EFFECT OF INCORPORATING LEGUME HEDGEROW PRUNINGS ON PROPERTIES OF AN OXIC PALEUDULT IN SOUTH WESTERN NIGERIA

Abstract

A field experiment was conducted from 1994 to 1996 on a degraded Ultisol at the University of Agriculture, Abeokuta, Nigeria, to monitor changes in nutrient status as influenced by the incorporation of prunings of planted Leucaena leucocephala and pigeon pea (Cajanus cajan) for a period of 60 weeks. Although increases in soil pH were small decreases in exchangeable acidity were observed to be highly significant in the first few weeks after incorporation of the prunings. The soil pH decreased by 47% and 49% in the leucaena and pigeon pea treated plots, respectively, and became stabilized thereafter while the exchangeable acidity increased steadily in the control plots. The total nitrogen levels in leucaena pruning incorporated plots increased by 120 and 213% compared to 90 and 175% respectively in pigeon pea within the first 6 and 12 weeks, respectively. However, the soil nitrate levels were consistently higher in pigeon pea than in leucaena pruning incorporated plots. Increases in total phosphorus (P) levels were marginal in the first few weeks after incorporation. However by the 18th week, significantly higher values were observed in the pigeon pea pruning incorporated plots (18%) than in leucaena pruning incorporated plots. The organic P followed a similar trend. The calcium-P (Ca-P) and the aluminum-P (Al-P) did not change significantly as a result of pruning incorporation. The exchangeable calcium (Ca), magnesium (Mg), and potassium (K) levels increased significantly with time in the pruning incorporated plots. The increases were more rapid in the leucaena pruning incorporated plots. It was concluded that pigeon pea compared favorably with leucaena in terms of long-term nutrient releasing ability of their incorporated prunings and consequently may be better alternative to leucaena and other woody species because of its immediate cash and food values and ease of establishment and control.