Use of the SWB-Sci model for nitrogen management in sludge-amended land

Eyob H. Tesfamariam, John G. Annandale, Joachim M. Steyn, Richard J. Stirzaker and Ikenna Mbakwe

Agricultural Water Management, 2015, vol. 152, issue C, 262-276

Abstract: Process-based computer simulation models are often used as reasoning support tools to integrate the complex processes involved in the soil-plant-atmosphere system. The objectives of this study were to evaluate the performance of the SWB-Sci model as a reasoning support tool for sludge management in agricultural lands, and use the validated model to assess the long-term agronomic and environmental implications of water availability and crop intensity on sludge-amended land. The model was calibrated for the test crops, maize (Zea mays Pan6966) and oats (Avena sativa L.), using data collected during the 2004/2005 growing season from irrigated plots at the East Rand Water Care Works, Gauteng, South Africa. Model validation was performed using independent data sets collected during the 2004/2005 to 2007/2008 growing seasons. The model was successfully calibrated for maize and oats as all the statistical parameters were within the prescribed ranges [index of agreement (d) >0.8; relative mean absolute error (MAE%) <20%; coefficient of determination (R2) >0.8]. The results indicate that SWB-Sci simulated aboveground biomass (TDM) and grain yield (GY) of maize and oats with high accuracy (d>0.85, MAE% ≤20%, and R2>0.91) but with a slight overestimation by 0.2–4Mgha−1. The model predicted nitrate leaching and crop N uptake reasonably well (d>0.85, MAE% ≤14%, and R2>0.8), with slight overestimation of TDM and GY N uptake by 11–57 and 4–48kgha−1, respectively. Long-term model simulations indicate that fixed sludge application rate recommendations generated from laboratory incubation studies may in the long-term result in spontaneous excessive nitrate leaching below the active root zone during high rainfall events, if recommendations do not consider N contribution from soil organic matter. Modelling also showed that leaving room for rain during each irrigation event may minimize the risk of nitrate leaching.

Keywords: Nitrogen; Modelling; Irrigation; Nitrate leaching; Maize; Oats (search for similar items in EconPapers)
Date: 2015
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Citations: View citations in EconPapers (3)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:agiwat:v:152:y:2015:i:c:p:262-276

DOI: 10.1016/j.agwat.2015.01.023

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