5 billion humans. Furthermore, about 70% of the
15 million humans who die of starvation each year live in arid and
semi-arid zones. The world needs to develop these areas to contribute more to global agricultural production particularly as the global popu-
lation continues to expand. Better use and protection of the limited
soil and water resources in these areas become a necessity in the
light of these facts.
In the United States, approximately 90% of the crop land is farmed without irrigation. Water is the factor most limiting to crop production. Under such conditions of limited water supply, practices
that will increase yield per unit of precipitation will be of great help. The practices which should receive major emphasis include those which are directed toward manipulating the soil surface to catch more of the limited available rainfall and retaining more runoff water resulting from intense monsoon thunderstorms, trap snow in cold areas, maximize infiltration, and minimize evaporation, along with crop selec- tion for ease of establishment and high water use efficiency.
Historically, cropland tillage implements have been modified and redesigned in an attempt to revegetate dryland areas. The resulting 2 implements are referred to in the literature as the eccentric disk pitters, brushland disk plows, moldboard plows, land rippers, land furrowers, brush cutters, and shredders. Most recently, in the seventies, a 3-scalpers interseeder was developed in San Dimas, California and the so-called overhead conveyer which was developed at New Mexico State
University.
The seedbed that is produced by any of these implements is usually not good enough to insure vegetative establishment in arid and semi-arid regions. These implements generally require a large amount of energy to perform each tillage function. Tillage functions for each of the above implements are often too few in number, inappropriate in kind or intensity, and conflicting in purpose. Consequently, both the durability and the initial suitability of the seedbed are diminished.
Even when these implements are used in combinations, vegetative estab- lishment is highly erratic. All of these implements operate unsatisfac- torily in brushy, steeply sloping, deeply gullied, and rocky terrain.
The surface geometries that are produced by these implements may be characterized as irregular, imprecise, and highly unstable. Very little control over point infiltration, runoff, and surface evaporation is provided by any of these implements even though such control is essen- tial for revegetation and efficient use of both soil and water resour- ces, especially in arid regions. Moreover, many of the traditional methods for revegetation destroy the existing protective cover and in- crease soil detachability, therefore rendering the land more susceptible 3 to erosion. These hazards are especially pronounced whenever the seed- ing effort is followed by weather extremes of either drought or intense rainstorms.
In an attempt to overcome the limitations of traditional tillage implements, Dr. R. M. Dixon of the U.S.D.A. developed what is known now as the "land imprinter." The land imprinter was constructed in 1976 after 20 years of research under a wide range of edaphic and climatic conditions. The invention of the land imprinter is based on concentra- tion and conservation of rainwater by applying an infiltration concept, called the air-earth-interface concept, which establishes the principle underlying infiltration control (Dixon, 1966, 1975, and 1977).
The land imprinter converts the smooth, closed soil surface into a rough open one. It increases soil macroporosity - (directly by break- ing up the sealed soil surface and indirectly by increasing the activity of soil burrowing macroorganisms through the litter provided) - and microroughness. Consequently, land imprinting establishes high infil- tration rates needed to replenish the soil water reservoir, and in turn revegetates the soil. The land imprinter creates a geometric design in such a way that half of the implement forms seedbed strips along its path whereas the other half forms strips perpendicular to its path to direct water runoff into seedbed strips and in effect double the amount of water available for seed germination and establishment (Fig. 1).
In a preliminary test of the imprinter, Dixon (1980) reported significant increases in forage yield of Lehmann's lovegrass 10 4
Fig. 1. The imprintation pattern of land imprinter. 5 months after planting near Fort Huachuca, Arizona. A yield of 3,248 kg of grass/ha was produced on the imprinted land area compared to only
56 kg/ha on the unimnrinted adiacent land area. Eight months later, the imprinted area produced 4,592 kg/ha compared to 325 kg/ha on the unimprinted land. These results have been compared with grass produc- tion of 1,568 kg/ha in the lush Kansas Flint Hills. The Kansas region has an average rainfall of 30" per annum while the average rainfall at
Fort Huachuca is only 14" per annum. From these results, it appears that the land imprinter should have a promising future in the arid
Southwestern region of the U.S. and similar dry areas of the world.
These promising results encourage further testing of this im- plement. Consequently, one of the objectives of this study was to test the land imprinter with and without mulch in conserving soil moisture and enhancing germination and establishment of some grasses and legumes under rainfed conditions. Another objective of the study was to test the possibility of introducing important leguminous forage species such as sweet clover (Melilotus spp.) and spreading types of alfalfa
(Medicago sativa L.) into predominantly grass vegetation of arid range- lands. Results of previous studies, in Canada and other areas of the
United States, indicated that creeping rooted alfalfa varieties are available and have great potential for use in arid rangelands. These alfalfas are aggressive (have sufficient vigor for establishment and more compatible with grasses and other vegetation), hardy, persistent, drought resistant, and withstand grazing (Kilcher and Heinrichs, 1966;
Heinrichs, 1971; Rauzi et al., 1974; Townsend et al., 1975; Cooper,
1977; Rumbaugh and Pederson, 1979). 6 A third objective of this study was to evaluate the relative performance of legumes and grasses as a pure stand and as a mixture under rainfed conditions. It is well known that grasses benefit when grown in mixture with legumes which fix atmospheric nitrogen and in- crease soil fertility under favorable conditions of soil water.
Furthermore, legumes when present with grasses in a mixture increase forage quality as well as quantity and thus improve animal performance
(Heinrichs, 1963; Wilton et al., 1978; Lorenz et al., 1983). CHAPTER 2
LITERATURE REVIEW
Land Shaping and Types of Seedbeds
Land shaping and types of seedbeds have received major emphasis
in revegetation studies of dry lands. The National Academy of Sciences
Study Committee on the Potential for Rehabilitating Lands Surface Mined
for Coal in the Western United States (N.A.S., 1974) emphasized that
seedbed preparation should create a planting medium which will provide moisture, nutrients, and the protection needed by the particular species
to insure vegetative establishment. Hodder (1979) stated that surface manipulation to roughen the surface traps precipitation, encourages
infiltration, minimizes runoff, and reduces erosion.
Contour furrowing is a land surface treatment that has been used
to increase herbage production and reduce runoff and erosion on Western
rangelands of the United States (Wight et al., 1978a, 1978b; Lacey et al.,
1981; Kartchner et al., 1983). On sloping lands, with scant precipita-
tion and poor infiltration, contour furrowing has been effective. In
studies that covered sixteen arid land range sites in Southern Montana
(U.S.D.A., Agric. Info. Bull. 447, 1982), contour furrowing increased
forage production by 123%, soil water recharge by 157% on saline upland
sites and 162% on pan spot sites. On a well-levelled area in India;
however, Ali and Prasad (1974) found that flat beds were significantly
7 8 more effective in conserving soil moisture than ridged or furrowed beds.
Neff (1980) found contour furrowing was effective in snow trapping in
cold areas of Northern United States.
Pitting and ripping have been used extensively on northern plain rangelands of the U.S.A. Rauzi (1968) reported that pitted pastures
supported a 25% heavier stocking rate than moderately flat pastures over a 24-year period. Tromble (1976), in a study conducted in Cochise
County, Arizona to evaluate the effect of root plowing and pitting treatments on surface runoff, concluded that surface roughness of the root plowed and pitted plots provided detention storage for average- sized storms and the pitting treatments significantly decreased runoff as compared to the untreated control.
Furrow diking or basin tillage (the practice of putting minia- ture dams in the furrow designed to obstruct the flow of water) is used to reduce runoff and increase moisture storage for crop production in the high plains of Texas (Bilbro and Hudspeth, 1977; Hudspeth, 1978;
Lyle and Dixon, 1977; Jones and Clark, 1982; Gerard et al., 1984).
Jones (1981), in a study conducted at Bushland, Texas, concluded that mini-bench, conservation mini-bench, wide contour furrows and Orthman contour furrows are conservation land forming systems that can be used to control erosion, runoff, and increase sorghum yield on drylands in the Southern Great Plains of the United States.
Water harvesting and microwatershed systems have been used in an attempt to redistribute and confine precipitation to small crop 9
areas, (Gardner and Gardner, 1969; Frasier and Myers, 1983). This will
reduce cumulative evaporation with time and increase the amount of soil water available for plant use. Fairbourn and Gardner (1974) reported
that microwatersheds with vertical mulching reduced water evaporation,
increased infiltration and increased grain yield of sorghum from 37 to
150% above the control. They also concluded that vertical mulched microwatersheds have the potential for increasing and stabilizing annual yields in semi-arid regions.
Soil Mulching
The practice of soil mulching is effective in reducing evapora- tion, conserving soil moisture, and regulating soil temperature. Mulch- ing regulates soil temperature due to the lower thermal conductivity of the mulching material compared to that of the soil (Hanks et al., 1961;
Ali and Prasad, 1972). The usual effect of mulching is to lower soil temperature during summer and increase it during winter (McCalla and
Duley, 1946; Isenberg and Odland, 1951) for the same conductivity reason.
Researchers have reported positive results for various types of mulches. Beneficial effects of mulching on moisture conservation and crop yield have been reported for stubble mulch (McCalla and Army,
1961; Schuman et al., 1980), for plastic mulch (Waggoner et al., 1960;
Lavin et al., 1981), for encap mulch (Yowell, 1963), for straw mulch
(Greb et al., 1967; Raghavula and Singh, 1982), and for gravel mulch
(Corey and Kamper, 1968). Wheat straw, pearl millet husk, and other 10
organic mulches of crop residues have been reported to be effective in
increasing soil moisture storage, increasing yield, and reducing erosion
(Mannering and Meyer, 1963; Moody et al., 1963; Singh et al., 1967;
Greb et al., 1970; Patil et al., 1972; Saxton et al., 1981).
Lavin et al. (1981) reported that mulching with plastic films,
cinders, or Juniper slash; deep furrowing; and fallowing increased water penetration and retention of soil moisture, delayed soil surface
crusting and lowered seeding zone temperatures in tests at five differ-
ent pinyon juniper (Pinus edulis Engelm and Juniperus spp.) range loca-
tions in Arizona.
Raghavula and Singh (1982) concluded that straw mulch maintained a higher moisture status both in soils and plants by controlling Evapora-
tion losses and increased water use efficiency and yield of grain sorghum under dry land conditions in Northwestern India. Increases in yield of grain sorghum due to mulching under dry conditions have also been reported by Ravindranth et al. (1974) and Umarani et al. (1973). Jones et al.
(1969) found that straw mulching reduced runoff, increased soil water content, and yield of corn. The differences in soil moisture content with and without mulching were significant to a depth of 30 cm. In addition, they found that mulch treatments gave significantly taller corn plants, greater infiltration rates, and less runoff than the un- mulched treatments. Ries and Power (1981) reported that grass stubble was effective in trapping snow for overwinter storage of soil water and the subsequent increase in forage production the following season in
North Dakota. 11
Artificial Revegetation
Most arid lands have deteriorated to the degree that natural revegetation through enhancement of secondary succession has become difficult if not impossible. Thus, the only way to bring these lands back into production will be through artificial revegetat ion or seeding.
Artificial revegetation can be achieved by till or no-till practices and each approach has its supporters and critics. Tillage practices such as deep plowing, contour cultivation, and bounding have been effective in moisture conservation with various dry farm- ing systems in India (Kanitkar, et al., 1960). Moody et al. (1963),
Shanholtz and Lillard (1968) reported that conservation tillage practices have shown that runoff and evaporation losses from the soil surface can be reduced. In addition, they showed that no-till or sod-seeding provided greater protection against short-duration droughts by contributing to a more efficient water use as well as more effective erosion control during severe storms.
