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An on-farm trial was conducted in the northern Guinea savanna of Nigeria, over a period of five years, with the objectives of quantifying the effects on maize of applying cattle manure in combination with synthetic fertilizer with regard to soil characteristics, yield, plant nutrition and profitability. Maize grain yield was significantly increased by the annual application of cattle manure, compared to maize receiving an equal amount of N through synthetic fertilizer, but only from the third year of the experiment. The application of manure resulted in higher soil Kjel N, Bray-I P and exchangeable K values, and an increased N utilization efficiency by maize, suggesting that yield-limiting factors other than N deficiencies were of lesser importance than in the treatment receiving sole inorganic fertilizer. Nutrients other than N applied via the manure, particularly P, K and/or B, may have contributed to the higher grain yields in treatments receiving manure. A partial budgeting analysis revealed that, over a 5-year period, investments in the application of manure, in combination with synthetic fertilizer, resulted in higher margins than the application of fertilizer alone. However, analyses of marginal rates of return of changes from low urea N to high urea N or additional manure applications suggested that it was more profitable to invest in additional urea than in organic manure in the first two years of the experiment. The results suggested that manure applications, even when applied at relatively high rates, did not serve as a quick fix to on-farm soil fertility problems, but over a longer period, manure applied in combination with synthetic fertilizers did provide a significant and profitable contribution to enhanced cereal production. [ABSTRACT FROM PUBLISHER]

Striga hermonthica is a serious parasite of cereals in most of the semi-arid savanna zone of West Africa, causing substantial yield loss. It has been observed that some soybean cultivars are capable of stimulating germination of S. hermonthica seed, which would reduce the seed bank in the soil. This study was undertaken to quantify the effect of a soybean crop (compared with a sorghum control) on S. hermonthica emergence in subsequent maize in three farmers' fields in northern Nigeria. Soybean cultivar TGx 1740-7F, previously identified as efficacious for S. hermonthica seed germination, was grown at four densities without P fertilizer to test the effect of increasing plant density of soybean on subsequent S. hermonthica parasitism. The effect of P as single super phosphate was tested on the two highest soybean densities. S. hermonthica parasitism on maize was significantly lower after unfertilized soybean than after the sorghum control treatment at two of three trial sites. Soybean rotation increased maize yield by approximately 90% for the three sites combined. Increasing soybean plant density did not result in lower emerged S. hermonthica. Application of P to soybean at the higher soybean densities resulted in higher root length density, lower emerged S. hermonthica on maize (P<0.15), and significantly higher maize yield. The results suggest that an efficacious cultivar of soybean reduces S. hermonthica parasitism on a succeeding maize crop and that the effect is increased by application of P to the soybean. [ABSTRACT FROM AUTHOR]