BINDURA UNIVERSITY OF SCIENCE EDUCATION
ENVIRONMENTAL SCIENCE DEPARTMENT The effects of Soil Type and Different Pre-sowing Treatments on seedling emergence and vigor of Senegalia polyacantha.
BY ANESU HASVE B1337016
A DISSERTATION SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS OF THE BACHELOR OF ENVIRONMENTAL SCIENCE HONOURS DEGREE IN NATURAL RESOURCES MANAGEMENT
DATE OF SUBMISSION 31/03/17 DEDICATION
This project is dedicated to my inspiring mother Irene Mutemaringa and my late father James Hasve.
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ACKNOWLEDGEMENT All gratitude is extended to the men and women who made this study possible. Mostly important is my academic supervisor Ms C. Masona. My profound gratitude to my beloved husband Alphius Nyamayarwo and my family who sacrificed their time to help in all ways they could. Above all, I praise the Lord Almighty for permitting me to reach this far.
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ABSTRACT The study investigated the effects of soil type and pre sowing treatment on seedling emergence and vigor of Senegalia polyacantha . The experiment was laid out in a (3*3) completely randomized design with three replications. Soil type had three levels (sandy loam, humus and clayey loam) while seed treatments were soaked ( in hot water for thirty minutes, cold water for twenty four hours, concentrated sulphuric acid (0.3 M H 2SO 4) for sixty minutes) and no treatment (control). Results showed that soil type and seed treatment affected seed germination of S.polyacantha seed . Seeds subjected to hot water treatment and then sown in sandy loam soil had the highest emergence, followed by cold water treatment then sulphuric acid treatment and lastly control. Germination percentage was highest from hot water treated seeds across all soil types with sandy loam having (46%), then humus (31.6%) and lastly clay loam soil (6.6%). For Height performance, in humus soils, was significantly taller (p<0.05) than clayey and sandy soils across pre sowing seed treatments except for the hot water treatment. Non treated Senegalia polyacantha seedlings had the least mean height (29.28±5.18 cm) in sandy loam soils whereas hot water and sulphuric acid treated Senegalia polyacantha seeds performed favorably (mean height 48.38±4.93 cm and 46.05±3.37 cm respectively) in sandy loam soils. Results suggest that planting S.polyacantha in sandy loam soil after hot water treatment reduces time taken for emergence and germination of Senegalia polyacantha seeds. Pre treatment of seeds in sulphuric acid for 60 minutes and sowing them in humas soils can improve height performance. The refare pre sowing treatment of Senegalia polyacantha seeds and planting in sandy loam and humus soil is more preferable to facilitate fast seedling emergence and growth rate.
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TABLE OF CONTENTS BINDURA UNIVERSITY OF SCIENCE EDUCATION ...... i DEDICATION ...... i ACKNOWLEDGEMENT ...... ii ABSTRACT ...... iii TABLE OF CONTENTS ...... iv LIST OF FIGURES ...... vi LIST OF TABLES ...... vii LIST OF ACRONYMS AND ABREVIATIONS ...... viii LIST OF APPENDICES ...... ix CHAPTER 1 ...... 1 1.0 INTRODUCTION ...... 1 1.1 Research background ...... 1 1.2 Problem statement ...... 3 1.3 Aim ...... 3 1.4 Research Objectives ...... 3 1.5 Research Questions ...... 4 1.6 Justification of the study ...... 4 CHAPTER 2 ...... 5 2.0 LITERATURE REVIEW ...... 5 2.1 Introduction ...... 5 2.2 Botany of S.polyacantha ...... 5 2.3 The effects of soil type on seedling emergence and vigor of S polyacantha ...... 6 2.4 The effects of pre sowing treatments on the seedling emergence and vigor of S.polyacantha ...... 8 CHAPTER 3 ...... 10 3.0 METHODOLOGY ...... 10 3.1 Study area...... 10 3.2 Soil textural analysis ...... 11 3.3 Pre sowing treatments and growing media ...... 12 3.4 Experimental Design ...... 13 3.5 Data collection ...... 14 3.8 Data Analysis ...... 15 CHAPTER 4 ...... 16
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4.0 RESULTS ...... 16 4.2 Height performance ...... 16 CHAPTER 5 ...... 20 5.0 DISCUSSION ...... 20 CHAPTER 6 ...... 22 6.0 CONCLUSION AND RECOMMENDATIONS ...... 23 6.1 Conclusion ...... 23 6.2 Recommendations ...... 23 REFERENCES ...... 23
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LIST OF FIGURES
Fig 3.1 Map showing Astra campus nursery at Bindura University of Science Education…13
Fig 4.1 Height performance of S.polyacantha …………………………………………...... 19
Fig 4.2 Branchlet development of S.polyacantha …………………………………………...20
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LIST OF TABLES Table 3.1 Experimental layout……………………………………………………………14
Table 3.2 Variables measured in the nursery during trial period…………………………16
Table 4.1 Seedling emergence of S.polyacantha after a period of two weeks……………17
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LIST OF ACRONYMS AND ABREVIATIONS
ANOVA – Analysis Of Varience
BD – Branchlet Development
C – Control
CWT – Cold Water Treatment
DFID Department of International Development
HWT – Hot Water Treatment
K Potassium
N – Nitrogen
P – Phosphorus
SAT – Sulphuric Acid Treatment
SPSS – Statistical Package For Social Sciences
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LIST OF APPENDICES
Appendix 1 Post hoc analysis: comparison with soils…………………………………………..39
Appendix 2 Mean Heights for S. Polyacantha ...... 32
Appendix 3 Means for branchlet development………………..…………………………...……32
Appendix 5 Post hoc – soils comparison…………………….………………………...………..34
Appendix 4 Post hoc for branchlet development………………………………………………..35
Appendix 6 Comparison of treatments………….…………………………………………...... 36
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CHAPTER 1
1.0 INTRODUCTION
1.1 Research background Senegalia polyacantha is an important tree species for social forestry and agroforestry programs due to its rapid growth and capability to fix nitrogen. The genus Senegalia has more than 500 species found throughout the world, with most being native to Australia. However, some of the most attractive of these trees and shrubs are native both to Zimbabwe and South Africa (Steyn, 1994). There are several species within this genus of senegalia and these include S. albida; S. galpinii; S. polyacantha; S. karoo; S.nitotica; S. tortilis and S. sieberana .
