Authors: Sogbedji, Jean; Es, Harold; Agbeko, Kofi

Source: Nutrient Cycling in Agroecosystems, Volume 74, Number 2, February 2006 , pp. 99-113(15)

Publisher: Springer

Abstract:

Mathematical models may be applied to simulate nitrogen (N) dynamics under different types of soil and environmental conditions to assess fertilizer N needs or to predict nitrate-N (NO₃-N) potential impact on water quality. The research version of LEACHMN was evaluated using data from lysimeters and field experiments conducted at the University of Lomé Research Farm in Togo, West Africa. The model was calibrated for the mineralization, nitrification, denitrification and volatilization rate constants with measured values of NO₃-N leaching losses and maize (Zea mays L.) N uptake collected from the lysimeter experiment. The model was then tested against measured data of soil profile NO₃-N distribution and maize N uptake from the field experiment and drainage water collected from the lysimeter experiment. The testing procedure involved two scenarios with increasing level of generalization for transformation rate constants (i) rate constant values for each N treatment and (ii) rate constant values averaged over N treatments. LEACHMN effectively simulated drainage water volume and rate (r²= 0.94 to 0.99). During the calibration efforts, the model satisfactorily simulated NO₃-N leaching losses (r²= 0.98) and accurately simulated growing season cumulative maize N uptake. The variation of the calibrated rate constants among N treatments was primarily linked to the model's incapacity to accurately simulate maize N uptake throughout the growing period. When tested using calibrated rate constants for each treatment, the model was successful in simulating soil profile NO₃-N distribution (r² = 0.52 to 0.94). Simulations of soil profile NO₃-N distribution were not satisfactory (r²= 0.03 to 0.49) when rate constants were averaged over N treatments. Improvement of the plant N uptake routine of the model is needed to increase the model's performance. Using the LEACHMN model to predict N dynamics on the Ferralsols of southern Togo appears feasible when appropriate calibrations are performed.

Keywords: Ferralsols; Fertilizer N; LEACHMN model simulations; Maize; Nitrogen dynamics

Document Type: Research article

DOI: http://dx.doi.org/10.1007/s10705-005-5729-7

Affiliations: 1: Email: mianikpo@yahoo.com

Publication date: 2006-02-01

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