Theses And Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/20.500.11837/354

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Effects of oats and vetch cover crops on light organic matter fractions and activities of selected enzymes in an irrigated maize based conservation agriculture system on Alice Jozini Ecotope in the Eastern Cape, South Africa
(University of Fort Hare, 2014) Mukumbareza, Caroline
Low soil fertility in the Eastern Cape Province (EC) is attributed to poor agricultural management, which reduces organic matter, among other factors. Conservation agriculture (CA), consisting of no-till, soil cover and rotations, is being promoted to improve soil quality and productivity. Soil biological parameters respond to the overall effects of management on the physical and chemical components of soil. This study was conducted to evaluate the effects of oat (Avena sativa) and grazing vetch (Vicia dasycarpa) cover crops on soil biological activity after five years under CA and evaluate light organic matter fractions, MBC and activities of selected enzymes as early indicators of organic matter build up under in no-till maize based CA system. The study was based on soil samples collected from a five year trial with rotations of maize and sole cover crops and two younger trials (4 and 28 months) with oat and grazing vetch bicultures. In the five year old trial, oat and grazing vetch were planted at four fertiliser regimes (i) Fertilizer applied to cover crops and maize (F1), (ii) fertilizer applied to cover crops only (F2), (iii) fertilizer applied to maize only (F3) and (iv) no fertilizer applied (F4)) to give a 2 × 4 factorial plus control laid out in a randomized complete block design (RCBD) with three replications. Fertilizer was applied at 10 kg P ha-1, as a compound (6.7% N; 10% P; 13.3% K) at planting and grazing vetch was inoculated with Rhizobium legunominosarium biovar viciae. Oat was top dressed using limestone ammonium nitrate (LAN – 28% N) at 7 weeks after planting (WAP) to make a total of 45 kg N ha-1. Three weeks after termination of the cover crops, all plots were split in half and maize was planted and fertilizer applied at 0 and 60 N kg ha-1. A third of the N was applied at planting (6.7% N; 10% P; 13.3% K). In the biculture trials, the treatments were 90% oat + 10% vetch, 70% oat + 30% vetch, 50% oat+ 50% vetch, 100% vetch and 100% oat and laid out in a RCBD with three replicates. Only basal fertilizer was applied to the cover crop at planting at 13.34 kg N ha-1, 20 kg P ha-1 and 26.66 kg K ha-1 using 2:3:4 (30 + 0.5% Zn) compound fertiliser. After cover crop termination, SC701 maize variety was planted, and fertilised at 60 kg N ha-1 with a third of the N applied as a basal. In the five year old trial, oat and vetch gave significantly (P < 0.05) higher MBC and activities of all soil enzymes measured than the weedy fallow at 0-5 and 5-20 cm depths. Fertilization of cover crop (F2) and maize (F3) gave similar MBC. The F4 in cover crops gave similar dehydrogenase activity with F3 under weedy fallow and that for vetch rotation was the same for F3 in oat. The F4 for grazing vetch had similar β-glucosidase activity as F1 and similar urease activity as F1, F2 and F3 of oat rotations. Acid and alkaline activity in F1 had similar results to F2. In the younger trials, biculture treatments did not improve total C, and N when compared with the weedy fallow. Dehydrogenase, β-glucosidase, arylsulphatase and alkaline phosphatase activities were higher in the 28 month trial compared to the 4 month one while urease was higher in the 4-month old trial. Treatments with more than 50% oat content had higher acid phosphatase activity in the 4- than 28 month old trial. Effects of cover crop, as the main factor, was significant in all enzymes (P < 0.05), with 70% oat + 30% vetch treatment having the highest dehydrogenase and arylsulphatase while for alkaline phosphatase it had similar results to 90% oat + 10% vetch. For β-glucosidase and urease, effects of cover crop as the main factor were also significant with sole vetch giving the highest activity for both enzymes. Acid phosphatase activity was highest in sole oat. Particulate OM was highest in the 100% oat treatment and declined with decrease in the proportion of oat in the biculture. The 50% oat + 50% vetch treatment had similar POM to the 70% oat +30% vetch in the 4 month old trial and to the 90% oat + 10% vetch in the 28 months old trial in the 0-5 cm depth (P < 0.05). In the 5-20 cm depth, the 70% oat +30% vetch treatment had similar POM to the 90% oat + 10% vetch in the 28 month old trial. The 70% oat+30% vetch had greatest WSC and MBC followed by the 90% oat +10% vetch, with the 50% oat + 50% vetch being similar to 100% vetch and 100% oat (MBC only). The 28 months old trial had greater POM and WSC than the 4 months trial. The findings of this study imply that the use of grazing vetch and fertilization of cover crops only improves soil biological activity, represented by MBC and enzyme activities, after 5 years of maize-cover crop rotations in low input conservation agriculture system. Bicultures, particularly the 70% oat + 30% vetch, work better than their sole crops in improving organic matter fractions, MBC and enzyme activities and that POM, WSC, MBC, enzyme activities are useful early indicators of soil organic matter build-up of CA systems.