Growing of senegalias started in Zimbabwe after the attainment of Independence in the 1980's and S.polyacantha pods and leaves have been used to feed livestock and game. This is common in Matabeleland were pods from senegalias are harvested from the trees and given to livestock as a source of protein (Hayward, 2004). Fuel wood, seeds, timber and gum are also obtained from senegalia species and in Bulawayo gum is used as a source of income through selling and trading to local traders providing income for the local people in the area and their families. Stem and branches are used as bush fencing. The tree also has some aesthetic and practical value as shade around homesteads as well as the bark having some medicinal properties (Steyn, 1994).
The Forestry Commission and other rural development agencies have encouraged local people to plant and manage indigenous trees including senegalias. However, this has been hampered by lack of information on the most appropriate species and seed source for a particular area (Hayward, 2004). To address this problem, the Forestry Commission of Zimbabwe joined hands with the Department of International Development (DFID), Forestry Research Program to fund a series of research projects to investigate how senegalias can help rural communities in Africa. Research stations were established for assessing senegalia species performance and breeding potential in Chesa and Matopos, and this promoted the planting of senegalias. This project was done using the grassroot level approach to encourage and introduce the species to the participating local people and other species of senegalias were also being explored in this project (Hayward, 2004).
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Moreover, the tree has some soil improving properties and can coppice easily, thus making it a suitable landscape plant for degraded environments (Landis, 1990). However, all species of senegalia are propagated from seeds with a particularly hard seed coat, which under natural conditions would take a long time to germinate (Srivastava, 2004). The factors which affect the germination of senegalia species in a given micro environment are soil type, seed dormancy and water availability (Al Khateeb, 2005). Extensive reduction in seed germination has been shown in many species of senegalia (Miller, 1995). The situation is exacerbated by the fact that seeds are the only means of propagation for senegalia species (Ahmed, 2008), hence seed dormancy could present a serious problem for seed germination of S. polyacantha thereby affecting establishment of this agroforestry tree species. Therefore, the seeds must be artificially subjected to some physical and chemical pre sowing treatment so as to break the dormancy and obtain uniform and rapid germination (Niranjani et al. , 2010). External stimuli to promote seed coat rapture of hard seeded species like S.polyacantha is thus recommended (Islam et al ., 2009). Baskin and Baskin (1998), noted that treating the seeds is done to either completely remove the germination impeding seed coat or reduce its thickness so that seeds could emerge. Removal or reduction in thickness of the seed coat allows the seed to take up water and respiratory gases thus the germination process can be initiated. Therefore, one can conclude that pre sowing seed treatments are of great importance in facilitating seed germination for seeds with hard seed coats. A study by Daldoum (2016) , showed that pre sowing treatments had the potential to break seed coat dormancy and enhance the germination of S. polyacantha . Chemical and water pre germination treatments were effective in improving and accelerating seed performance of certain crops at a wide range of environmental conditions ( Zaghdani 2002).Hence, this study highlights the effects of pre sowing treatment on S.polyacantha under different soil types and climatic conditions. The physical, chemical and biological characteristics of the growing media affect seedlings growth and other aspects of nursery operations (Landis, 1990). This study also highlights the effects of soil type on seedling emergence and growth of S.polyacantha.
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1.2 Problem statement Senegalia polyacantha has hard coated seeds and this poses problems in germination because their seed coat forms an impermeable cover that restricts water absorption (imbibition) (Demel, 1996; Baskin and Baskin, 1998; Walters et al., 2004). Natural cracking leads to water permeability, but takes months or even years. Artificial cracking is effective but takes a lot of time and one loses a lot of the seed through damage. All these are not suitable in nurseries, where fast seed germination, with uniformity is desirable. Concerns on the benefits of growing senegalias have been highlighted in the local communities in Zimbabwe but this has been affected by lack of sufficient propagation knowledge (Hayward, 2004). Therefore there is urgent need to address issues concerning improving propagation techniques of hard seed coated plants like Senegalia polyacantha as this will enhance adoption by the small scale to commercial farmers in order to attain the benefits of the tree.
1.3 Aim To evaluate the effects of soil type and pre sowing seed treatments on seedling growth and survival of S. polyacantha .
1.4 Research Objectives
a) To determine the effects of three pre sowing treatments on the seedling emergence of Senegalia polyacantha . b) To identify the effects of soil type (clay loam, sandy loam and humus), and pre sowing treatment on the germination percentage of Senegalia polyacantha . c) To determine the effects of soil type (clay loam, sandy loam and humus), and pre sowing seed treatment on the seedling vigor (height, branchlet development and tree survival rate) of Senegalia polyacantha .
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1.5 Research Questions a) What are the effects of each of the pre sowing treatments on seedling emergence of S.polyacantha ? b) What are the effects of soil type and pre sowing seed treatment on the germination percentage of S.polyacantha ? c) Does soil type and pre sowing seed treatment have effects on the seedling vigor?
1.6 Justification of the study The knowledge generated in this study is important because it will be relevant to forest managers. This study is important because it aims to add on existing information in a way which other scholars can make references to the effects of soil type and pre sowing seed treatment on seedling emergence and vigor. The current pre sowing treatment methods being used in Zimbabwe are effective for seedling propagation but most nurseries use sand and humus as growing media. In this study other growing media are tested with follow up on seedling performance, this is going to solve the problem of forest loss as the best methods promoting seed germination will be explored. This discussion will formulate knowledge on the best pre sowing treatment and soil type that promotes fast germination of S.polyacantha , this will help to solve the problem of massive forest lost that has spread all over Bindura. There is also a knowledge gap on the effects of soil type and pre sowing treatments on seedling emergence and vigor of Senegalia polyacantha . Although many studies have investigated the effect of fire or heat on seed germination in African savannas (Sabiiti and Wein 1987; Gashaw and Michelsen, 2002 ; Danthu et al. 2003; Walters et al. , 2004; Banda et al. , 2006), it is important to investigate the effects of soil type on seedling emergence and vigor on S. polyacantha as it is also a variable that affects seedling emergence and vigor. In Bindura S.polyacantha grows naturally in low lying areas and this have been indicated in other researches. Shamva Gold Mine is an example where S.polyacantha was used in reclamation of active tailing dams, (Muzilane et al. , 2005) and the nickel tailings dam at Trojan Nickel Mine (Nyakudya et al. ,2010). This study will explore other options for the growing media as clay loam and sandy loam is being used. Moreso, highlighting the next best option between humus and sand in order to help and maintain rapid germination which is much needed to be used in the nurseries in Zimbabwe. 4
CHAPTER 2
2.0 LITERATURE REVIEW 2.1 Introduction The genus Senegalia has more than five hundred species found throughout the world, with most being native to Australia and some of the most attractive of these trees and shrubs are native both to Zimbabwe and South Africa (Steyne, 1994). The genus of senegalia has other several species and these include S. albida; S. galpinii ; S. polyacantha ; S. karoo ; S. nitotica; S. tortilis and S. sieberana . Nursery failures with senegalias are too common and are usually related to poor seed quality. Danthu et al., (2003) mentioned that a substantial proportion of these failures can be directly linked to inappropriate pre sowing treatments. Most species of the family Leguminosae exhibit physical dormancy that is caused by a hard and impermeable seed coat or fruit enclosure which hampers imbibition of water and some gaseous exchange (Danthu et al., 2003). This dormancy must be broken before germination can occur (Bewley, 1997) because it blocks the completion of germination of an intact viable seed under favourable external conditions (Ogawa et al, 2003). Dormancy has evolved differently across species through adaptation to the prevailing environment, to allow seeds to germinate only when conditions are likely to be favourable for a new plant to establish itself (Baskin and Baskin, 2004).
