Corn needs nitrogen and phosphorus in the soil to produce quality grain. For years, farmers have added these nutrients to the soil through manure applications and, more recently, directly injecting them into the soil.
However, the actual use of nitrogen and phosphorus per bushel has decreased in recent years. Corn yields are going up and nutrient applications are decreasing, allowing farmers to use 36 percent less fertilizer for their crops than they did only three decades ago. In addition, new tillage practices are reducing soil erosion which, in turn, decreases nutrient run off. If you look at their numbers, there is less phosphorus and nitrogen per bushel of corn now than ever before.
Increased ethanol production has had no impact on phosphorus and nitrogen run off.
Recent information is now looking at “legacy phosphorus and nitrogen” – a term coined by the EPA to indicate nutrients that were washed into the streams and rivers and deposited 50 years ago and are now being moved downstream by the heavy rainfall events of the last few years. It is estimated that it may take 30-50 years before this huge reservoir of sediment and nutrients will be washed out of the River system. Thus the significant reduction in applied nutrients/bushel currently is actually keeping the levels of nutrients in our water systems from being as high as they could be.
Ex Officio Director, ICGA & U of I Extension Specialist