Density and Nitrogen Effects on Forage Dry Matter Yield and Productivity Indices of Crop Residues in Rice-Cowpea Intercropping

Abstract

Two field experiments were conducted in 2003 and 2004 cropping seasons to ascertain the competitive behavior of rice-cowpea intercrops with regard to the forage dry matter productive capacity of the crop residues.  Three treatments were used for the study. This consist of four nitrogen rates (0, 15, 30 and 45kgNha^-1) applied as urea {CO(NH₂)₂}, three cropping patterns (sole rice, sole cowpea and rice-cowpea mixture) and three cropping densities (50000, 100000 and 200000 plants ha^-1). Treatments were arranged in a 4x3x3 factorial with randomized complete block design. Results indicated that forage dry matter yield (DMY) of crop residues of both rice and cowpea were higher in monocropping than in the intercropping mixtures. Forage DMY had a linear relationship with mineral and residual nitrogen. Maximum density resulted in maximum forage DMY. Productivity of forage DMY of crop residues as indicated by LER and SPI values was better achieved with nitrogen rate of 30kgNha^-1 at 200000plants ha^-1. Relative crowding coefficient (K) and aggressivity index (A) values showed cowpea to be dominant over rice in the intercropping system. The study suggests that residues from rice and cowpea forages are potential livestock feed for ruminant nutrition.

Keywords: plant density, system productivity index, aggressivity index, forage dry matter yield, rice, cowpea