2.2 Botany of S.polyacantha Hyde et al. , (2016), describe Senegalia polyacantha as a deciduous tree that is medium sized to large with a layered crown. The bark peels off to show its inside whitish layer and it is pale to dark yellowish brown in colour. It has strongly hooked prickles on woody bosses that are sometimes on the trunk but more frequently on the branches (Orwa et al. , 2009). The leaf petioles has an oblong flattened gland near its base. The tree has got inflorescences axillary and elongated spikes of creamy white flowers. The fruit is flat and thin but not papery and it splits whilst it is still on the tree ( Hyde et al. , 2016). S. polyacantha provides fuel from its wood and it burns well, but the thorns make it difficult to handle. It is believed to produce poison from its smell of the tree that is useful as a repellent against snakes and crocodiles (Missanjo et al ., 2014). Medicine extracted from the species, can be used as
5 a cure for snakebite and as a mixture for bathing children who are restless at night (Orwa et al ., 2009). In Tanzania and Zimbabwe the roots have considerable magical properties (Missanjo et al ., 2014).Wooded grasslands, deciduous woodlands, river land and ground water forests are where the species occurs. S.polyacantha grow well in areas showing eutrophic and fresh soils and occasionally, it favours stony slopes and compact soils (Shapo, 2004). The seed coat of S.polyacantha requires pre sowing treatments in order to overcome seed coat dormancy and to attain good germination results. Drummond (1981), is of the view that with good pre sowing treatments, germination of the seed occurs within ten to twenty days. Senegalias are the most abundant plants in sub Saharan Africa (Smith, 1999). Hot and dry conditions are experienced in the African savanna, hence ways of retaining moisture are much needed by the plants. The leaves of senegalias are divided into tiny leaflets (pinnae) that is held horizontally in order to capture sunlight or vertically to moderate transpiration. However, seedling emergence and field stand establishment is one of the problems associated with senegalias especially in early planting where adverse conditions prevail low temperature and high soil moisture (Zaghdani, 2002). This is due to that, viable seeds do not germinate even under favourable environmental conditions for many cases, as a result of seed dormancy. Seed dormancy is caused by internal factors which include seed coat, embryo or inhibitors, which influence seed germination (Agrawal and Ddlani,1995). This results in the use of S.polyacantha in agroforestry practices being limited as there is low seedling growth and survival at the nursery stage (Missanjo et al, 2014). The presence of seed coat delays water entry and reduces the leakage of solutes (Larson, 1968). Simon (1974) reported that the presence of the seed coat does more than just act as a protective function from the external adverse conditions and as a barrier slowing down the exudates to the external medium but it actually reduces the extent of leakage from the embryo itself, delaying seed germination. The latter process starts with water uptake by the seed and terminates with the extension of the embryonic axis out of the seed coat (Bewley and Black 1994; Bewley 1997).
2.3 The effects of soil type on seedling emergence and vigor of S polyacantha .
Moisture stress in soil often limits emergence of crops in semi arid regions. Germination percentage and seedling growth rate have been reported to decrease with decreased available soil
6 moisture (Nyakudya et al ., 2010). Rate of decline in germination percentage and seedling growth has been reported to be genetically inherited and will vary with crop species and cultivar (Schneider and Gupta, 1985). Organic matter/humus provides plant nutrients, mainly nitrogen and sulfur and smaller amounts of phosphorus. About 9 kg of nitrogen is released by decomposition of every 1 percent of organic matter in the soil. Organic matter is a primary reservoir for available forms of micronutrients mainly zinc and boron, (University of Missouri Extension, 1993). Okello and Young (2000) observed that germination of S. drepanolobium seeds was higher in red sandy soils than in clay loams. Sandy soils have loosely aggregated particles that allow free exchange of gases between the germination medium and the embryo. Oxygen is essential for respiratory purposes in germinating seeds and oxygen uptake is proportional to the amount of metabolic activity taking place (Hartmann et al, 2007). Thus, sandy soil is the most suitable germination medium for tropical tree seed germination due to its availability, low cost, capacity to hold moisture and suitability for large tree seeds (Spicer et al , 2004).This can be supported in a study by (Pahla et al , 2014), where seeds planted in sand soil took the shortest time to emerge across all seed treatments as compared to clay planted seeds. Soils such as clays delay the germination and seedling emergence of plants. Marshall and Grace (2008) noted that poorly drained soils like clay have their pore spaces filled with water so that little oxygen is available to seeds. The amount of oxygen in the medium is affected by its low solubility in water and its ability to diffuse in the medium. For proper germination to occur sufficient oxygen needs to be present in the growing medium since oxygen facilitates seed germination. (Landis et al ., 1990) is of the view that gaseous exchange between the germination medium and the atmosphere, where oxygen concentration is 20%, is reduced significantly by the hard crust on the surface of clay soils which can limit oxygen diffusion. Moreover, clay particles are closely packed together and remain saturated with moisture for long periods of time, they are therefore slow to warm up, thus temperatures for germination are not easily attainable, (Pahla et al. , 2014). This might be due to the physical properties of clay which retain moisture, does not leach out nutrients easily and its temperatures do not fluctuate rapidly and easily in relation to the surrounding temperatures.
