|Vories, Earl - Earl|
Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/19/2012
Publication Date: 9/12/2012
Citation: Tremblay, N., Bouroubi, M.Y., Belec, C., Mullen, R.W., Kitchen, N.R., Thomason, W.E., Ebelhar, S., Mengel, D.B., Raun, W.R., Francis, D.D., Vories, E.D., Ortiz-Monasterio, I. 2012. Corn response to nitrogen is influenced by soil texture and weather. Agronomy Journal. 104(6):1658-1671. DOI:10.2134/agronj2012.0184. Interpretive Summary: Crop yield response when nitrogen fertilizer is applied can be highly variable. For example, adding adequate nitrogen fertilizer to corn will typically increase yield from 25 up to as much as 500 percent when compared to unfertilized corn. This range of responsiveness varies with year-to-year weather variations, and from one soil type to another. The challenge is determining how responsive the crop will be in a given growing season for a specific field location to know how much nitrogen should be added to achieve economically optimal yield. In this research we examined the influence of soil and weather parameters on corn nitrogen response across 51 studies representing a wide range of diverse weather and soil conditions in North America. Soil and weather properties were found to have a fairly pronounced effect on corn response to nitrogen fertilization. Corn response with nitrogen fertilization was 2.7 times greater than unfertilized corn for fine-textured soils. In coarse-textured soils corn yield increase with nitrogen fertilization was only 1.6 times greater. We developed a new precipitation measurement we called “abundant and well-distributed rainfall” that further helped explain corn nitrogen response. When this measure was optimal on fine-textured soils, yield increase with fertilization was 4.5 times greater than unfertilized corn. To a lesser extent, growing season temperature also affected crop response. These results demonstrate that soil texture, precipitation, and temperature can be used to derive improved recommendation rules for in-season nitrogen fertilization of corn. If long-term weather forecasts become more reliable, it will be possible to make adjustments not only for past weather conditions but also for those expected up to 30 days after N in-season applications. Such recommendations would lead to improved crop profitability for farmers, and reduced negative environmental impacts since fertilizer over-application will be reduced.
Technical Abstract: Soil properties and weather conditions are known to affect soil nitrogen (N) availability and plant N uptake. However, studies examining N response as affected by soil and weather sometimes give conflicting results. Meta-analysis is a statistical method for estimating treatment effects in a series of experiments to explain the sources of heterogeneity. In this study this technique was used to examine the influence of soil and weather parameters on N responses of corn (Zea mays L.) across 51 studies involving the same N rate treatments which were carried out in a diversity of North American locations between 2006 and 2009. Results showed that corn response to added N was significantly greater in fine-textured soils than in coarse-textured soils. A new metric called “abundant and well-distributed rainfall” and, to a lesser extent, accumulated corn heat units enhanced N response. At high N rates corn yields increased by a factor of 1.6 (over the unfertilized control) in coarse-textured soils and 2.7 in fine-textured soils. Subgroup analyses were performed on the fine-textured soil class based on weather parameters. Rainfall patterns had an important effect on N response in this soil texture class, with yields being increased 4.5-fold by in-season N fertilization under conditions of abundant and well-distributed rainfall. These findings could be useful for developing N fertilization algorithms that would allow for N application at optimal rates taking into account rainfall pattern and soil texture, which would lead to improved crop profitability and reduced environmental impacts.