Masters Degrees (Crop Science)

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Agronomic characterization and evaluation of pigeon pea landraces in KwaZulu-Natal Province of South Africa.
(2015) Hluyako, Lindah London.; Magwaza, Lembe Samukelo.; Odindo, Alfred Oduor.
Abstract available in PDF file.
Agronomic performance of sugarcane varieties derived from tissue culture (NovaCane®) and conventional seedcane under rainfed conditions.
(2017) Shezi, Sbonelo Nicholus.; Ramburan, Sanesh.; Modi, Albert Thembinkosi.
The use of tissue culture (TC) plants have been promising for the production of true-to-type, disease free planting material. However, TC plants have been shown to possess an altered phenotype (high tillering and thinner stalks) compared with conventionally propagated sugarcane from setts (hereafter referred to as conventional or Con). Limited information is available for the response of different varieties to the TC process. Additionally, the effects of any altered phenotype in subsequent stages has not been evaluated. Three field experiments were conducted under rainfed conditions at South African Sugarcane Research Institute (SASRI) Mount Edgecombe experiment station to gain insights into these factors. The aim of experiment 1 was to investigate growth and yield differences between the TC and the Con plants for different varieties. Here, a field trial was established as a randomised block design with four replications of four varieties (N12, N31, N41, and N48) planted using three methods: 1) TC derived plants (spaced at either 30 (TC30) or 50 (TC50) cm apart; 2) conventional hot water treated seedcane setts (Con); and 3) single-budded sett derived plants (speedlings) planted 50 cm apart (SP50). The aim of experiment 2 was to investigate the effects of different in vitro procedures on several phenotypic and agronomic characteristics of TC plants of sugarcane. A field trial was established as a randomised block design with four replications consisted of two varieties (N41 and N48) derived through three variations of the in vitro NovaCane® procedure, namely i) the standard procedure, ii) plantlets exposed to CoCl2 (NovaCane® (CoCl2)) and iii) plantlets that underwent a secondary meristem excision process (NovaCane® (secondary)) from in vitro material. The plantlets from all three treatments were planted using two (30 and 50 cm) plant spacings. The aim of experiment 3 was to compare the performance of seedcane obtained from TC (stage 1) and Con when planted at different planting rates. The seedcane for experiment 3 was derived from the corresponding treatments in experiment 1, which were: 1) stalks derived from TC50 and planted at a lower planting rate (TC50 low); 2) stalks derived from TC50 and planted at a higher planting rate (TC50 high); 3) stalks derived from TC30 and planted at a lower planting rate (TC30 low); 4) stalks derived from TC30 and planted at a higher planting rate (TC30 high); and 5) stalks derived from Con and planted at a normal planting rate. Yield and yield component measurements for these experiments were taken at harvest and data were analysed by ANOVA. For experiment 1, there were no significant differences in cane yield, stalk height and stalk mass between propagation methods for all varieties in both crops harvested. For varieties N12 and N31, both TC treatments produced significantly thinner stalks and higher stalk population compared with the Con treatment when averaged across crops. Variety N48 was insensitive to the TC process, indicating that the phenotype of this variety was maintained during the TC process. The TC30 and TC50 treatments did not differ significantly for any parameter in both crops for all varieties, showing that plant spacing did not affect growth. The SP50 treatment produced significantly thicker stalks compared with the TC50 for varieties N12, N31 and N41 in the plant crop. For experiment 2, the plants produced through the NovaCane® (CoCl2) procedure resembled those produced through NovaCane® for all phenotypic and agronomic characteristics in the plant and first ratoon crops. The plants produced through the NovaCane® and the NovaCane® (secondary) procedures differ significantly for stalk population only, with the NovaCane® treatment having significantly lower stalk population compared with the NovaCane® (secondary) treatment for variety N41. Planting at closer (30 cm) or wider (50 cm) spacings did not have an effect on plant growth and to the response of varieties to the in vitro treatments. For experiment 3, crop derived from TC had a significantly higher mean cane yield and TERC compared with the crop derived from the Con. The crop derived from TC had a significantly higher mean stalk population compared with the crop derived from Con. This was observed for varieties N12 and N41 in particular. The crop derived from TC produced significantly thinner and taller stalks compared with the crop derived from Con. The effects of planting rates and TC source (TC30 vs TC50) were not significant for any parameter. Varieties responded differently to the TC process (N48 did not show phenotypic variations). As a result, screening of varieties for phenotypic to TC is recommended to make grower aware of expected changes in the phenotype. This should mitigate the risks of possible poor adoption of varieties based on thin stalks. It is recommended that TC plants be propagated using wider (50 cm) plant spacings, as this is more economical. The lack of differences between in vitro procedures suggests that propagation of new genotypes through standard NovaCane® procedures for commercial release should continue. The seedcane derived from the TC at stage 1 can be used as planting materials for commercial production without any negative effects on productivity in subsequent propagation stages. This is despite persistence of the reduce stalk diameter, higher stalk population phenotype. Lack of differences between the higher and the lower planting rates of TC-derived crops suggests that lower planting rates should be used for economic reasons.
Agronomic performance of wild mustard in an intercropping with green beans.
(2005) Phiri, Nathan.; Modi, Albert Thembinkosi.
Wild mustard (Brassica spp.) is used as an edible wild leafy vegetable by indigenous people in South Africa. The potential of wild leafy vegetables in agriculture is not well understood, because there is generally no agronomic research on their production practices. The objective of this study was to examine the performance of three wild mustard species (herein referred to as I, K and M) over four cropping seasons in an intercropping system with green beans (Phaseolus vulgaris L. cv. Imbali). The crops were grown with and without organic fertiliser under dryland conditions at two sites (The University of KwaZulu-Natal Research Farm, Ukulinga and in a rural area of Umbumbulu, KwaZulu-Natal within the farmers' locality) during autumn, winter, spring and summer of 2004 to 2005. Plant development (leaf number, plant height and fresh biomass) during the first six weeks after sowing and seed yield were used to determine agronomic performance of each species. Nutrient status of the rhizosphere soil was determined at 42 days after sowing for each species to determine what effect growing the species would have on mineral availability. Wild mustard production significantly (P < 0.01) performed better at Ukulinga than Umbumbulu. Polyculture was beneficial for wild mustard leaf accumulation and green bean production as determined by land equivalent ratios greater than one for all species combinations, regardless of fertiliser application. Cool environmental conditions occurring in autumn and spring were more favourable (P < 0.05) for wild mustard and green bean biomass accumulation than summer and winter conditions. However, wild mustard seed yield was highest in winter compared with autumn and spring, and there was no measurable seed production in summer. Soil analysis results at 42 days after sowing showed an increase in P, K, Cu and Mg in the rhizosphere of wild mustard without organic fertiliser. Polyculture improved Zn, Cu, Mn and K in wild mustard leaf tissue. It is concluded that wild mustard can be grown as a leafy vegetable throughout the year, but it requires cool environmental conditions to enhance seed yield. Species M significantly yielded better biomass and seeds than species I and K during all the seasons. However, species K performed the least in all aspects.
