Cover crops have been found to prevent nitrogen leaching into waterways. They have also been found to reduce soil erosion — an implication of legume cover crops to be integrated with synthetic fertilizer in the future.
Non-point pollution is one of the major concerns of many scientists today. They have been looking for ways to lessen non-point pollution that results from agricultural practices. Recently, a group of scientists have found a possible and practicable solution. They found that using straw residue in conjunction with legume cover crops the leaching of nitrogen into the waterways has diminished. However, the economic return may also be relatively lower.
The practices applied in agriculture are considered as a major contributor of nitrogen non-point pollution as what is observed in the waterways in the United States. These contaminated waterways aggravate the situation as they flow into streams and rivers through erosion from farmlands or through nitrogen leaching into groundwater. If the contaminated water source reaches the aquatic systems, the excess nitrogen leads to aquatic ecosystem degradation. For instance, the pollutants in the water leas to oxygen deprivation, which in turn results in fish kills and the existence of dead zones. As for the potential health risks of nitrate leaching, nitrates reaching the drinking water supplies can truly be a health concern for they are associated with blue-baby syndrome, many cancers, and birth defects.
A research study by Penn State scientists identified the potential of straw residue to retain legume-derived nitrogen in a corn cropping system. In their study, straw residues were spread on plots that were later planted with to hairy vetch (a legume cover crop). Next, they planted a corn grain crop into the vetch with straw residues. Based on their findings, the soil inorganic nitrogen was about seven percent lower in the treatments with straw residue retention. Not only did the magnitude of the peak of nitrogen in soil is reached with this type of residue but also the timing of this peak. Timing is important since the nitrogen availability should coincide with the corn nitrogen demand. Although the results were promising, the reduced availability of nitrogen in the soil affects the corn grain yields negatively. In one year of the study, the yield is 16 percent below of the county average. Their study, however, has not been conclusive in terms of the use of straw residue to help retain nitrogen would be able to compensate the income losses from harvesting the straw.
~ Prepared and adapted by Vicki Mozo from a press release from American Society of Agronomy entitled "Straw Residue Helps Keep Nitrogen on the Farm" in https://www.agronomy.org/news-media/releases/2010/0524/356/.