“…Values of between 3.0 and 5.0 mmol c kg" 1 soil, have been used for soils with heavy textures or high CEC soils, while lower values are generally applied to sandy loams (Skene, 1956), i.e., soils with lower CEC values. For example, little response to applied K was found for ryegrass on some Tasmanian soils with exchangeable K (=RAK) levels greater than 1.0-1.5 mmol c kg" 1 (Piper and De Vires, 1960). For millet however, response to applied K was found when exchangeable K was below 1.1 mmol c kg' 1 in some soils in Eastern Nigeria (Ekpete, 1972), while 1.8-2.0 mmol c kg 1 exchangeable K was found to be critical for maize crop (Z mays L.) in Southern Nigeria (Sobulo, 1980;Agboola and Obigbesan, 1974).…”