Alleviation of cotyledonal cracking in green beans (Phaseolus vulgaris L.) by calcium seed treatment.
(2003) Mazibuko, Tholakele Gladness.; Modi, Albert Thembinkosi.
Cotyledonal cracking is a physiological disorder of common beans, and rarely, soybeans that occurs as transverse fissures across the cotyledons. The phenomenon is generally referred to as transverse cotyledonal cracking (TVC). Although TVC has been known for decades now, factors contributing to its occurrence, and how the disorder can be alleviated, are still not well understood. The objective of this study was to investigate the effect calcium seed treatment on cotyledonal cracking in green bean (Phaseolus vulgaris L.) seeds. Six cultivars (Imbali, Sodwana, Outeniqua, Elangeni, Tokai and Tongati) were examined for water absorption patterns during a 6-h imbibition in distilled water. Cultivars were categorised according to the rates of water absorption, in the presence of seed coat, and there was a significant correlation between seed size and water absorption rate. To examine seed predisposition to TVC, seeds were imbibed with and without seed coats and TVC was scored every hour for the 6-h duration of imbibition. There was a significant positive correlation between water absorption rate and TVC. Genetic analysis of the cultivars using SDS-PAGE revealed that there are possible differences between the resistant cultivars and sensitive cultivars, with respect to protein patterns. Imbali, one of the small cultivars (-1.5 g seed -1) that imbibed water uniformly, was resistant to cotyledonal cracking compared to the largest cultivar (Sodwana -2.5 g seed -1), which also had a high rate of water absorption. Priming seeds with calcium (CaS04, Ca(N03)2 and CaCl2) osmolarities (0, 1, 10, 50, 100, and 100 mM) increased seed calcium content and reduced susceptibility to TVC. Comparison of priming and seed coating with respect to field emergence, TVC, stand establishment and seed yield showed that coating was better than priming. However, greenhouse studies showed that the effect of priming in the progeny of treated seeds was significantly better than that of coating, with respect to TVC reduction. In both laboratory and field studies, it was clear that applying calcium concentrations greater than 50 mM was not necessary to alleviate TVC and improve seed performance. Seed germination and emergence were reduced at calcium concentrations greater than 50 mM. It is concluded that calcium is effective in controlling TVC under both laboratory and field conditions. The effect of calcium is associated with regulation of imbibition and improvement of seed calcium content. Enhanced seed calcium content likely improved cell wall integrity.
Application and evaluation of aquacrop, dssat and simple model in modelling yield water use of selected underutilised cereal crops.
(2021) Nzimande, Thembelihle Nkosingiphile Millicent.; Mabhaudhi, Tafadzwanashe.; Chimonyo, Vimbayi Grace Petrova.
The study compared yield, biomass, and water use (WU) for maize, sorghum, and millet simulated using three crop models of varying complexity: AquaCrop, DSSAT and the SIMPLE model. The hypothesis was that there is no significant difference between simple and complex models of estimating yield, biomass and WU. A standard set of crop parameters was used to develop crop files for all three models. Similar soil, climate and management descriptions attained from the Ukulinga Research Farm were used across the models. Six general circulation models (GCMs) were used as climate input data to model past, present, mid-, and late-century climate change impacts on cereal crops. The effect of irrigation (as a management practice) on yield and water use was assessed using the mid-century projections. The performance of the three models was observed to be statistically different. Based on the mean bias error, all models overestimated yield, but the lowest overestimation was with AquaCrop (0.22 t/ha) followed by DSSAT (0.24 t/ha) and the SIMPLE model (0.69 t/ha). Other statistical indicators, viz., RMSE and R2, illustrate that the simulation of yield and WP in AquaCrop was more satisfactory than DSSAT and the SIMPLE model. Across all the time scales, it was observed that AquaCrop simulated the highest yield and biomass, and the SIMPLE model simulated the lowest yield across the GCMs, which were inconsistent. Applying a higher amount of irrigation at more frequent intervals resulted in higher yield, biomass and WP. AquaCrop showed the highest simulated mean yield for maize (8.34 t/ha), millet (6.86 t/ha) and sorghum (5.28 t/ha). Highest WP was observed under AquaCrop for maize (21 kg/ha/mm) and millet (15.10 kg/ha/mm), the SIMPLE model for sorghum (13.37 kg/ha/mm). The study confirms that DSSAT requires relatively more input data but does not always perform more satisfactorily. The SIMPLE model requires fewer input requirements than AquaCrop and DSSAT; however, it is less sensitive to management changes. AquaCrop had relatively incomparable results to DSSAT and the SIMPLE model and was observed as the most suitable model for simulating yield, biomass, and WU of the selected cereal NUS under climate change and irrigation management scenarios. Before their application, it is essential to calibrate crop growth parameters for local conditions or use parameters from local field studies when applying complex crop models such as DSSAT specifically for marginal environments, such as South Africa. On the other hand, AquaCrop performed reasonably well with minimal input requirements, confirming its application in datalimited and marginal environments. However, it is recommended that there must be calibration for all the models using inputs specific to locations.
Artificial soil profile for vegetable production: a potential case of urban agriculture.
(2020) Phungula, Nosipho Precious.; Modi, Albert Thembinkosi.
A significantly large population of South Africa migrates from rural to urban areas, leaving opportunities for small-scale subsistence agriculture for a perceived better livelihood. Food insecurity and poverty seem to increase in the peri-urban areas because of poor opportunities for food production and the inescapable need for money to survive. The advantages of urban farming have been published in the literature for many years, but there are still opportunities to introduce innovative methods that are confirmed by scientific findings. This study aimed to determine the efficiency of portable bags and artificial soil profiles on year-round production of common vegetables in South Africa, namely, Swiss chard, lettuce, onion, beetroot, and green pepper. Artificial soil profiles were created in the bags using commonly found urban homestead common organic garden refuse (grass and wood) garden soil and collected rock, respectively. One vegetable, lettuce was used to represent fertilizer requirements and three recommendations (0, 50, and 100%) were applied. Measured crop growth parameters included plant height, leaf number, stomatal conductance, chlorophyll content index, leaf area index, and photosynthetically active radiation. Soil moisture content, soil water potential, and soil temperature were also determined. Crop biomass yield and mineral content at harvest were also determined. The artificial environment was compared with soil plot environment (sandy loam soil with 110 mm depth) under rainfed conditions, with limited supplemental irrigation during dry periods. Results showed that vegetable production is possible all year round in both artificial and real profile conditions. The vegetable yield was reduced in non-soil artificial profiles, but the fertilizer application supported it all year round. Vegetable nutritional value, in terms of selected minerals, differed significantly between seasons and less between normal and artificial profiles, where even no fertilizer application produced yield all year round. The study concludes that disposable bags have a potential role for vegetable production in urban areas, where land area is limited. Potential food security benefits are linked more to nutrient access than quantity access. There is a need to test the findings of the study a different environmental and socio-economic conditions, to influence government policy. Keywords: artificial soil profile, fertilizer, season, temperature, vegetable nutrient content.
Assessing nutritional water productivity of selected African leafy vegetables using the agricultural production systems simulator model.
