Nitrogen is an essential plant macronutrient, and while 78% of the earth’s atmosphere is composed of nitrogen, it is not in a form available to most plants (with the exception of some nitrogen-fixing legumes that harness it with a bacterial symbiosis).
Therefore, fertilizer is applied to crops in forms that are readily taken-up by plant roots, as nitrate (NO3-) and ammonium (NH4+).
While this provides a boost in crop growth and yields, there is a problematic outcome: because both soil particles and nitrate (NO3) ions have negative charge, soils cannot retain nitrates for later uptake. This means that nitrates move in soils together with the water flow and might end up in groundwater and even surface water. The extent of leaching depends mainly on soil properties, amount of water applied and timing of nitrogen application. For the farmer, nitrate leaching means loss of money and yields.
Nitrates are toxic to humans: causing problems with oxygen absorption. They do roughly the same thing in waterways: causing eutrophication—or de-oxygenation—of water, which has adverse effects on aquatic ecosystems and the environment.
There are a number of ways in which you can minimize nitrate leaching, and most of them have to do with SMART! management of crop inputs.
First and foremost, over-fertilization is a problem to eliminate in preventing nitrate leaching. It’s a waste of product and money, as well as an environmental hazard. Managing fertilizer inputs precisely can go a long ways towards maximizing value for money on inputs, as well as taking care of the local environment.
Plants take-up different nutrients at different stages of growth. Applying fertilizer at the wrong time is a common mistake that is easily corrected with the right information. Splitting applications and using different concentrations according to growth phase will both increase yields and prevent excess leaching.
As nitrates move with water, proper irrigation management—based on an understanding of the topography and soil composition of the cultivated area as well as the needs of the particular crop—can help manage nitrate leaching.
The rate of nitrogen application hinges upon the yield goals, which were defined by Dahnke et al. (1988) as the, “yield per acre you hope to grow.” This is different from the maximum or potential yield, which presupposes perfect conditions. Yield goals can be informed by data from previous years, as well as expected conditions. The required rate of nitrate application should correspond to a realistic yield goal, and not to a maximum possible yield.
Technological interventions such as software decision support tools are a vital part of best management practices in agriculture in the 21st century. SMART! Fertilizer Management software tools can help you maximize yields while saving up to fifty percent on fertilizer costs.