Effects of sheep kraal manure and intercropping with maize on growth, nutrient uptake and yield of a vegetable amaranthus accession in the central region of the Eastern Cape, South Africa
(University of Fort Hare, 2008) Mhlontlo, Simphiwe
Amaranthus is among the nutritious indigenous plant species that are gathered from the wild in the Eastern Cape to prepare a traditional meal known as ‘imifino’ or ‘isigwampa’ to supplement the necessary proteins, vitamins and minerals which are poor in maizebased meals. Amaranthus species are adapted to wild conditions unsuitable for exotic vegetables and could be cultivated but information on its fertility requirements, as sole or intercrop, is the key for its domestication and production as a leafy vegetable, particularly where manure is used. Two dry-land and one glasshouse experiments were conducted to study the effects of sheep kraal manure application rate, intercropping with maize and soil type on growth, fresh and dry matter yields, nutrient uptake and grain yield of a local Amaranthus accession that grows wild in the Eastern Cape. Sheep kraal manure rates ranging from 0 to 10 t ha-1 and an NPK {2:3:4(30) + 0.5% Zn} fertilizer as a positive control, applied at rates recommended for spinach, were tested. In the Gqumahashe experiment, where Amaranthus was grown as a sole crop, low manure rates (≤ 2.5 t ha-1) resulted in plant heights and fresh matter yields which were comparable to those in the unfertilized control, whereas higher rates (5 and 10 t ha-1) and recommended NPK fertilizer had higher levels both at 30 and 60 days after transplanting (DAT) at p < 0.05. At 30 DAT, manure application rates of ≥ 2.5 t ha-1 and the NPK fertilizer treatment, produced greater shoot dry-matter yields (29.35, 30.75 and 37.68 g plant-1) than the unfertilized control (17.11 g plant-1) at p < 0.05. Uptake of N and P in the leaves increased with increase in manure application rate with N uptake reaching a maximum (308 mg plant-1) at a manure rate of 2.5 t ha-1 which corresponded with the maximum dry matter yield. There was no effect of manure rate or fertilizer on residual soil N and Ca, whereas P, K, Mg and Zn increased. In a pot experiment with soils from Ntselamanzi and Gqumahashe Villages, manure rates ≥ 2.5 t ha-1 resulted in plant heights and fresh matter yield that compared well with the NPK fertilizer treatment in the Gqumahashe soil whereas only the 10 t ha-1 manure treatment was comparable to the NPK fertilizer treatment in the Ntselamanzi soil. Only treatments with ≥ 5 t ha-1 manure had stem girth (1.00 and 1.07 cm) that compared well to NPK fertilizer (1.03 cm) in the Ntselamanzi soil whereas in the Gqumahashe soil, all manure levels compared well to NPK fertilizer (1.02 cm). However, no significant difference was observed in plant height and stem girth and fresh matter due to soil type. In both soils, the 1.3-10 t ha-1 manure treatments had dry leaf weight comparable to plants fertilized with NPK fertilizer (3.72 g plant-1 for the Ntselamanzi soil and 3.65 g plant-1 for the Gqumahashe soil) and were bigger than the unfertilized control (2.2 g plant-1 for the Ntselamanzi soil and 1.38 g plant-1 for the Gqumahashe soil) at p < 0.05. Uptake of N, P and K increased as result of manure application but nonetheless, it was less when compared to plants fertilized with NPK fertilizer in both soils. In a field intercropping experiment carried out at Ntselamanzi, growth and yield of sole and intercropped Amaranthus plants grown with manure improved when compared to the unfertilized control and compared well to NPK fertilizer. At 30 days after transplanting (DAT), both sole and intercropped plants grown with ≥ 2.5 t ha-1 manure had fresh and dry matter yield comparable to plants fertilized with NPK fertilizer. At 60 DAT, intercropped plants grown with all manure levels had bigger fresh matter yield when compared to unfertilized control (836.0 g plant-1) whereas for sole cropped plants only those grown with ≥ 2.5 t ha-1 compared to NPK fertilizer (1467.7 g plant-1) at p < 0.05. Uptake of N, P, K, Ca and Mg increased with increase in manure application in both sole and intercropped Amaranthus. Whereas Amaranthus did not suffer from the competition in the intercrop, maize biomass and grain yield were severely reduced with the effects being evident after 60 DAT. Based on results of this study, it is therefore suggested that, if Amaranthus is to be intercropped with maize under dry land conditions of the Central Region of the Eastern Cape, sheep manure should at least be applied at rate of ≥ 2.5 t ha-1 and Amaranthus be harvested at 30 DAT.
