The relationship between light intensity and dry forage yield of cowpea and maize under intercropping

Two field experiments were conducted at the Agricultural Experiments and Research Station Faculty of Agriculture Cairo University Giza Egypt during 2008 and 2009 summer seasons gas to study the intercropping of forage cowpea (Vigna unguiculata L. var. Buff) with maize (Zea mays L) stay green and single cross hybrid 122. The experiment was planted at the 1st of July after wheat in both seasons. The experimental design was a split-split plot design arranged in randomized complete blocks with three replicates. The main plots were devoted to three intercropping patterns: 1) Maize on one side of the ridge and forage cowpea on the other side 2) Solid maize 3) Solid forage cowpea. Subplots were arranged with plant density of forage cowpea one and two plants hill-1 at 20 cm between hills. Sub-sub plots were four nitrogen levels viz., zero, 60 90 and 120 kg N fed.-1 N was added in two equal doses after 21 and 60 days from planting (after the 1st cut of forage cowpea). The results indicated significant differences between intercropping patterns plant density and nitrogen levels for dry yield. Light intensity at top middle and bottom of cowpea and maize were obtained at each cut in both seasons. Light intensity under solid cowpea was greater for the three levels of light intensity reading than intercropped cowpea plants. At the top of intercropped cowpea plants light intensity was greater as compared with readings at the middle and bottom of plants. At the middle light intensity was greater for solid cowpea compared to intercropped cowpea. One plant hill-1 was superior to two plants hill-1 in light intensity at top middle and bottom of cowpea plants intercropped with maize at each cut in both seasons. The percentage of increases in light intensity gave lower values between the two plant intensities it could be recommended with planting two plants hill-1 when intercropped cowpea with maize for obtaining high dry forage yield of cowpea. Nitrogen application was significantly decreased light intensity at top, middle and bottom plant of forage cowpea at each cut in both seasons. Nitrogen from zero to 120 kg N fed-1caused reduction in light intensity While total dry forage yield of cowpea was increased. The highest value of light intensity was obtained by solid cowpea one plant hill-1 and zero nitrogen fed-1 while the lowest value of light intensity was at intercropped cowpea with maize two plants hill-1 and 120 kg N fed.-1 For maize plants there were significant differences in light intensity as affected by intercropping patterns at top middle bottom of maize plants in both seasons except between intercropping two plants hill-1 of cowpea with maize and solid maize at top plant before the 1st cut of cowpea in the first season. Nitrogen levels was significantly decreased light intensity at top middle and bottom plant of maize with not significant differences between 90 and 120 kg N fed.-1 While grain yield and dry stover yield were increased. Zero N level had the highest value of light intensity at top middle and bottom of maize plants compared with the other N levels. The highest value was obtained by solid maize and zero nitrogen fed, while the lowest value was at intercropping two plants hill-1 of cowpea with maize and 120 kg N fed-1