Author
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Jaynes, Dan |
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Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/27/2015 Publication Date: 7/24/2015 Citation: Jaynes, D.B. 2015. Corn yield and nitrate loss in subsurface drainage affected by timing of anhydrous ammonia application. Soil Science Society of America Journal. 79:1131-1141. Interpretive Summary: High nitrate concentrations in the Nation’s surface waters are a recurring environmental and public health problem. The source of much of this nitrate is agricultural use of N fertilizers. Thus, there is much interest in developing farming practices that reduce off-site effects of fertilizer use while maintaining the economic viability of crop production. The effects of application timing of N fertilizer on both crop yield and water quality has been little studied in the Midwest cornbelt. In this study, we measured crop yield and loss of nitrate in tile drainage from a production field applying anhydrous ammonia fertilizer either in the fall, or in the spring before planting, or as an early season sidedress. We showed that sidedressing N makes the greatest use of the fertilizer N, maximizes crop yield, and minimizes nitrate leaching to tile drains compared to either fall or spring pre-plant applications. These findings will be of use to soil fertility and environmental experts, farmers, and crop consultants. Technical Abstract: Surprisingly little research has examined the corn yield, N use efficiency, and water quality implications of N fertilizer timing. We applied anhydrous ammonia either in the fall after harvest (F) at 196 kg ha-1, or in the spring before planting (PP) or as an early sidedress (SD) at rates of 168 kg ha-1 on replicated plots within a producer’s field used to grow corn and soybean in a two year rotation. The field was underlain with subsurface drainage pipes (tiles) which were used to collect drainage and nitrate lost from the root zone for each plot. A fourth treatment was added when the initial fall N application was accidentally over applied by 3 fold on two plots (FH), allowing us to follow this one time application over four years. There were no significant differences among treatments for soybean yield. Over the two corn years, yields for the FH and SD treatments were at least 1.5 Mg ha-1 greater than for the F and PP treatments. The Nitrogen Use Efficiency and Partial Factor Productivity for N metrics in corn followed similar patterns; SD>PP>F>FH and SD>PP=F>FH, respectively. Flow-weighted annual nitrogen concentrations in the tile drainage were significantly different and followed the pattern FH>F>SD>PP. Effects of the over application of N for the FH treatment could still be measured after 4 years and impacted yield and nitrate losses well after the first year. Considering yield, N use efficiency, and nitrate losses, sidedressing N was clearly superior to fall application in a corn – soybean rotation. |
