Corn—the principal crop produced by America’s robust agricultural industry—generates billions of dollars of income annually and supports millions of farms across the country. This level of production feeds populations around the world and sustains the U.S. economy—but it could be higher.
Although farmers, lawmakers, and scientists may be able to improve corn yields with careful management, policy, and genetic modifications, some of the biggest influences on production are beyond human control. For example, having water in the right place at the right time can make or break a harvest, but it is still fairly unclear how variables such as water table depth, soil texture, and growing season weather conditions interact to influence agricultural production.
Here Zipper et al. apply a systematic approach to help untangle this uncertainty using a combination of field observations and modeling to clarify how each variable impacts corn yields.
Working with a local farmer, the scientists collected data from soil samples and groundwater monitoring wells in two neighboring fields in south central Wisconsin, and the farmer provided maps of yield data at harvest time. The silt and silt loam soils are kept moist by rainfall and shallow groundwater, rather than irrigation. The study spanned two growing seasons, in 2012 and 2013, a time period with major differences in precipitation levels due to a drought that struck in 2012. All of this information was plugged into Agro-IBIS, a computer model built to simulate crop growth and the movement of water, energy, and carbon.
Examining the harvest data, the researchers found that the shallowest water tables, which were 1 meter or less below the ground’s surface, had a negative effect on crop yield during wet years—but boosted productivity during drought, when rainfall did not provide enough water for the plants. An intermediate water table depth, between 1 and 3 meters, had a positive impact on crop yield regardless of weather. Parts of the field with a water table more than 3 meters below the surface performed poorly, particularly during drought, as did areas with coarser soils.
Overall, computer simulations indicated that coarser soil textures benefited more frequently from a shallow water table, especially during dry growing seasons. Because of this, the scientists concluded that soil texture was the key variable in determining whether the amount of precipitation and the depth of the water table had net positive or net negative impacts on crop yield. A better understanding of these interactions is key to improving agricultural yields and feeding a growing global population sustainably. (Water Resources Research, doi:10.1002/2015WR017522, 2015)
—Lily Strelich, Freelance Writer
Citation: Strelich, L. (2016), Soil texture determines how groundwater and rain impact crops, Eos, 97, doi:10.1029/2016EO043945. Published on 20 January 2016.