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2.4 The effects of pre-sowing treatments on the seedling emergence and vigor of S.polyacantha Alvarado et al., (1987), discussed that, successful stand establishment of seedlings is enhanced by pre sowing seed treatments as these will improve seed germination. Acid pre sowing treatment can effectively reduce the seed coat thickness, allowing the seed to take in oxygen and water through the micropyle (Iqbal, 1994). Acid pre treatment causes wet combustion of the seed coat and works equally well in legumes and non legumes (Lars Schmidt. 2000). Pre sowing treatments like sulphuric acid will destroy the integrity of impermeable cover and so permit the imbibition of the embryo (Niranjan et al. , 2010). A study by (Hyde et al., 2016), resulted in the highest germination percentage from the treatment of cold water of 80%.This influenced the germination period and germination percentage of senegalia seeds. However on the other hand, a study by Shapo, (2004) showed that soaking senegalia seeds in cold water promotes germination as seeds soaked for twelve and twenty four hours were equally ineffective for germination to occur as it gave a germination percentage of 20% which was not statistically different from the control except for the Senegalia sesban with 100% germination A study in Senegal, reported a germination rate of 83% for scarified seeds of S. sieberana, as scarification removes the hard coat layer on the seed that causes impermeability (Dantu et al., 2003). This inhibits water from entering into the seed and this compares well with the maximum seedling emergence rate of 95% observed in a study by Missanjo et al ., (2014) in Zambia where the overall mean seedling emergence rate was 62%. This was supported by a study conducted by Missanjo et al., (2014) as it was indicated that nicking out performed all the other pre treatment methods for the parameters studied. Nicking is known to breaks the physical dormancy of seeds with hard coats that impedes water uptake and gaseous exchange (Azad et al ., 2010, Mwase and Mvula 2011). Botsheleng et al (2014), also found similar results on germination of Afzelia quanzensis seeds where they increased significantly by mechanical scarification. Mechanical scarification breaks the physical dormancy of hard coated seeds which inhibit water uptake and gases for example in senegalia species (Hossain et al ., 2005). Mechanical scarification allows water and air to enter into the seed and stimulate germination. The enhanced germination observed in the mechanical treatment could be attributed to water uptake by the quiescent dry seed, which ended up with the elongation of the embryonic axis (Holdsworth et al ., 2008). This is in agreement with (Nainar et
8 al ., 1999) who used different pre treatments in Terminalia chebula seeds and found that mechanical scarification gave the highest germination percentage of 60%. Missanjo et al, (2014), stated that S polyacantha trees can be propagated from seeds, which may be immersed in boiling water as a pre sowing treatment. The boiling water will soften the hard outer seed coat when soaked overnight. They may then be sown in well drained, sifted potting soil and placed in a warm place until they germinate. Thus, placing the seeds in boiling water overnight as a pre sowing treatment, affects the seeds by softening the hard outer seed coat making germination to be easy to occur between a period of one and four weeks. On the same note, a research by Srinidhi et al , (2011), showed that hot water treatment promoted germination significantly amongst four exotic senegalia species S.holosericea,S. auriculiformis, S. amplices and Faidherbia albida where the germination percentage were 69.33%,77%, 69.33% and 68.66% respectively. Brant et a l., 1971 stated that hot water treatment overcomes physical dormancy in Leguminosae by creating tension which consequently causes cracking of the macrosclerid layer or by affecting the strophiolar plug (Dell 1980). However, the boiling water treatment with prolonged time of immersion cause damage to most species with relatively thin seed coats and non resistant embryos. This reduce the germination percentage of S.sesban , causing death of the embryo and resulted in high level of mortality. This is largely due to the negative effect of heat, which is transmitted into the embryo and damaged it, (Srinidhi et al , 2011).
However, contrary to these findings Pahla et al ., (2014), stated that soil type and seed treatment had no significant effect on the subsequent seedling height in the twenty one days of observation from planting. This could be because during this period, all the seedlings that had germinated were still drawing their nutrients from the seed endosperm, thus eliminating the effect of soil on their growth rate (Bewley, 1997). Moreover, all the seed treatments did not have any effect on the endosperm, thus giving a shoot height that was not significantly different from each other.
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CHAPTER 3
3.0 METHODOLOGY 3.1 Study area The study was carried out at the Bindura University of Science Education, Astra campus Nursery located at longitude 031 0 19 ` 23 `` S and latitude 17 0 18 ` 58 `` E. The campus is located in the Mashonaland Central Province in Zimbabwe Agro ecological Region 2 (Agritex, 1996).The mean annual rainfall is 700 mm, and temperature is 20 ○ C.Rainfall is received in the summer between November and April in the area and cold winters from May to August are experienced (Nyakudya et al ., 2010). Bindura have a Miombo ecosystem and soils that are mostly alfisols, oxisols and ultisols that are highly acidic,low total exchangeable bases, low in cation exchange capacity and the available phosphorus is low (Frost,1996). These soils are made up of a catenary series of well drained soils that are deeply weathered on higher areas, with narrow zones of sandy soils and poorly drained soils along foot slopes. The seeds were bought at Forestry Commission Bindura. Brachystegia boehmii , Bauhinia petersiana and Julbernardia globiflora dominates the Miombo vegetation. Deciduous trees are mainly found in the area with woodlands that have open stands of trees that are six ten metres high, conditional to the soil type, depth and drainage (Agritex, 1996). The root competition and shading of trees forms an irregular ground layer of shrubs, herbs and grasses in these woodlands. S. polyacantha and S. karoo dominates the low lying areas of the area. The herbaceous layer is dominated by Heteropogon contortus , Hyparrhenia species, Chloris gayana , Gloriosa superba , Melinis repens , Bidens pilosa and Roetbolia exaltatata amonst others (Agritex, 1996).
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Figure3 . 1 The map is showing location of Astra Campus (where the nursery was).
3.2 Soil textural analysis The Finger assessment of soil texture was the method used on determining the soil types used, (Thien, 1979).
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3.3 Pre-sowing treatments and growing media
Three different pre sowing treatments were used. The treatments were conducted in the Astra campus laboratory with assistance from the Laboratory Technician, these are: i) Hot water treatment Seeds were soaked in boiling water at 100 degrees Celsius for 5 minutes. The seeds were then removed from the water and soaked in cold water for 30 minutes and then planted into the soil. ii) Cold water treatment Seeds were immersed in cold clean tap water at room temperature for twenty four hours before sowing. iii) Concentrated Sulphuric acid treatment (0.3 M H2SO 4) Selected seeds were put in a glass beaker and 50 ml of concentrated sulphuric acid was poured into the beaker until all the seeds were covered in acid for 60 minutes (Botsheleng et al. 2014 ). The seeds were then washed thoroughly in cold water to remove the acid and rinsed and were left in cold water to soak for thirty minutes. IV) Control The seeds selected for control were not treated. Three types of soils was used as growing media these are Sandy loam, Clayey loam and a commonly used growing media in nurseries Humus (murakwani).The growing media was provided by the staff from the Nursery and it was already available.
