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WWW.POTATOGROWER.COM 43 Zeba is a starch-based soil enhancement that reduces nutrient leaching and plant water stress. Crops produce more and yield higher quality. Learn more at www.Zeba.com Boost your potato yield, quality, and profits Zeba is a starch-based soil enhancement that reduces nutrient leaching 170774UniPho12h.indd 1 12/7/17 1:57 PM from an irrigated continuous corn rotation. (No data is currently available on how other rotations might alter the residue removal effect on plant-available water.) However, residue removal did not just diminish plant-available water; it also reduced water infiltration. After six years of removing 60 percent of corn residue, the rate of water infiltration into the soil decreased from 2.13 inches per hour to 1.43 inches per hour. In short, residue removal caused the soil to allow less water to enter the soil and less water to be available for plant use between rain and irrigation events. That could mean greater loss of water in runoff rather than the water being stored in the soil to support crop growth. How do CoVer Crops aFFeCt plant-aVailaBle water and water inFiltration? Long-term, 12-year experiments in Kansas and Maryland have found that cover crops do increase water infiltration. Cover crops were found to increase plant-available water after 12 years in an experiment in Iowa using cereal rye and in Kansas using legume cover crops. In Nebraska research, after six years, cover crop use did not increase water infiltration, but we expect to see an effect in the longer term. so, Can CoVer Crops mitigate or oFFset tHe negatiVe eFFeCts oF Corn residue remoVal on water inFiltration and plant aVailaBle water Content? After six years of research in south- central Nebraska, cover crops had no effect on plant-available water or on water infiltration; however, they did partially offset soil carbon losses caused by aggressive corn residue removal. This is not necessarily bad news, as there is a positive relationship between plant-available water and soil organic carbon. This relationship exists due to the greater water absorption capacity of organic particles compared with inorganic particles. Also, as you increase soil organic carbon, soil aggregates become more stable and can support more pore spaces that can store more plant-available water. As soil carbon is lost from the soil, the aggregates become weaker and the larger pore spaces collapse into smaller pores, decreasing water storage capacity of the soil for plant use. Therefore, if soil organic carbon is lost from the soil, plant-available water is lost from the soil. Unfortunately, it is easier to lose than to build carbon in soils. summary It is easy to rapidly lose plant-available water and soil organic carbon when removing plant residues. However, it takes time (more than 10 years) to increase soil organic carbon in the soil and improve the soil structure to increase plant- available water. The same is true for water infiltration. Soil aggregate stability and organic carbon can decrease in just three years due to high rates of corn residue removal, but their restoration with cover crops may take much longer. This means that management decisions made now will affect the future productivity of your field and the sustainability of your farming operation. Michael Sindelar is a cropping systems extension educator, Humberto Blanco an associate professor of soil science, and Richard Ferguson an extension soil fertility specialist, all with the University of Nebraska. Virginia Jin is a research soil scientist with the USDA's Agricultural Research Service.