By Scout Nelson
Determining the right amount of nitrogen (N) for corn production requires understanding how much N is already available from natural and management-based sources. According to University of Nebraska research, fertilizer is just one of several contributors to plant nitrogen uptake.
When accounted for accurately, N credits from soil, manure, legumes, and irrigation can significantly lower fertilizer requirements while maintaining yields.
Legume crops such as alfalfa, clover, and soybeans play an important role in nitrogen management. While soybeans use most of their own N, alfalfa and clover can leave behind substantial nitrogen that benefits the following corn crop. Research-based nitrogen credit values are assigned from studies comparing yields with and without preceding legume crops, but results vary by field and season.
Soil residual inorganic nitrogen — nitrate (NO3-N) and ammonium (NH4-N) — is another key source. These forms come from mineralization of organic matter and manure. Soil testing for nitrate is the standard practice in Nebraska, as nitrate levels tend to align with ammonium concentrations. Adjusting fertilizer rates based on soil tests helps ensure efficient nutrient use.
Organic matter continuously releases small amounts of inorganic nitrogen through microbial activity. This mineralization process depends heavily on temperature, moisture, and soil type. Since this rate varies, nitrogen credit for organic matter is estimated through long-term research trials across diverse soil conditions.
Manure provides both organic and inorganic nitrogen, as well as other essential nutrients. Its nutrient availability depends on the manure type, application rate, and soil conditions. University guidelines help estimate the amount of nitrogen available from manure applications.
In regions with nitrate-rich irrigation water, crops can also benefit from nitrogen delivered during watering. However, late-season irrigation provides limited benefits since crops absorb most nitrogen earlier in growth.
While cover crops are an emerging nitrogen source, current recommendations in Nebraska do not yet include them in nitrogen credit calculations, though research in this area continues.
By effectively accounting for these nitrogen sources, producers can optimize fertilizer rates, reduce costs, and enhance environmental sustainability in corn production.
Photo Credit:gettyimages-oticki
Categories: Nebraska, Crops, Corn, Alfalfa, Energy, Sustainable Agriculture