Danga, B.O., Department of Agricultural Resource Management, Kenyatta University, PO Box 43844-001001, Nairobi, Kenya
Hadas, A., Department of Soil Chemistry and Plant Nutrition, Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization - the Volcani Center, POB 6, Bet Dagan 50250, Israel
Wakindiki, I.I.C., Department of Agronomy, University of Fort Hare, Private Bag X1314, Alice 5700, South Africa
Ouma, J.P., Department of Crops, Horticulture and Soils, Egerton University, PO Box 536-20115, Egerton, Kenya
Bar-Tal, A., Department of Soil Chemistry and Plant Nutrition, Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization - the Volcani Center, POB 6, Bet Dagan 50250, Israel

Chickpea (Cicer arietinum) grown in a rotation can contribute significant nitrogen (N) if its decomposition and nutrient-release dynamics are known and synchronised with the maximum demand by the succeeding crop. The aims of the study were to investigate the decomposition rates of two chickpea residues, mature (CHR) and green manure (GM), and use their properties to predict N dynamics in acid soils. The N dynamics were predicted by the NCSOIL model using neutral and acidic detergent fibres (NDF and ADF, respectively) measured by near-infrared reflectance spectroscopy (NIRS) for defining residue pools. The GM released 50-60% of total N in 84 d, whereas CHR immobilised N. Simulations based on the two residue pools indicated that NIRS predicted the carbon (C) and N dynamics reasonably well for both residues. The decay rate constants of the NDF - soluble pool varied between 0.5 and 0.2 d-1. Adding an intermediate pool NDF + ADF improved the prediction of C and N dynamics for CHR but not for GM. Therefore, successful prediction of N dynamics required the search of N partitioning among pools by NCSOIL, as long as no chemical analysis of N was suitable for this purpose. Copyright © 2013 Combined Congress Continuing Committee.