No-till seedings are becoming increasingly popular as a soil conservation practice. In addition to conserving valuable top soil, no-till methods save the producers time, labor, machinery and fuel costs. No-till practices for many crbps are well established and widely acceptable. However, no-till establishment procedures for small-seeded legumes, such as alfalfa (Medicago sativa L.), are only being developed (White et al., 1982; Sperow, 1983; Hinish, 1983;
Mueller and Chamblee, 1984; Rechcigl et al., 1985). 12
The no-till principle has shown promise in several geograph-
ical regions under a wide range of conditions (Free et al., 1963; Spain and Klingman, 1965; Triplett et al., 1968). However, in a
study on infiltration and runoff in the Northern Corn Belt,
Lindstorm et al. (1984) concluded that soil surface conditions under no-till systems were vulnerable to runoff and their recommendation was that caution should be taken in assuming that no-till farming by- itself will solve water runoff problems.
Competition
One common problem with no-till or sod-seeding is the com- petition from the already existing vegetation. Groya and Sheaffer
(1981) stated that competition between a grass sward and a legume seedling is one of the most important growth-limiting effects en- countered when sod-seeding legumes into perennial grass sods. Effec- tive suppression of grass competition by physical or chemical means during the establishment of legumes sod-seeded into grass enhances legume establishment (Taylor et al., 1969; Fairbourg et al., 1978).
Fairbourg et al. (1978) reported that seeding legumes into an undis- turbed tall fescue sod resulted in poorer stands than when tillage or chemicals were used for sod suppression.
A combination of suppressant herbicides and no-till seeders have been used successfully to introduce legumes into grass sods
(Vogel et al., 1983; Taylor and Allinson, 1983; Taylor et al., 1969;
Waddington and Bowren, 1976; Oleson et al., 1981), yet there is 13 evidence that sward improvement can be accomplished without the use of herbicides. Decker et al. (1964, 1969), indicated some success in
seedings of birdsfoot trefoil (Lotus corniculatus L.) and crown vetch
(Coronilla varia L.) into Kentucky blue grass (Poa pratensis L.) pasture without herbicide sod suppression. Oleson et al. (1981) found no significant differences in stand counts, plant heights, and, in most years, legume and legume-grass dry matter yields between red clover (Trifolium pratense L.) seeded in tall fescue (Festuca arundincea Schreb.) with and without chemicals.
Adapted Species and Suitable Planting Tools
For artificial revegetation or seeding to be successful, the right selection of adapted species and a suitable tool to plant these adapted species are of prime importance. Cox et al. (1984) stated that artificial seeding has been going on for the past 92 years in the Southwestern United States and Northern Mexico. More than 300 forbs, grasses, and shrubs have been tested. Of the grasses tested, the most widely adapted species within the Sonoran and Chihuahuan deserts of North America, are Boer lovegrass (Eragrostis curvula var. conferta Nees.), Lehmann lovegrass (Eragrostis lehmanniana Nees.), and
Cochise lovegrass (Eragrostis lehmanniana Nees. X-Eragrostis tricophera
Coss. and Durr.). Moreover, Cox and Jordan (1983) showed that the establishment of lovegrasses appears to be more influenced by rainfall distribution rather than by total summer rainfall. 14
Judd and Judd (1976) tested 48 exotic species in semi-desert shrub, chapparal, semi-desert grassland, and pinyon juniper at the
Tonto National Forest, AZ. Their results showed that 13 species were able to survive for 20 years; and seven species for 30 years. Among those surviving for 30 years were Lehmann lovegrass and Boer love grass.
The selection of a suitable tool to plant the adapted species, on the other hand, is of equal importance. Over the years, arid land seeding equipments have been in continuous change and modifications to create more favorable conditions for seedling establishment in the harsh conditions of arid environments. The latest generations of these implements include the overhead conveyor developed at New
Mexico State University (Abernathy and Herbel, 1973), the 3-scalpers interseeder machine developed at San Dimas, California by the Forest
Service Equipment Development Center (Steven et al., 1981), and the land imprinter developed by R. M. Dixon of the USDA-ARS at Tucson,
AZ (Dixon, 1977).
In drier regions, overgrazing and short-duration droughts create a vicious cycle of decreasing soil micro-roughness and macro- porosity, decreasing water infiltration, increasing surface runoff and evaporation, and increasing land barrenness (Dixon and Simanton, 1977).
Barren lands characteristically possess low infiltration rates which are often only one-tenth of that for woodlands and grasslands (Dixon,
1966; Dixon et al., 1978; Wadleigh et al., 1974). Consequently, barren soils shed most of the rain water from intense thunderstorms, 15 whereas litter-covered soils infiltrate most of the water where it
falls. Bare soils shed water readily since they possess well devel- oped surface drainage patterns and are sealed tightly by rain drops impacting on their surfaces. The small amount of water that does in- filtrate barren land areas penetrates the soil so superficially that most of it is lost by surface evaporation. Thus, a vicious cycle be- gins that is responsible for desertification, increasing aridity, and irreversible deterioration of vital soil and water resources and loss of vegetation.
The fabrication of the land imprinter takes into account all of the above facts and is based on the concentration of rainwater by applying an infiltration concept, called the air-earth-interface con- cept, which establishes the principles underlying infiltration control
(Dixon, 1975; and 1977). The land imprinter converts the smooth closed soil surface into a rough open one without inverting the fer- tile top soil. Thereby, higher water-infiltration rates are estab- lished which are needed to replenish the soil water reservoir; in turn, required to revegetate the soil. Thus, the vicious cycle is converted into a virtuous one.
About this machine,Anderson (1981, 1982), among others, wrote
"The land imprinter appears to be the long-sought answer to semi-arid grass land revegetation. The imprinter does not need to operate on the contour for, wherever it goes, it leaves downslope imprints for collecting rain water and across slope imprints for receiving water.
Erosion is reduced and infiltration of rainwater is greatly increased.
Since potential drought is the major risk in revegetation projects, it 16
is this characteristic of retention of rainwater where it falls which
allows germination and plant growth to occur even under conditions of
less than normal rainfall."
Grass-Legume Mixture
The seeding of legumes into primarily grasslands has the poten-
tial of becoming a useful practice for range improvement as compatible
species and interseeding technology become available. Millions of
acres of rangelands in Western United States and in other countries
could be improved by the successful establishment of legumes in their
existing grasslands (Kneebone, 1959; Atkins, 1962; Bleak et al., 1965;
Rumbaugh et al., 1965; Mueller-Warrant and Koch, 1980; West et al.,
1980; Taylor and Allinson, 1983; McGinnies and Townsend, 1983). Cox
et al. (1984), indicated that there are approximately 2.5 million acres of abandoned irrigated farm lands in the Southwestern U.S. that might be developed into a valuable forage base if such areas were
seeded with adapted range grasses, legumes, and shrubs.
Among the legumes suited for interseeding in these areas and other grassland areas is alfalfa (Medicago sativa and M. falcata) as reported by Rumbaugh et al. (1981), Rumbaugh (1982), and Taylor and
Allinson (1983). Hewitt et al. (1982) reported that alfalfa appeared
to have the greatest potential for reseeding on arid rangeland sites, of 15 legume species tested.
Introduction of legumes, particularly alfalfa, into grass pastures has the following merits: 1) The legume itself will be a major contributor to forage yield and quality. 2) The legume will 17 fix additional atmospheric nitrogen for the grasses in the plant community. 3) The fixed nitrogen would result in increased produc- tivity and protein content of the associated grass, and 4) The in- creased quality and quantity of forage would increase livestock production.
The ability of alfalfa in fixing atmospheric nitrogen, in- creasing crude protein, and forage yield is well documented. Gomm
(1964) observed that mixtures of either sweet clover or 'Ladak' alfalfa with 'Nordan' crested wheat grass produced more forage than either legume or grass alone. Furthermore, protein content of grass grown in mixtures with legumes was higher than when grown in pure stand. The leguminous forage itself contributed directly to both the quality and quantity of feed produced.
Dubbs (1971) found that the percentage crude protein of crested wheat grass increased when it was grown with alfalfa. Similar results were reported by Comstock and Law (1948), Peterson and Bendixon (1961),
Van Riper (1964), and Wedin et al. (1965). Dubbs (1971) also found
that grasses grown - with a legume, especially alfalfa, grew taller, produced more forage, and usually contained a higher percentage of crude protein. Hervey (1960) reported that lamb gains increased after alfalfa and crested wheat grass were interseeded into native sod in
Wyoming. Lee and Rothwell (1966) and Norman (1968) successfully used alfalfa pastures to supplement native pastures for sheep and cattle in
Australia. 18
The value of alfalfa as a legume component is commonly recog-
nized. Its contribution to livestock production in dry land pastures
and modified rangelands of semi-arid areas is well-documented. At-
tempts have been made to introduce these species into more arid
situations to supplement range vegetation for some usages. Townsend
et al. (1975) regarded alfalfa as one of the most promising forage
legumes for dryland seedings in the Great Plains. Vallentine et al.
(1963) recommended the use of alfalfa in sagebrush zone range sites in
Utah where annual precipitation averages 30 cm or more.
The merits of using alfalfa for supplementary native pastures
or for interseeding would depend on the longevity of the plants and
the ability of the species to reseed itself in a drought environment while subjected to grazing. Kilcher and Heinrichs (1966), Pearse
(1965), and Rumbaugh and Pederson (1979), presented evidence that
alfalfa survived up to 23 years in an environment that received 20 to
30 cm average annual precipitation. At the end of that time period,
the alfalfa yielded 121% as much oven dry forage as the crested wheat
grass in an adjacent planting.
The legume-grass mixture can be achieved either by mixing the
seeds of both species before sowing or by seeding each in separate alternating rows. Gomm (1964) found that there was no significant effect on yield from mixing legume and grass seeds before seeding or
seeding legume and grass in alternate rows.
Persistence of alfalfa in pastures and in hay fields is a very important requirement in dry regions for maximum production, as 19 was noted by Campbell (1963), Clark and Heinrichs (1957), and Kilcher and Heinrichs (1958). They reported that alfalfa varieties which ex- hibited the creeping root character were superior in persistence to most other non-creeping types, and would therefore be more reliable and productive in dry climates. Rumbaugh (1982) seeded eight alfalfa populations in dryland pastures in Northern Utah and found that the higher rate of seedling survival for populations that primarily originated from Medicago sativa rather than Medicago falcata. In a
6-year study conducted on a strip mineland at Southeastern Montana,
Holecheck et al. (1982) reported that spreader alfalfa was superior to ranger alfalfa with respect to establishment, survival, canopy cover, and productivity characteristics. CHAPTER 3
MATERIALS AND METHODS
Three field experiments were conducted at the University of
Arizona Oracle Agricultural Center and Campus Agricultural Center during the period July 83 to October 1985. Two of the three experi- ments were conducted at the Oracle Agricultural Center, 30 miles north of Tucson, AZ. at an elevation of 1125 meters (3688 ft.). The third experiment was conducted at the University of Arizona Campus
Agricultural Center in Tucson. The first experiment at the Oracle
Agricultural Center was intended to serve as a pilot study to gain site specific information.
