In semiarid regions, rainfall is one of the primary factors affecting soil erosion and crop production under rain-fed agriculture. The study sought to quantify the effect of rainfall characteristics on sheet erosion and maize grain yield under different tillage systems. It was carried out under semiarid conditions and infertile sandy soils of Zimbabwe. Rainfall amount and intensity were recorded every 24 hours, while sheet erosion was measured from four tillage systems (Conventional Tillage (CT), Mulch Ripping (MR), Tied Ridging (TR) and Bare Fallow (BF)). Maize (Zea mays L.) was grown on three tillage systems (CT, MR, and TR). Rainfall amount varied significantly (P<0.001) between seasons (164–994 mm). CT recorded the highest average soil losses (15 t/ha), while MR and TR recorded 1.3 and 1.2 t/ha, respectively. Maize grain yields increased with increasing seasonal rainfall giving yield-responses of 0.9 t/ha (TR) to 1.3 t/ha (MR) for every 100 mm rainfall increment. Overall, treatments didnot differ significantly (P<0.497), except during drier seasons (P<0.025). Regression equations showed that yields can be confidently predicted using rainfall amount and time, withR2values of 0.82 to 0.94. Maize grain yields proved to be mostly dependent on rainfall amount than fertility. The productivity of the soils decreased with increased length of cultivation.
Smallholder farmer productivity in developing countries is limited by diverse biophysical, political and socioeconomic factors. The objective of this study was to establish current agronomic practices of smallholder farmers in semi-arid Lower Gweru and Lupane areas of Zimbabwe and to identify possible research and extension interventions that may improve crop productivity of these farmers. Focus group discussions, interviews and desktop study were used to collect data. Horticultural production is the main livelihood in Lower Gweru, while field crop and livestock production are livelihoods in both areas. Conventional tillage is the predominant tillage system. Important crops include maize (Zea mays L.), pearl millet (Pennisetum glaucum (L) R.Br.), sorghum (Sorghum bicolor L.) and groundnuts (Arachis hypogea L.). Farmers grow both hybrid and open-pollinated maize varieties (OPVs) with more farmers in Lupane than in Lower Gweru, growing these OPVs. The number of farmers growing improved varieties of small-grain crops has increased, since mid 1990s. The method and frequency of weeding depends on tillage system used and availability of equipment as well as draft power. Adoption rates for technologies such as water conservation and use of adequate soil ameliorants as well as effective crop rotations are low due to limited resources. The study identified some research and extension interventions that may be employed to improve crop productivity in semi-arid areas of Central and Western Zimbabwe.
The study assessed toxic heavy metal concentrations in the upper Sanyati catchment in the Midlands Province in Zimbabwe and predicted their movements and potential impacts on ground water quality. Topographic surveying was used to determine borehole locations, elevations, hydraulic conductivity and water yields. Monthly ground water samples were analyzed to determine concentrations of Cr, Pb, Cd and Ni for a period of two-years. The results obtained for the wet season showed mean concentration levels of Cr, Pb, Cd and Ni at 0.25, 0.015, 0.042 and 0.031mg/L respectively. Dry season mean concentration levels for Cr, Pb, Cd and Ni were 0.15, 0.07, 0.06 and 0.025 mg/L respectively. Water samples from boreholes located in areas where mining, mineral processing and agricultural activities were dominant, yielded the highest values of toxic heavy metals. Dilution Attenuation Factor (DAF) for each toxic heavy metal was calculated to observe metal behaviour along the contaminant path for each season. The results showed seasonal variation in the spatial distribution of each toxic heavy metal during the wet season between October to March and during the dry season between April to September. Overall, research results showed that concentrations of Cr, Pb, Cd and Ni were above the standard limits set by the World Health Organization.
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