MSCAGR (Soil Science) / Department of Soil Science / Maize (Zea mays L.) is widely grown in the semi-arid regions of South Africa mainly for its grain that is used for direct human consumption, feed for animals and raw materials for the industries. The challenges of soil infertility, water supply, and availability of high yielding cultivars remain a major constraint for its production in this environment. These constraints are a major threat to sustainable crop production and food security. Maize/lablab Zea mays L.\ L. purpureus) intercropping system could thus become an option for food security among small scale maize producers in dry environments. Preliminary studies show the huge potential of maize/lablab intercropping in the semi-arid environments of the North-Eastern South Africa. Therefore, this study aimed to assess the effects of maize/lablab intercropping on soil water content, nitrogen dynamics and crop productivity based field experiments and crop simulation modeling using the model APSIM. The trials were conducted at two sites (Univen and Syferkuil) in Limpopo province, South Africa, for two seasons (2015/2016) and 2016/2017). The treatments consisted of; (i) sole maize (ii) sole lablab (iii) maize and lablab planted at the same time (Maize+lablab-ST) and (iv) maize with lablab planted 28 days after maize (Maize+lablab-28).The treatments were laid out in an RCBD replicated 4 times, with individual plots size measuring 4.5 m × 4 m (18 m2) and the layout of the field as consisting of 4 plots per block giving a total of 16 plots in 4 blocks. The following parameters were determined: soil water content, soil NO3--N and NH4+-N levels, dry matter and grain yield. The APSIM-model (version 7.7) was then used to simulate maize grain yield and dry matter production to assess risks associated with the production of maize/lablab intercropping. The results obtained from this study showed that maize/lablab intercropping had significant effects on measured parameters (grain, biomass yield soil water content, and N-minerals). Maize+lablab-28 produced 46 % higher grain yield than sole cropping (24%) and maize+lablab-ST) (30%). The results also showed variation in soil water content at different depths among the treatments. The soil water content was increased with depth. The intercropped plots and lablab sole had significantly higher soil water content than the sole maize. At all depths, the highest soil water content was obtained under sole lablab followed by maize+lablab-ST and maize+lablab-28. It was notable however that maize/lablab intercropping showed a higher NO3--N and NH4+-N levels at all depths. At both sites, the soil NO3--N showed a sharp drop at V7 sampling time. The results showed the benefits of intercropping in comparison to sole cropping as demonstrated by positive land equivalent ratios of >1 for both cropping systems in both years and sites. Modelling exercises showed that APSIM was able to simulate the results sufficiently. In the simulation experiment, a stronger negative effect of planting lablab with maize simultaneously was found. Hence, delayed planting of lablab should be a standard practice / NRF

MENVSC / Department of Ecology and Resource Management / The study investigated the impact of cover crops (Medicago sativa, Lotus corniculatus, Trifolium pratense, Melilotus alba and Phacelia tanacetifolia), bare soil and natural ground cover on pest and beneficial arthropods, soil health, crop yield, pest damage and weed suppression in avocado orchards. The trial plots were sited within established commercial avocado orchards with trees of similar cultivar (‘Hass’), soil-type and age, located in Levubu, Limpopo, South Africa. Mixtures of cover crops were planted in the alleys of avocado orchards and the effects were compared to that of a control (other half of the orchard). Mechanical clearing of vegetation in half of the alleys of different avocado orchards were compared to the other half that was left undisturbed. Data were collected during the flowering and fruit set stages of the avocado trees in the months of September - November 2019. Results revealed that there was higher abundance and diversity of flowering plants in the orchard alleys of the cover crop treatment compared to the control comprising of natural vegetation. Cover crops had a significantly positive effect on the soil health of the orchard but little or no effect on beneficial arthropods within the orchard nor any positive effect on the pests of avocados. However, the number of thrips scouted on the fruit were significantly less where cover crops were established. Avocado scale infection rates were also significantly lower where cover crops were established. There were significantly less arthropods, and specifically pests, pollinators and herbivores where the topsoil was removed mechanically. The yield resulting from the orchard half where cover crops were established were significantly higher. More research still needs to be done about the use, management and impact of cover cropping on not only commercial avocado orchards but on other fruit crops. This study shows good evidence for the benefits for using cover crops and the negative effects in having no vegetation cover in the orchards. / NRF