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Table 3.1 Experimental layout
Growing media Sandy Clay loam Humus loam
Treatments
CWT C SAT
CWT C SAT
CWT C SAT
HWT CWT C HWT CWT C HWT CWT C SAT HWT CWT SAT HWT CWT SAT HWT CWT C SAT HWT C SAT HWT C SAT HWT
CWT Cold water treatment. HWT Hot water treatment SAT Sulphuric acid treatment C Control All the seeds were subjected to the treatments stated above, except for control which was not treated and was directly sown 2 cm deep in small black polythene pots and were kept moist by watering daily. Seeds were germinated under a 50 % light shade net. 3.4 Experimental Design The experiment had sixty randomly selected seeds per soil type (clay loam, sandy loam and humus), making a total of one hundred and eighty seeds that were planted. The seeds was all planted for the three different pre sowing treatment methods (hot water, sulphuric acid and cold water treatment), including the other untreated seeds (control). Fifteen seeds were replicated three times for each soil type. Fertilizer was not used during sowing as the soil nutrient content were being used in determination of the best soil to use.
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3.5 Data collection
Data were collected at two week and at four week intervals in measuring the germination parameters in Table 3.2. Seedling emergence was recorded daily according to the day each seed emerged. Data were then collected seven months after planting for the same germination parameters and survival of the seedlings. Germination assessment Germination was recorded daily from the day of sowing by counting the number of germinated seeds for a period of two weeks. A seed was considered to have germinated when the hypocotyls hook was evident above the soil surface (Azad et al ., 2010). Data collected on germination was used to calculate Germination Percentage using equation 1. Germination percentage • GP = (Total germinated seeds/Total seeds sown *100) Equation 1.
Where GP is the germination percentage
Height and Branchlet development measurements Height was defined as the vertical distance from the ground to the top living part of a plant (Iqbal, 1994). Tree height was measured using a flexible metal 5 m tape measure (Iqbal, 1994). Height was measured two weeks after planting and after twenty one days from the date of sowing. The growth and development indicators were measured through sampling. Branchlet development was determined by physical counting of branchlet shoots and established branchlet. Survival was determined after seven months by counting number of live plants as compared to the trees initially planted.
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Table 3. 2 Variables measured in the nursery during trial period
Variable Material/method Germination rate Total germinated seeds/ Total seeds sown * 100 Height Tape measure Branchlet development Physical counting of the trees Tree survival rate Physical counting of the trees, mathematical calculation (trees survived/ trees planted * 100)
3.8 Data Analysis Data were collected and statistically analyzed using SPSS statistical software to explore possible treatment variation, (Hossain et al., 2005). One way Anova was used to test the effect of seed treatments on seed germination (Aref et al. , 2011).
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CHAPTER 4
4.0 RESULTS 4.1 Seed germination rate assessment The results (table 4.1) show that, HWT>SAT>CWT>Control with 46%, 40%, 36% and 11% respectively. Hot water treatment had the highest germination percentage whilst Control had the least germination percentage for S. polyacantha in sandy loam soil. Clay loam followed a similar trend with, HWT>SAT>CWT at 6.6%, 5% and 3.3% respectively (table 4.1). Hot water treatment had the highest germination percentage across all treatments in clay loam soil. However, control had no germination within the first two weeks trial. Humus soil had, HWT>CWT>SAT>Control with 31.6%, 26.6 %, 20% and 11.6% respectively. Humus soil had the highest germination across all treatments with HWT having the highest percentage and Control with the least percentage. Table 4.1 Seedling emergence for S.polyacantha after a period of two weeks.
HWT CWT SAT Control Sandy loam 46% 36% 40% 11% Clay loam 6.6% 5% 3.3% 0% Humus 31.6% 26.6% 20% 11.6%
4.2 Height performance Humus soils had significantly taller S. polyacantha trees (p<0.05) than clay soils and sandy soils across pre sowing seed treatment except for HWT (fig 4.1). S. polyacantha recorded highest and least heights of 64.5±0.84cm and 44.68±1.55cm in humus respectively under SAT. The trend for S. polyacantha height performance in humus soils was as follows SAT>CWT>non treated>HWT. There was a significant difference of S. polyacantha height performance in humus soils between SAT vs. non treated (p=0.017); SAT vs . CWT (p=0.043); sat vs. HWT (p=0.007). However, there was no significant differences between non treated vs. CWT (p=0.626); non treated vs. HWT (p=0.654); CWT vs. HWT (p=0.357).
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The trend for S. polyacantha height performance in clay loam soils was as follows: HWT>non treated>CWT>SAT with a significant difference between SAT vs non treated (p=0.000); SAT vs. HWT (p=0.000); non treated vs. CWT (p=0.021); non treated vs. HWT (p=0.000); CWT vs. HWT (p=0.000). However, there was no significant difference between SAT vs CWT (p=0.054) . Non treated S. polyacantha seedling recorded the least height (29.28±5.18 cm) in sandy loam soils whereas hot water and sulphuric acid treated S. polyacantha seeds performed well (height 48.38±4.93 cm and 46.05±3.37 cm respectively) in sandy loam soils. There was a significant difference between SAT vs non treated (p=0.013); non treated vs CWT (p=0.036); non treated vs HWT (p=0.006). However, there was no significant difference between SAT vs CWT (p=0.0602); SAT vs HWT (p=0.695). Seedlings treated with sulphuric acid was significantly taller (p=0.000) in humus soils than clay loam (p=0.010) and sandy loam soils (p=0.015) being lowest in clay loam soils. There was a significant differences (p=0.010) in SAT between clay loam vs. sandy loam soils. Seedlings for non treated S. polyacantha seeds performed better in humus soil than in sandy loam soil and clayey soils. However, there were no significant differences in SAT between humus vs clay loam (p=0.806); humus vs. sandy loam (p=0.051); clay loam vs. sandy loam (p=0.077). General trend for tree height performance revealed that seedlings from cold water treated seeds in humus soils significantly outperformed seedlings in clay loam soils (p=0.002) and sandy loam soils (p=0.010). However, the difference between clay loam and sandy loam seedling height performance was not significant (p=0.334). S. polyacantha seedlings for hot water treated seeds performed significantly well (p<0.05) (62.58 cm) in clay loam soils compared to humus (p=0.003) (44.68 cm) and sandy loam soils (p=0.003) (48.38 cm). There were no significant differences between humus and sandy loam (p=0.426).
