Low maize yields in the midst of abundant arable land, favourable climatic conditions, input and financial support programs, plagues smallholder maize farming in Eastern Cape Province. These scenarios have led the province to be a net importer of maize. In essence, low production may signify a mis-match between maize varieties being promoted amongst smallholder farmers and their farming system. Thus, the main objective of the study was to investigate the productivity and profitability of different maize varieties and cropping system under smallholder agriculture in selected villages of the Eastern Cape Province of South Africa as well as, the implications posed on the household food security. The study sought to assess: (i) the productivity of different maize varieties and cropping systems, (ii) the effect of GM maize adoption on food security among smallholder farmers, (iii) the profitability of GM, conventional hybrids and OPV maize varieties produced by farmers under different agro-ecological conditions and (iv) the impact of different maize varieties and cropping systems on food security in the smallholder agriculture. A cross sectional quantitative-based survey study was carried out to obtain information from a total of 650 small holder farmers. The study was conducted in three local municipalities in Oliver Reginald (OR) Tambo District Municipality of the Eastern Cape Province of South Africa. Descriptive statistics, partial factor productivity, gross margin analysis, household food insecurity access score (HFIAS), ordinal logistic and linear regression were the analytical techniques used in establishing correlations among variables. Results obtained from the survey indicated that under mono-cropping system, Genetically Modified (GM) maize variety was highly productive with an average yield of 1.9 t/ha whilst, improved OPV maize variety was productive (with an average yield of 1.6 t/ha) under mixed cropping system. Furthermore, GM maize (GM = -R418.10), and landrace (GM = -R1 140.29) maize varieties had negative gross margins whilst, conventional hybrids (GM = R5 181.21) and improved OPV (GM = R1 457.41) were profitable. There was a significant and negative correlation between use of GM maize variety and reduction of household food insecurity. GM maize varieties, improved OPV, white maize, white as well as yellow GM maize varieties had a significant impact in reducing household food insecurity; whilst using more than one variety of maize (landraces and GMO) positively influenced household food insecurity. In light of these research findings, it is recommended that, there is need to address household food security by growing improved OPVs under a mixed cropping system and GM maize under monocropping system.

Municipal sewage sludge is used as source of plant nutrients world wide for agriculture. However, many countries do not make full use of this opportunity. A lack of local knowledge about the benefits and disadvantages of sludge contributes to this low utilisation. For instance, only 28% of the sludge produced in South Africa is beneficially utilized on agricultural lands. The overall objectives of this study were 1) to determine responsible sludge loading rates for a range of cropping systems 2) to investigate the agronomic benefits and sustainability of using municipal sludge according to crop N demand, and 3) to develop a tool to enable extrapolation of these results to other regions (soils, climates) and other cropping systems. Field experiments were conducted on a wide range of cropping systems including dryland maize, irrigated maize-oat rotation, dryland pasture, and turfgrass sod production. An 8 Mg ha-1 control (South African old annual upper limit norm) was compared with sludge rates of 0, 4, and 16 Mg ha-1 for the agronomic crops and dryland pasture. Under the turfgrass sod production, the aim was to export large volumes of sludge with the sod without compromising the environment. Therefore, an 8 Mg ha-1 control treatment was compared with sludge rates of 33, 67, and 100 Mg ha-1 which are equivalent to depths of 5, 10, and 15 mm sludge, respectively. Doubling of the old annual upper limit significantly increased grain and forage yield of both the dryland maize and the irrigated maize-oat rotation. This rate also improved weeping lovegrass hay yield, water use efficiency and crude protein content. Residual nitrate in the soil profile after harvest, and solution samples collected from wetting front detectors were used as indicators of groundwater pollution through nitrate leaching in the medium term. For the irrigated maize-oat rotation and dryland pasture, a low leaching risk was indicated even at high sludge loading rates of 16 Mg ha-1 in this clay loam soil. In contrast, residual nitrate for similar sludge rates under dryland maize cropping did reveal the potential for pollution through leaching. Sludge loading at all rates resulted in the accumulation of total P and loading rates of 16 Mg ha-1 increased Bray-1P in all agronomic and pasture cropping systems. In the case of turfgrass for sod production, sludge loading rates up to 67 Mg ha-1 significantly improved turfgrass establishment rate and colour. The ability of sods to remain intact during handling and transportation improved as the sludge loading rate increased to 33 Mg ha-1, but deteriorated at higher rates. A sludge loading rate of 100 Mg ha-1 was needed to eliminate soil loss at harvest, but this rate was associated with unacceptably high N leaching losses and poor sod strength. The variation in sludge quality, crop nutrient removal across a range of cropping systems, and seasons indicates that a dynamic, mechanistic decision support tool is needed to estimate responsible sludge loading rates. A mechanistic N module was adapted and incorporated into an existing soil water balance/crop growth model (SWB). The model was calibrated with statistically acceptable accuracy for dryland maize, irrigated maize-oat rotation, and dryland pasture. The model was tested against independent data sets and was able to predict the measured variables of interest with acceptable accuracy for dryland maize, irrigated maize and oats. For dryland pasture, the model predicted similar variables of interest with lower accuracy for medium-term simulations, but this improved with updating the profile water content after every hay cut. The ideal sludge loading rate to satisfy crop N demand is dynamic and should be adjusted according to cropping systems, seasonal rainfall variability, sludge N concentration, and sludge application strategy (N or P based). The ultimate cumulative sludge loading of an area will depend on the accumulation of total and Bray-1P, and the risk this poses for pollution, as long as the risk from other pollutants remains minimal. The SWB model shows promise as a decision support tool for sludge management in agricultural lands. / Thesis (PhD)--University of Pretoria, 2010. / Plant Production and Soil Science / unrestricted

