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AGRONOMY TALK: NITROGEN TIMING AND PLACEMENT

Published on Tuesday, March 10, 2020

Nitrogen (N) is a mobile nutrient. When we look at the N cycle, we think of NO3 - is the N form most readily taken up by the plant, followed by NH4 +. Loss of N when applying urea or UAN can occur as ammonia volatilization (lost in gaseous form). In the case of UAN applications, N loss can also occur in the form of NO3 - leaching if a heavy rain follows or denitrification. Two ways to prevent N loss are more accurate timing and more precise placement. If we can supply N to the plant when it needs it, this allows less time for N loss. If we supply N near the base of the plant where it can more easily access the nutrient, this could increase N use efficiency.

WHAT HAPPENS WHEN N IS APPLIED?

A number of things can happen to N once it is applied as a mobile nutrient. Regardless of the N form you apply, once it's in the ground it will either be taken up by the plant, be immobilized (tied up by soil microbes in the soil), or be lost via one of four methods:

  1. Surface Displacement
  2. Volatilization 
  3. Denitrification
  4. Leaching

Utilize the 4R approach to N management to maximize crop productivity while minimizing N loss. This includes: considering the right form, at the right rate, at the right time, and in the right place. 

WHEN IS N USED?

A corn plant uses a great deal of its N later in the growing season. In fact, over 75 percent of N uptake occurs after the V10 growth stage. The most rapid uptake usually occurs between V8 and VT when the corn plant takes up between 7 to 9 lb. of N each day. Ensuring that ample N is available in the correct form during the corn plant’s growth is key to maintaining the potential in every field.

 

 

N TIMING

Four years of replicated PFR data has shown an advantage to sidedress applications of N. Does that mean sidedress applications will pay every year and in every environment? No. But when it comes to N, managing risks is a solid approach. Sidedress applying N decreases your risk from the four N loss mechanisms because less is exposed at any one time to large losses. It also helps provide an adequate supply during the key growth stages. 

 

 

PFR TESTED PRODUCTS THAT MAY HELP REDUCE LOSS OR IMPROVE N TIMING AND PLACEMENT.

Through our multi-year research, we have learned that a few products have provided a positive yield return. One of those products is nitrogen sealers, which are a pair of coulters that attach to the sidedress bar. The coulters help seal the knife trench, which aids in reducing the potential for volatilization of the urea portion of 28% UAN.

 

WHAT ABOUT OTHER PRACTICES AND PRODUCTS?

Beck's PFR continues to research other products and practices such as placement of N via 360 Y-DROP® next to the row, which has yielded some positive results. We've also tested 2x2x2 systems Yetter Dual 2968 Series and Precision Planting's Conceal system over the past three years and witnessed consistent yield gains of 7.0 Bu./A. more when placing nutrients on both sides of the plant. Instead of using one coulter, we now have two. Fertilizer is applied in the same amount in the 2x2x2 as the 2x2 system, but with a reduced salt load on the plant. Nutrients can be more evenly applied to the plant in a 2x2x2 system, resulting in improved root and plant health, as well as root uniformity. An unintended result of placing nutrients only on one side of the row is preferential root growth. Roots proliferate in the direction of higher nutrient concentrations, leaving the other side of the row relatively underdeveloped. 

 

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Author: Jim Schwartz

Categories: Agronomy, Agronomy Talk

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