Protecting Corn Yield with Nitrogen Management
Nitrogen is one of the most critical nutrients in corn production, and a well-planned nitrogen management strategy helps position growers for stronger performance and greater success at harvest.
Crop Demand and Timing
Corn needs ample nitrogen throughout its lifecycle but has different uptake throughout the season. The plant consumes 55% of its total nitrogen demand from V6 to VT and 40% from R1 to R6.
“We know from extensive research that corn uses a lot more nitrogen later in the season than it has in the past,” said Ron Joiner, Pioneer territory manager. “In the last 10 years or so, corn is utilizing way more nitrogen post tassel than it did in the years past, and that’s one of the reasons it’s a good idea to think about split applications of nitrogen.”
Soil Testing
Corn can only take up ammonium and nitrate forms of nitrogen from the soil. However, the most critical factor to consider is not the form, but the amount of actual nitrogen applied. Testing the soil before or during the season can determine the amount of nitrogen needed throughout the season.
The preplant soil nitrate test is generally most useful in fields where substantial carryover of nitrogen is expected and has historically been used where rainfall amounts are low enough to prevent substantial leaching during the fall to the early spring.
The late-spring soil nitrate test, also called the pre-sidedress nitrate test, is generally used for humid areas where soil testing for residual nitrogen has not been effective. This test is essentially an in-situ mineralization test to determine if additions of fertilizer nitrogen are needed.
Nitrogen Management Strategies
Split nitrogen applications are the best way to address the plant’s varying needs, specifically one application right before planting and another around the V5 growth stage. It is preferred that the second application is sidedress nitrogen to ensure access for plant roots. It is also possible, though less desirable, to apply nitrogen by aerial application or high-clearance equipment.
Use historical weather data to determine how much applied nitrogen may be lost in a typical month, estimate how many days are available for fieldwork and develop a nitrogen timing strategy with a high probability of working most years. A backup plan should be in place for in-season applications in case of adverse weather. A quickly implemented backup plan can help avert significant nitrogen deficiency and impact yield by at least 10% to 15%.
Applications should be weighted heavily for soil type and topography, which impacts retention and ability to apply additional nitrogen. These factors vary by region and individual field, so split applications will not work for every field.
Spring and fall applications are the next most common timings. Spring timing is preferred over fall, because it provides less time for nitrogen loss. For fall applications, it is best to use only ammonium sources of nitrogen as it is more stable.
Whenever farmers apply nitrogen, it’s important to maximize the return on investment by ensuring availability to the plant. The type of nitrogen applied and field conditions play a large role in determining availability later in the season.
Soils can lose nitrogen in several ways. Nitrates can leach from the soil as water carries nitrogen below the crop root zone. Microbial activity can cause denitrification by converting nitrogen to N2O or N2 gas that is lost to the atmosphere, especially in warm, saturated soils. Soil-applied urea can be lost to volatilization as unincorporated manure or urea-containing fertilizers are converted to ammonia gas (NH3), especially with a wet soil surface and warm weather.
Nitrogen stabilizers, such as N-Serve and Instinct NXTGEN, can help protect previous nitrogen applications by slowing the chemical reactions in the soil that cause nitrogen loss. Nitrogen losses can also be reduced by incorporating fertilizer into the soil, improving drainage and adjusting the application timing.
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