The soil of the site at the Oracle Agricultural Center is classified as a White House, fine mixed thermic, ustollic haplargid soil with a sandy loam texture. The average annual precipitation for the area during a 41-year period (1931-1972) reported by Sellers and Hills (1974) was 35 to 40 cm.
On the other hand, the soil at the Campus Agricultural Center is classified as a Brasito, mixed thermic, typic torripsamment soil with a sandy loam texture. The average annual precipitation at the Campus
Agricultural Center is 20 to 25 cm (8 to 10"). Natural rain was the only means of irrigation at the Oracle Agricultural Center. Since the average annual rainfall at the Campus Agricultural Center is lower
20 21
than that at the Oracle Agricultural Center, a pivot sprinkler system
was installed at the Campus Center experiment to simulate rain to
match that at the Oracle Center. Irrigation with the sprinkler system
was scheduled on a weekly basis to deliver the difference in rain be-
tween that at the Oracle and that at the Campus Center. If it rained
at Campus but not at Oracle, the amount of rain would be subtracted
from the difference between the two sites supposedly to be delivered
by sprinkler the following week. Furthermore, a hand imprinter
(Fig. 2) rather than a land imprinter (Fig. 3) was used at the
Campus Agricultural Center due to experimental area limitations.
Treatments
Three lovegrasses (Lehmann lovegrass (Eragrostis lehmanniana
Nees.), Boer lovegrass (Eragrostis curvula var. conferta Nees.), and
Cochise lovegrass (Eragrostis lehmanniana Nees. X Eragrostis trichophera
Coss and Cur.)) and three legumes (spreader alfalfa II, white sweet
clover (Melilotus alba), and yellow sweet clover (Melilotus officinalis) were used in these experiments. The three grasses and the three legumes were sown together to form the mixture, the three grasses together to
form the grass pure stand, and the three legumes together to form the
legume pure stand. Thus, three cover treatments of a pure stand of
grasses, a pure stand of legumes, and a grass-legume mixture were established. The three cover treatments were used together with four
surface treatments which consisted of an imprinted surface, a mulched
surface, an imprinted-mulched surface, and an untreated surface to 22
Fig. 2. The hand imprinter. 23
U.S. DEPARTMENT OF AGRICULTURE
Fig. 3. The land imprinter 24
serve as a control (check). The three cover treatments together with
the four surface treatments produced a combination of 12 treatments
as follows:
1. A grass pure stand on an imprinted surface.
2. A grass pure stand on a mulched surface.
3. A grass pure stand on an imprinted-mulched surface.
4. A grass pure stand on an untreated surface.
5. A grass-legume mixture on an imprinted surface.
6. A grass-legume mixture on a mulched surface.
7. A grass-legume mixture on an imprinted-mulched surface.
8. A grass-legume mixture on an untreated surface.
9. A legume pure stand on an imprinted surface.
10. A legume pure stand on a mulched surface.
11. A legume pure stand on a mulched-imprinted surface.
12. A legume pure stand on an untreated surface.
Three blocks (replications) were used in each experiment.
Each block consisted of 12 plots (experimental units). The size of
the plot was 5 by 20 meters at the Oracle Agricultural Center and 5 by 6
meters at the Campus Agricultural Center. A randomized complete block
design was used in both sites.
Barley straw was used as a mulch at a rate of 2000 kg/ha
(2 tons/ha) for the mulched treatments and at a rate of 1000 kg/ha
for the imprinted-mulched treatments. The straw was spread evenly
with a hand rake on the soil surface after broadcasting the seeds. 25
Seed sources were Northrup King Co., Woodland, Calif., for the
spreader alfalfa, and Valley Seed Co., Phoenix, AZ. for the lovegrasses
and the sweet clovers. The recommended seedling rates for the six
species used in the experiments, as reported by Dennis (1966) are:
Species Pure Stand Mixture
Lehmann lovegrass 03.36 kg/ha 01.68 kg/ha
Boer lovegrass 03.36 kg/ha 01.68 kg/ha
Cochise lovegrass 03.36 kg/ha 01.68 kg/ha
Spreader alfalfa 28.00 kg/ha 14.00 kg/ha
White sweet clover 16.80 kg/ha 08.40 kg/ha
Yellow sweet clover 16.80 kg/ha 08.40 kg/ha
Since each species represented one-third of the mixture in the
pure stand form and one-sixth in the mixed form, the following seeding rates were used:
Species Grass Mixture Legume Mixture Grass-legume Mix.
Lehman lovegrass 01.12 kg/ha - 00.56 kg/ha
Boer lovegrass 01.12 kg/ha - 00.56 kg/ha
Cochise lovegrass 01.12 kg/ha - 00.56 kg/ha
Spreader alfalfa - 09.33 kg/ha 04.67 kg/ha
White sweet clover - 05.60 kg/ha 02.80 kg/ha
Yellow sweet clover - 05.60 kg/ha 02.80 kg/ha
In each of the experiments, four rain gauges were installed, one at each corner of the experiment. In addition to the rain gauges, a 26 catch can was installed in each treatment at the Campus Agricultural
Center to determine the distribution pattern of the sprinkled water over the treatments. This made it possible to assure that all treat- ments received equal amounts of water.
Results of the pilot study conducted during the first year at the Oracle Agricultural Center showed that competition from natural grasses and heavy grazing by jackrabbits were the main limiting fac- tors in the establishment of legumes in that area. As a result of those problems, an adjacent experimental area was ripped to reduce the existing natural vegetation and a poultry wire fence was established to exclude jackrabbits and other animals.
Meteorological data including precipitation, atmospheric temperature, and relative humidity were monitored throughout the course of the study at both sites (Atmospheric temperature and rela- tive humidity at the Oracle Center were provided by Sheri Musil, Dept.
Soil and Water Sciences, University of Arizona).
Parameters Measured
Percent soil moisture (on a volume basis) was measured at both sites during the study period. Aluminum access tubes were permanently installed at the center of each treatment for moisture determinations using a Campbell Pacific Neutron Moisture Meter, Model 503 (Manufactured by Campbell Pacific, San Francisco, California). Soil water content was determined at the following depths from the soil surface: 15, 30, 45,
60, and 75 cm for each treatment. At the beginning of each experiment, 27 soil samples were taken from the same depths for gravimetric determina- tions of moisture content and for field calibration of the neutron probe (Nakayama and Reginato, 1982). Measurements of soil moisture were taken at an interval of 15 days for 10 consecutive months at the Oracle
Agricultural Center and for 12 consecutive months at the Campus Agricul- tural Center. Regression analysis was applied to the soil moisture data and then a response surface plot (Neter and Wasserman, 1974) was estab- lished. The response surface plot is a form of a 3-dimensional graph with the X-axis representing time (months), the Y-axis soil depth (cm), and the Z-axis representing the percent soil moisture.
Germination, seedling establishment and survival were monitored throughout the course of the study. Two, one-square-meter areas, were permanently marked in each treatment at one-third and two-thirds of the plot length at the beginning of each experiment. Seedling emergence and plant count were made on the above-mentioned areas two weeks after the first rain at each site and at 1-month intervals up to the third count. Then a fourth, and final, count was done later in the growing season.
A one-square-meter frame was used in sampling for plant bio- mass, plant height, and estimation of the percent canopy cover. Three random samples were taken from each treatment using this one-square- meter frame. Five Lehmann lovegrass plants were randomly selected from each sample area to measure grass height both in the pure grass stand plots and the grass-legume mixture plots to determine the effect of legumes 28 when grown with grass in a mixture. Plant height was measured from
the soil surface to the tip of the tallest stem. Lehmann lovegrass was selected for plant-height measurements because it was the dominant grass at both sites.
Canopy cover was estimated by standing near the frame and visually estimating the percent of the ground inside the frame that was covered by vegetation.
After measuring plant height and estimating the percent ground cover, the forage inside the frame was harvested, oven dried at 76 C for 48 hrs until a constant weight was obtained. Then oven-dry weights were recorded for the biomass. Data were collected on four sampling dates for plant height, percent cover, and biomass at the
Oracle experiment, and on six sampling dates for the Campus experiment. -2 -1 Physiological data for transpiration (pg cm s ),leaf diffu- -1 sive resistance (S ), and leaf temperature (C) were taken for the legumes in the grass-legume mixture and in the pure legume stand plots using a Licor model LI-1600 Steady State Porometer (manufactured by
Licor Inc. Lincoln, Nebraska). Spreader alfalfa was the dominant legume at the Campus experiment whereas white sweet clover was the dominant one at the Oracle site. Therefore, spreader alfalfa and white sweet clover were selected for the physiological measurements at the Campus and at the Oracle sites, respectively. Three plants from each treatment were randomly selected and the two upper fully expanded growing leaflets from each plant were used for the measurements. Eight sampling dates were used in each experiment. 29
Analysis of the data was conducted by the Statistical Package for the Social Sciences (SPSS) in a Cyper 175 computer HP 41-CV at the University of Arizona Computer Center. The percent canopy cover, however, was transformed using the arc sin transformation technique before the final analysis. The rest of the data were analyzed using the standard analysis of variance. Means were compared using the
Student-Newman-Keul's test as described by Little and Hills (1978). CHAPTER 4
RESULTS AND DISCUSSION
Meteorological Data
Although the two sites of Oracle Agricultural Center and Campus
Agricultural Center are only 48 kilometers apart, they have quite diff-
erent growing conditions due to elevation. The Oracle Agricultural Center
is located at an elevation of 1125 meters (3688 ft) above sea level * whereas the Campus Center is located at an elevation of 710 meters
(2330 ft.).
Average monthly precipitation for a 30-year period (1952-1982) versus the study period is shown in Fig. 4 for both sites. The annual average precipitation at the Oracle Agricultural Center during the study period was 514 mm. This is compared to 393.4 mm which was the annual average of 30 years for the same site. At Campus Agricultural Center, on the other hand, the annual average precipitation during the study period was 392.3 mn compared to 300.2 mm long term average. Since the rainfall at the Campus Farm experiment was supplemented by a sprinkler system to deliver the difference in rainfall between the two sites, the total amount of water received by treatments in each location was equal.
With respect to rainfall distribution, both sites show a simi- lar pattern of distribution both for the long-term average and the
30 31
LONG TERM AVE. (30 YRS.)
----. STUDY PERIOD AVE. (2 YRS.)
150
120
I s 90
60
30
0 s - - 1 t t JANI FEBFEEI MAR APR MAYUN J11 JUL AUGP SE OCT NOV DEC Time (months) CAMPUS AGRICULTURAL CENTER
150
120
90
60
30
0
JAI N FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Time (months) ORACLE AGRICULTURAL CENTER
Fig. 4. Precipitation at the Campus and Oracle Agricultural Centers: Long term average vs. study period average. 32 study-period average (Fig. 4). In both locations, the winter rains for long-term and study-period were more or less equal. For summer rains, however, the study-period in both sites exceeded the long-term average.
The average monthly atmospheric temperature for both sites is presented in Table 1. With the exception of February and November 1984 and January 1985, the monthly average temperature at Oracle was always less than that at the Campus site. This difference was anticipated since the elevation at Oracle was 414 meter (1358 ft.) higher than that at the Campus site.
The percent relative humidity at both locations is presented in
Table 2. On an overall average monthly basis, relative humidity at the
Campus site was higher than that at Oracle in 1984 and 1985. In 1983, though, the opposite was true when relative humidity at Oracle exceeded that at the Campus site.
Soil Moisture
Neutron probe soil moisture calibration curves for the Oracle and Campus Agricultural Centers are shown in Fig. 5a and b, respectively.