17
80 70 60 50 40 30
Height (cm) Height 20 10 0 SAT nontreated CWT HWT Trees in Treatment
Humus Clay loam Sandy loam
Figure 4.1 Height performance of S.polyacantha after a period of seven months SAT Sulphuric acid treatment,CWT – Cold water treatment, HWT – Hot water treatment. 4.2 Branchlet development of S.polyacantha Across all pre sowing treatments, branchlet development of S. polyacantha was not influenced (P>0.05) by growing media variability. Branchlet development performed best on SAT on humus soils compared to other soils, (fig 4.2).
10 9 8 7 6 5 4
mean mean branches 3 2 1 0 cwt hwt sat non treated soils and treatments
Clayloam Humus Sandyloam
Figure 4. 2 Branchlet development of S.polyacantha after a period of seven months
18
4.3 Survival rate after a period of seven months Sandy loam has the highest survival rate of across all soil types, Humus 19 CHAPTER 5 5.0 DISCUSSION 5.1 Seedling emergence rate effects of soil The seedling emergence rate for sandy loam soil (table 4.1) , could be as a result of the loosely aggregated particles of sand that permits free exchange of gases between the germination medium and the embryo. Germinating seeds require oxygen for respiratory purposes and the amount of metabolic activity taking place is proportional to oxygen uptake (Hartmann et al. , 2007). Sand soil is the most suitable germination medium for savanna tree seed germination due to its availability, low cost, capacity to hold moisture and suitability for large tree seeds (Spicer et al. , 2004). These results correspond to the findings by Pahla et al. , (2014), who had similar results. Clay loam had the lowest seedling emergence rate may be as a result of the physical properties of clay that inhibits water movement as the soil particles are closely packed (Dey, 2001). The results are similar to Okello and Young (2000), who observed that S. drepanolobium seed germination was lower in clay loam soil than other soil types. Humus soil had germination across all treatments as a result of the physical properties of humus soil that promotes germination of seeds. Organic matter/humus also provides plant nutrients. About 9 kg of nitrogen are released by decomposition of every 1 percent of organic matter in the soil (University of Missouri Extension, 1993). Nitrogen is primarily required for increasing plant growth and crop yield more than any other nutrients. The absence of Nitrogen in the plants is often associated with slow growth, reduced leaf size, yellowing; short branches, premature fall color and leaf drop, and increase the likelihood of some diseases (Evans, 2000). 5.1.2 Seedling emergence rate effects of presowing treatments Hot water treatment had the highest germination percentage across all treatments in clay loam soil. This could be as a result of the effect of hot water treatment on seeds. Hot water treatment soften the hard seed coat by creating tension which consequently causes cracking of the macrosclerid layer (Brant et al ., 1971), or by affecting the strophiolar plug (Dell 1980).This can be supported by findings from Daldoum (2016) who obtained the similar results. However, the control had no germination within the two weeks trial. 20 Hot water treatment had the highest percentage and Control had the least percentage of seedling emergence. Control had the least seedling emergence percentage. This could be as a result of the presence of seed coat that delays water entry and reduces the leakage of solutes (Larson, 1968). This can be supported by findings from Simon (1974) who reported that the presence of the seed coat does more than just act as a protective function from the external adverse condition and as a barrier slowing down the exudates to the external medium but it actually reduces the extent of leakage from the embryo itself, delaying seed germination. Seedling emergence was highest in HWT and lowest in Control. This could be as a result the boiling water that had softened the hard outer seed coat whilst soaked overnight. This was supported in a study by Daldoum (2016) who reported that S. polyacantha trees can be propagated from seeds, which may be immersed in boiling water as a pre sowing treatment. 5.2 Height performance Humus soil had the tallest trees compared to clay loam and sandy loam, across all treatments except for HWT. The pattern proves the effects of soil physical properties on growth. Organic matter/humus improves the soil structure by acting as a bonding agent that holds soil particles together in aggregates. Aggregates are less stable and can be easily broken apart in the absence of organic matter. Good soil structure promotes water movement and root penetration while reducing soil crusting, clod formation and erosion (University of Missouri Extension, 1993). Hence this promoted the height performance in the study. The height performance in clay loam soils has HWT with highest height performance with SAT with the least height performance across all soil types. This could be as a result of the physical and chemical characteristics of clay. These results can be supported by Dey (2001) who discussed that clay can cause a major challenge to germination and emergence due to its poor drainage, and it tends to clod easily. Excess water must drain away in the soil for a propagation media to be ideal as this, permits adequate penetration of oxygen to the seed, of which all these attributes are lacking in clay soils. Non treated S. polyacantha seedling recorded the least height in sandy loam soils whereas hot water and sulphuric