An integrated approach for the delineation of arable land and its cropping suitability under variable soil and climatic conditions in the Nkonkobe Municipality, Eastern Cape, South Africa.
(University of Fort Hare, 2014) Manyevere, Alen
Arable crop production in Nkonkobe Municipality is low due to abandonment of potentially productive land and low productivity of the cultivated land. Little attention has been given to farmers‟ perspectives with regards to crop production and land abandonment. Understanding the relationships of indigenous knowledge systems, where local approaches to soil classification, appraisal, use and management and land evaluation, and scientific approaches could be important for the effective use of available soil resources while avoiding those resources that are vulnerable to degradation. In addition, the interactions between soil factors and climate could be useful in understanding the erodibility of soils. The intergration of scientific research and indigenous knowledge systems could help in the identification and delineation of high potential land and on crop suitability evaluation. The objectives of the study were: (i) to determine farmers‟ perspectives with regards to land utilisation and abandonment, constraints on crop production and crop preferences, (ii) to integrate and compare indigenous knowledge systems with scientific approaches of soil classification and potential, (iii) to determine the effect of climate and soil factors on erodibilities of soils in the Municipality (iv) to delineate arable land and evaluate its suitability for maize, potato, sorghum and cowpea under rainfed agriculture. Using semi-structured and open-ended interviews, information on limitations to crop production, cropping preferences, indigenous soil classifications, cropping potential ratings and erosion was captured. Descriptive and correlation statistics were used to analyse farmers‟ responses. The information was later used for a pilot participatory mapping and the determination of the agricultural potential of the soils in three selected villages of the Municipality. Field boundaries of soil texture, colour, depth, and slope position were captured using global positioning systems (GPS). The relationship between the degree of erosion and soil and slope factors was analysed by step-wise regression. Crop suitability for rainfed agriculture was done using the FAO guidelines for Land evaluation for rainfed agriculture. The spatially referenced crop suitability classes were produced by applying the Law of Limiting Combinationusing GIS Boolean Logic. The major biophysical factors, affecting crop production and land utilisation were soil degradation and low and erratic rainfall, while other factors included lack of farming equipment and security concerns. Maize, spinach and cabbage were the main crops grown, with maize, sorghum and wheat the most abandoned crops. While it was difficult to accurately correlate indigenous classification with international scientific classification, the importance of colour, texture and soil depth for both classification and soil potential, suggests that some form of correlation is possible which enabled communication and other extension information to be conveyed. The shallow and stony soil (urhete) correlated well with the Leptosols in World Reference Base (WRB) or Mispah and shallow Glenrosa soils in the South African system. The red structured clays (umhlaba obomvu) matched the Nitisols in WRB or Shortlands in the South African system. The non-swelling black clayey soils (umhlaba omnyama) matched soils with melanic A horizons in both the WRB and South African soil classification systems. The dongwe and santi soils developed in alluvial sediments belonged to the Dundee, Oakleaf or Augrabies soils in the South African classification system and fluvisols or Cambisols in the WRB system. There was good agreement between farmers‟ assessment of the cropping potential and scientific approaches but scientifically high potential red soils were rated lowly by the farmers due to difficulties in management caused by shortages of farm machinery, especially under dryland farming. Overall, the soil factors affecting erosion were influenced largely by climate, while parent material was also important. Climate had a dominant influence on soil factors most notably fine sand and very fine sand fractions and exchangeable sodium percentage being more important on soil forms occurring in arid and semi-arid climate and less in the sub-humid and humid areas, where clay mineralogy, particularly kaolinite and sesquioxide dominated. Dolerite derived soils were the most stable and should be given the highest priority for cropping development while mudstone and shale derived soils had a lower cropping potential. While slope gradient and length had some effect on soil erosion in arid and semi arid environments its influence was generally overshadowed by soil factors especially in humid zones. Cow pea and sorghum were the most adapted crops in the region while potato and maize were marginally suitable under rainfed agriculture. The study revealed that most adapted crops were not necessarily the most preferred crops by the farmers. A small percentage of the land was delineated as arable and therefore optimisation of this available land should be prioritized.
