There are economic and environmental pressures for farmers to consider applying their nitrogen at more than one time. Nitrogen that is lost to nitrification and nitrate leaching is not available for crop use. In addition, nitrate-nitrogen lost from farm fields can move into ground and surface waters resulting in water quality and potential regulatory issues.
This summer the Illinois EPA released the final draft of the Illinois Nutrient Loss Reduction Strategy. In the NLRS, "Splitting fertilizer applications to align with when plant uptake is greatest", essentially side-dressing nitrogen, is highlighted as one of the changes in fertilizer application practices that could significantly reduce nitrate-nitrogen losses.
Each year's weather seems to bring management challenges. One need only think back to this June and July when record-setting rains throughout Illinois seemed never ending. The saturated soil conditions that kept sprayers out of many fields could have just as easily kept out side dress equipment.
To help farmers pencil out some potential costs and benefits of splitting nitrogen applications, a group of university-based economists, agronomists and climatologists developed a free decision support tool called Corn Split N. This tool takes into account acreage and equipment size and uses more than 30 years of climate data to estimate the consequences of splitting N under both the best- and worse-case scenarios. Climate data is used to estimate how quickly corn grows - and may outgrow existing N supply- and how many days have historically been favorable for field work during weeks in which side dress applications are estimated to need to take place. The tool allows one to input current prices (N price, corn price) and helps to estimate side dress costs and savings. There is even a "Help" function that guides users through program features.