(2020) Kunene, Thobeka Gladness.; Modi, Albert Thembinkosi.
Food and nutrition insecurities are regarded as one of the main challenges in the Sub-Saharan region. While substantial progress has been made to address food and nutrition challenges, this progress has varied across the region and over time in response to climate change hazards. Agriculture has been used as the main driver to improve food and nutrition security; however, productivity in these marginalised communities remains low. African leafy vegetables (ALVs) provide an unprecedented opportunity to ensure food security, lessen poverty and diversify farming systems while improving human health and increasing income. Crop modelling can generate information about the crop's growth, development, water, and nutritional needs. The primary objectives of this study were (i) to assess the growth and productivity of selected ALVs (amaranth (Amaranth spp), cowpea (Vigna unguiculata), sweet potato (Ipomoea batatas) and wild mustard (Sinapis arvensis)) under different management practices, and (ii) assess water productivity (WP) and nutritional water productivity (NWP) of the selected ALVs. Desktopbased research was conducted to achieve the mentioned objectives. Here, information on the studied crops' agronomy secondary data was gathered through a careful literature search. This secondary information was then used to model growth and productivity and quantify nutritional water productivity at different management practices. The Agricultural Production Systems Simulator (APSIM) was used to simulate growth and productivities under different management scenarios of planting date, plant density, fertiliser application and irrigation. We used the soil and climatic data from the University of KwaZulu-Natal's research farm (Ukulinga Research Farm) situated in Pietermaritzburg, South Africa (29°37′S; 30°16′E; 775 m a.s.l.), to calibrate the model. All data analysis was done using descriptive statistical analysis (R software). All mean values were subjected to a t-test set at p<0.05 significance. The results showed that depending on crop species. Different management practices can be relevant to achieve optimum growth and productivity for various purposes. The investigated ALVs were found to have high nutrient content. Compared to one another, amaranth was more nutrient-dense and wild mustard the least dense crop. On the other hand, NWP was comparatively high on both amaranth and cowpea.
Assessing the effect of crop intensification in improving aricultural productivity in smallholder farmers' fields : a case study of northern KwaZulu-Natal, South Africa.
(2017) Mthembu, Hloniphile.; Odindo, Alfred Oduor.
Crop intensification is adopted by different countries to address their challenges, which may include low standards of food and nutrition security, limited arable land and land degradation. To assess the effect of crop intensification in improving agricultural productivity in smallholder farmers in Northern KwaZulu-Natal, a qualitative study and in-field experiment were conducted. In a qualitative study the Participatory Rural Appraisal (PRA) tools namely, focus group discussions, transect walks and key informant interviews was used. A random purposive sample of 249 smallholder farmers from 5 local municipalities of uMkhanyakude district was undertaken. The following information was explored: different farming systems; landscape; availability of irrigation systems or water sources; classification of farming soil types; perception of soil fertility; planting and rainfall patterns. Smallholder farmers’ demographics, socio-economic status, typical farming systems, differences between backyard gardens and crop fields, water sources, knowledge and skills on farming systems and practices, understanding and benefits of mixed farming, crop mixing and intercropping, soil fertility and soil acidity management were also explored. The findings of the study revealed that the age of the smallholder farmers ranged between 40-65 years. About 90% of the smallholder farmers who participated in this study were females. 45% of smallholder farmers’ households are headed by females. A typical household of the smallholder farmers, is characterised by more than two dwelling places in one household compound with mixed farming. Water is a serious problem in uMkhanyakude district. 70% of the farmers primarily used indigenous knowledge and acquired their skills on farming systems and practises from generation to generation indigenous knowledge system. In-field experiment was conducted. It was laid out in a randomized complete block design (RCBD) with three replicates having a net plot size of 3.6m x 5m. The following treatments were evaluated: Maize intercropped with beans (T1), Maize intercropped with pumpkins (T2), Maize intercropped with beans and pumpkins (T3), Maize sole crop control (T4), Beans sole crop control (T5), Pumpkins sole crop control (T6) and Bean intercropped with pumpkins (T7). Productivity was measured using the following indices: Land Equivalent Ratio (LER), Area Time Equivalent Ratio (ATER), Competition Ratio (CR), Relative Crowding Coefficient (K) and Aggressivity (A), Actual Yield Lost (AYL), Intercropping Advantage (IA) and Monetary Advantage Index (MAI). The study revealed that the intercropping system with three crop species in all three location showed greater values of LER (1.8, 1.9, and 1.7) and ATER (1.8, 1.9, 1.7). The crowding coefficient (K) was the highest in Mtubatuba and Hluhluwe treatment 3 (maize/bean/pumpkin) (80.72 and 61.78) respectively. Intercrops showed positive Agressivity, and greater competition ratio and actual yield loss when compared with the main crops. Intercropping advantage (IA) and monetary advantage (MAI) in treatment 3 (maize/bean/pumpkin in all locations showed greater values (58327, 12850, 5532) and (54573, 59487, 19606) respectively. The productivity of the intercropping system where there are more than two crops is considered greater in terms of land equivalent ratio (LER), area time equivalent ratio, (ATER).
Assessing the fertiliser value of co-composted biochar compost made from black soldier fly larvae faecal residue.
(2021) Nkomo, Nqobile.; Odindo, Alfred Oduor.; Missengue, Roland.
The Black Soldier Fly Larvae (BSFL) technology can treat faecal sludge emptied from full Urine Diverting Dry Toilets (UDDT’s). A residue containing residual mineral elements such as nitrogen (N), phosphorus (P), potassium (K), and high organic matter, pathogens, and potentially heavy metals is left behind. Improper disposal of the residue can pose a challenge and lead to environmental pollution and health threats. However, there is potential for recycling BSFL Residue. The fertiliser value of BSFL Residue as an organic fertiliser has not been studied in South Africa. This study was carried out to evaluate the use of co-composted biochar compost made from BSFL Residue as a plant nutrient source for maize production. The residue was pyrolysed for 120, 90, and 60 minutes at 300 °C, for 60 and 45 minutes at 400 °C, and 60, 45, and 30 minutes at 500 °C. Biochar pyrolysed at 300,400, and 500 °C for 60, 45, and 30 minutes, respectively, was not burned and was analysed for physico-chemical, and biological characteristics. Biochar yield decreased significantly with increasing pyrolysis temperature. Surface area, pH, extractable phosphorus (P), exchangeable bases, trace metals significantly increased with pyrolysis temperature. Pathogens were destroyed with pyrolysis. Biochar pyrolysed at 500 °C for 30 minutes was chosen based on its characteristics as a bulking agent in the co-composting experiment. Co-composting of the residue was carried out, and chemical and physical characteristics of BSFL Residue composts (COMBI (compost with biochar) and (COMP (compost without biochar)) were compared to chicken manure (CM) and BSFL Heated Residue (HR). pH and exchangeable bases in BSFL Residue COMBI were higher than BSFL Residue Compost but less than BSFL HR and CM. Composting with biochar significantly increased trace elements, water holding capacity, total P, and total N in the BSFL Residue COMBI compared to BSFL Residue Compost. The BSFL Residue COMBI, BSFL Residue COMP, BSFL Residue, HR, CM, Chemical Commercial Fertiliser (CCF), and control were incubated in a sandy Cartref soil over a 112-day incubation period to determine phosphorus and nitrogen release patterns. Phosphorus decreased in all treatments during the first 21 days except for the control. Phosphorus release started after day 21, and the pattern for BSFL Residue COMBI and BSFL residue Compost were comparable, indicating the potential of using these amendments for crop production. Chicken manure had the least phosphorus released at the end of the incubation. Ammonium decreased with a concomitant increase in nitrates for all treatments. Nitrate release was lower for BSFL Residue COMBI compared to BSFL Residue Compost. An additional source of N is needed if BSFL Residue COMBI is to be used as a fertiliser based on P. The highest nitrate release was observed in CM. Amendments used in the incubation were used at the recommended and double recommended application rate to grow maize in a greenhouse pot trial. Statistically similar yields were obtained in grain harvested from COMBI, COMP CCF, and CM. More researchshould be carried out on the residual effect of BSFL COMBI on subsequent maize growth to establish possible residual fertility on the second cycle of growth. Keywords: biochar; biochar co-compost; black soldier fly larvae;faecal matter; fertiliser-value; nutrient recycling; phosphorus; pyrolysis; crop growth.
