Yield and nitrate leaching in a rainfed maize crop using swine manure and mineral fertilizer as nitrogen sources

Swine Manure (SM) has great potential as fertilizer and can replace part or all of the nitrogen from mineral fertilizer (MF) required in crop production. However, SM also has high potential as contaminant and must be managed properly to avoid environmental pollution. Crop models coupled to decision support systems can be an efficient tool to evaluate alternative strategies for manure management. The goal of this study was to use a simulation approach to evaluate the sustainability of rainfed maize production fertilized with different rates of nitrogen from SM and MF. The SM-CERES-Maize model of the Decision Support System for Agrotechnology Transfer was used to assess the long-term effects of the fertilization strategies on maize yield, nitrogen uptake soil-nitrogen accumulation and nitrate leaching. Nitrogen rates ranging from 100 to 250 kg ha^-1 from both SM and MF, by a combination of 50% SM and 50% MF, and the rate of 415 kg ha^-1 (60% MF and 40% SM) currently used by the farmer, were simulated. Our results indicate that a rate of 200 kg ha ^-1 (50% MF and 50% SM), proved to be advantageous as yield increased and the nitrate leaching and soil-nitrogen accumulation were within acceptable levels. Our results also indicated the farmers' rate to be unsustainable due to nitrate leaching and nitrogen accumulation in the soil. Additional strategies, such as using higher proportion of MF at the beginning and then reducing it over time are also discussed.