The potassium status of soils and its absorption by cassava in selected farms in the Central Region

Abstract

Potassium (K) plays an outstanding role in plants and animals. Cassava, a widely grown staple in Ghana is noted for extracting large amounts of K from the soil. Cassava’s ability to absorb K from the soil is worth studying as it is vital for sustainable production and biofortification. The study was conducted to assess cassava’s ability to absorb K under fertilized and unfertilized systems. Two cassava genotypes, Cape Vars and Botan were grown under different fertilizer treatments; a control, NPK and NPK + KCl in a randomized complete block design. A survey was also undertaken to assess the K status of some cassava farms and cassava tuber produced on such soils in the Central region of Ghana. Composite soil samples were taken at a depth of 0 – 30 cm and analysed for exchangeable and non-exchangeable K. Aside these, the study also compared the extractability of exchangeable K by Nitric Acid, Ammonium Acetate and Calcium Chloride in soils cultivated to cassava. The outcomes of the study revealed that most cassava farms have low levels of exchangeable K (0.76 – 0.06 cmolc kg-1) likewise the K content of cassava tuber produced from them (0.84% - 0.61%). A significant increase in K content of tubers was however observed in cassava that was treated with NPK + KCl fertilizer (1.13% - 0.86%). Cassava tuber yield also saw a significant increase with the highest yield (20.5 t ha-1) produced from NPK + KCl plots. The study also revealed that Cape Vars variety has a greater ability to absorb K in both fertilized and unfertilized soils. NH4OAc, HNO3 and CaCl2 extracted 0.21, 0.64 and 0.23 cmolc kg-1 exchangeable K respectively. However, CaCl2 – K was found to be more predictive of the K status of cassava soils. The study recommends the sensitization of cassava farmers on fertilizer application as well as a further research into cassava’s ability to absorb K in marginal soils.