Submitted to: International Conference on Precision Agriculture Abstracts & Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/20/2010
Publication Date: 7/18/2010
Citation: Allphin, E.B., Kitchen, N.R., Sudduth, K.A., Thompson, A.L. 2010. Nitrogen Loss in Corn Production Varies as a Function of Topsoil Depth. 10th International Conference on Precision Agriculture, July 18-21, 2010, Denver, Colorado. 2010 CDROM. Interpretive Summary: There are many soil factors which contribute to lower grain yields on farmers’ fields. While insufficient stored water is a major factor for many soils in rainfed environments, the effects of excessive rainfall can also be detrimental to crop yields, as well as to the environment. Excessive rainfall is of particular concern for crops needing N fertilizer to optimize grain production. Nitrogen fertilizer is unstable when rainfall is excessive, and can leach into ground water or be lost into the atmosphere as a greenhouse gas. As nitrogen fertilizer costs for corn production increase, the importance of preventing loss of N also increases. Farmland that has high amounts of clay in the subsoil (often called a claypan) seem especially vulnerable to gaseous losses of nitrogen to the atmosphere. These soils stay wet for days after rain and therefore are prone to having nitrogen convert to nitrous oxide gas and dissipate out of the soil into the atmosphere. This study was conducted to evaluate the influence of the depth of topsoil above the claypan on nitrogen loss from an excessively wet growing season. We found that a greater proportion of the soil nitrogen available to the crop was lost with less topsoil depth. Loss was estimated between 60 and 120 lbs N/acre with the greatest losses coming from soils with little or no topsoil. The significance of this research is that it will show farmers the need for site-specific N management strategies that can be targeted to landscape variations.
Technical Abstract: Understanding availability and loss potential of nitrogen (N) for claypan soil landscapes that vary in topsoil depth could help producers make better decisions when managing crops for feed grain. While it has been well documented that topsoil depth on these soils plays an important role in storing plant-available water, it is not well known how this same soil property affects N loss for growing seasons that are abnormally wet, such as was the case in 2008 and 2009 for much of Missouri. This 2009 plot study was conducted to evaluate, for an excessively wet growing season, the influence of depth to claypan (DTC) on unaccounted for N (UN) in corn grain production. In order to understand this relationship, N recovered in grain and stover, grain yield, and SPAD chlorophyll meter readings were taken from corn grown on a range of topsoil depths (0 to 50 cm) and fertilized with 168 kg N/ha. Observations during this growing season showed that N stress to the corn crop increased as DTC decreased. Yield in the shallow DTC soils was also suppressed. The loss of inorganic N (IN) increased from 70 to 140 kg N/ha, as DTC decreased. We attribute the loss largely to denitrification. The significance of this research is that it helps to establish the need for site-specific N management strategies that can be targeted to landscape variations.