Cabbage and Swiss chard yield, irrigation requirement and soil chemical responses in zeolite-amended sandy soil

Cabbage ( Brassica oleracea var . capitata L.) and Swiss chard ( Beta vulgaris L. var. cicla ) are important vegetables for food and nutrition in many parts of the world. Like many other crops, vegetable production is affected by poor soil fertility and shortages of irrigation water. Climate change-related drought has led to shortages of irrigation water in many countries, including South Africa. Farmers have used amendments such as inorganic fertilisers, organic manure, and compost to improve soil fertility. However, organic soil conditioners fall short in providing stable non-decomposable soil amendments, and inorganic fertilisers are expensive. A greenhouse pot experiment was conducted at the Agricultural Research Council Infruitec-Nietvoorbij, Stellenbosch, to assess the effect of zeolite (a soil conditioner) on cabbage and Swiss chard yield, water, and nutrient retention ability of the soil. Zeolite to sandy soil (zeolite: sandy soil) was applied in the ratio of 0:100%, 10:90%, 20:80% and 30:70%. Both cabbage and Swiss chard yields increased, irrigation requirements decreased, and soil acidity was ameliorated due to zeolite application. Cabbage yields were improved by the residual effects of zeolite, while the Swiss chard yield increase was due to vigorous vegetative growth of Swiss chard in zeolite-amended treatments, which led to more N and water utilisation, particularly in the second season. The study also highlighted the potential of zeolite in ameliorating the pH of acidic soils, as well as the water and nutrient-saving ability of zeolite, which are major challenges for crop production in sandy soils. However, there is a need to carry out further studies to find the cost-effective application rates of zeolite under on-farm conditions.