Factors affecting potassium status of flood plain soils, eastern Nigeria

Abstract

Plant nutrient deficiency especially that of potassium (K) due to fixation and leaching losses poses problem in hydromorphic soils and highly weathered soils. We studied five soil profiles on the flood plain of River Niger for the distribution of potassium and their relationships with some soil properties. The properties determined were morphological soil characteristics, particle size distribution, clay mineralogy, pH, cation exchange capacity (CEC) and soil organic matter. Other parameters were exchangeable K, total K in whole soil, clay, silt, fine and coarse sand. The clay minerals are dominated by kaolinite which developed in the soil while the feldspars were transported from the upper course of the river. Exchangeable K is the least of all the K forms. Total K in clay is between 9.1–19 g kg−1; 29.6–36.4 g kg−1 in silt and 12.4–37.5 g kg−1 in fine sand. Total K in soils decreased in most cases with depth. All potassium fractions show an increasing amount from the upland towards the river. The reason for this was attributed to the change in ratio of kaolinite and illite, the clay content, the rate and type of materials deposited or formed. Silt, fine and coarse sand fractions and pH correlate significantly with different forms of K. The factors which affect the K forms were therefore, the clay minerals, leaching, particle size distribution and the low CEC of the soil and possibly phosphate compounds in the soil.