acid treated seeds performed well in sandy loam soils. This might be as a result of seed coat dormancy that restrict water uptake to the embryo (Srivastava, 2004). This can be supported (Pahla et al ., 2014), where straight sown seeds in all soil types had a significantly 21 reduced initial seedling growth of S. sieberana while those pre treated with water for sixty minutes had the highest growth rate in terms of plant height Seedlings for sulphuric acid treated seeds were taller in humus soils compared to clay loam and sandy loam soils, (fig 4.1).The least height for seedlings from sulphuric acid treated seeds was observed in clay loam soils. This could be as a result of the acid treatment that can effectively reduce the seed coat thickness, allowing the seed to take in oxygen and water through the micropyle (Iqbal, 1994).These findings are similar with Okello and Young (2000), where clay loam had the least results. It was observed that seedlings for non treated seeds performed better in humus soil followed by seedlings in sandy loam soil. General trend for tree height performance revealed that seedlings for cold water treated seeds in humus soils significantly outperformed seedlings in clay loam soils Senegalia polyacantha seedlings for hot water treatment performed significantly well in clay loam soils compared to humus and sandy loam soils, (fig 4.1). Literature validates the finding as observed by James (1983) who showed that S.polyacantha can grow fast with a fertile clay soil. 5.2 Branchlet development and survival rate of S. polyacantha Across all pre sowing treatments, branchlet development of S. polyacantha was influenced by growing media variability. Branchlet development performed best on humus soils compared to other soils. This could be as a result of the nutrient content of humus that promotes growth and development (Walters et al. , 2004). Humus had the highest survival rate followed by sandy loam then lastly clay loam. The findings of this study could be as a result of the nutrient content of humus soils that promotes growth. Organic matter/humus provides plant nutrients, mainly nitrogen and sulfur and smaller amounts of phosphorus. About 9 kg of nitrogen are released by decomposition of every 1 percent of organic matter in the soil. Organic matter is a primary reservoir for available forms of micronutrients mainly zinc and boron. Thus promoting the survival of the trees over the period of seven months. This is supported by findings from University of Missouri Extension (1993). CHAPTER 6 22 6.0 CONCLUSION AND RECOMMENDATIONS 6.1 Conclusion High seedling emergence rate can be achieved by sowing hot water treated seeds in sandy loam soils. Clay loam soil had the least germination percentage and no germination under control within the trial period of two weeks. Hence, clay loam soils requires pre sowing treatments to achieve desired outcomes. It can be concluded that ssubjecting seeds to sulphuric acid for 60 minutes before sowing in humus soils can improve height performance. Clay loam had the least height performance. Clay loam soils affect the growth of S.polyacantha , and are not suitable for use in tree nurseries targeting high growth rates. Branchlet development was promoted by sowing seeds after cold water treatment in sandy loam soils. 6.2 Recommendations Senegalia polyacantha seeds must be subjected to pre sowing treatment to improve germination and early growth. A combination of HWT and sandy loam soil can be used to give highest survival rate. Sulphuric acid treatment can be used in humus soil. REFERENCES 23 Agrawal, P.K and M.Ddlani, (1995).Techniques in seed Science and Technology, South Asian Publisheres,New Delhi,India,2 nd edition. Agritex, (1996).The natural farming regions in Zimbabwe, Ministry of Agriculture and Irrigation Development, Harare. Ahmed, M.A.J., (2008). Effect of bruchid beetles (Burchidius arabicus decelle) infestation on the germination of Acacia tortilis (forssk.) Hayne) seeds. American Journal of Environmental Sciences , 4(4), p.285. Al Khateeb, S.A., (2005). Germination Response Of Acacia (Acacia Tortilis (Forssk.) Hayne) To Seed Treatments And Incubation Temperatures. 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APPENDICES Appendix 1 Post hoc analysis: comparison of soils Multiple Comparisons LSD Dependent Variable (I) control (J) control Mean Std. Error Sig. 95% Confidence Interval Difference (I-J) Lower Bound Upper Bound SAT Humus Clayloam 27.875 * 2.909 .000 21.29 34.46 28 Sandyclay 18.450 * 2.909 .000 11.87 25.03 Humus -27.875 * 2.909 .000 -34.46 -21.29 Clayloam Sandyclay -9.425 * 2.909 .010 -16.01 -2.84 Humus -18.450 * 2.909 .000 -25.03 -11.87 Sandyclay Clayloam 9.425 * 2.909 .010 2.84 16.01 Clayloam 2.050 8.117 .806 -16.31 20.41 Humus Sandyclay 18.225 8.117 .051 -.14 36.59 Humus -2.050 8.117 .806 -20.41 16.31 nontreated Clayloam Sandyclay 16.175 8.117 .077 -2.19 34.54 Humus -18.225 8.117 .051 -36.59 .14 Sandyclay Clayloam -16.175 8.117 .077 -34.54 2.19 Clayloam 10.025 * 2.350 .002 4.71 15.34 Humus Sandyclay 7.625 * 2.350 .010 2.31 12.94 Humus -10.025 * 2.350 .002 -15.34 -4.71 CWT Clayloam Sandyclay -2.400 2.350 .334 -7.72 2.92 Humus -7.625 * 2.350 .010 -12.94 -2.31 Sandyclay Clayloam 2.400 2.350 .334 -2.92 7.72 Clayloam -17.900 * 4.441 .003 -27.95 -7.85 Humus Sandyclay -3.700 4.441 .426 -13.75 6.35 Humus 17.900 * 4.441 .003 7.85 27.95 HWT Clayloam Sandyclay 14.200 * 4.441 .011 4.15 24.25 Humus 3.700 4.441 .426 -6.35 13.75 Sandyclay Clayloam -14.200 * 4.441 .011 -24.25 -4.15 *. The mean