Assessing the potential use of struvite and effluent from decentralized wastewater treatment systems (dewats) as plant nutrient sources for early maize ( zea mays) growth.
(2021) Sokhela, Fortunate Sthabile.; Odindo, Alfred Oduor.; Muchaonyerwa, Pardon.
The Decentralised Wastewater Treatment System (DEWATS) effluent has been shown to contain considerable concentrations of mineral elements such as nitrogen (N) and phosphorus (P), which are important for plant growth. The use of effluent for agriculture as a sole nutrient source is limiting in terms of macronutrient and micronutrient content supplied to plants. There is little information about the effects of combining the effluent with struvite and commercial fertilizer for crop production. The study aimed to determine the effect of applying struvite and DEWATS effluent as nutrient sources combined or in combination with urea/single superphosphate (SSP) fertilizers on the growth, nutrient uptake, and biomass production of maize. The specific objectives were: (1) to determine N and P release pattern of struvite when applied solely or combined with urea relative to SSP fertilizers combined with urea in a sandy soil, (2) to determine N and P release pattern of DEWATS effluent applied solely or combined with struvite and or SSP fertilizers in a sandy soil, (3) to investigate the effect of applying struvite and DEWATS effluent as nutrient sources combined together or with urea/SSP fertilizers on the growth, nutrient uptake and biomass production of maize. Two soil incubation experiments were set up under controlled room temperature at 25oC and 80% atmospheric humidity to determine the N and P release pattern of human excreta derived materials (HEDMs) (struvite and DEWATS effluent) with supplementary chemical fertilisers urea and SSP. The first experiment was laid out as a single factor analysis with the following treatments: (i) struvite alone, (ii) urea alone, (iii) SSP alone, (iv) struvite + urea, (v) SSP + urea. Each treatment was replicated 3 times to give 15 experimental units (in 5 litre ventilated containers). The second experiment was also laid out as a single factor comprising the following treatments: (i) effluent alone, (ii) struvite + effluent, (iii) effluent + SSP, and (iv) a control, all replicated 3 times to give 12 experimental units (in 5 litre ventilated containers). The fertiliser materials were applied to achieve an equivalent of 200 kg N/ha and 60 kg P/ha to meet maize nutrient requirements from the Cartref (sandy soil). The effluent in the study was applied as an irrigation source to achieve a 100% soil water holding capacity while supplying nutrients at the same time. Data was collected on the ammonium N, nitrate N, and extractable P release weekly, for 56 days. A pot trial was set up in 20 litre pots in the tunnel at 26oC air temperature and 65% atmospheric humidity to determine the effect of applying struvite and treated effluent from the anaerobic filters (AF) on growth, nutrient uptake, and biomass production of maize. The pot experiment was set up as a 9 x 2 factorial experiment in a completely randomised design (CRD) with the following treatments: fertilizer combinations (8 levels- (i) struvite + urea (recommended rates); (ii) ) struvite + urea (half recommended), (iii) struvite + effluent (recommended rates); (iv) struvite + effluent (half recommended); (v) SSP + effluent (recommended rates); (vi) SSP + effluent (half recommended); (vii) SSP + urea (recommended rates); (viii) SSP + urea (half recommended) and the control. The second treatment was maize variety with 2 levels –‘Colorado’ and ‘IMAS’. The treatments were replicated three times. Three maize seeds were planted per pot and were thinned 3 weeks after planting to one plant per pot. The amount of water applied as irrigation was based on Cartref soil water requirements. Soil moisture was maintained at 70-100% field capacity. The soil incubation experiment showed that there were significant (P<0.05) differences among treatments- struvite (S), effluent (E), SSP (P), urea (U), struvite + urea (SU), struvite + effluent (SE), effluent + SSP (PE), SSP + urea (PU) and zero fertilizer. The combination of HEDMs and commercial nutrient sources released higher ammonium-N and nitrate-N than sole applications and when commercial SSP + urea was applied together. Ammonium N declined over time and nitrate N increased rapidly over time. The findings suggested that the fertiliser combination of HEDMs and commercial fertiliser increased nutrient N availability to the soil. Phosphorus did not change over time in all treatments. The pot experiment result showed that there were significant (P<0.05) differences observed in plant height, leaf number, chlorophyll content, dry matter, N and P uptake, and grain + cob yields among the different fertiliser combinations (SE, SU, PE, PU) at both recommended and half recommended application rates. In conclusion, optimising N and P supply through a combination of the effluent and struvite or with inorganic fertilisers could potentially be considered as a better option for providing a balanced supply of nutrients than when applied separately.
Assessment of bambara groundnut (vigna subterranean L. verdc) recombinant inbred lines (rils) for agro-morphological traits, cooking quality properties and nutritional composition.
(2022) Ruzive, Amanda.; Mabhaudhi, Tafadzwanashe.; Shayanowako, Admire Isaac Tichafa.; Govender, Laurencia.
Bambara groundnut response to controlled environment and planting date associated water stress.
(2011) Sinefu, Fikile.; Modi, Albert Thembinkosi.
