RETENTION AND LEACHING OF NUTRIENTS IN A LIMED ULTISOL UNDER CROPPING

The response of maize (Zea mays L. cv. TZB) to liming and the retention and leaching of Ca and other nutrient ions were studied in the greenhouse using an acid Ultisol from southern Nigeria. The soil was limed to various pH levels and maize was grown for 10 wk. The largest growth response occurred when the soil pH was raised from 4.3 to 5.0 by liming (1.3 metric ton/ha). The highest yield was obtained when the soil pH was between 5.5 to 6.0. Substantial downward movement of Ca from the limed surface layer (0-15 cm) was noted, but these Ca ions were mostly adsorbed in the unlimed subsurface layer. The vertical distribution of exchangeable Ca in the limed soils followed a similar trend with pH, but was inversely related to exchangeable Al. Leaching losses of applied nutrient ions (Ca, Mg, K, NO3) during the 10 wk cropping period were relatively small. There was a significant increase in nitrate content in leachates when soil was limed above pH 7.0. Only 1% of the applied Ca was in the leachate while about 80% of the applied Ca was retained in exchangeable form when the soil was limed at a rate of 2 metric ton/ha.