These figures represent the regression of volumetric moisture content on count ratio for the probe used to estimate soil moisture at both sites
(Nakayama and Reginato, 1982). The correlation coefficient 'R' was 0.91 and 0.90 at Oracle and the Campus centers, respectively. Calibration curves for both sites were very highly significant (P < 0.00001). 33
Table 1. Monthly average temperature (C) at the Oracle and Campus Agricultural Centers.
Year 1983 1984 1985
Site Oracle Campus Oracle Campus Oracle Campus Month
Jan. 08.4 09.8 13.9 09.3
Feb. 11.0 10.3 08.6 10.8
March 13.5 14.6 11.9 14.0
April 15.1 16.8 18.1 19.3
May 24.3 25.4 21.9 23.5
June 25.8 27.9 25.9 28.4
July 26.9 30.1 25.8 28.1 27.6 30.4
August 25.7 28.8 24.8 27.9 26.7 29.9
Sept. 25.3 28.6 21.5 27.2 21.9 23.7
Oct. 18.1 20.1 15.8 18.7 18.1 20.3
Nov. 10.9 13.2 16.7 13.5 11.6 13.7
Dec. 08.8 11.4 07.2 09.7 10.5 12.6
Overall Monthly 19.3 22.0 17.5 19.2 18.1 19.7 Average 34
Table 2. Monthly average relative humidity (%) at the Oracle and Campus Agricultural Centers.
Year 1983 1984 1985
Site Oracle Campus Oracle Campus Oracle Campus Month
Jan. 57.14 39.03 16.86 50.46
Feb. 26.75 28.15 42.33 47.44
March 20.17 26.07 46.55 41.80
April 27.19 28.02 28.61 38.48
May 15.72 23.97 20.83 32.82
June 21.17 37.32 15.87 29.93
July 58.12 30.08 51.86 45.62 38.68 39.69
August 61.61 35.55 57.12 46.95 41.96 38.25
Sept. 58.44 36.63 43.60 39.87 48.45 41.83
Oct. 72.17 39.69 37.05 46.67 48.86 50.55
Nov. 72.03 40.33 18.64 44.12 55.22 59.10
Dec. 71.07 39.27 31.18 53.15 56.30 60.11
Overall Monthly 65.50 36.93 33.96 38.25 38.38 44.21 Average 35
35.50
28.40
21.30 a) Oracle 14.20 Y= 0.13 +0.03 X R=0.91 Sig.= (0.00001)
7.10
1.36 1.70
35.5
cc" 28.40
ca 21.3
b)Campus 14.20 Y= -4.81+ 29.63X 274::)11E R =0.90 ILl °/1* Sig = (0.0000 1) Ci 7.10 /41( a
0 34 0 68 1.02 1.36 1.70 COUNT RATIO Fig. 5. Neutron probe calibration curves for the Oracle and Campus Agricultural Centers. 36
Soil surface manipulation had a significant effect on soil mois- ture conservation and storage. At both sites soil surface imprinting, mulching, or the combination of both resulted in significantly higher soil moisture compared to the untreated surface (Tables 3 and 4).
At the Oracle Center the imprinted-mulched surface significantly in- creased soil moisture over the mulched and the untreated surfaces
(Table 3). In contrast to the results at the Oracle site, the imprinted surface without mulch at the Campus site had significantly more soil moisture than the mulched and the untreated surfaces (Table 4). The addition of the mulch to the imprinted surface in both sites had no effect, yet the mulch added separately without imprinting significantly increased soil moisture over the control (untreated surface). This might be due to the fact that the land imprinter in its path chops the above-ground vegetation which acts as a mulch. Therefore, the addition of more mulch to the imprinted surface had no increased benefit. The imprinted surface increased soil moisture over the untreated surface by 33% at Oracle, and by 54% at the Campus Center. This substantial increase in soil moisture as a result of imprintation might have been due to the stable angular pockets (imprints) formed by the imprinter.
These angular pockets serve as reservoirs to hold rainwater which is in excess of the infiltration capacity of the soil. The excess water that is held in these reservoirs will be infiltrated later after the rain ceases; therefore increasing the soil moisture. Compared with the im- printed surface, the untreated surface lacks these water pockets, and having a relatively sealed surface, will shed most of the rainwater. 37
Table 3. Effects of treatments on percent soil moisture at the Oracle Agricultural Center.
Cover Tr Grass Mixture Legumes Row Surface 1 Means Tr
Imprinted 2 Surface 26.57 ef 24.19 de 24.57 de 25.11 bc
Untreated Surface 20.72 bc 19.23 ab 16.92 a 18:95 a
Mulched Surface 23.19 cd 24.42 de 23.72 d 23.77 b
Imprinted- Mulched 24.46 de 27.76 f 25.76 def 25.99 c Surface
Column Means 3 23.73 23.89 22.74 NS
1 2 Surface treatment means Individual treatment means
3 Cover treatment means - Figures followed by the same letter(s) within the row means, the column means, or the individual treatments means are not signifi- cantly different at the 5% level according to the SNK method. 38
the Table 4. Effects of treatments on the percent soil moisture at Campus Agricultural Center.
Grass Mixture Legumes Row 1 Means
Imprinted 2 17.47 def 18.51 c Surface 19.75 f 18.30 ef
Untreated a Surface 13.07 abc 11.87 ab 11.08 a 12.01
Mulched 15.59 b Surface 16.95 def 14.48 bcd 15.33 cde
Imprinted- Mulched Surface 20.09 f 14.22 abcd 19.96 ef 17.42 bc
Column Means3 17.47 b 14.72 a 15.46 a
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 39
The land imprinter, beside creating these angular pockets, also breaks
the smooth, sealed soil surface into a rough open one. Dixon, 1966;
Dixon et al., 1978; and Wadleigh et al., 1974 stated that barren lands
characteristically posses low infiltration rates which are often only
one-tenth of that for woodlands.
The effect of cover treatments on soil moisture is shown in the
column means of Table 3 for the Oracle Center and Table 4 for the
Campus Center. Both tables show higher soil moisture under grass treat-
ment compared to legume treatment. This increase in soil moisture under
the grass treatment was only significant at the Campus Agricultural
Center. The presence of more soil moisture under grass treatment com-
pared to legume treatment could be explained on the basis of consumptive
use for each group. The annual consumptive use for alfalfa is about
139 ancompared to about 38 cm for lovegrasses. Therefore, legumes de-
pleted most of soil moisture available to satisfy their water require- ments, whereas the soil moisture avaialble for grasses was more than
enough for their water requirements.
With regard to individual treatments, at the Oracle Center a maximum soil moisture of 27.8% was recorded for the grass-legume mixture on imprinted-mulched surface, and a minimum of 16.9% was recorded for
legumes on an untreated surface (Table 3). This is compared to a maxi- mum of 20% for grass - imprinted-mulched and a minimum of 11% for legumes on an untreated surface at the Campus Center (Table 4).
When plotting soil moisture data in a response surface to show
the effect of treatments on soil moisture through time and depth, it 40 is clear that treated soil surfaces remained wetter over time at dif- ferent depths compared to the untreated surface (Figs. 6, 7, 8, and
9). The general trend of soil moisture, over time in all treatments at both sites, was that soil moisture dropped during summer months and then increased to reach a peak during fall and winter months. This is not unusual since rainfall distribution in southern Arizona, as repre- sented by Fig. 4, follows the same pattern. Moisture in soil is a reflection of the seasonal rainfall distribution pattern. Moreover, grasses are dormant during winter and legumes are partially dormant during this period. Therefore, moisture extraction from soil by plants will be minimal.
Soil moisture tended to increase with soil depth in all treat- ments at both sites. Minimum values were always at or near the surface, whereas maximum values were found at the deepest soil layer measured
(75 cm). Root activity in the upper layers plus surface evaporation losses could be the explanation for this trend. At the Oracle
Agricultural Center, a maximum of 35 to 39.9% soil moisture at 75 cm depth was recorded for the treated surfaces compared to 30 to 34.9% on the untreated surface for the same depth (Fig. 6). In the upper surface layer, however, a maximum of 15 to 19.9% was recorded for imprinted sur- faces with and without mulch, 10 to 14.9% for mulched surface, and only
0 to 4.9% for the untreated surface.
In comparison with Oracle, soil moisture in the deepest soil layer of 75 cm at Campus reached a maximum of 35 to 39.9% for imprinted surfaces with and without mulch, 30 to 34.9% for the mulched surface,
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(2) -- 211111100000000000000001111111112222222222222333322222222211f h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e6666655555 3322222222222222222233333334444444555555566666666666666655555 3322222222222222222223333333444444555555556666666666666655555 75 3222222222222222222223333333444444555555556666666666666555555
O -- 1111000000000000000000000000000111111111111111111111111110000 a 211111100000000000000000011111111111222 7 222222272222221111110 22111111111000000011111111111112222222222221133 11 372222222111 MIXTURE 15 _212211111111111111111111112222222222333111331113 1 333333322222 222222111111111111111112222222223333333333133444 44 33333333322 32222222:11111111112222222222333333333 4 44 444 44 4444444444 33333 3122222222222222222222222223333333344444 44444444444 4 4 444 4 4333 3322222222222222222222222333333334 4 4444 44 4 4 53355555555 4444 4 4 3 30 -- 3332222222222222222222233333333 44444444 555 55 5 55555555 55 554444 333222222222222222222333333334 4 44 4444 553 5 5555 5 5555 3 5555555 44 4 33332222222222222222333333334444444 4 555335555 5 555 53 555555555 4 311322222222222222233333333444 44 4 44 55555 5 5 3 56666 6 666665555555 45 --31332222222222222233333333344 44 4 4 4555535 35 666 6 6666 9, 6666655555 31332222222222222233333333 444444 455555 555666 6x6E6 666 66 66 65555 33332222222222222233331333 44 444443555553 , 65 6 66666666666666555 33322222222222222233333331 444 44 4 4555555 56 e", 666666666666666555 33322222222222222233333333444 444 45555555666666 0166666666E555 60 -- 33222222222222222223333331 4444444 5555 .35”66666666466666666555 322222222222222222231333333 444444 55::55 ,6 6 5 66h A, 56 ., 66t6666655! 322222222222222222271333333 444444 355555 53 6666 4, 666t66t6555 75 __2222222222222222222223333333 444444 5555.35 3 6 6 66 1, 6t66h06t66665!5 1 t I I 1 I 1 1 1 I I I 1 J/84FM AMJ J AS OND/84 Z- Scale TIME (Months) (Vo soil moisture) 0=0- 4.9 2=10-14.9 4:20.24.9 6=30- 34.9 1=5 -9.9 3=15-19.9 5:25_29.9 7=35-39.9 Fig. 9. Response surface plots showing the effects of cover treat- ments on soil moisture at the Campus Agricultural Center. 45
and only 25 to 29.9% for the untreated surface (Fig. 7). When mulching was combined with imprinting, it affected maximum soil moisture by shifting it upward to the upper soil layers compared to imprinting without mulch (Fig. 7a and d). Generally, the surface treatments affected soil moisture mostly in the upper soil layers. This should have been an advantage in seed germination, seedling survival, and plant growth since the major portion of the root system, especially in grasses, is confined to that region. A maximum of 20 to 24.9% soil moisture was recorded in the upper soil layer on the imprinted-mulched surface, followed by 10 to 14.9% on mulched, and imprinted surfaces.
The upper soil layer of the untreated surface was obviously the driest one (0 to 4.9%). The dry condition extended down to deeper layers in the untreated surface (Fig. 7b).
