|Bakhsh, A - IOWA STATE UNIVERSITY|
|Kanwar, R - IOWA STATE UNIVERSITY|
|Bailey, T - IOWA STATE UNIVERSITY|
Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 23, 2001
Publication Date: August 20, 2001
Citation: BAKHSH, A., KANWAR, R.S., KARLEN, D.L., CAMBARDELLA, C.A., BAILEY, T.B., COLVIN, T.S. N-MANAGEMENT AND CROP ROTATION EFFECTS ON YIELD AND RESIDUAL SOIL NITRATE LEVELS. SOIL SCIENCE. 2001. V. 166(8). P. 530-538. Interpretive Summary: Swine production facilities are becoming more concentrated in Iowa, and public is concerned about the impact of using swine manure for crop production on soil and water quality. In the Midwestern U. S., non-point-source pollution of surface water and groundwater resources has been identified as an unintended off-site impact of this agricultural management practice. Field studies evaluating the impact of the use of swine manure for crop production on soil and water quality are needed to provide the information for developing more economically and environmentally sustainable soil and crop management systems. This study was conducted to evaluate the effects of swine manure application on residual soil nitrate N and crop yield. We found that using swine manure as an N supplement results in greater soil nitrate without increasing corn grain yield compared with conventional fertilizers. The results of this study suggest that swine manure application can lead to a build up of soil nitrate which can increase the potential of nitrate leaching into groundwater. The information from this study will be useful to researchers, producers, crop consultants, and NRCS for the development of nutrient managment plans and environmentally sound agricultural management practices.
Technical Abstract: Swine production facilities are becoming more concentrated in Iowa, and public is concerned about the impact of using swine manure for crop production on soil and water quality. This field study was conducted to compare the effects of liquid swine manure and urea ammonium nitrate (UAN) application on crop yield and residual soil nitrate for continuous corn (Zea mays L.) and corn-soybean (Glycine max L. Merr.) rotation systems. Injected UAN provided 135 kg N ha**-1 to continuous corn and 110 kg N ha**-1 to corn grown in rotation with soybean. The 3-year average amount of N from swine manure was 123 kg N ha**-1 for continuous corn and 97 kg N ha**-1 for rotated corn. The average grain yield for continuous corn for UAN and manure treatments (7.8 vs. 7.5 Mg ha**-1, respectively) was not significantly (P = 0.05) different. Corn yields from plots rotated with soybean were significantly different averaging 9.4 and 8.9 Mg ha**-1 for UAN and manure plots, respectively. Similarly, rotation effects reduced the residual soil nitrate by 25% (18 vs. 24 kg N ha**-1) and 33% (20 vs. 30 kg N ha**-1) under UAN and manure N-management systems, respectively, compared with continuous corn plots. The plots fertilized with swine manure also showed greater levels of residual soil nitrate over the winter months (12 vs. 5 kg N ha**-1) compared with UAN-fertilized plots. The results of this study suggest that using swine manure as a nitrogen supplement results in greater residual soil nitrate without increasing corn grain yield, compared with UAN-application, and can, therefore, build up excessive nitrate amounts in the root zone causing increased potential for NO3-N leaching to groundwater.