Critical soil and plant potassium for maize

Abstract

Abstract Ten soils from bench mark sites found in four different ecological zones of western Nigeria were enriched with 0, 50 and 100 ppm K and equilibrated for two weeks in the greenhouse. Three extractants: 0.01 M calcium chloride, IN ammonium acetate (pH 7.0), and 0.13 N HCl were used to determine K status of the soils after being cropped for three cycles of 17 days per cycle. The critical soil K level for optimum K in the plant was estimated graphically by Cate/Nelson technique. The critical soil K levels were 7.5, 12.5 and 15 meq K/100g determined by extraction with 0.01 M CaC12, 0.13 N HCl and 1N ammonium acetate (pH 7.0), respectively. Critical K in the maize plant at 17 days was 4.0–4.50%. Potassium deficiency symptoms were observed when the tissue content was 2 to 3% K and the exchangeable K was less than 5 meq K/100g.