Department of Soil Science

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    Land Use, Vegetation Type and Erosion Patterns in Selected Catchments of the Keiskamma River Basin, Eastern Cape
    (University of Fort Hare, 2003) Pheto, Petunia Lebogang
    The southern African region is designated as an area which is susceptible to soil erosion. This is particularly true for the former Ciskei, where it is estimated that 4 7 % of the area is moderately to severely eroded (Ciskei Commission, 1980). The Keiskamma River Basin is located entirely within the borders of the former Ciskei in the Eastern Cape, South Africa. The river basin is populated by rural settlements with limited water resources. Five small catchment areas with a variety of environmental conditions were selected for study. The following aspects were assessed for each catchment selected.
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    Optimization of bio-conversion and nutrient release from coal fly ash amended cow dung – waste paper composts using earthworms (eisenia fetida) and effective micro-organisms
    (University of Fort Hare, 2015) Mupambwa, Hupenyu Allan
    Improving the fertilizer value of fly ash can create an abundant nutrient source in agriculture, whilst reducing the landfill deposition of this coal waste. This study was undertaken to address this challenge and was guided by the following specific objectives, (i) to characterize fly ash samples from selected South African coal powered electricity stations (ii) to optimize the fly ash incorporation into cow dung – waste paper mixtures for enhanced biodegradation and nutrient mineralization (iii) to determine the ideal Eisenia fetida (E. fetida) stocking density for the vermicomposting of fly ash - cow dung-waste paper mixtures (FCP) (iv) to determine the effectiveness of Effective Micro-organisms (EM) during vermicomposting in enhancing the biodegradation of FCP (v) to determine the effectiveness of FCP vermicompost substituted into pine bark compost on media physico-chemical properties and marigold growth. The eight South African fly ashes evaluated had a total phosphorus content ranging from 553.3 to 1514 mg/kg and the Olsen extractable P from 130 to 345.5 mg/kg. Across all three soils, fly ash incorporation increased extractable P content from a P deficient level to about 20 mg P/kg. Except for Cu, all metal species investigated (Cr, Pb, Ni and Fe) showed significantly (P ≤ 0.05) low extractability under fly ash treated soils compared to the soil alone control. To enhance the nutrient mineralization in fly ash, it was mixed with optimized cow dung – waste paper (CP) mixtures at ratios of (F: CP) 1:1, 1:2, 1:3, 2:1, 3:1 and CP alone and composted for 14 weeks with or without E. fetida earthworms . Based on C: N ratio, the extent of vermi-degradation of the waste mixtures followed the decreasing order (F: CP) of 1:3 > 1:2 > 1:1 > CP alone > 2:1 > 3:1. Olsen P was significantly higher (P < 0.05) where earthworms were added. The mean percentage increase in extractable P was in the order CP alone > 1:2 > 1:3 > 1:1 > 2:1 > 3:1, with earthworm addition almost doubling P release across the 1:1; 1:2 and CP alone treatments. Fly ash incorporation at the 1:2 ratio proved to be the most appropriate, as it enhanced biodegradation and nutrient release to a greater extent than all other treatments with fly ash incorporation. To optimize stocking density of fly ash vermicompost, the optimum fly ash incorporation level of 1: 2 was treated with four stocking densities of 0; 12.5; 25 and 37.5 g –worm/kg; including and control with cow dung- waste paper only (CP alone). Though the treatments 12.5; 25 and 37.5 g – worm/kg all resulted in mature vermicompost, a stocking density of 25 g-worm/kg and above resulted in faster maturity; higher humification parameters and a low C: N ratio range (11.1 – 10.4). The activity of ß-glucosidase and fluorescein di-acetate hydrolysis enzymes showed faster stabilization at stocking densities of 25 g-worm/kg and above, indicating vermicompost stability and maturity. These enzymes also showed significant (P < 0.05) correlation with changes in C: N ratio in the vermicompost. Similarly, a stocking density of 25 g-worm/kg resulted in the highest potential to increase nitrate/nitrite and Olsen extractable P. The treatments 0; 12.5; 25 and 37.5 g-worm resulted in a net Olsen P increase of 16.3%; 38.9%; 61.0% and 53.0%, respectively, after 10 weeks. Though vermicompost maturity can be attained at a stocking density of 12.5 g-worm/kg, for faster more humified and nutrient rich fly ash vermicompost, a stocking density of 25 g-worm/kg seemed most appropriate. Inoculation of fly ash vermicompost with EM alone did not result in significantly (P < 0.05) different changes in C: N ratio and dissolved organic matter (DOC) compared to the