Cropping systems effects of a newly-cleared ultisol in Southern Nigeria

Abstract

A 4-yr. study was conducted to investigate the effects of five cropping systems on soil erosion, earthworm activity and crop production on an Ultisol in southern Nigeria. Five cropping systems were casava-based, oil palm-based alley cropping, plantain and traditional farming system. The traditional farming system for this region involves cultivation of vam ( Dioscorea sp.) and several other crops grown in partially cleared land. The first four systems were tested on mechanically-cleared plots, and the traditional system was evaluated on manually-cleared plots with partial clearing and intact stumps. Soil erosion was observed only during the first year after clearing. Soil erosion was high in the oil-palm- (170 kg/ha/5 months) and plantain systems (157 kg/ha/5 months), and was negligible in the forested control (0.4 kg/ha). During the rainy season, earthworm activity was the highest in traditionally-farmed plots and the lowest in the forested control. Earthworm activity significantly decreased in all systems during the dry season. On the basis of agronomic yield, cassava-based cropping system was the most productive (10.8 Mg/ha/yr. of produce) followed by traditional farming (8.0 Mg/ha/yr.), and the plantain system was the least productive (0.74 Mg/ha/yr.). Measured in terms of the calories output, productivity of different cropping systems followed the other cassava-based > alley cropping > traditional farming > oil palm-based > plantain. Results indicate that Ultisols can produce high yields of cassava, yam and maize, provided that soil degradation and fertility depletion are minimized by practicing no-tillage, returning crop residue to soil at harvest, and maintaining favorable nutrient status through supplemental application of fertilizers.