No description available.

No description available.

M.S.

Doctor of Philosophy / Department of Agronomy / Kraig L. Roozeboom / Previous research has revealed that winter wheat (Triticum aestivum L.) yields are often reduced following grain sorghum [Sorghum bicolor (L.) Moench] compared to wheat after other summer crops. The objectives of the study were to: (a) evaluate grain sorghum residue management strategies to improve the performance of a following winter wheat crop in no-till systems; (b) determine grain sorghum hybrid characteristics that facilitate planting wheat following grain sorghum, and identify winter wheat cultivars that are suitable for planting after grain sorghum; (c) evaluate effect of environment, sampling time, and grain sorghum hybrid plant pigmentation on phenolic acid concentration in sorghum residues. Experiments were conducted in environments suitable for planting winter wheat following a summer crop. Treatments for objective one were: glyphosate (pre-harvest application, post-harvest, none), residue (removed, chopped, left standing), and nitrogen (34 kg ha⁻¹ applied to residue, none). Treatments for objective two and three were grain sorghum hybrids representing three maturities (early, medium, medium-late) and two plant pigmentations (red, tan), wheat cultivars occupying significant planted acreage and having favorable performance within the region. Wheat yields increased in two environments by 217 and 630 kg ha⁻¹ when glyphosate was applied to the sorghum pre-harvest. Residue chopping or removal either had no effect or a negative effect on wheat yields compared to residue left standing. Nitrogen applied to the sorghum residue increased wheat yields in only one environment. Grain sorghum hybrid characteristics did not influence winter wheat yields in any environment, but winter wheat cultivar did influence grain yields of the winter wheat in three of the four environments. Breakdown of phenolic acids depended on environment. Results for these studies indicate that wheat yield after a grain sorghum crop can be maximized by planting a red-pigmented sorghum hybrid of an early or medium maturity, desiccating the sorghum crop with pre-harvest glyphosate if it can be applied to the sorghum roughly 45 to 50 days before a frost, and with a wheat cultivar that is well suited to no-till planting.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

No description available.

An intercropping study was carried out with three legumes (field beans, cowpeas, and soybeans) and three cereals (sorghum, corn, and pearl millet) in all combinations to define the most appropriate intercropping under near optimum irrigation. The sorghum x soybean intercropping was chosen as the most appropriate for the environment.

No description available.