control. Also, though inoculation with EM together with E. fetida resulted in greater changes in C: N ratio and DOC compared to the E. fetida alone treatment, this difference was not statistically significant. Inoculation with EM coupled with E. fetida, however, resulted in significantly (P< 0.05) higher rates of Olsen phosphorus release compared to the E. fetida alone treatment. On average, the EM + E. fetida treatment resulted in a rate of weekly Olsen P release of 54.32 mg/kg, with the E. fetida alone, EM alone and control releasing 48.39; 28.71 and 16.56 mg-P/kg/week, respectively. It was observed that inoculation of fly ash based composts with EM alone is not beneficial, whilst combining EM with E. fetida may result in faster compost maturity and greater Olsen P release. By substituting pine bark growing media with fly ash vermicompost up to 50% significant improvements in water holding capacity, total porosity and air filled porosity was observed, with germination over 90%. The 25% FA treatment also resulted in significantly higher number of flowers and buds compared to the 50% and 75%, despite the higher concentration of essential nutrients in the 50% FA treatment. For effective marigold seedling germination and growth, the 50% FA: 50% PB growing medium is recommended whilst for maturity and flower production, the 25% FA: 75% PB combination is to be preferred as it performed better than all treatments regardless of the nutrient composition of the media. The results of this study have shown that fly ash can be an effective phosphorus source when vermicomposted at an incorporation ration of 1:2 (fly ash: cow dung – waste paper) and a stocking density of 25 g-worm/kg. The fly ash vermicompost can be an important part of planting media which can be used for land reclamation and horticultural crop production. However, optimization of EM incorporation may be required for significant effects of on biodegradation and mineralization of fly ash vermicomposts following EM inoculation.
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    Optimization of the vermidegradation of cow dung –waste paper mixtures
    (University of Fort Hare, 2014) Unuofin, Frank Oshioname
    Vermicomposting is an eco-friendly waste management strategy. Its successful performance necessitate that key functioning parameters like earthworm stocking density, nutrient enrichment be established for each target waste/waste mixture. One main target waste mixture in South Africa, and in the University of Fort Hare in particular is waste paper mixed with cow dung and rock phosphate (RP) for phosphorus (P) enrichment. This study was carried out to address the following specific objectives, to determine (i) the effect of Eisenia fetida stocking density on the bioconversion of cow dung waste paper mixtures enriched with rock phosphate, (ii) an optimum application rate of low grade South African Rock Phosphate and time required for efficient vermicomposting of cow dung-waste paper mixtures, and (iii) to determine if the phosphorus in RP is responsible for improved biodegradation during the vermicomposting of cow dung-waste paper mixtures. Results of this study revealed that bioconversion of cow dung waste paper mixtures enriched with RP was highly dependent on E. fetida stocking density and time. The stocking density of 12.5 g-worms kg-1 feedstock of the mixtures resulted in highest earthworm growth rate and humification of the waste mixture as reflected by a C: N ratio of < 12, polymerization index (PI) or humic acid/fulvic acid ratio of > 1.9, and a humification index of >13 for the cow dung waste paper mixtures. A germination test carried out also revealed that the resultant vermicompost had no inhibitory effect on the germination of tomato, carrot, and radish. Extractable P increased with stocking density up to 22.5 g-worm kg-1 feedstock, suggesting that for maximum P release from RP enriched wastes, a high stocking density should be considered. Informed by an earlier study which demonstrated that RP improved vermidegration, a follow up study was done to determine the optimum amount of rock phosphate necessary for efficient vermidegradation of cow dung waste paper mixtures while ensuring a phosphorus rich vermicompost. The results showed that addition of RP at rates ≤ 1% P as RP efficiently enhanced the bioconversion of cow dung waste paper mixtures as reflected by low C: N ratio, high polymerization index (PI), HI and HR used as maturity indicators for matured compost. Final vermicompost products obtained at minimum amounts of RP application rates resulted highly humified vermicompost with finer morphological structure, with no inhibitory effect on the germination of tomato, carrot, and radish similar to the ones obtained at higher RP rates. The findings suggest that 1%P as RP application rate is optimum for