PROTECTING SURFACE AND GROUND WATERS IN EMERGING FARMING SYSTEMS OF THE NORTH CENTRAL UNITED STATES
Location: Soil and Water Management Research
Title: Coupling landscape water storage and supplemental irrigation to increase productivity and improve environmental stewardship in the US Midwest
Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 21, 2012
Publication Date: May 4, 2012
Citation: Baker, J.M., Griffis, T.J., Ochsner, T.E. 2012. Coupling landscape water storage and supplemental irrigation to increase productivity and improve environmental stewardship in the US Midwest. Water Resources Research. Available at: http://www.agu.org/journals/wr/wr1205/2011WR011780/.
Interpretive Summary: Due to ever-increasing population and higher standards of living, agricultural production must continue to increase to satisfy demand for food and renewable energy. At the same time, it is necessary to improve the environmental footprint of agriculture, particularly losses of sediment, nitrogen, and phosphorus. We suggest that these goals can be simultaneously addressed within the U.S. corn belt by combining increased landscape water storage with supplemental irrigation. This will reduce flooding and associated nutrient losses while stabilizing yields and permitting the adoption of alternative cropping practices, like cover crops and living mulches, that provide environmental benefits but increase the risk of soil moisture depletion. Data show that both mean annual precipitation and stream flow have increased substantially over the past 50 years. Consequently, there is water available to supply supplemental irrigation if it can be stored during periods of excess. Restoration of wetlands and construction of ponds could provide that storage. This would also provide wildlife habitat and would serve as a buffer to reduce downstream losses of sediment and nutrients. Additional biomass from cover crops and companion crops could be used as forage or as a renewable fuel source. Producers would benefit from this additional productivity and also from the reduced financial risk associated with irrigation-stabilized yields, while the broader public would enjoy the environmental benefits.
Agriculture must expand production for a growing population while simultaneously reducing its environmental impacts. These goals need not be in tension with one another. Here we outline a vision for improving both the productivity and environmental performance of agriculture in the US Corn Belt. Mean annual precipitation has increased throughout the region over the past 50 years, consistent with climate models that attribute it to a warming troposphere. Stream gauge data indicate that higher precipitation has been matched or exceeded by higher stream flows, contributing to flooding, soil loss, and excessive nutrient flux to the Gulf of Mexico. We propose increasing landscape hydrologic storage through construction of ponds and restoration of wetlands to retain water for supplemental irrigation while also reducing flood risks. Primary productivity is proportional to transpiration, and analysis shows that in the US Midwest both can be sustainably increased with supplemental irrigation. This will reduce interannual yield variability by limiting losses due to transient drought, while facilitating adoption of cropping system modifications, such as inclusion of companion crops and winter cover crops, that “perennialize” the landscape to take advantage of the full potential growing season. When implemented in concert, these practices would reduce the riverine nitrogen export that is a primary cause of hypoxia in the Gulf of Mexico. Erosive sediment losses would also be reduced through the combination of enhanced hydrologic storage and increased vegetative cover. Successful implementation would require watershed-scale coordination among producers and landowners. An obvious mechanism to encourage this is governmental farm policy.