Bambara groundnut is a protein-rich legume, with food security potential in drought-prone regions. It has been grown for many centuries and has remained an important crop to most African subsistence farmers. However, despite its high nutritional status and yield advantages in poor soils, it remains one of the neglected crops by science. There have now been recent efforts to study underutilised crops, with the aim of promoting them as healthy alternatives for people facing resource and environmental challenges and to contribute to food security. In order to do this, there needs to be information that can be used to advise farmers on the agronomic aspects of producing the crop. The overall aim of the study was to evaluate the response of bambara groundnut landraces to drought under controlled environment and field conditions. Seeds were initially collected from subsistence farmers in Jozini, KwaZulu-Natal, and characterised into three seed lots distinguished by seed coat colour: red, white and brown. In the initial study (Chapter 2) seed quality of bambara groundnuts was evaluated. Seed lots were used for standard germination (SG) and cold test (CT). Seeds were germinated under two conditions, 25°C for 8 days (SG) and 4°C for 7 days followed by 8 days at 25°C (CT). Germination percentage, seedling size and mass were determined. Desiccation tolerance was evaluated by suspending 30 seeds of each seed lot over saturated salt solutions of NaCl, LiCl, KNO3 and H2O (control) for 0, 2, 4, 8, 24 and 48 hours. Five seeds were sampled at each interval and stored at -21°C for 7 days. Samples were ground and analysed for proline content. In addition, early establishment performance of bambara groundnut was evaluated under controlled environment conditions in seedling trays using two water regimes (Chapter 2). The experimental design had three factors: seed lot (colour), priming (NaCl, LiCl, KNO3, H2O and control) and water regimes [25% and 75% Field Capacity (F.C.)]. The experiment was replicated three times. Seedling emergence was determined daily for 21 days. Seedling height and leaf number were determined weekly for three weeks, thereafter, seedling leaf area, root and shoot mass (fresh and dry), root and shoot lengths and root to shoot ratio were also determined. Seedlings were later transplanted in 90 pots for a pot trial in order to evaluate growth responses of bambara groundnut to water stress; plant height, leaf number and yield components were determined (Chapter 3). Lastly, the use of planting date selection as a management strategy for managing the occurrence of water stress under field conditions was evaluated in field trials. The experimental design was a split-split-plot design with planting date as main factor (early, optimum and late), irrigation and rainfed as sub-main factor, and seed colour as sub-plots (brown, red and white) arranged in a randomised complete block design (RCBD), with three replications. There were three planting dates: 7 September (early planting), 24 November (optimum planting) and 19 January (late planting). Results from Chapter 2 showed that the brown seed lot had the highest germination across treatments, followed by red and white seeds, respectively. There were significant differences between seed lots (P < 0.05) and salt solutions (P < 0.05) with respect to proline content. Seed proline content increased from 0 to 8 hours and later declined; NaCl was associated with the highest proline accumulation. There were highly significant differences (P < 0.001) between seed colours, priming treatments and F.C., as well as their interaction, with respect to seedling emergence. White seeds had the highest emergence, followed by brown and red, respectively. Priming seeds improved their emergence compared to the control, with highest emergence being observed in seeds treated with LiCl. Priming also improved emergence under water stress; 25% F.C. had the highest emergence compared to 75% F.C. Results from Chapter 3 showed that, seeds primed with NaCl and KNO3 resulted in tallest plants with the highest number of leaves per plant. However, NaCl and KNO3 were also the most affected under water stress. Priming was shown to improve germination and early crop establishment of bambara groundnut landraces under water stress. However, yield per plant did not improve in response to either halo- or hydro-priming. Results from field trials showed that in terms of the measured plant growth parameters (plant height, leaf number and LAI), bambara groundnut landraces were sensitive water stress. Water stress decreased yield components, and hence yield. However, selection of planting dates was shown to be a useful management tool for managing water stress under water limited field conditions. Choice of planting date significantly affected both plant growth and yield. The optimum planting date resulted in the best crop growth for all measured plant growth parameters followed by late and early planting dates, respectively. Seed quality was shown to be associated with seed lot colour. Darker coloured (red and brown) seeds performed better than light (white) seeds with respect to germination. Priming was also shown to improve germination and early crop establishment of bambara groundnut landraces under water stress. However, yield per plant did not improve following priming. Growth of bambara groundnut landraces was shown to be sensitive to water stress. Water stress decreased yield components and hence yield under both controlled and field conditions. Choice of planting date significantly affected both plant growth and yield. The optimum planting date was shown to be the best performing planting date. The findings of this study suggest that bambara groundnut seed performance in terms of germination, stand establishment and productivity is associated with seed lot colour. Seed priming improves seed performance and enhances crop capacity to withstand water stress. If the optimum planting date for groundnuts (late spring to early summer) is missed, better crop performance and yield are obtained from late planting (late summer to early spring) compared with early planting (early spring). Bambara groundnut has a potential for production under water stress conditions in controlled and field environments.
Chemical mutagenesis of wheat for herbicide resistance.
(2012) Ndou, Vuledzani Nico.; Shimelis, Hussein Ali.; Odindo, Alfred Oduor.
Weed infestation is one of the yield limiting factors in crop production. Weeds have negative effect on crop growth and productivity due to competition, allelopathy or hosting other harmful organisms. For large-scale wheat production, the use of wide spectrum pre-emergence or post-emergence herbicides remains the most valuable weed control tool. In South Africa, annual grass weeds are a major wheat production constraint, which is usually managed through application of pre-emergence herbicides. Due to limited water availability and low soil moisture content, these herbicides can often become ineffective and result into high weed infestations, which then have to be managed by manual cultivation or post-emergence herbicidal applications. However, there are no effective selective post-emergence herbicides available to control grass weeds in wheat. There is also limited option to use broad-spectrum post-emergent herbicides because they non-selectively kill the crop and weeds. Consequently, the use of herbicide resistant crops is a viable weed management system in wheat production. Breeding herbicide resistant crop varieties would allow farmers to safely use post-emergence herbicides without damaging the crop. Subsequently yield and quality losses will be reduced significantly. Thus, the development of herbicide resistant crop varieties through mutation breeding is a novel approach for effective weed management under both small-scale and commercial farmers. Mutagenesis has been recognized as one of the most efficient method to induce genetic variation in plants. Through induced mutations, development of new variants is possible that could be manipulated in plant breeding programs. Mutation leads to alteration of various traits in crop plants including plant height, improved nutritional quality, shorter growing period, increased tolerance or resistance to abiotic and biotic stresses. Ethylmethanesulphonate (EMS) is one of the most widely used chemical mutagens to induce mutagenesis in crop plants. The objectives of this study were to: 1) determine the optimum EMS concentration, treatment temperature and duration that would provide desired germination percentage and vigorous and healthy seedlings for effective mutagenesis in wheat, 2) investigate variations in agro-morphological traits in