efficient vermidegradation of cow dung waste paper mixtures. Since P or Ca happen to be the most prevalent elements in most rock phosphate used for compost enrichment, a study was carried out to determine if P or Ca in RP is predominantly responsible for the improved biodegradation of cow-dung waste paper mixture observed during vermicomposting. Phosphorus sources in form of triple superphosphate (TSP), phosphoric acid (PHA) and Ca in form of calcium chloride (CaCl2) salt were compared with rock phosphate. The results from the study indicated that TSP, a water soluble P source, resulted in greater and faster degradation of the waste mixtures than RP while the Ca source had the least effect. With TSP incorporation the compost maturity C: N ratio of 12 was reached within 28 days while RP, PHA and CaCl2 needed 42, 56 and more than 56 days, respectively. The results indicated that P was largely responsible for the enhanced bioconversion of the waste mixtures. This appeared linked to the effect of P to stimulate microbial growth as reflected by higher microbial biomass carbon levels where water soluble P sources were applied. The C: N ratios of the final vermicomposts at day 56 were 10, 11.5, 13, 14, and 23 for TSP, RP, PHA, Control (No P added) and CaCl2 treatments, respectively. Although TSP gave superior superior performance, RP may still be the preferred additive in the vermicomposting of cow dung waste paper mixtures as it is cheaper and produces mature compost in a shorter period of 8 weeks. Generally, the results of this study have shown that the vemidegradation of cow dung waste paper mixtures can be optimized through adoption of an E. fetida stocking density of 12.5g- worm kg-1 and an RP incorporation rate of 1% P as RP. However, higher rates of RPincorporation may be adopted where final vermicomposts with higher P fertilizer value are desired. Phosphorus appears to be the RP constituent responsible for its ability to enhance the vermidegradation of cow dung waste paper mixtures. Future studies should explore the effectiveness of other P-bearing minerals for their effectiveness in enhancing vemidegradation.
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    Tillage effects on the aggregate-associated organic carbon and bulk density in some South African soils with different texture.
    (University of Fort Hare, 2015) Njeru,Sarah Kangai
    Tillage operations disrupt the soil structure resulting in aggregates of various sizes and altered bulk density. Moreover, tillage influences soil carbon pools and many other soil physical properties. The objectives of this study were to determine, in various South African soils under different tillage systems, the following. (1) Amount of aggregate-associated soil organic carbon (SOC), (2) soil compressibility, and (3) relationship between compressibility, texture and the aggregate-associated SOC. The soil samples used in this study were collected from six different sites in Eastern Cape Province, South Africa. Soil samples were taken from conventional tillage (CT) and no-till (NT) land. To keep the soil aggregates intact sampling was done using a spade and carefully carried to the laboratory in rigid containers. For SOC determination, treatments were the two tillage systems, CT and NT, and four aggregate sizes. The experimental design was completely randomized design with a factorial layout and was replicated three times. Aggregate-associated SOC was determined using Walkley-Black method. Proctor compaction test was used determine the dry bulk density with varying moisture content and consequently the maximum bulk density (MBD) and critical water content (CWC). The aggregate-associated SOC content differed with tillage system and was significant higher (p < 0.05) in CT than NT. The amount of aggregate-associated SOC was 1.67 times higher in CT than NT plots. The MBD ranged between 1.77 g/cm3 and 10.27 g/cm3 and the CWC ranged from 9.1% to 10.3%. The higher amounts of SOC in CT were attributed to the annual crop residue returns while the lower amounts of SOC in the NT fields were due to grazing. Therefore, tillage influenced the amount of aggregate-associated organic carbon irrespective of the resulting size of the aggregate. The positive relationship between tillage and aggregate-associated SOC challenges the conversion of land to no-till for carbon sequestration. The overall gradient for correlation between the MBD and CWC was negative with r2 = 0.23 and a p value of 0.0076. The compressibility curves indicated higher values under CT if the texture class was silt clay.
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    Water footprint of growing vegetables in selected smallholder irrigation schemes in South Africa
    (University of Fort Hare, 2014) Nyambo, Patrick
    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.