CONTRIBUTION OF LEGUMINOUS CROPS TO NUTRIENT AVAILABILITY AND PRODUCTIVITY OF YAM BASED SYSTEMS

Abstract

A trial was conducted at Umudike, Nigeria in 2000/2001 and 2001/2002 to determine the contribution of leguminous cover crops Voandzea subterranea (bambara nut), Arachis hypogea (groundnut) and Cajanus cajan (pigeon pea) to the conservation of soil resource base and productivity of yam minisett based systems. The systems studied were sole yam minisett, yam minisett/bambara nut, yam minisett/groundnut, and yam minisett/pigeon pea. Intercropping yam minisett with either ground nut or bambara nut decreased seed yam yield relative to sole yam minisett. Highest seed yam yields of 4.70 t/ha and 4.67 t/ha were obtained with yam minisett/pigeon pea and sole yam minisett respectively and these were significantly higher (P < 0.05) than 3.41 t/ha and 3.84 t/ha obtained with yam minisett/bambara nut and yam minisett/groundnut respectively. Highest benefit cost ratio of 5.76 was obtained with yam minisett/pigeon pea followed by yam minisett/bambara nut with 2.55, sole yam minisett with 2.11 and lastly by yam minisett/groundnut with 1.78. Intercropping yam minisett with the legumes improved soil organic matter content of the soil resource base and also ensured that large quantities of biomass was left on the soil after crop harvest in form of legume haulms. Largest amount of legume haulm of 4.57 t/ha was obtained with yam minisett/pigeon pea followed by yam minisett/groundnut with 3.94t/ha and yam minisett/bambara nut with 0.54 t/ha. Quantities of nutrients (N,P,K,Ca,Mg) in legume haulms which could be released to a subsequent crop if these haulms are incorporated into the soil were determined. For nitrogen the value was 89.52 kg N/ha in yam minisett/pigeon pea system and 8.66kg N/ha in yam minisett/groundnut system.



[Niger Agric. J. 34 (2003): 44-48]