difference is significant at the 0.05 level. Appendix 2 Mean Heights for A. Polyacantha Report control SAT nontreated CWT HWT Mean 64.50 47.50 50.58 44.68 N 4 4 4 4 Humus Std. Deviation 1.681 16.903 2.235 3.093 Std. Error of Mean .841 8.451 1.118 1.547 Mean 36.63 45.45 40.55 62.58 Clayloam N 4 4 4 4 29 Std. Deviation 1.573 1.484 3.305 3.397 Std. Error of Mean .787 .742 1.653 1.699 Mean 46.05 29.28 42.95 48.38 N 4 4 4 4 Sandyclay Std. Deviation 6.744 10.364 4.149 9.860 Std. Error of Mean 3.372 5.182 2.075 4.930 Mean 49.06 40.74 44.69 51.88 N 12 12 12 12 Total Std. Deviation 12.652 13.427 5.382 9.860 Std. Error of Mean 3.652 3.876 1.554 2.846 Appendix 3 Means for branchlet development Report control Clayloam Humus Sandyloam Mean 3.67 5.67 8.33 cwt Std. Error of Mean .667 1.764 1.453 Mean 5.33 6.67 5.33 hwt Std. Error of Mean 1.764 .882 1.333 Mean 5.00 8.33 6.00 sat Std. Error of Mean .577 .333 .577 Mean 5.33 7.00 4.33 non-treated Std. Error of Mean 1.202 3.512 1.202 Mean 4.83 6.92 6.00 Total Std. Error of Mean .534 .908 .674 Appendix 4 Post hoc for branchlet development Multiple Comparisons LSD Dependent (I) control (J) control Mean Std. Error Sig. 95% Confidence Interval Variable Difference (I- Lower Bound Upper Bound J) Clayloam cwt hwt -1.667 1.633 .337 -5.43 2.10 30 sat -1.333 1.633 .438 -5.10 2.43 non-treated -1.667 1.633 .337 -5.43 2.10 cwt 1.667 1.633 .337 -2.10 5.43 hwt sat .333 1.633 .843 -3.43 4.10 non-treated .000 1.633 1.000 -3.77 3.77 cwt 1.333 1.633 .438 -2.43 5.10 sat hwt -.333 1.633 .843 -4.10 3.43 non-treated -.333 1.633 .843 -4.10 3.43 cwt 1.667 1.633 .337 -2.10 5.43 non-treated hwt .000 1.633 1.000 -3.77 3.77 sat .333 1.633 .843 -3.43 4.10 hwt -1.000 2.858 .735 -7.59 5.59 cwt sat -2.667 2.858 .378 -9.26 3.92 non-treated -1.333 2.858 .653 -7.92 5.26 cwt 1.000 2.858 .735 -5.59 7.59 hwt sat -1.667 2.858 .576 -8.26 4.92 non-treated -.333 2.858 .910 -6.92 6.26 Humus cwt 2.667 2.858 .378 -3.92 9.26 sat hwt 1.667 2.858 .576 -4.92 8.26 non-treated 1.333 2.858 .653 -5.26 7.92 cwt 1.333 2.858 .653 -5.26 7.92 non-treated hwt .333 2.858 .910 -6.26 6.92 sat -1.333 2.858 .653 -7.92 5.26 hwt 3.000 1.683 .113 -.88 6.88 cwt sat 2.333 1.683 .203 -1.55 6.21 non-treated 4.000 * 1.683 .045 .12 7.88 cwt -3.000 1.683 .113 -6.88 .88 hwt sat -.667 1.683 .702 -4.55 3.21 non-treated 1.000 1.683 .569 -2.88 4.88 Sandyloam cwt -2.333 1.683 .203 -6.21 1.55 sat hwt .667 1.683 .702 -3.21 4.55 non -treated 1.667 1.683 .351 -2.21 5.55 cwt -4.000 * 1.683 .045 -7.88 -.12 non-treated hwt -1.000 1.683 .569 -4.88 2.88 sat -1.667 1.683 .351 -5.55 2.21 31 *. The mean difference is significant at the 0.05 level. Appendix 5 Post hoc – soils comparison Multiple Comparisons LSD Dependent Variable (I) control (J) control Mean Std. Error Sig. 95% Confidence Interval Difference (I- Lower Bound Upper Bound J) Humus -2.000 1.944 .343 -6.76 2.76 Clay loam Sandy loam -4.667 1.944 .053 -9.42 .09 Clay loam 2.000 1.944 .343 -2.76 6.76 cwt Humus Sandy loam -2.667 1.944 .219 -7.42 2.09 Clay loam 4.667 1.944 .053 -.09 9.42 Sandy loam Humus 2.667 1.944 .219 -2.09 7.42 Humus -1.333 1.944 .518 -6.09 3.42 Clay loam Sandy loam .000 1.944 1.000 -4.76 4.76 Clay loam 1.333 1.944 .518 -3.42 6.09 hwt Humus Sandy loam 1.333 1.944 .518 -3.42 6.09 Clay loam .000 1.944 1.000 -4.76 4.76 Sandy loam Humus -1.333 1.944 .518 -6.09 3.42 Humus -3.333 * .720 .004 -5.10 -1.57 Clay loam Sandy loam -1.000 .720 .214 -2.76 .76 Clay loam 3.333 * .720 .004 1.57 5.10 sat Humus Sandy loam 2.333 * .720 .018 .57 4.10 Clay loam 1.000 .720 .214 -.76 2.76 Sandy loam Humus -2.333 * .720 .018 -4.10 -.57 Humus -1.667 3.186 .620 -9.46 6.13 Clay loam Sandy loam 1.000 3.186 .764 -6.79 8.79 Clay loam 1.667 3.186 .620 -6.13 9.46 nontreated Humus Sandy loam 2.667 3.186 .435 -5.13 10.46 Clay loam -1.000 3.186 .764 -8.79 6.79 Sandy loam Humus -2.667 3.186 .435 -10.46 5.13 *. The mean difference is significant at the 0.05 level. 32 Appendix 6 comparison with treatments Multiple Comparisons LSD Dependent Variable (I) control (J) control Mean Std. Error Sig. 95% Confidence Interval Difference (I-J) Lower Bound Upper Bound Humus SAT Control 17.000 * 6.155 .017 3.59 30.41 33 CWT 13.925 * 6.155 .043 .51 27.34 HWT 19.825 * 6.155 .007 6.41 33.24 SAT -17.000 * 6.155 .017 -30.41 -3.59 Control CWT -3.075 6.155 .626 -16.49 10.34 HWT 2.825 6.155 .654 -10.59 16.24 SAT -13.925 * 6.155 .043 -27.34 -.51 CWT Control 3.075 6.155 .626 -10.34 16.49 HWT 5.900 6.155 .357 -7.51 19.31 SAT -19.825 * 6.155 .007 -33.24 -6.41 HWT Control -2.825 6.155 .654 -16.24 10.59 CWT -5.900 6.155 .357 -19.31 7.51 Control -8.825 * 1.842 .000 -12.84 -4.81 SAT CWT -3.925 1.842 .054 -7.94 .09 HWT -25.950 * 1.842 .000 -29.96 -21.94 SAT 8.825 * 1.842 .000 4.81 12.84 Control CWT 4.900 * 1.842 .021 .89 8.91 + HWT -17.125 * 1.842 .000 -21.14 -13.11 Clayloam SAT 3.925 1.842 .054 -.09 7.94 CWT Control -4.900 * 1.842 .021 -8.91 -.89 HWT -22.025 * 1.842 .000 -26.04 -18.01 SAT 25.950 * 1.842 .000 21.94 29.96 HWT Control 17.125 * 1.842 .000 13.11 21.14 CWT 22.025 * 1.842 .000 18.01 26.04 Control 16.775 * 5.781 .013 4.18 29.37 SAT CWT 3.100 5.781 .602 -9.49 15.69 HWT -2.325 5.781 .695 -14.92 10.27 SAT -16.775 * 5.781 .013 -29.37 -4.18 Control CWT -13.675 * 5.781 .036 -26.27 -1.08 HWT -19.100 * 5.781 .006 -31.69 -6.51 Sandyloam SAT -3.100 5.781 .602 -15.69 9.49 CWT Control 13.675 * 5.781 .036 1.08 26.27 HWT -5.425 5.781 .367 -18.02 7.17 SAT 2.325 5.781 .695 -10.27 14.92 HWT Control 19.100 * 5.781 .006 6.51 31.69 CWT 5.425 5.781 .367 -7.17 18.02 34 *. The mean difference is significant at the 0.05 level. 35