Potassium recovery from farm wastes for crop growth

Abstract

Potassium (K) is a scarce agricultural chemical, which is being depleted from Nigerian soils at a fast rate. There are no known resources in Nigeria and farmers depend on imported muriate of potash (KCl) for their needs. A study has been undertaken on the potential for resource utilization of potash from known farm wastes available in plentiful supply. Thirteen farm wastes were assessed for their K and other mineral contents. Among them, cocoa waste, plantain waste, market waste, and water hyacinth were found to be rich in their K contents. Varying levels (0, 10, 15, 20, 25, and 30 tons/ha) of these wastes in ash form along with recommended NPK fertilizer were examined in greenhouse experiments using Amaranthus cruentus L. as a test crop. The results indicated that water hyacinth and cocoa waste promoted maximum crop growth and yield when applied at 10 tons ha−1, respectively. Crop growth and yield were significant at the 0.05% level as compared to application of conventional NPK fertilizer at K levels 10 and 20 kg ha−1. From the soil residual K levels and plant uptake, it was observed that the K from water hyacinth seems to be more available to the plant as compared to sources from other farm wastes. Samples of potassium salt in the carbonate form were recovered and concentrated from ash of water hyacinth and cocoa waste which may prove to be economical for farmers in the country to meet K demand of their soils.