Remediation of Heavy Metals ( Cd and Pb) and Phthalate Easters in Contaminated Soil Treated with Composts.
(University of Fort Hare, 2003-02) Sibali, Linda Lunga
The availability of heavy metals (lead and cadmium) and phthalate esters ( dimethyl phthalate, diethyl phthalate and di-2-ethylhexyl phthalate) from artificially contaminated soil samples to which were added compost of different compositions, were measured weekly for 28 days. Heavy metals and phthalate esters were determined by atomic absorption spectroscopy (AAS) and gas chromatography (GC), respectively. Six different types of composts (C l-C6) were used for heavy metals whilst three different types of composts (Cl, C2 and C4) were used for phthalate esters. For heavy metals, the total metal sorption in composts changed with time and the changes were dependent on type of compost and its formulation. Generally, for all the composts used lead was highest on 7th day and cadmium on 14th day. The highest rate of compost appeared to give the most efficient fixing of the metals.
Soil fertiltiy enhancement through appropriate fertilizer management on winter cover crops in a conservation agriculture system
(University of Fort Hare, 2012) Dube, Ernest
A study was carried out to determine the effects of oat (Avena sativa) and grazing vetch (Vicia darsycapa) winter cover crops and fertilizer application on SOM, phosphorus (P) pools, nutrient availability, nutrient uptake, maize yield and seedbanks of problematic weeds in an irrigated maize-based conservation agriculture (CA) system. A separate experiment was carried out to investigate the effects of the winter cover crops on nitrogen (N) management, N use efficiency and profitability. After four years of continuous rotation, the winter cover crops significantly (p<0.05) increased particulate SOM and hot water soluble carbon in the 0 – 5 and 5 – 20 cm soil depths. When fertilized, oat was better able to support SOM sequestration in water stable aggregates at 0 – 20 cm whilst grazing vetch was more effective at 20 – 50 cm. Where no fertilizer was invested, there were significant (p<0.01) reductions in biomass input and SOM on oat-maize and weedy fallow-maize rotations whereas vetch-maize rotations did not respond, both at 0 – 5 and 5 – 20 cm. Targeting fertilizer to the winter cover crop required less fertilizer, and yet gave a similar SOM response as targeting the fertilizer to the maize crop. In addition to increasing SOM in the surface soil (0 – 5 cm), the winter cover crops significantly (p<0.05) increased labile pools of P, including microbial P. The cover crops also significantly (p<0.05) increased maize P concentration during early growth, extractable soil P, Cu, Mn, and Zn but had no effect on Ca and K. Grazing vetch increased soil mineral N but reduced extractable soil Mg. Without fertilizer, there were sharp declines in maize grain yield on oat and weedy fallow rotations over the four year period, but less so, on the grazing vetch. Grazing vetch increased maize growth, grain yield response to N fertilizer, nitrogen use efficiency (NUE) and profitability for fertilizer rates below 180 kg N ha-1. Oat effects however on maize yield and NUE were generally similar to weedy fallow. Based on the partial factor productivity of N, the highest efficiencies in utilization of fertilizer N for maize yield improvement under grazing vetch and oat are obtained at 60 kg N ha-1 and would decline thereafter with any increases in fertilizer application rate. Grazing vetch gave N fertilizer replacement values of up to 120 kg N ha-1 as well as the highest marginal rates of return to increasing N fertilizer rate. The cover crops were more effective than the weedy fallow in reducing seedbank density of Digitaria sanguinalis, Eleusine indica, Amaranthus retroflexus and Datura stramonium at 0 – 5 cm soil depth, causing weed seed reductions of 30 - 70%. The winter cover crops however, selectively allowed emergence of the narrow leafed weeds; Cyperus esculentus and Digitaria sanguinalis in the maize crop. The findings of this study suggested that grazing vetch is suited for SOM improvement in low fertilizer input systems and that fertilizer is better invested on winter cover crops as opposed to maize crops. Oat, on the other hand, when fertilized, would be ideal for C sequestration in water stable aggregates of the surface soil. Grazing vetch is ideal for resource poor farmers who cannot afford mineral fertilizers as it gives grain yield improvement and high fertilizer replacement value. Grazing vetch can produce enough maize yield response to pay its way in the maize-based systems and oat may not require additional N than that applied to the weedy fallow. Phosphorus and Zn are some of the major limiting essential plant nutrients on South African soils and the winter cover crops could make a contribution. The cover crops also hasten depletion of some problematic weeds from seedbanks, leading to reduced weed pressure during maize growth.
