Value of In-Season N Shows in 2015
By Andy Heggenstaller, DuPont Pioneer agronomy research manager
Rainy spring weather in recent years has led many growers to move away from fall application of nitrogen (N) and toward spring application. Most growers can get N applied before planting with little trouble. However, research is showing that in many cases, particularly with rainy spring weather, in-season application can give the plant the nitrogen it needs at the time it needs it most. This was true in many locations in 2015. Here are a few issues to consider based on what we’ve learned through last year.
Be flexible about nitrogen application timing. It pays to be willing to apply some N by sidedressing after planting.
Based on observations over the past 2 growing seasons, we often see benefits from multiple N applications, including applications in the late vegetative phases of crop development.
When growers apply all of their nitrogen before planting and heavy rains follow, chances are a substantial portion of that N will be lost. Research by Tony Vyn at Purdue and Emerson Nafziger at the University of Illinois has shown that corn can respond to late-season N applications.
In-season application options depend on your equipment.
Most growers can use toolbars with coulters to inject liquid N into the soil after planting (32% UAN, for instance). This requires only a small investment, which is much less than potential yield losses if the crop suffers from a lack of N during critical development phases. In fact, DuPont Pioneer research shows modern corn plants take up 37% of their N need at tasseling or later. Get more information on N uptake in corn.
For late-season N application, growers will need highboys or aerial application, which require a greater investment.
|Percent of N taken up by the plant before and after flowering, and percent
of N in the grain from post-flowering (after VT-R1) uptake and remobilized
In-season N application may not be cost-effective every year.
Spring rains can cause a major loss of N. However, in drier years, growers may not see as large a benefit from in-season N application in some soils. Sandy soils tend to lose N easier than soils with higher clay content. In wet years, research indicates that in-season N applications usually offer a benefit
Don’t make fall applications when it’s too warm.
In 2015, most growers experienced a warm fall. If you’re going to apply N in fall, consider soil temperatures and weather forecasts. If you apply when soil temperatures are 50 degrees or warmer, you can get rapid nitrification of anhydrous ammonia. An N inhibitor may help, but losses are still possible if soil temperatures remain warm for an extended period of time after application. In this case, rainfall after application can cause significant N losses. The crop will never see a benefit from the application.
Get More Tips for Managing Nitrogen