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Effects of Tillage and Crop Residue Application on Soybean Nitrogen Fixation in a Tropical Ferralsol
Tropical Soil Biology and Fertility (TSBF) Institute of CIAT, Box 30677, Nairobi 00100, Kenya
Zentrum für Entwicklungsforschung (ZEF), Walter-Flex Str. 3, Bonn 53113, Germany
Alliance for Green Revolution in Africa (AGRA-Alliance), CSIR Office Complex, #6 Agostino Neto Road, Airport Residential Area, PMP KIA 114, Airport-Accra, Ghana
* Author to whom correspondence should be addressed.
Received: 25 October 2011; in revised form: 6 December 2011 / Accepted: 8 December 2011 / Published: 20 December 2011
Abstract: This study was aimed at quantifying soybean (Glycine max) nitrogen fixation under reduced tillage (RT) and conventional tillage (CT) in a tropical Ferralsol of the sub-humid zone of western Kenya, using the isotope 15N dilution method. Crop residue (CR) management was a superimposed treatment in soybean-maize rotation and intercropping systems. This study quantified N in abscised soybean leaves. Soybean-N derived from the atmosphere (%NDfA) ranged between 41–65%; it was higher (P < 0.05) in RT (55.6%) than in CT (46.6%). Total fixed-N under ‘RT + CR’ was more than in the other treatments by at least 55% in intercropping and 34% in rotation system. Nitrogen fixed in soybean aboveground parts was 26–48 kg N ha−1 with intercropping and 53–82 kg N ha−1 with rotation. Seasonal litter fall contained about 15 kg N ha−1, with 54% NDfA. Annual nitrogen balances with soybean and maize grain removed were better in RT (−9 to −32 kg N ha−1) than in CT (−40 to −60 kg N ha−1). Application of P increased nodule weight (P < 0.05) by 3 to 16 times over the control. Soybean residues should be returned to the field after harvest to reduce soil N mining. We conclude that ‘RT + CR’ increases biological nitrogen fixation in soybean, over CT, and that phosphorus application is needed for better soybean nodulation in western Kenya.
Keywords: intercropping; litter fall; N balance; %NDFA; 15N dilution
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Kihara, J.; Martius, C.; Bationo, A.; Vlek, P.L.G. Effects of Tillage and Crop Residue Application on Soybean Nitrogen Fixation in a Tropical Ferralsol. Agriculture 2011, 1, 22-37.
Kihara J, Martius C, Bationo A, Vlek PLG. Effects of Tillage and Crop Residue Application on Soybean Nitrogen Fixation in a Tropical Ferralsol. Agriculture. 2011; 1(1):22-37.
Kihara, Job; Martius, Christopher; Bationo, Andre; Vlek, Paul L. G. 2011. "Effects of Tillage and Crop Residue Application on Soybean Nitrogen Fixation in a Tropical Ferralsol." Agriculture 1, no. 1: 22-37.