Response surface plots of soil moisture for cover treatments at the Oracle Center (Fig. 8) show that the grass-legume mixture treatment resembled that of the grass treatment, whereas at the Campus Center
(Fig. 9), it resembled that of the legumes. It was observed that the mixed treatment was dominated by grasses at Oracle and by legumes at the
Campus site. This seems natural since the Oracle site is basically a grassland region whereas campus site is not. Furthermore, there was more soil moisture in the grass treatment compared to the legume treat- ment, especially in the deep layers, at both experimental sites. Dif- ferences in water requirements and root habits between legumes and grasses could provide an explanation for this phenomenon. Legumes have 46
a higher water requirement than grasses and have deep tap roots that
extract soil water from deep layers. Unlike legumes, grasses possess
a fibrous root system that is restricted to the upper soil layers, and
their water requirement is less than that of legumes.
Plant Population
Results of germination, seedling establishment and plant sur-
vival for the pilot study conducted at the Oracle Center are shown in
Fig. 10. Grasses on imprinted surface with or without mulch outnumbered
other surface treatments throughout the three observation periods
(Fig. 10a). The imprinted surface exceeded the imprinted-mulched sur-
face during the first and second counting dates. However, by the final
count this trend was reversed. This might have been a result of mulch
degradation that released nutrients to benefit the plants.
The legumes, on the other hand, presented quite a different
story. No legumes germinated on the untreated surface (Fig. 10b).
Possibly absence of a suitable seedbed resulting from no-till seeding
and the uncovering of seeds had something to do with this germination
failure. Even those legumes which did germinate on the treated surfaces
disappeared by the third count. It was noted that heavy grazing on
_legumes by jackrabbits and competition with natural vegetation already
present accounted for their disappearance. Groya and Sheaffer (1981)
stated that competition between a grass sward and a legume seedling is
one of the most important growth-limiting factors encountered when sod-
seeding legumes into perennial grass sods. Similar observations were
made by other researchers (Taylor et al., 1969; Fairbourg et al., 1978). 47
50 la 45 \1 Imprinted surface ; 40 .V414 4111 0. 2 35 ',...! Untreated surface ci 30 O cn 7— n 25 c 0 Mulched surface 0 20 a ) co 'a' OL. 611 i5 0 Imprinted-mulched surface
9/83 12/93 5/84 Counting Dates s •=•• _ Imprinted surface 'AOVIV Untreated surface _..z.7— Mulched surface b)
Imprinted-mulched surface
9/83 12/ 83 5/84 Counting Dates
Legumei
— }Grass
0 9/83 12/83 5/84 Counting Dates Fig. 10. Plant population count at the Oracle Agricultural Center (Pilot Study). 48
The trend of the mixture was similar to that when each group was sown as a pure stand (Fig. 10c). Grass in the mixture that was planted on the imprinted surface outnumbered other surface treatments up to the second count. By the third count, grass on imprinted surface with mulch exceeded that on imprinted surface without mulch. As was ob- served in legumes grown as a pure stand, legumes in the mixture dis- appeared by the third count.
The result of the pilot study, which was aimed at gaining site specific information, led us to rip an adjacent area. Ripping was intended to reduce competition by subduing the growth of natural vegetation. In addition, a poultry wire fence was established around the perimeter to exclude jackrabbits from the treated area.
After ripping the area and establishing a fence, we were able to get legume plants established successfully in all treatments (Fig. llb and c).
At the Oracle Agricultural Center, the imprinted surface without mulch increased grass germination by 126% over the untreated surface, and by 87% over the mulched one (Fig. 11a). In comparison to grass, the imprinted surface increased legume germination by 800% over the un- treated surface, and by 367% over the mulched surface (Fig. 11b). When grasses and legumes were grown together as a mixture, the increase was 295% over the untreated surface and 190% over the mulched surface for the grass; 123% over the untreated surface and 109% over the mulched surface for the legumes (Fig. 11c). • • ▪
49
150 cc, 135 Imprinted surface cp 120 • 105 I w Untreated surface • 90 0 • 75 co co Mulched surface a) 60 2 0 Er. 45 Imprinted— mulched o• 3° surface Z 15 0
7/18/84 8/18/84 9/30/84 12/30/84 Counting Dates 50
6- 45 • Imprinted surface , 40 Pay" • 35 Untreated surface Ci 30 O CO • 25 0 Mulched surface 20 b) g 0 0 15 —t ô 1 Imprinted—mulched surface 5 o 7/18/84
limn•• Legume{
1n11 /Grass
7/18/84 8/8/84 9/30/84 12/30/84 Counting Dates Agricultural Fig. 11. Plant population count at the Oracle Center (Second Study). 50
The imprinted surface planted with legumes outnumbered all other surface treatments except during the final count when the im- printed surface with mulch took the lead. As suggested earlier, this might have been due to degradation of mulches which released nutrients upon decomposition.
At the Campus Agricultural Center, substantial increases in germination as a result of surface imprinting were also noticed (Fig.
12). The imprinted surface without mulch resulted in the highest num- ber of grasses over other surface treatments except during the final count when imprinted surface with mulch outnumbered imprinted surface without mulch (Fig. 12a).
The imprinted surface with or without mulch substantially in- creased the number of legumes over other surface treatments (Fig. 12b).
The same increasing pattern in seed germination and seedling establish- ment as a result of surface imprinting that is observed in Figs. 12a and b was repeated when both legumes and grasses were grown as a mix- ture (Fig. 12c). Within the leguminous species planted, it was ob- served that white sweet clover was the dominant species at Oracle whereas spreader alfalfa dominated the Campus experiment.
It is obvious from the soil-moisture data that soil surface imprinting had resulted in a significant increase in soil moisture com- pared to other surface treatments. Therefore, the substantial increase in germination, seedling establishment and survival was a reflection of this increase in soil moisture in the imprinted treatments. This
51
1 50 1-135 Imprinted surface Z120 •• ••• 2 105 Untreated surface air 90 CO 75 Mulched surface
4f.1 60 a) 45 t:Z3 a Imprinted—mulched 30 surface 0 15 0 /10/84 2/10/84 3/10/84 11/23/84 Counting dates
225 k..200 Imprinted surface 4,1; 175
2 150 Untreated surface
7— 6'125 œ cts 7'0100 Mulched surface E b) c 75 CS 4 0 Z. 50 Imprinted—mulched surface 6 25 0
1/10/84 2/10/84 3/10/84 11/23/84 Counting dates 0 6. 160 !!140 G ras s{ ••n•n• 2 120 ••••n•nn•
c) 14e_ Igo - cn .11n11 411n111n ".• o - In11 c n•n•=1, 60 WOMM vianol 1 aS . • el) Z. 40 41nn• 6 20 111=n1, Z 0 2/10/84 3/10/84 11/23/84 Counting dates
Fig. 12. Plant population count at the Campus Agricultural Center. 52
is especially true under arid conditions where soil moisture is by far
the most important factor limiting plant growth and crop production.
Moreover, as noted by Dixon (1977, 1980), the seedling cradles created
by'the imprinter provide a good protection for the young seedlings
against desiccating winds, hot sun, and early morning frosts. This
would be of particular significance to these seedlings since they are
most vulnerable at this age.
Physiological Data (Legumes)
Transpiration
The treated surfaces - (whether imprinted, mulched, or the
combination of both) - significantly increased transpiration over the
untreated surface both at Oracle (Table 5) and at the Campus Center
(Table 6). The treated surfaces retained more soil moisture for plant
growth compared to the untreated surface which represented the dry
treatment in this case. The higher soil moisture level in the treated
surfaces was reflected in higher transpiration rates. These results
are consistent with the results of Singh and Misra (1985), who repor-
ted that leaf water status and transpiration rates decreased as soil moisture stress increased in a field study with some C and C grasses 3 4 in a seasonal dry tropical region in India.
Differences •in transpiration rates between the cover treatments,
on the other hand, were not significant. Transpiration rates of
legumes, whether grown as a pure stand or as a mixture, were similar
at both sites. 53
-2 -1 Table 5. Effects of treatments on transpiration rates cm s ) at the Oracle Agricultural Center (Overall means of 8 sampling dates).
Cover Legumes Legume 1 Tr Pure Stand Grass Mixture Row Means Surface Tr
2 Imprinted Surface 33.28 b 28.08 ab 30.68 b
Untreated Surface 17.43 a 19.06 a 18.25 a
Mulched Surface 25.95 ab 26.86 ab 26.41 b
Imprinted-Mulched 32.26 b 32.78 b 32.52 b Surface
3 Column Means 27.23 26.70 NS
2 ' Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatments means are not signifi- cantly different at the 5% level according to the SNK method. 54
-2 -1, Table 6. Effects of treatments on transpiration rates .,ÇY cm s) at the Campus Agricultural Center (overall means of 8 sampling dates).
Cover Legumes Legume Tr Pure Stand Grass Mixture Row Means Surface Tr
2 Imprinted Surface 30.00 b 29.14 b 29.57 b
Untreated Surface 14.05 a 15.46 a 14.75 a
Mulched Surface 24.42 ab 23.78 ab 24.10 b
Imprinted-Mulched Surface 29.91 b 29.34 b 29.63 b
3 Column Means 24.60 24.43 NS
1 .2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 55
Leaf Diffusive Resistance
The sane trend observed with transpiration was duplicated for leaf diffusive resistance in a reciprocal way for both sites (Tables 7 and 8). Plants grown on treated surfaces showed significantly lower diffusive resistance compared to the untreated surface. Stomates of plants grown under stress conditions (untreated surface in this case) close. This reduces water losses through transpiration and enables them to survive. Consequently, this would result in an increase in leaf dif-
• fusive resistance. This would explain why plants grown on treated sur- faces showed significantly higher transpiration rates and lower diffusive resistance than those plants grown on untreated soil surface.
This was a reflection of water status in the soil. There was adequate soil water in the treated surfaces and plants on those treatments trans- pired normally. Unlike plants grown on the imprinted surfaces, those on the untreated surface (water stress) had to close their stomates and increase their leaf diffusive resistance in order to cope with the limited water supply available in the soil.
No significant differences were recorded between treated and untreated surfaces regarding leaf temperature at both sites (Tables 9 and 10). However, plants grown in the treated soil surface areas main- tained lower leaf temperature than those in the untreated surface areas.
This is due to the cooling effect of transpiration. Plants grown on the treated surfaces, as reported earlier, had a significantly higher trans- piration rate which lowered their leaf temperature. 56
-1 Table 7. Effects of treatments on leaf diffusive resistance (s cm ) at the Oracle Agricultural Center (overall means of 8 sampling dates).
Cover Legumes Legume 1 Tr Pure Stand Grass Mixture Row Means Surface Tr
2 Imprinted Surface 0.59 a 0.68 a 0.64 a
Untreated Surface 1.56 b 1.41 b 1.43 b
Mulched Surface 0.85 a 0.81 a 0.83 a
Imprinted-Mulched Surface 0.63a 0.57 a 0.60 a
3 Column Means 0.91 0.87 NS
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 57
Table 8. Effects of treatments on-leaf diffusive resistance (S cm-1 ) at the Campus Agricultural Center (overall means of 8 sampling dates).
