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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

Location: Agricultural Systems Research Unit

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

Authors
item Ma, Liwang
item Malone, Robert
item Jaynes, Dan
item Thorp, Kelly
item Ahuja, Lajpat

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 5, 2008
Publication Date: October 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: 9/2/2014