Now Reading: Iowa Crops Experience High Yields Despite the Effects of Drought

Iowa Crops Experience High Yields Despite the Effects of Drought

by Iowa State Professors Sotirios Archontoulis and Michael Castellano

January 18, 2018


The Climate Corporation is proud to partner with Professors Archontoulis and Castellano and fund their research.

2017 was a dry growing season in Iowa but yields were better than expected. Most of Iowa was wet and cool during planting time (end April to mid-May), warm and dry during vegetative growth (June to July), and cool and wet during reproductive development (August to September). In some locations, the June-July drought was severe with precipitation deficits exceeding eight inches (Figure 1). Despite this drought, yields were high and above the long-term trend for a third straight year.

Soil Moisture as Crop Irrigation During Drought

Apparently, in-season rainfall is not the only source of water for crops in Iowa. Stored soil water and shallow groundwater were significant contributors to total water uptake. For this reason, crops survived the June-July drought. Field measurements revealed that the depth to water table was approximately five to six feet below the soil surface in mid-July (corn silking time) and crop roots had reached that depth.

Presence of Shallow Groundwater on Soil Health During Drought

In terms of grain yield equivalent, model analyses suggest that root access to shallow groundwater accounted for 1% to 46% of total grain yield. The contribution was lower in sites with sufficient rain and higher in sites with drought. In addition to water, the same analyses indicated that the subsoil had more than enough nutrients for sustaining high crop yields. Furthermore, cool temperatures in August extended the growing period. The benefit of the extra growth was evidenced by larger than normal kernel size in corn.

High Crop Yields Moving Science of Digital Agriculture Forward

Together, all these factors contributed to surprisingly high corn yields in 2017. Deep roots and shallow water tables compensated for much of the precipitation deficit. In fact, below normal June precipitation is favorable in Iowa for two reasons: i) rapid and unconstrained root growth (up to 1.3 inches per day); ii) given generally high soil water content in the early spring, additional precipitation will stimulate nitrogen loss. Quantifying water table dynamics across the state has been an important component of moving the science of digital agriculture forward to enable better predictions of yield and will greatly assist management decisions and predictability of crop yields and nitrogen losses.

Figure 1: Cumulative difference between 2017 precipitation and 35-yr average for different locations in Iowa. SW = southwest, NE = Northeast, NW = Northwest, SE = Southeast. Grain yields ranged from 190 to 235 bu/ac.

About the Authors

Sotirios is an agronomist and cropping systems modeler by training. His main interest is to more deeply understand interactions between Genotype, Management and Environment to predict outcomes that can be used on the farm to inform more efficient management decisions.

Mike is excited to work in ag, as it offers an opportunity to work toward greater environmental quality and human health. He has particular interest in nitrogen because it frequently limits production but is easily lost to the surrounding environment where it becomes an economic loss to farmers that can diminish air and water quality.

Sotirios Archontoulis and Michael Castellano are professors at Iowa State University where their research, teaching and extension focuses on linking soil, plant and weather processes to develop better predictions of yields and efficient management practices. This research and future research about the importance of shallow groundwater also was made possible by a “New Innovator in Agriculture Award” to Dr. Archontoulis that was funded by the USDA Foundation for Food and Agricultural Research and the Iowa Crop Improvement Association.