Nitrogen School Part 1: Back to Basics
When is the last time you went to school? Well we are going to school today, and the topic is Nitrogen. Before you click the back button and decide you’d rather go look up videos of antique tractors or grain markets, give us a chance here.
Why is Nitrogen important for corn? We know plants need it, but what do they need it for? Nitrogen is a major component in chlorophyll and ADP and ATP. This means that if we don’t have enough nitrogen, a plants photosynthetic capacity is reduced, which means less vegetative and reproductive growth. ADP and ATP are compounds that help transfer energy in the plant. Nitrogen is a part of ADP and ATP, so in order to adequately transfer energy throughout a plant, adequate N is needed. So, we all get the picture, right? For the very very very necessary functions in a plant, photosynthesizing and then moving that light energy throughout the plant, nitrogen is super necessary. We see that manifested in fields with adequate N; they have high photosynthetic rates, grow very vigorously, and are dark green in color. We’d love all fields to look that way. However, obtaining adequate nitrogen comes at a cost, both monetarily and in regards to timing.
Plants can pull nitrogen from the soil---but available resources of nitrogen are limited both by quantity and form of N in the soil. Essentially, a plant can utilize N in two forms, N03 and NH4. NH4 is a little more energy efficient for a plant, but both are viable sources. In the soil, the majority of N is held in organic forms as amino acids, or proteins or bound up NH4. This is not readily available to a plant. Mineralization is the process that turns those organic N sources into available NH4. This process is completed by microorganisms. This process can go the other way, with available NH4 converting back to organic N through the process of immobilization. Some of the NH4 produced by mineralization is converted to N03 during nitrification. There are many other steps in the nitrogen cycle converting N2 to NH4 and NO3 back to N2 and movements of NO3 throughout the soil. But that’s enough about the nitrogen cycle.
For crop production, synthetic fertilizers are derived from NH3. This compound is created from N2 in the air, and natural gas CH4. Since this is a limited fossil fuel, N costs may increase as this resource becomes scarcer. All other synthetic N fertilizers are made from this source. These fertilizers are applied in the fall or early spring in preparation for the growing season. However, the critical period for corn uptake is not really occurring until V10. During the growing season, very little N is necessary due to size and function of the plant. This is also theoretically when we have the largest amount of N available after fertilizing. It is with this in mind that we consider practices such as in season nitrogen applications to better match demand with application in an attempt to both reduce nitrogen loss and increase profitability by tailoring applications to the demand of the plant and growing season. This is particularly beneficial during wet growing seasons when a large amount of N may have been lost due to leaching and runoff. While logistically, applying your total nitrogen at one time in fall or spring may make the most sense, financially and often economically, a single application may result in wasted and lost N as well as wasted input costs. In season applications help match nitrogen availability to the time period when the crop is taking up nitrogen.
In season N is a large and challenging topic to cover. To do so, we’ve lined up some great guests on the blog. This is the first of a three part series. You’ve made it through part one. In part two, we will hear from UNL extension educator Laura Thompson who researches in season nitrogen applications both with a UNL team focused on nitrogen use efficiency called Project SENSE and also by using drones for assessing crop health and making nitrogen recommendations based on imagery. Part three will feature Cody Boeck with Encirca Services, who will touch on the nitrogen components of Encirca and its use of imagery and weather models to predict available N throughout the growing season. We are excited to have them here on the blog and learn more about in season nitrogen!