Response of Late Season Maize/Soybean Intercropping to Nitrogen in the Humid Environment of South Southern Nigeria

Abstract

Intensification of maize/legume production during early rains in the High Rainforest region of South Southern Nigeria is limited by heavy rainfall. Production of late season maize/legume by peasant farmers is gaining prominence though yields are low due to low soil fertility and improper crop arrangement. The objective of this research was to investigate the yield performance of late season maize/soybean intercropping in response to nitrogen fertilization and spatial arrangement of the intercrops. The trial was a split-plot design in randomized complete block with three replications. Treatments consisted of five rates of nitrogen (0, 25, 50, 75 and 100 kg ha^-1) and five crop arrangements (sole maize at 53,333 plants ha^-1, sole soybean at 266,666 plants ha^-1 and maize: soybean additive mixture arrangements of 1:1, 2:2 and 1:2). Nitrogen fertilization increased yield in both maize and soybean at all the treatment levels, when grown sole or in mixtures. Application of 100 kg N ha^-1 to maize increased number of ears per plant, 100-grain weight, cob yield and grain yield by 46, 35, 138 and 153 percents, respectively in 2007, and by 15, 48, 88 and 109 percents, respectively in 2008, over no nitrogen application. Similarly, application of 100 kg N ha^-1 to soybean increased number of pods per plant, number of barren pods and 1000-seed weight by 53, 120 and 16 percents, respectively in 2007, and by 55, 99 and 14 percents, respectively in 2008, over no nitrogen application. Optimum seed yield in soybean was obtained at 50 kg N ha^-1. The yield values of 1,352.8 and 1,158.2 kg ha^-1 were higher than those obtained at 0 kg N ha^-1 by 31 and 21 percent in 2007 and 2008. Increasing the nitrogen level further to 100 kg ha^-1 depressed seed yield by 8 percent in 2007 over 0 kg ha^-1. The nitrogen x crop arrangement interaction effects on grain yield and all other parameters were not significant (p< 0.05). Late season maize and soybean populations may be superimposed on each other and fertilized with 50 kg N ha^-1 to take advantage of optimum soybean seed yield and 66-76 percent of the maize grain yield.

Key words: maize, soybean, intercropping, additive mixtures, nitrogen fertilizer