Cover Legumes Legume 1 Tr Pure Stand Grass Mixture Row Means Surface Tr
2 Imprinted Surface 0.97 a 0.88 a 0.92 a
Untreated Surface 3.60 b 3.37 b 3.49 b
Mulched Surface 1.21 a 1.47 a 1.34 a
Imprinted-Mulched Surface 0.91a 1.08 a 1.00 a
3 Column Means 1.67 1.70 NS
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the indivi4ua1 treatment means are not signifi- cantly different at the 5% level according to the SNI( method. 58
Table 9. Effects of treatments on leaf temperature (C) at the Oracle Agricultural Center (overall means of 8 sampling dates).
Cover Legumes Legume Tr Pure Stand Grass Mixture Row Means" Surface Tr
2 Imprinted Surface 26.20 25.73 25.96
Untreated Surface 26.10 26.05 26.07
Mulched Surface 25.87 25.76 25.82
Imprinted-Mulched Surface 26.05 25.68 NS 25.86 NS
3 Column Means 26.05 25.80 NS
1 2 Surface treatment means Individual treatment,means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 59
Table 10. Effects of treatments on leaf temperature (C) at the Campus Agricultural Center (overall means of 8 sampling dates).
Cover Legumes Legume 1 Tr Pure Stand Grass Mixture Row Means Surface Tr
2 Imprinted Surface 30.15 29.76 29.95
Untreated Surface 32.04 31.87 31.95
Mulched Surface 30.54 30.79 30.66
Imprinted-Mulched Surface 30.79 30.87 NS 30.83 NS
3 Column Means 30.88 30.82 NS
1 2 Surface treatment means IndividuaL treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 60
Similar to transpiration and leaf diffusive resistance, no
significant differences with respect to leaf temperature were reported
for the cover treatments.
Plant Height (Grass)
Overall means of plant height at the different sampling dates are shown in Table 11 for the Oracle Agricultural Center and in
Table 12 for the Campus Agricultural Center. At both sites the im- printed surface with and without mulch resulted in significantly taller plants than those grown on either the mulched or the untreated surface.
The mulch had no detectable impact on plant height within the imprinted
surfaces since no significant differences were recorded between imprin- ted surface with mulch and imprinted surface without mulch. It did have an impact, however, when the mulch was used as a separate treatment.
Plants grown on the mulched surface were significantly taller than those on the untreated surface.
Planting legumes with grasses significantly benefited the grass component and resulted in taller grass plants compared to those grown in a pure stand at both sites (Tables 11 and 12). Apparently the legumes benefited the grass through atmospheric nitrogen fixation that became available for the grass. These results are in line with the results reported by Dubbs (1971), who reported that grasses grown with legumes, especially alfalfa grew taller, produced more forage, and usually contained a higher percentage of protein. At both sites the tallest plants were recorded for the mixture grown on an imprinted sur- face. 61
Table 11. Effects of treatments on grass height (cm) at the Oracle Agricultural Center (overall means of 4 sampling dates).
Cover Grass Grass 1 Tr Pure Stand Legume Mixture Row Means Surface Tr
2 Imprinted Surface 097.0 d 108.4 e 102.7 c
072.3 Untreated Surface a 089.0 c 080.6 a
Mulched Surface 081.5 b 097.3 d 089.4 b
Imprinted-Mulched 093.8 cd 108.3 e 101.0 c Surface
3 Column Means 085.1 a 100.8 b
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 62
Table 12. Effects of treatments on grass height (cm) at the Campus Agricultural Center (overall means of 6 sampling dates).
Cover Grass Legume Tr Pure Stand Grass Mixture Row Means Surface Tr
2 Imprinted Surface 096.6 c 108.9 d 102.8 c
Untreated Surface 074.4 a 077.6 a 076.0 a
Mulched Surface 086.0 b 092.11 bc 089.1 b
Imprinted-Mulched Surface 090.8 bc 111.0 d 100.9 c
3 Column 11eans 085.9 a 097.4 b
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 63
The effects of surface treatments and cover treatments on plant height at each sampling date are shown in Appendix A for Oracle and Appendix B for the Campus site. The same trend shown in the overall means of the different sampling dates was repeated for each sampling date.
Canopy Cover
Overall means of percent canopy cover for the different sampling dates are shown in Table 13 for the Oracle Center and Table 14 for the
Campus Center. The same effects of surface manipulation observed in plant height were repeated on percent canopy cover. The treated sur- faces resulted in a significantly higher percent cover compared to the untreated surface. The imprinted surface with or without mulch had a higher percent cover over the mulched and the untreated surfaces at both sites. Adding mulch to the imprinted surface did not increase canopy cover, since no significant differences were observed between imprinted surfaces with or without mulch. Yet, the mulch applied separately sig- nificantly increased the percent cover over the untreated surface.
Mixing legumes with grasses resulted in a significantly higher percent cover over the grass grown as a pure stand at the Campus site
(Table 14). The same trend of a higher percent cover with the mixture was observed at Oracle (Table 13), although it did not reach the stat- istical significance level.
The effects of cover and surface treatments on percent canopy cover during each sampling date are shown in Appendix C for the Oracle experiment and in Appendix D for the Campus experiment. 64
Table 13. Effects of treatments on percent canopy cover at the Oracle Agricultural Center (overall means of 4 sampling dates).
Grass Mixture Legumes Row 1 Means
Imprinted Surface 922 c 94c 91c 92c
Untreated Surface 47a 48a 53a 50a
Mulched Surface 72 ab 78b 68 ab 72b
Imprinted- Mulched Surface 85c 92c 90c 89c
Column Means 3 74 78 76 NS
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 65
Table 14. Effects of treatments on percent canopy cover at t'le Campus Agricultural Center (overall means of 6 sampling dates).
Cover Tr Grass Mixture Row Surface Legumes Means Tr
Imprinted 2 Surface 81 bc 97 ef 98 ef 92 c
Untreated Surface 67 a 83 b 84 bc 78 a
Mulched Surface 74 a 91 de 90 cd 85 b
Imprinted- Mulched Surface 80 b 95 ef 94 ef 90 c
Column Means 3 75 a 91b 91b
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 66
Biomass
Individual Harvests
Surface treatments significantly affected biomass production
both at Oracle and at Campus throughout the different harvesting dates
(Tables 15 to 24). The only exception to that was at the Campus site
during the first harvest (Table 19). Though no significant difference
in forage production was observed among surface treatments at that time,
yields were substantially greater than forage production from the un-
treated surface. At the Oracle Agricultural Center, no significant
differences in forage production between the treated surfaces were re-
corded for the first cutting date (9/29/84), but they were significant
over the untreated surface (Table 15). From the second cut onward
(Tables 16, 17, and 18), the imprinted surfaces with or without mulch
significantly outyielded both the untreated and the mulch treatment.
At Campus, the highest biomass throughout the different harvest-
ing dates was recorded for the imprinted surfaces with and without mulch. The imprinted surface scored the highest biomass among the
treated surfaces at the first, second, third, and final (sixth) har- vests (Tables 19, 20, 21, and 24). On the other hand, the imprinted- mulched surface outscored the imprinted surface at the fourth and fifth
harvests (Tables 22 and 23). No significant differences were reported
between imprinted surface with mulch and imprinted surface without mulch except during the third harvest (Table 21). 67
Table 15. Effects of treatments on forage dry matter production (kg/ ha) at the Oracle Agricultural Center (First harvest on 9/29/84).
Grass Mixture Legumes Row 1 Means
Imprinted 2 Surface 2126.7 2203.3 2363.3 2231.1 b
Untreated Surface 1846.7 1670.0 1386.7 1634.4 a
Mulched Surface 2366.7 2000.0 2043.3 2136.7 b
Imprinted- Mulched Surface 2400.0 2373.3 2126.7 NS 2300.0 b
Column Means 3 2185.0 2061.7 1980.0 NS
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 68
Table 16. Effects of treatments on forage dry matter production (kg/ha) at the Oracle Agricultural Center (Second harvest on 5/25/85).
Cover Tr Grass Mixture Legumes Row Surface 1 Tr Means
Imprinted 2 Surface 3673.3bc 4033.3 c 3960.0 c 3888.9 d
Untreated Surface • 1426.7 a 1503.3 a 1343.3 a 1424.4 a
Mulched Surface 2326.7 ab 2543.3 ab 2810.0 bc 2560.0 b
Imprinted- Mulched Surface 3213.3 bc 2950.0 bc 3250.0 bc 3137.8 c
Column Means3 2660.0 2750.0 2840.8 NS
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 69
Table 17. Effects of treatments on forage dry matter production (kg/ha) at the Oracle Agricultural Center (Third harvest on 8/5/85).
Cover Tr Grass Mixture Legumes Row Surface 1 Tr Means
Imprinted 2 Surface 2850.5de 3230.0 e 3266.7 e 3115.6 c
Untreated Surface 1380.0 a 1836.7 abcd 1606.7 ab 1607.8 a
Mulched Surface 1673.3 abc 2486.7 abcde 2196.7 abcde 2118.9 b
Imprinted- Mulched Surface 2623.3 bcde 3243.3 e 2770.0 cde 2878.9 c
Column Means 3 2131.7 a 2699.2 b 2460.0 ab
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method.
70
Table 18. Effects of treatments on forage dry matter production (kg/ha) at the Oracle Agricultural Center (Fourth harvest on 10/12/85).
Grass Mixture Legumes Row 1 Means
Imprinted 2 4240.0Surface d 4250.0 d 3913.0 d 4134.4 c
Untreated Surface 2266.7 abc 1606.7 a 2000.0 ab 1957 8 a
Mulched Surface 3176.7 bcd 3216.7 bcd 2926.7 bcd 3106.7 b
Imprinted- Mulched Surface 3666.7 cd 3550.0 cd 3860.0 d 3692.0 c
Column Means 3 3337.5 3155.8 3175.0 NS
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 71
Table 19. Effects of treatments on forage dry matter production (kg/ha) at the Campus Agricultural Center (First harvest on 5/15/84).
Cover Mixture Legumes Row Tr Grass 1 Surface Means Tr
Imprinted 2 Surface 0317.0 ab 1333.0 c 1327.0 c 0992.0
Untreated Surface 0167.0 a 0787.0 abc 0843.0 abc 0599.0
Mulched Surface 0277.0 ab 0580.0 abc 0970.0 abc 0609.0
Imprinted- Mulched Surface 0417.0 abc 0627.0 abc 1183.0 bc 0742. ONS
Column Means 3 0294.0 a 0832.0 b 1081.0 b
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 72
Table 20. Effects of treatments on fprage dry matter production (kg/ha) at the Campus Agricultural Center (Second harvest on 6/28/84).
Cover Tr Grass Mixture Legumes Row Surface 1 Means Tr
Imprinted 2 Surface 1757.0 ab 2780.0 b 2633.0 b 2390.0 b
Untreated Surface 1163.0 ab 2100.0 ab 2057.0 ab 1773.0 ab
Mulched Surface 0683.0 a 1933.0 ab 2037.0 ab 1551.0 a
Imprinted- Mulched Surface 1743.0 ab 2007.0 ab 2550.0 b 2100.0 ab
Column Means 3 1337.0 a 2205.0 b 2319.0 b
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 73
Table 21. Effects of treatments on forage dry matter production (kg/ha) at the Campus Agricultural Center (Third harvest on 8/20/84).
