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United States Department of Agriculture

Agricultural Research Service

Research Project: OBJECT MODELING AND SCALING OF LANDSCAPE PROCESSES AND CONSERVATION EFFECTS IN AGRICULTURAL SYSTEMS

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Title: Simulated Effects of Nitrogen Management and Soil Microbes on Soil Nitrogen Balance and Crop Production)

Author
item Ma, Liwang
item Malone, Robert - Rob
item Jaynes, Dan
item Thorp, Kelly
item Ahuja, Lajpat - Laj

Submitted to: Soil Science Society of America Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/5/2008
Publication Date: 10/1/2008
Citation: Ma, L., Malone, R.W., Jaynes, D.B., Thorp, K.R., Ahuja, L.R. 2008. Simulated Effects of Nitrogen Management and Soil Microbes on Soil Nitrogen Balance and Crop Production. Soil Science Society of America Journal. 72:1594-1603.

Interpretive Summary: System models are important tools in evaluating N loss from non-point agricultural sources in the Midwestern US. In this study, an agricultural system in central Iowa, managed using a corn-soybean rotation, were evaluated with the RZWQM-DSSAT4.0 for crop yield, grain N, annual N loss in tile drainage flow, and residual soil nitrate-N under a high (H, 199 kg N/ha), medium (M, 138 kg N/ha), and low (L, 69 kg N/ha) N application rate shortly after planting, and a split (S, 69 kg N/ha shortly after planting and at midseason) N treatment. The model adequately simulated the responses of yield and N loss to H, M, and L nitrogen treatments, but it failed to simulate the lower corn yield and higher N loss under the S treatment than under the M treatment, where both received the same amount of N applications.

Technical Abstract: Searching for environmental friendly nitrogen management practices in the Midwestern US is an on-going task in the agricultural community. Many practices have shown promise in reducing N in tile drainage that may contribute to hypoxia in the Gulf of Mexico. In this study, an agricultural system in central Iowa, managed using a corn-soybean rotation, were evaluated with the Root Zone Water Quality Model (RZWQM)-DSSAT4.0 for crop yield, grain N, annual N loss in tile drainage flow, and residual soil nitrate-N under a high (H, 199 kg N/ha), medium (M, 138 kg N/ha), and low (L, 69 kg N/ha) N application rate shortly after planting, and a split (S, 69 kg N/ha shortly after planting and at midseason) N treatment. The model adequately simulated the responses of yield and N loss to H, M, and L treatments, but it failed to simulate the lower corn yield and higher N loss under the S treatment than under the M treatment, where both received the same amount of N applications. Experimental differences in yield between the two treatments were statistically significant, whereas the differences in N loss were not significant experimentally. Further improvement on model responses to late fertilizer application in terms of yield and N leaching was needed before it could be applied to simulate other N scheduling, such as the late spring N test (LSNT). The study also showed that, with a constant soil microbial population implemented in RZWQM, the model produced very similar simulation results for crop production and soil N balances compared to a dynamic soil microbial population in RZWQM.

Last Modified: 8/24/2016
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