two selected wheat varieties (SST56 and SST875) after EMS mutagenesis and 3) select herbicide resistant wheat germplasm after inducing genetic variation using EMS using two selected wheat varieties (SST56 and SST875). The objectives were achieved through three independent studies as outlined below: In the first study seeds of four selected wheat varieties (B936, B966, SST387 and SST875) were treated in two replicates with three EMS concentrations (0.3, 0.5, and 0.7%), three temperature regimes (30, 32.5 and 35 °C) at four time durations (0.5, 1, 1.5 and 2 hrs). Results showed highly significant interactions (P<0.01) among varieties, EMS concentrations, temperature and exposure time on seedling emergence, germination and seedling height. Seeds treated with the highest EMS dose (0.7%), temperature (35ºC) and long exposure time (2 hr) showed delayed emergence by 18 days. At 30ºC, 0.5hr and 0.3% EMS varieties B936, B966 and SST875 had early emergence (6 days). B936 and SST387 had 50% while B966 and SST875 had 53% and 57% germination, respectively. These results were observed at EMS level of 0.7%, 300C and 1.5 hr exposure time in B936 and EMS at 0.5%, 350C and 1.5 hr in B966. SST387 and SST875 required EMS dose at 0.5%, 32.50C and 2 hr treatment time. Other low or high treatment combinations were invariably ineffective comparedto untreated control. During the second study two selected varieties (SST56 and SST875) were subjected to EMS mutagenesis using 0.5% v/v EMS at 32.5oC for 1 hr. Field trials were carried out at Ukulinga research farm of the University of KwaZulu-Natal in the randomized complete block design with two replicates. Data on nine important agro-morphological traits were collected and analyzed using the analysis of variance (ANOVA), correlation and principal component analysis (PCA) procedures. Significant variations were found among the agro-morphological traits between M1 individuals compared to untreated checks. The mutagenesis significantly reduced seed germination in the field at 40% in both varieties. The treatment significantly delayed days to heading by 8 days and shortened days to maturity by 13 days in both varieties. EMS treatment also significantly reduced plant height at 18 cm in SST56 and 21 cm in SST875 and spike length reduced by ~2.5 cm in both varieties. Plant height had positive and significant correlation with number of tillers, number of seeds per spike, flag leaf length and 100 seed weight. However, it had negative correlation with the number of days to maturity. The PCA revealed that three principal components (PC1, PC2 and PC3) accounted to 57% of the total variations among the agro-morphological traits in both varieties. PC1 alone contributed to 27.7% of the variation which was well-correlated with plant height (0.767), tiller number (0.812), number of seeds per spike (0.599) and seed yield (0.720). PC2 explained 15.6% of the variation and well-correlated with germination percentage (0.784), spike length (0.554) and flag leaf length (0.772). PC3 accounted to 12.4% of the variation and had negative correlation with days to maturity (-0.730). In the last study, seeds of two selected wheat varieties (SST56 and SST875) were treated with EMS at 0.5% concentration for 2 hr at 32.5ºC. Treated seeds and comparative controls were planted at the experimental farm of the University of KwaZulu-Natal using the randomized complete block design. Four weeks after planting M1 plants and untreated standard checks were sprayed with two herbicides, i.e. metsulfuron-methyl and bromoxynil at three different doses viz. 2x, 4x and 8x above the recommended rate of 4 g ha-1 and 2 kg ha-1, respectively. Two weeks after the treatment herbicide resistance were assessed. Results showed significant difference among varieties, tested herbicides and doses used. The EMS treated wheat lines showed variable degree of herbicide resistance compared to untreated controls. Overall, the study established the requirement of variety specific EMS dose and treatment temperature and duration that could be used for inducing large-scale mutation to select targeted mutant individuals in wheat. Further, the study found that EMS has the potential to increase agro-morphological variations in wheat to select useful and novel mutants with desired phenotypic traits and herbicide resistance which will be subjected for further selections to identify stable and herbicide resistance lines.
Closure of the Umlazi landfill : meeting statutory requirements for engineering and plant cover.
(2008) Mannie, Neeraj Mannie.
This study investigated the establishment of vegetation cover planted in plug and seedling form in the closure phases of the Umlazi Landfill. It also investigated the various facets of the closure process of the Umlazi Landfill and the effect these have on the establishment and choice of vegetative cover, and the grass technology used to make the establishment of vegetation a success. The setting up of trials and the gathering of basic data were undertaken to assess the alternative vegetation options available to researchers. The cover provided by the grasses was assessed in the investigation. The capping of landfill sites is a relatively new approach and it is soon to become a mandatory requirement by the Department of Water Affairs and Forestry (Minimum Requirements for Waste Disposal) (DWAF, 1998). This systematic investigation used in the closure of the Umlazi Landfill, will provide a model for the capping of landfills in South Africa. Seeing that this was the first hazardous (H:h) landfill site in the country to be closed according to the Minimum Requirements for Waste Disposal (DWAF, 1998), every attempt was made to ensure that all aspects in the closure of the site met with the Minimum Requirements. The Minimum Requirements document mentions only briefly that the landfill must be vegetated with some grass type. Prior to 1994, capped landfill sites were usually planted with traditional grass seed mixes and these were not widely successful, as seen on many older landfills that have been partially or completely capped, and where vegetation cover is sparse. There is much literature in the developed countries on the closure of landfills (e.g., Erickson, During the site inspections in June 2001 and February 2002, it was noted that many species of alien plants had established themselves in the poor soil conditions. This made it even more important to find indigenous vegetation to vigorously establish itself that would prevent the establishment of alien invaders. Samples of grass species established on some part of the site were also taken for identification. The dominant grass was identified as Cynodon dactylon. In view of establishing a balanced vegetative cover on top of the Umlazi Landfill, Acacia karoo trees (in seedling form) were also planted. Three bunch grass species, Melinis nerviglumis, Melinis minutiflora and Hyparrhenia hirta, were tested to see if thatching grass could be grown on the site to generate a cash crop for local residents of Umlazi township. Preparation and planting of the capped areas took place in the latter part of 2003 and were completed in early 2004. Measurements and field data were recorded and statistically analysed. The trials revealed three key findings: Firstly, both creeping grasses studied, namely Cynodon dactylon var. “Sea Green” and Panicum natalense var. ”Natal Buffalo Grass” grew well on the site. Initially P. natalense grew faster but after a month, C. dactylon overtook it. At the end of the trial (six months, P. natalense provided a higher level of soil cover. However, C. dactylon grew more consistently over this period. Hence both species provided good growth and cover on this site. Secondly the three bunch grasses, Melinis nerviglumis, Melinis minutiflora and Hyparrhenia hirta, all grew well and had similar survival rates. Hence the potential for growing these grasses as a cash crop has potential. Thirdly, all the Acacia karoo trees survived, i.e., they achieved 100% survival. The average height increase and stem width was similar in all trials and growth was consistent over the six month growing period. Hence the tree species would be a good choice for planting on landfills in its ecologically suitable zones. It is therefore feasible to envisage the planting of a mixture of grasses under the cover of A. karoo trees, to provide a balanced mixture of indigenous grasses to cover a freshly capped landfill. Such a system should provide for stable growth of vegetation for many years.
Comparative responses of fodder and grain teff (Eragrostis tef (Zucc.) Trotter) cultivars to spatial, temporal and nutritional management.
(2002) Kassier, Sigrun Barbara.; Greenfield, Peter L.