The Effect of Ramial Chipped Wood (RCW) and Litter Compost of of Casuarina equisetifolia Forst & Forst on Growth of Tomatoes, Soil Fertility improvement and Phytonematode Dynamics in Sandy Soil of Niayes, Senegal
(University of Fort Hare, 2000-12-04) Soumare, Mariame Dia
Plantations of Casuarina equisetifolia in the Niayes area Senegal produce two important by products, namely, litter and ramial chipped wood (RCW) which are organic materials that were suspected to have potential as organic soil amendments. However, their potential as sources of nutrients and their effects on biological pest control upon decomposition in soils remained to be established in infertile sandy soils of Niayes area.
The Effects of Spring Debanking and Defoliation by Goats on Acacia Karroo Trees in the False Thornveld of the Eastern Cape, South Africa
(University of Fort Hare, 2008-08) Macanda, Mfundo
In the study the early flush phenophase induced response of A. karroo were investigated. The investigation was carried out in the False Thomveld of the Eastern Cape, a vegetation type that is dominated by A. karroo species and herbaceous layer dominated by Increaser II grass species. In the study two treatments were investigated; debarking and defoliation. A· simple randomized block design, with 6 treatments; replicated three times was set up. Debarking was done manually by hand and defoliation by 12 goats for two weeks in October 2004.
Water footprint of growing vegetables in selected smallholder irrigation schemes in South Africa
(University of Fort Hare, 2014) Nyambo, Patrick; Wakindiki, I I C
Knowledge of water use, through water foot printing (WF) in smallholder agriculture crop production is the key to the global fight against poverty, achievement of food security and sustainability within the world’s rural community. Water footprint of a crop can be defined as the volume of fresh water used to produce a certain crop in all the steps in the production line. This study, therefore aimed at contributing towards improvements in rural livelihoods by raising awareness of the increased productive use of green, blue and grey water in smallholder agriculture in South Africa. This was done through determination of water footprints of five vegetable crops, i.e. potatoes (Solanum tuberosum), tomatoes (Solanum lycopersicum), dry beans (Phaseolus vulgaris), cabbage (Brassica oleracea spp) and spinach (Spinacia oleracea) in the 2000-2013 period. Quantification of water footprints has been done worldwide but, in South Africa (SA) focus has mostly been on the industrial and domestic sector. Water footprint assessment framework, was used to estimate the full impact of vegetable production on water resources at Zanyokwe, Thabina and Tugela Ferry irrigation schemes as case studies. The CROPWAT@ model was used to calculate crop evapotranspiration, differentiating green and blue water. Local climatic data were obtained from SA weather services, while the crop and soil parameters were obtained from the FAO data base. Nitrogen was considered the main pollutant hence its use in the grey water footprint calculation. Generally, Thabina irrigation scheme had the highest water footprint, followed by Tugela Ferry irrigation scheme whilst Zanyokwe irrigation scheme had the lowest. Green beans had the highest water footprint at all the three irrigation schemes with Thabina irrigation scheme having the highest (3535.1 m3/ton). For Tugela Ferry irrigation scheme, the calculated WF was 2753 m3/ton whilst the lowest was observed at ZIS i.e. 2407.6 m3/ton. Cabbage had the lowest water footprint. The highest water footprint for growing cabbage was 254.5 m3/ton in TFIS, 223.1 m3/ton in TIS and the lowest was 217.8 m3/ton in ZIS. The differences observed in the WF of a crop at each scheme maybe attributed to the differences management, weather and environmental characteristics, in the three locations. Moreover, the needs for ET are related to soil type and plant growth, and primarily depend on crop development and climatic factors which are closely related to climatic demands. The grey water footprint was calculated using the recommended fertilizer application rates for all the three sites. Green beans had the highest WFgrey i.e. 373 m3/ton and the lowest was cabbage with 37 m3/ton. Potato, spinach and tomatoes had 156 m3/ton, 214 m3/ton and 132 m3/ton, respectively. Grey water footprint in this study was higher as compared to other studies, possibly because of the high rates of nitrogen fertilizers used in the calculations and the low yields farmers get. Compared with estimates from other studies, the water footprints of vegetable production within smallholder irrigation schemes was relatively high. There is therefore, a need to focus on crop management and tillage practices that will help in increasing yield while minimizing water usage.

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