Cover Tr Grass Mixture Legumes Row Surface 1 Means Tr
Imprinted 2 Surface 5550.0 b 2987.0 a 3667.0 a 4068.0 b
Untreated Surface 3483.0 a 2910.0 a 2860.0 a 3084.0 a
Mulched Surface 3450.0 a 2877.0 a 2507.0 a 2944.0 a
Imprinted- Mulched 3977.0 a 3277.0 a 2710.0 a 3321.0 a Surface
Column Means 3 4115.0 b 3012.0 a 2936.0 a
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 74
Table 22. Effects of treatments on forage dry matter production (kg/ha) at the Campus Agricultural Center (Fourth harvest on 10/24/84).
Cover Tr Grass Surf ac Mixture Legumes Row 1 Tr Means
Imprinted 2 Surface 3967.0 b 3140.0 ab 2717.0 ab 3274.0 bc
Untreated Surface 2497.0 ab 2340.0 a 2287.0 a 2374.0 a
Mulched Surface 3490.0 ab 2503.0 ab 2503.0 ab 2832.0 ab
Imprinted- Mulched Surface 3833.0 b 3397.0 ab 3397.0 ab 3542.0 c
Column Means 3 3447.0 b 2845.0 a 2726.0 a
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 75
Table 23. Effects (..f treatments on forage dry matter production (kg/ha) at the Campus Agricultural Center (Fifth harvest on 5/22/85).
Cover Surface Tr Grass Mixture Legumes Row Tr Means
Imprinted 2 Surface 2903.3 ab 4440.0 bcd 4696.7 bcd 4013.3 c
Untreated Surface 1350.0 a 2130.0 a 1750.0 a 1743.3 a
Mulched Surface 1600.0 a 3873.3 bc 4166.7 bcd 3213.3 b
Imprinted- Mulched Surface 2143.3 a 5820.0 d 5573.3 cd 4512.2 c
Column Means3 1999.2 a 4065.8 b 4046.7 b
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 76
Table 24. Effects of treatments on forage dry matter production (kg/ha) at the Campus Agricultural Center (Sixth harvest on 8/5/85).
Cover Tr Grass Mixture Legumes Row Surface 1 Means Tr
Imprinted 2 Surface 4790.0 c 4383.3 c 4310.0 c 4494.4 c
Untreated Surface 2490.0 ab 2183.3 ab 1916.7 a 2196.7 a
Mulched Surface 4266.7 c 3466.7 bc 2266.7 ab 3333.3 b
Imprinted- Mulched Surface 4850.0 c 4616.7 c 3860.0 c 4442.2 c
Column Means 3 4099.2 b 3662.5 b 3088.3 a
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 77
The effect of cover treatments on biomass production seemed to
be affected by the time of cutting (seasonal variation). At the Campus
Center, harvests that were made during the summer (1st, 2nd, and 5th
cut), legume plots were always dominant and significantly outyielded the
grass plots (Tables 19, 20, 23). This trend was reversed during the
fall which coincided with the peak growth period of the lovegrasses. In cuts that were made during the fall (3rd, 4th, and 6th cut), the grasses
significantly outyielded the legumes (Tables 21, 22, 24).
This same trend of seasonal variation was observed at the Oracle
Center. Harvests that were made during the fall (1st, 3rd, and 4th cut), the grasses outyielded the legumes (Tables 15, 17, 18). In cuts that were made during the summer (2nd cut), however, the opposite was true (Table 16). This observation of seasonal change could be explained by the fact that lovegrasses remain dormant throughout the winter, start regrowth in summer, and reach their peak of growth during the fall which coincided with the maximum rainfall. Legumes, on the other hand, are partially dormant during the fall.
With respect to individual treatments (the combination of cover and surface treatments) - at Campus, the highest biomass of 8520 kg/ha was recorded for the grass-legume mixture on the imprinted-mulched surface during the summer of 1985 (5th cut, Table 23). This is compared to 5550 kg/ha recorded for the grass on imprinted surface during the fall of 1984 (3rd cut, Table 21).
At the Oracle Center, on the other hand, the highest biomass of 4033 kg/ha was recorded for the legumes on imprinted surface during 78
the summer of 1985 (2nd cut, Table 16). This is compared to 4240 kg/ha recorded for the grasses on imprinted surface during the fall of 1985
(4th cut, Table 18).
Overall Means of the Different Cutting Dates
Soil surface manipulation through imprinting and mulching sig- nificantly increased biomass production in both sites as seen in the overall means of the different harvesting dates (Table 25 for Oracle and Table 26 for the Campus Center). Imprinted surfaces with or with- out mulch significantly increased biomass production over mulched and untreated surfaces. The mulch alone significantly increased biomass production over the untreated surface. The imprinted surfaces, how- ever, were not affected by mulch addition. This could be related to the fact that only half of the mulch added in the mulched treatment was added to the imprinted-mulched surface treatment. Furthermore, the imprinter by itself breaks the above-ground vegetation to serve as
a mulch, and this could have masked the effect of the additional mulch - added in the imprinted-mulched treatment.
It is worth mentioning here that similar effects of surface treatment on biomass production were observed for plant height and per- cent cover. Since biomass production is largely determined by both plant height and the percent of the ground that is covered by vegeta- tion (plant cover), it seems logical to observe the same effects for plant height and cover on biomass production. The imprinted surface without mulch increased biomass production by 102% over the untreated surface, and by 35% over the mulched surface at the Oracle Center 79
(Table 25). In comparison to Oracle, at the Campus Center, the imprin- ted surface increased biomass production by 63% over the untreated sur- face, and by 33% over the mulched surface (Table 26).
The substantial increase in biomass production due to surface imprintation at both sites reflects the importance of this technique for retaining a higher amount of natural rainfall for plant growth in a desert environment. These results are in agreement with the results reported by Dixon (1980) at Fort Huachuca, Arizona. He reported a sub- stantial increase in Lehmann lovegrass herbage production from an im- printed surface compared to forage production in an adjacent untreated but seeded area.
The seasonal variation, reported earlier in the discussion of individual harvesting dates, masked the effects of cover treatments on biomass production for the overall means of the different cutting dates.
No significant differences were recorded for cover treatments on the overall means of the different cutting dates at both sites (Tables 25 and 26). However, both at Campus and at Oracle Centers the grass-legume mixture treatment scored the highest biomass, followed by legumes, and then grasses. S O
Table 25. Effects of treatments on forage dry matter production (kg/ha) at the Oracle Agricultural Center (overall means of 4 harvesting dates).
Cover Tr Grass Mixture Legumes Row Surface 1 Means Tr
Imprinted 2 Surface 3222.5bc 3429.2 c 3375.8 bc 3342.5 c
Untreated Surface 1730.0 a 1654.2 a 1584.2 a 1656.1 a
Mulched Surface 2385.8 ab 2561.7 bc 2494.2 bc 2480.6 b
Imprintad- Mulched Surface 2975.8 bc 3029.2 bc 3001.7 bc 3002.2 c
Column Means 3 2578.5 2668.5 2614.0 NS
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 81
Table 26. Effects of treatments on forage dry matter production (kg/ha) at the Campus Agricultural Center (overall means of 6 harvesting dates).
Cover Tr Grass Mixture Legumes Row Surface 1 Means Tr
Imprinted 2 Surface 3213.9 d 3177.2 d 3225.0 d 3205.4 c
Untreated Surface 1858.3 a 2075.0 ab 1952.2 ab 1961.8 a
Mulched Surface 2294.4 abc 2538.9 bc 2408.3 abc 2413.9 b
Imprinted- Mulched Surface 2827.2 cd 3290.5 d 3212.2 d 3110.0 c
Column Means3 2548.5 2770.4 2699.4 NS
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. CHAPTER 5
SUMMARY AND CONCLUSION
A study was conducted over a 2-year period at the University of Arizona Campus Agricultural Center and the Oracle Agricultural
Center to evaluate surface imprintation and soil mulching as means of improving revegetation of arid rangelands. The study also aimed at testing the possibility of introducing important leguminous forages, such as alfalfa and sweet clover, into arid rangelands vegetated predom- inantly by grass species to improve forage quality. Moreover, evalua- tion of the relative performance of legumes and grasses grown as a pure stand and as a mixture was a third objective of this investigation.
Three cover treatments along with four surface treatments were used in this investigation. The three cover treatments included plant- ing grasses as a pure stand, legumes as a pure stand, and a mixture of both grasses and legumes. The surface treatments, on the other hand, included surface imprintation by a land imprinter at the Oracle
Agricultural Center and by a hand imprinter at the Campus Agricultural
Center, mulching the surface, a combination of imprinting and mulching, and an untreated surface to serve as a check.
The imprinted surface significantly increased soil moisture, number of plants per unit area, plant height, canopy cover, biomass, transpiration rate and reduced leaf diffusive resistance. At the
Oracle Agricultural Center during the year 1985, the imprinted surface
82 83
produced a total of 11,139.7 kg/ha of legume dry matter (a total of three cuts), and a total of 11,513.3 kg/ha dry matter of legume grass mixture. The total annual precipitation at Oracle for that year was
395 mm. Comparing this amount to the consumptive use of alfalfa,
which is 1887 mm (74.3"), surface imprintation appeared very im-
pressive.
Mulching the surface substantially improved soil moisture
storage, germination of seeds, plant height and cover, and total bio-
mass production. It also increased transpiration rates and reduced
leaf diffusive resistance as more soil moisture became available for
plant growth. Mulching effects on the different parameters measured,
however, were significant over the untreated surface but not over the
imprinted surface. The imprinted surface, as a matter of fact, was more effective than mulching in all the parameters measured.
The effect of cover treatments on soil moisture appeared to be
influenced by the differences in root systems of legumes and grasses, and by the differences in their water requirements. Relatively less
soil moisture was recorded for legumes compared to grasses. The ef- fects of cover treatments on growth parameters and final yield was largely affected by time of sampling. During the summer, legumes out- yielded grasses, but the opposite was true in the fall.
It could be concluded from the results of this study that:
1. Surface imprintation by land or hand imprinter has proven to be an effective way of soil surface manipulation to revegetate arid lands. 84
2. Introduction of forage leguminous species, like spreader alfalfa and sweet clovers, into predominantly grass rangelands proved possible. It is worth mentioning, however, that protection of young seedlings from grazing by jackrabbits and other range pests through fencing is essential.
3. The problem of jackrabbits and other range pests could be minimized by planting larger areas.
4. The relative performance of grasses and legumes as a mix- ture is affected by time of sampling. Grasses tend to be superior over legumes in the fall and the opposite is true in the summer.
Differences in growth peaks and dormancy periods for each group accounts for this seasonality. The seasonality pattern should be an advantage to growers and ranchers since it insures forage availability all the year round. Moreover, having grasses and legumes in a mixture insures a more uniform and deeper utilization of water and minerals in the soil profile, improves forage quality through symbiotic nitrogen fixation by legumes which benefit grasses, and reduces the occurrence of bloating of livestock. APPENDIX A
EFFECTS OF TREATMENTS ON PLANT HEIGHT
AT THE ORACLE AGRICULTURAL CENTER FOR
THE DIFFERENT SAMPLING DATES
85 86
Table A.1. Effects of treatments on grass height (cm) at the Oracle Agricultural Center (First Sampling on 9/29/1984).
Cover Grass Grass 1 Tr Pure Stand Legume Mixture Row Means Surface Tr
2 Imprinted Surface 123.7 c 126.7 c 125.2 b
Untreated Sutface 091.7 a 113.7 bc 102.7 a
Mulched Surface 103.3 ab 116.3 bc 109.8 a
Imprinted-Mulched 117.0 bc 121.3 c 119.2 b Surface
Column Means 3 108.9 a 119.5 b
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatments means are not signifi- cantly different at the 5% level according to the SNK method. 87
Table A.2. Effects of treatments on grass height (on) at the Oracle Agricultural Center (Second sampling on 5/22/85).