Teff has its origin in Ethiopia as grain crop, while in South Africa it is primarily a forage crop for hay and recently as summer grazing pasture. The response of teff herbage and grain production to planting date, growth stage at cutting, seeding rate and N fertilizer application was studied. Previously limited research data were available for teff production in South Africa. Spring plantings (September to October) are required to maximise total herbage yield with 9.40, 8.48 and 7.64 t DM ha -1) recorded for 1996/97, 1997/98 and 1998/99 respectively. Summer plantings (November to December) give maximum herbage yield from the first cut, yielding 4.42, 4.72 and 3.78 t DM ha -1) for 1996/97, 1997/98 and 1998/99 respectively. The exact planting date is season dependent. Temperature and rainfall determine the beginning of the growth season regarding favourable conditions for teff germination and growth. Herbage yield of cut 1 increases with advancement in growth stage at cutting. Cutting at the vegetative and piping stages gives most number of cuts , up to five yielding 7.45 t DM ha -1) (1996) while the full flowering stage gives the least (one or two cuts , 4.75 and 7.72 t DM ha -1 in 1996 and 1997 respectively). Yield is also affected by environmental conditions influencing germination, biomass accummulation and regrowth after cutting and by lodging. A trade-off results between herbage quantity and quality. Yield increases while quality decreases with advancing phenological stage, resulting in reduced digestibilty and CP and increased fibre content. Seeding rate differences were manifested primarily in weed infestation level, which varied between cultivars depending on leafiness and associated sward density. Nitrogen application levels gave maximum response between 75 and 150 kg N ha -1, with some cultivar differences. Split N application according to expected yield distribution related to planting date is recommended. Grain yield response to seeding rate and N fertilization levels could not be established. Heavy grain losses through thunderstorms and wet conditions at grain maturity precluded yield measurements. Teff yield responses are influenced by day length, environmental factors, such as temperature and rainfall. and phenological stage at cutting. These variables influence biomass accumulation and regrowth.
Conserving soil moisture for soybean growth as a climate change adaptation strategy.
(2017) Maphumulo, Nomthandazo.; Modi, Albert Thembinkosi.
Low crop productivity among smallholder farmers in rural areas is mainly associated with low and variable rainfall as well as factors such as soil fertility. Climate change projections show that rainfall is going to become more variable and hence a major constraint to rain-fed rural cropping systems. There is a need to assist farmers in these areas to cope with current challenges and develop long-term adaptation to climate change. Therefore, the aim of this study was to evaluate the use of soil water conservation strategies and nitrogen fixing legumes as part of climate smart agricultural practices. Specifically, the study evaluated the effect of mulching and fertiliser levels on growth and yield of soybean under rain-fed conditions in the Swayimane rural area of KwaZulu-Natal. The experimental design was a split-plot [hay-mulch (HM) and non-mulch (NM)] arranged in randomised complete blocks (0%, 50% and 100% of recommended fertiliser) replicated three times. Data collected included soil water content, plant height, leaf number, leaf area index (LAI), chlorophyll content index (CCI) and stomatal conductance (SC).Yield and yield components were determined at harvest. The results showed that the use of hay-mulch was effective (P<0.05) in retaining soil water in the root zone. Soil water content in the non-mulched plots frequently reached permanent wilting point hence exposing plants to intermittent water stress. However, mulching had no significant effect on plant growth (plant height, LAI) and SC. Highly significant (P<0.01) differences were observed in CCI, with hay-mulch having a higher CCI compared to non-mulch. Interestingly, plants in non-mulched plots had higher (P<0.05) leaf number compared to plants in mulched plots; this was partly due to a fungal disease that affected plants in mulched plots. Consistent with results of growth, there were no differences in yield of soybean plants grown under mulched relative to non-mulched plots. Subsequent to harvesting the soybean, the seeds were subjected to seed quality tests to assess the effect of production environment on seed quality of progeny. Results of seed quality showed highly significant differences (P<0.001) with progeny from non-mulched plots having relatively higher seed quality (germination percentage, mean germination time and germination velocity index). Overall, the study concluded that while mulching was effective in retaining soil water in the root zone, this did not translate to improved growth and yield as well as subsequent seed quality. The lower soil temperatures experienced under mulching may have inadvertently suppressed growth. Further research is still required over several seasons to confirm these findings and develop firm recommendations on the appropriate use of mulch.
Controlled environment determination of nitrogen uptake and its efficient utilisation by selected South African sugarcane varieties.
Makhubedu, Irvin Thabo.; Modi, Albert Thembinkosi.; Patton, Alana B.
Increasing nitrogen use efficiency (NUE) of sugarcane (Saccharum officinarum L.) has a potential of reducing farmers input costs associated with nitrogen (N) fertilizers. Although there is evidence for some genetic variability in NUE of sugarcane in South Africa, plant growth and physiological mechanisms underlying this variability are currently unknown. The study investigated the genetic variation in sugarcane for NUE (N-uptake efficiency; NUpE x N-utilisation efficiency; NUtE) as this could provide a basis for breeding varieties with reduced N demand. The study consisted of two separate successive pot trials at the South African Sugarcane Research Institute (SASRI) under outdoor conditions. A randomised block design preliminary trial (trial 1) was conducted in September 2013 to screen NUtE (biomass production/unit tissue N) of fifteen sugarcane varieties at three destructive (biomass) harvests that were conducted at four month intervals. Plants established from single nodal stem cuttings were, in six replicates, planted into pots that were immersed in metal troughs (5 pots/trough), which contained liquid nutrients (Schumann et al., 1998) with low (14.40 g N/pot) and high (28.80 g N/pot) N supply. In the subsequent trial (trial 2) conducted in November 2014, eight varieties were subjected to four N treatments, a no N (0 g N/pot), low (1.94 g N/pot), medium (5.81 g N/pot) and high (11.61 g N/pot) N, herein referred to as NN, LN, MN and HN, respectively. The trial was arranged in a randomised complete block design (RCBD) design with five replications. Non-destructive measurements (stalk height, stalk population, leaf relative chlorophyll (soil plant analysis development (SPAD) and leaf N, P and K concentration) were conducted at specific time intervals. Destructive measurements (whole plant sampling) were performed at 180 days after transplanting (DAT) to determine, green leaf counts and area (GLA), shoot biomass production, biomass partitioning, root length and NUE. Nitrogen concentration (% [g N/100 g DM]) in the tissue components was determined using the LECO TruSpec N analyser at the Fertilizer Advisory Service at SASRI. The data for trial 1 were not included in the thesis. The results of trial 2 showed that N supply significantly affected stalk height and counts, leaf counts, GLA, leaf SPAD and root length traits hence that varieties also differed significantly with respect to the physiological measurements. Stalk height was significantly enhanced by NN and LN supply whereas stalk counts were similar among the LN, MN and HN treatments. Variety N41 had taller stalks than N12 and N37 whilst the two latter varieties had higher stalk counts than the former. There were significant N level x variety interactions with respect to green leaf counts and GLA but not for SPAD and root length. The LN treatment increased the number of leaves more than the other treatments. Variety N37 and N12 had the highest number of leaves as compared with N32. The GLA and leaf SPAD increased linearly with increasing N supply. Amongst the test varieties, N12 had significantly greater GLA and NCo376, N48 together with N41 had higher leaf SPAD values as compared with other varieties. There was also a significant N level x variety interaction with respect to root fresh biomass and shoot, root and whole-plant dry biomass. Significant increases in shoot and whole-plant dry biomass occurred and plateaued with LN supply. Although N41 ranked the third in terms of root dry biomass, the variety ranked the highest in terms of shoot and whole-plant dry biomass. The NN and LN treated plants allocated greater proportions of biomass to the stalk component, whilst the MN and HN treated plants allocated greater biomass to green leaves. Significant N level x variety interaction was observed for shoot N concentration and N content, NUpE, NUtE and the overall NUE. Shoot N concentration and content of test plants increased linearly with increasing N supply. Contrarily, NUpE, NUtE and NUE decreased with increasing N supply. Overall genetic variability in NUE was greater under LN supply and can be explained mainly by differences in NUtE rather than NUpE. Among the varieties, N41 had the highest NUE when compared with the N37 and NCo376 which ranked the lowest. It is concluded that N supply has a significant effect on sugarcane growth, dry biomass yield and allocation, N allocation and NUE.
