Amendment ofTephrosiaImproved Fallows with Inorganic Fertilizers Improves Soil Chemical Properties, N Uptake, and Maize Yield in Malawi

摘要

Maize production in Malawi is limited mainly by low soil N and P. Improved fallows of N-fixing legumes such asTephrosiaandSesbaniaoffer options for improving soil fertility particularly N supply. The interactions ofTephrosiafallows and inorganic fertilizers on soil properties, N uptake, and maize yields were evaluated at Chitedze Research Station in Malawi. The results indicated that the level of organic matter and pH increased in all the treatments except for the control. Total N remained almost unchanged while available P decreased in all plots amended withT. vogeliibut increased inT. candidaplots where inorganic P was applied. Exchangeable K increased in all the plots irrespective of the type of amendment. The interaction of N and P fertilizers withT. vogeliifallows significantly increased the grain yield. The treatment that received 45 kg N ha−1and 20 kg P ha−1produced significantly higher grain yields (6.8 t ha−1) than all the other treatments except where 68 kg N ha−1and 30 kg P ha−1were applied which gave 6.5 t ha−1of maize grain.T. candidafallows alone or in combination with N and P fertilizers did not significantly affect grain yield. However,T. candidafallows alone can raise maize grain yield by 300% over the no-input control. Based on these results we conclude that high quality residues such asT. candidaandT. vogeliican be used as sources of nutrients to improve crop yields and soil fertility in N-limited soils. However, inorganic P fertilizer is needed due to the low soil available P levels.