Cover Grass Grass 1 Tr Pure Stand Legume Mixture Row Means Surface Tr
2 Imprinted Surface 56.0 abc 60.0 bc 58.0 b
Untreated Surface 43.0 a 43.0 a 43.0 a
Mulched Surface 47.3 ab 59.0 bc 53.2 b
Imprinted-Mulched Surface 53.7 abc 63.3 c 58.5 b
3 Column Means 50.0 a 56.3 b
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter-Es)-within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 88
Table A.3. Effects of treatments on grass height (an) at the Oracle Agricultural Center (Third sampling on 8/5/85).
Cover Grass Grass 1 Tr Pure Stand Legume Mixture Row Means Surface Tr
2 Imprinted Surface 104.3 b 122.3 c 113.3 b
Untreated Surface 084.3 a 105.0 b 094.7 a
Mulched Surface 091.7 ab 106.0 b 098.8 a
Imprinted-Mulched Surface 102.3 b 122.3 c 112.3 b
3 Column Means 095.7 a 113.9 b
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 89
Table A.4. Effects of treatments on grass height (cm) at the Oracle Agricultural Center (Fourth sampling on 10/12/85).
Cover Grass Grass 1 Tr Pure Stand Legume Mixture Row Means Surface Tr
2 Imprinted Surface 104.0 c 124.7 d 114.3 c
Untreated Surface 070.0 a 094.3 bc 082.2 a
Mulched Surface 083.7 ab 108.0 c 095.8 b
Imprinted-Mulched Surface 102.3 c 126.0 d 114.2 c
Column Means 3 090.0 a 113.3 b
1 2 Surface treatment means Individual treatment means
3 Cover treazment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. APPENDIX B
EFFECTS OF TREATMENTS ON PLANT HEIGHT
AT THE CAMPUS AGRICULTURAL CENTER FOR
THE DIFFERENT SAMPLING DATES
90 91
Table B.1. Effects of treatments on grass height (cm) at the Campus Agricultural Center (First sampling on 5/15/84).
Cover Grass Grass 1 Tr Pure Stand Legume Mixture Row Means Surface Tr
2 Imprinted Surface 13.2- ab 37.5 b 25.3
Untreated Surface 07.0 a 31.8 ab 19.4
Mulched Surface 13.3 ab 31.7 ab 22.5
Imprinted-Mulched Surface 13.2 ab 28.8 ab 21.0 NS
3 Column Means 11.7 a 32.4 b
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 92
Table B.2. Effects of treatments on grass height (cm) at the Campus Agricultural Center (Second sampling on 6/28/84).
Cover Grass Grass 1 Tr Pure Stand Legume Mixture Row Means Surface Tr
2 Imprinted Surface 076.0 095.3 035.7
Untreated Surface 065.0 957.3 061.2
Mulched Surface 075.0 077.3 076.2
Imprinted-Mulched. Surface 077.0 106.7 NS 091.8 NS
3 Column Means 073.3 084.2 NS
1 2 Surface treatment means Individua3. treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNI( method. 93
Table B.3. Effects of treatmants on grass height (cm) at the Campus Agricultural Center (Third sampling on 8/20/85).
Cover Grass Grass 1 Tr Pure Stand Legume Mixture Row Means Surface Tr
2 Imprinted Surface 120.7 bc 125.0 c 122.8 b
Untreated Surface 100.0 ab 086.0 a 093.3 a
Mulched Surface 114.3 bc 092.0 a 103.2 a
Imprinted-Mulched Surface 115.0 bc 127.3 c 121.2 b
3 Column Means 112.5 107.8 NS
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNI( method. 94
Table B.4. Effects of treatments on grass height (cm) at the Campus Agricultural Center (Fourth sampling on 10/24/84).
Cover Grass Grass 1 Tr Pure Stand Legume Mixture Row Means Surface Tr
2 Imprinted Surface 133.0 bc 144.3 bc 138.7 b
Untreated Surface 109.3 ab 089.0 a 099.2 a
Mulched Surface 126.7 bc 130.0 bc 128.3 b
Imprinted-Mulched Surface 127.3 bc 156.3 c 141.8 b
3 Column Means 124.1 129.9 NS
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 95
Table B.5. Effects of treatments on grass height (cm) at the Campus Agricultural Center (Fifth sampling on 5/22/85).
Cover Grass Grass 1 Tr Pure Stand Legume Mixture Row Means Surface Tr
2 Imprinted Surface 102.0 b 113.0 b 107.5 c
Untreated Surface 073.0 a 086.0 a 079.5 a
Mulched Surface 080.0 a 108.0 b 094.0 b
Imprinted-Mulched Surface 076.0 a 115.0 b 095.5 b
3 Column Means 082.8 a 105.5 b
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 96
Table B.6. Effects of treatments on grass height (cm) at the Campus Agricultural Center (Sixth sampling on 8/5/85).
Cover Grass Grass 1 Tr Pure Stand Legume Mixture Row Means Surface Tr
2 Imprinted Surface 134.6 c 138.3 c 136.5 b
Untreated Surface 092.0 a 115.0 b 103.5 a
Mulched Surface 106.7 b 113.7 b 110.2 a
Imprinted-Mulched Surface 136.0 c 131.7 c 133.8 b
Column Means 3 117.3 a 124.7 b
1 2 Surface treatment means Individual treatment means .
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. APPENDIX C
EFFECTS OF TREATMENTS ON PERCENT CANOPY
COVER AT THE ORACLE AGRICULTURAL CENTER
FOR THE DIFFERENT SAMPLING DATES
97 98
Table C.I. Effects of treatments on percent canopy cover at the Oracle Agricultural Center (First sampling on 9/29/84).
Cover Tr Grass Mixture Legumes Row Surface 1 Means Tr
Imprinted 2 Surface 89c 88 c 81 bc 86 c
Untreated Surface 55 ab 45a 45a 48a
Mulched Surface 71 abc 73 abc 71 abc 72 b
Lmprinted- Mulched 78 abc 80 abc 88 c 82 c Surface
Means 3 73 72 72 NS
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual trEatment means are not signifi- cantly different at the 5% level according to the SNK method. 99
Table C.2. Effects of treatments on percent canopy cover at the Oracle Agricultural Center (second sampling on 5/22/85).
Cover Tr Grass Mixture Legumes Row 1 Surface Means Tr
Imprinted 2 Surface 90 fg 92 g 85 efg 89 d
Untreated Surface 36 ab 28a 48 bc 38a
Mulched Surface 70 d 75 de 55 c 67 b
Imprinted- Mulched 84c Surface 82 def 90 fg 82 def
Column Means3 69 ab 71b 67a
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 100
Table C.3. Effects of treatments on percent canopy cover at the Oracle Agricultural Center (Third sampling on 8/5/85).
Row Grass Mixture Legumes 1 Means
Imprinted 2 Surface 092 abc 095 bc 100 c 096 b
Untreated Surface 048 a 060 a 061 a 057 a
Mulched Surface 067 a 080 ab 073 ab 073 a
Imprinted- Mulched 087 abc 097 bc 093 bc 092 D Surface
Column 082 NS Means 3 073 083
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) witnin the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 101
Table C.4. Effects of treatments on percent canopy cover ac the Oracle Agricultural Center (Fourth sampling on 10/12/85).
Cover Tr Grass Mixture Legumes Row Surface 1 Means Tr
Imprinted 2 Surface 098 b 100 b 099 b 099 c
Untreated Surface 050a 060a 057a 055a
Mulched Surface 078a 083a 072a 078b
Imprinted- Mulched Surface 093b 100 b 098b 097c
Column Means 3 080 086 081 NS
' Surface treatment means 2 Individual treatment means
3 Cover treatment . means
Figures followed by the same letter(s) within the row means, the column means, or the individual =eatment means are not signifi- cantly different at the 5% level according to the SNI( method. APPENDIX D
EFFECTS OF TREATMENTS ON PERCENT CANOPY
COVER AT THE CAMPUS AGRICULTURAL CENTER
FOR THE DIFFERENT SAMPLING DATES
102 103
Table D.1. Effects of treatments on percent canopy cover at the Campus Agricultural Center (first sampling on 5/15/84).
Cover Tr Grass Mixture Legumes Row Surface 1 Tr Means
Imprinted Surface 32 2 a 84b 89b 69
Untreated Surface 40 ab 72 ab 75 ab 63
Mulched Surface 25a 71 ab 81 ab 59
Imprinted- Mulched Surface 43 ab 74 ab 66 ab 61 NS
Column Means 3 35 a 75b 78b
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 104
Table D.2. Effect of treatments on percent canopy cover at the Campus Agricultural Center (second sampling on 6/28/84).
Cover Tr Grass Mixture Legumes Row Surface 1 Means Tr
Imprinted 2 Surface 076 a 100 b 100 b 092
Untreated Surface. 068 a 100 b 100 b 089
Mulched Surface 075 a 100 b 100 b 092
Imprinted- Mulched 060a 096b 100 b 085 NS Surface
Column Means 3 070a 099b 100 b
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 105
Table D.3. Effects of treatments on percent canopy cover at the Campus Agricultural Center (third sampling on 8/2/84).
Cover Tr Grass Mixture Legumes Row Surface 1 Tr Means
Imprinted 2 Surface 100 100 100 100
Untreated Surface 100 100 100 100
Mulched Surface 100 100 100 100 Imprinted- Mulched Surface 100 100 100 NS 100 NS
Column Means 3 100 100 100 NS
1 2 Surface treatment means Individual treatment means
3 . Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 106
Table D.4. :ffects of treatments on percent canopy cover at the Campus Agricultural Center (fourth sampling on 10/24/84).
Cover Tr Grass Mixture Legumes Row Surface 1 Tr Means
Imprinted 2 Surface 100 b 100 b 100 b 100 b
Untreated Surface 070 a 092 b 100 b 087 a
Mulched Surface 091 b 100 b 100 b 097 b
Imprinted- Mulched Surface 096 b 100 b 100 b 099 b
Column Means 3 089 a 098b 100 b
1 2 Surface treatment means Individual treatment means
3 Cover treatment means
Figures followed by tha same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 107
Talde D.5. Effects of treatments on percent canopy cover at the Campus Agricultural Center (fifth sampling on 5/22/85).
Cover Tr Grass Mixture Legumes Row Surface 1 Means Tr
Imprinted 2 Surface 078 ab 100 c 100 c 093 c
Untreated Surface 058 a 076 ab 075 ab 070 a
Mulched Surface 068 ab 098 c 086 b 084 b
Imprinted- Mulched Surface 078 ab 100 c 100 c 093c
Column 094b 090b Means 3 071 a
1 Surface treatment means 2 Individual treatment means
3 Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. 108
Table D.6. Effects of treatments on percent canopy cover at the Campus Agricultural Center (sixth sampling on 8/5/85).
Cover Tr Grass Mixture Legumes Row Surface 1 Means Tr
Imprinted 2 Surface 100 b 100 b 100 b 100 c
Untreated Surface 063 a 055 a 053 a 057 a
Mulched Surface 085 a 076 a 071 a 078 b
Imprinted- Mulched Surface 100 b 100 b 100 b 100 c
Column Means 3 087 083 081 NS
1 2 Surface treatment means Individual treatment means
Cover treatment means
Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not signifi- cantly different at the 5% level according to the SNK method. LITERATURE CITED
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