Distribution and severity of herbicide resistance in the Republic of South Africa.
(2001) Smit, J. J.
No abstract available.
Dormancy breaking methods and priming techniques to improve seed germination in gynandropsis gynandra (L.) briq syn cleome gynandra L. (Cleomaceae).
(2022) Mangena, Khungeka.; Odindo, Alfred Oduor.
Gynandropsis gynandra, commonly known as spider plant, is a leafy vegetable that belongs to the Cleomaeae family. Spider plant is used for its medicinal properties, but also as a nutritional supplement, and an animal (e.g., cows) feed. Farmers experience low and uneven germination when planting this species that studies ascribed to physiological dormancy which leads to low and uneven germination. The study was conducted to understand mechanisms involved in breaking dormancy in spider plant seeds. The objectives were (a) to determine the effects of packaging materials and storage period on seed germination, and (b) to determine the effects of priming agents and duration on seed germination of G. gynandra. These objectives were achieved through two experiments based on six accessions of G. gynandra originated from West Africa, East Africa, and Asia. In the first experiment, the seeds were stored for four months at room temperature of 25℃ in brown paper bags, aluminium foil paper, and black polystyrene bags. After every storage period, the seeds were tested for electrical conductivity (EC), viability using tetrazolium chloride and germination ability to study the effects of storage period and packaging material on seed viability and vigor of G. gynandra. In the second experiment, the six accessions were subjected to two priming agents, PEG-4000, and distilled water, and tested for germination. Final germination percentage (FGP), mean germination time (MGT), mean germination rate (MGR), coefficient of the velocity of germination (CVG), and radicle length (RL) were recorded. Data analysis was done using Genestat version 20th edition (VSN International, United Kingdom) at a 5% level of significance. The study showed that G. gynandra fresh seeds displayed physiological dormancy which can be broken by storing seeds for at least two months depending on the genotype in aluminium foil paper. In this study, seed priming with PEG-4000 and distilled water had no effect on seed germination of G. gynandra.
Effect of ABR effluent irrigation on Swiss chard (Beta vulgaris subsp. cicla) growth and nutrient leaching.
Musazura, William.; Odindo, Alfred Oduor.; Tesfamariam, Eyob Habte.
The Decentralised Waste Water Treatment System (DEWATS) is used in countries such as India and Indonesia for the treatment of human waste. The waste is passed through a series of baffles where it is anaerobically degraded, resulting in the production of the Anaerobic Baffled Reactor (ABR) effluent. Disposal of the effluent can still pose a challenge if not done properly and lead to environmental pollution. The effluent has been shown to contain high concentrations of mineral elements such as nitrogen and phosphorus, which are important for plant growth. There is little information on the use of effluent for agriculture particularly under the South African climatic and edaphic conditions. This study investigated the effect of using ABR effluent on the nutrient uptake, growth and yield of Swiss chard (Beta vulgaris subsp. cicla) on selected soil types. Field and tunnel experiments were carried out at Newlands Mashu Permaculture Centre in Durban (longitude of 30°57'E and latitude of 29°58'S). The initial experiment planted in the summer season of 2012 was designed to collect baseline data on growth and yield of Swiss chard and other selected crops under rain-fed vs. irrigated conditions using tap water. The treatments were laid out using a randomised complete block design (RCBD) with three replications. The treatments included: tap water irrigation without fertiliser application (TW); tap water irrigation with fertiliser application (TWF) and rain-fed with fertiliser application (RFF). The second experiment was conducted in winter 2012 with the aim of investigating growth and yield of Swiss chard irrigated with ABR effluent during the dry season. In the second study, the treatment “tap water irrigation without fertiliser application” was substituted with irrigation with ABR effluent while the other treatments were maintained. The third experiment was conducted in the summer season of 2013. The treatments remained similar to those of the winter 2012. Soil samples were collected from the top 30 cm before planting and after harvesting for chemical analyses. A neutron probe access tube was also installed in the middle of each plot in order to monitor soil water status and irrigate plots according to the root zone soil water deficit. Wetting Front Detectors (WFDs) were installed at 30 cm and 50 cm depths to monitor nutrient leaching. The leachates collected by WFDs were analysed for nitrates and phosphates using Merck Reflectoquant test kit. Similarly, the ABR was analysed for its chemical composition before each irrigation event. Treatment effect on Swiss chard and soil was tested by analysing fresh crop biomass, dry biomass, chlorophyll content, crop nutrient uptake and soil chemical properties. Parallel studies were conducted in a tunnel to investigate growth and yield response of Swiss chard grown on different soils (acidic, clayey loam and sandy loam soil) treated with varying fertiliser rates. The experiment was laid out as a factorial treatment structure with the following factors: Irrigation source (2 levels); soil type (acidic, clayey loam and sandy loam soil) and fertiliser application rate (No fertiliser, half-optimum recommended rate and optimum recommended rate based on soil analyses) replicated four times. The Swiss chard was grown in the tunnel in pots for 11 weeks. Crop growth and chlorophyll data, similar to that collected from the field was also collected from the pot trials. Data analysis was done using GenStat® 14th Edition (VSN International, Hemel Hempstead, UK). The results from the baseline study (experiment 1) did not reveal significant differences between treatments (TW, TWF and RFF) thus suggesting that the inherent soil fertility was high and could support Swiss chard growth. There were significant differences (P<0.05) between the treatments (ABR, TWF and RFF) during the winter season (experiment 2) with respect to Swiss chard biomass. Swiss chard plants produced under rain-fed conditions had lower dry mass compared with those that were irrigated using ABR effluent and tap water with fertiliser. However, the effect of using ABR effluent on Swiss chard biomass was comparable to tap water with fertiliser because these did not differ significantly. The results from the third experiment showed a lack of significant differences with respect to N and P leaching between the irrigation sources (ABR, TWF and RFF). Controlled experiments in the tunnel revealed a significant interaction between soil type and irrigation source. Swiss chard pots containing acidic soil and irrigated using the effluent showed significantly higher dry mass (P < 0.01), fresh mass (P< 0.05) and leaf area index (P < 0.001) compared to those irrigated with tap water. In conclusion the ABR effluent may have a liming effect which could have possibly increased Swiss chard growth in acidic soil. ABR effluent was more useful as an irrigation source in winter than in summer; however in summer the effluent could be more useful as a fertiliser source in areas where water is not limiting for crop production. N and P leaching and uptake could not be associated with irrigation using ABR effluent.

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