THE POTASSIUM STATUS OF THE SANDY SOILS OF NORTHERN IMO STATE, NIGERIA

Abstract

This project reviewed the potassium status of 19 profiles, 108 samples, from northern Imo State, Nigeria. The paper presents data on the contents of exchangeable potassium and difficultly available (boiling with 1 N HNO3) and nonexchangeable potassium in the soils, as well as mineralogical analyses of the clays and silts. Analyses showed that kaolinite was the dominant clay mineral, although significant amounts of a 2:1 intergrade mineral were also present. Illite, quartz, goethite, and anatase are minor components. The soils were found to be very low in potassium. The fine sand or fine sand plus silt separates were found to be the sources of K in these highly weathered soils. I therefore concluded that more detailed mineralogical analyses of the soil separates are called for to learn more about the K-supplying power of the different soil separates. These soils have been submitted to intensive cultivation for years without adequate potassium manuring; therefore they have lost their potassium content, mainly in the form of structural exchangeable K. Hence they need large quantities of K fertilizers. Because of the sandy soils and the high rainfall that prevail, leaching losses can be expected.-To avoid them, K fertilizers should be applied in small but frequent doses.