Residual effect of zeolite on soil exchangeable cations and cation exchange capacity in sandy soil cultivated with Swiss chard

Abstract

The increase in global food demand imposes pressure on agricultural soils, leading to soil fertility decline, particularly in African countries. Organic soil conditioners have been used to improve soil fertility although they are not stable and decompose with time. Zeolite is a stable inorganic material that is gaining popularity as a soil conditioner for its ion exchange capacity and high cation exchange capacity (CEC). Zeolites are aluminosilicate minerals, having a negative charge which is balanced by cations. The nature of zeolite in soil needs to be understood as it has a bearing on soil fertility and agricultural potential. A greenhouse pot experiment was conducted at the Agricultural Research Council, Stellenbosch to assess the residual effects of zeolite on soil exchangeable cations (Ca, Na, Mg, and K) and soil CEC. The exchangeability of all soil cations and CEC was increased with zeolite application. Soil exchangeability of Na, Mg, and K in the second growing season was generally reduced (p<0.05) on the zeolite-amended treatments, compared to the first growing season. However, the CEC of all treatments was larger in the second season compared to that of the first growing season. The results of this study show that zeolite can be used to improve sandy soil fertility. However, in continuous cropping systems some of the base cations will require replenishment.