Demand-Driven Technologies for Sustainable Maize ... - IITA

214(Table 8). However, within specifi c P treatments, percentage increasesin total N in grain from maize-after-soybean over that of maize-aftermaizeranged from 10 to 138% in the previous 0P plots, from 13 to86% in the 15P plots, from –42 to 56% in the previous TSP plots,and from –2 to 56% in the previous RP plots. These gains in totalN in grain were signifi cant only for values obtained from grain ofmaize-after-soybean genotypes TGm1511, TGm1251, TGm0944,and TGm1419 within the 15P plots, maize-after-soybean genotypeTGm1196 within the previous RP plots, and maize-after-soybeangenotype TGm1251, TGm1540, and TGm1039 plots within theprevious TSP treatments (Table 8). At Fashola, mean N exported inmaize-after-soybean was signifi cantly higher than that of maize-aftermaizeonly for the 15P plots. The increase in total grain N of maizeafter-soybeanover that of maize-after-maize at this location rangedfrom 0 to 164% within 15P plots, from –42 to 56% within previous0P plots, from –50 to 13% within previous RP plots, and from –35 to31% within the previous TSP plots. Only the total N in grain maizeafter-soybeangenotype TGm1511 within 15P plots was signifi cantly(P < 0.05) higher than that of maize-after-maize. At Davié, the meanN exported in maize-after-soybean was signifi cantly higher than thatof maize-after-maize from the previous 0P and TSP treatments (Table8). The increases in total N of grain of maize-after-soybean over thoseof their respective maize-after-maize treatments at this location rangedfrom –22 to 43%. Unlike the results at Fashola and Shika, none of thedifferences between specifi c maize-after-soybean genotype and thecorresponding maize-after-maize treatment were signifi cant.Phosphorus benefits to maizeIn 2002, P nutrition as measured by total P exported in maize grainfollowed a pattern similar to that of N. The mean total P exportedin maize grain from previous TSP plots (7.44 kg ha -1 ) of the 2001soybean crop cycle, was signifi cantly higher than that from previousRP plots (6.86 kg ha -1 ) but not that from previous 0P plots (7.68 kg ha -1) at Fashola. Unlike total N exported in maize grain, however, none ofthe differences between total P export in grain of maize-after-soybeangenotypes and their corresponding maize-after-maize treatments weresignifi cant at the two locations.In 2003, the mean total P in grain of maize from previous 0P plotsin the 2002 soybean crop cycle, at all the locations, was signifi cantlylower than that of the other P sources. The mean total P of grainof maize-after-soybean plots was signifi cantly higher than that of thecorresponding maize-after-maize plots from all P sources at Shika,the previous 0P and 15P plots at Fashola, and the previous RPand TSP plots at Davié (Table 9). Increases in total P of grain from