By Kyle Poling, Pioneer Field Agronomist, Ada, Ohio
Nitrogen (N) is typically the most yield-limiting nutrient in corn production. Additionally, nitrogen management is among the most uncertain and costly inputs of modern corn production. With N accounting for up to 20% of total crop cost, growers are faced with the challenge of how to meet N requirements without over-applying or under-applying.
An ideal nutrient management plan would be for a grower to make nitrogen available to the corn to supply adequate amounts of N as the crop needs it. Only about 10% of the total amount of nitrogen is taken up between the period of corn emergence to knee high. During the rapid vegetative growth phase, from V8 through tasseling, corn generally requires over half of its total N supply. Providing adequate N for this period is a key goal of N management.
The last one-third of a corn plant’s N requirement must still be met by uptake during the reproductive stages (ear-fill). Nitrogen uptake during the ear-fill period can minimize the remobilization of N from vegetative to reproductive tissues. This means that the plant does not have to cannibalize the leaves to provide N for kernel development when it can take up N from the soil during this period. A corn crop that carries plant health (green leaf area) into late summer/early fall extends the duration of photosynthesis, continues carbohydrate production, and maintains the opportunity to add additional grain yield.
Applying N at multiple times can spread the risks of nitrogen loss and crop deficiency, improve profitability by reducing N rates, and benefit the environment by not applying “insurance fertilizer” that can potentially be lost. To help reduce N losses from rainfall related losses, nitrogen “stabilizers” or “additives” can be applied along with N fertilizers.
Yield goal and generalized nitrogen response relationships are often the best benchmarks available to guide management. However, neither of these approaches account for how variability in soils and weather affect crop growth and nitrogen availability at specific locations. Crop models offer one way to bring field and weather variability information into the nitrogen management decision-making process. While crop simulation models have historically been used for research purposes, advances in cloud computing and data management now make it possible to effectively extend crop models to commercial production systems. One of the major advantages of using crop models to guide nitrogen management decisions is that they can integrate the numerous, complex processes that affect soil nitrogen and provide actionable information that has meaning in a management context. Crop models can also incorporate weather information dynamically, as it occurs, so that nitrogen can be monitored and managed in real time.
Key components that can be integrated into a nitrogen model include: (1) crop uptake of nitrogen during crop growth, (2) nitrogen mineralization by breakdown of organic matter, and (3) loss of nitrogen through leaching, denitrification, and volatilization.
The outcomes of nitrogen management decisions are inherently inexact due to imperfect knowledge of future weather events that strongly influence crop growth and soil nitrogen levels. Nitrogen modeling is a new tool that corn growers can incorporate into their nitrogen management system to account for uncertainty in the weather in conjunction with grower yield goals to provide estimates of the risk associated with planned management actions. This exciting new tool will allow growers to use science to remove some of the guesswork from corn nitrogen management.
For more information regarding nitrogen monitoring, contact your local Pioneer sales representative or visit Pioneer GrowingPoint agronomy at pioneer.com/agronomy.