Sidedress Nitrogen

Cornin-furrowNitrogenNutrientsidedressy-drops

4 Quarters to the Game!

If you’re playing a game of basketball, you know you’ll need to bring hydration with you so you can replenish your body throughout the game to keep you going.  The crop in our field is no different. We can lay down nutrients at the beginning of the season and hope the crop is fed for the whole season, or plan some in-season applications.  With the progression of equipment and application, adding additional nutrient applications throughout the year has become standard and an accepted practice.  So, when should you concentrate most on additional applications? 

V4-V5 Corn Application

Best practices would say the corn will reach V4 about 22-24 days after emergence, based on GDU’s.  By knowing this information, you can better plan that sidedress trip across the field.   When planning to sidedress corn at V4, it allows the nitrogen to be there for rapid uptake. It also allows extra time for weather that can interrupt and delay our plans.  Once we reach V8, corn absorbs between 4 and 8 lbs of nitrogen per day as the plant grows from about 12 inches to 12 feet tall. By tassel, it has taken up approximately 60% of what it needs for the season. This early application timeframe is ideal to ensure nitrogen availability during peak uptake demand. 

Sidedress application is one of the best ways to utilize your dollar spent on nitrogen fertilizer.  Since placement and timing are big factors in how well your nitrogen fertilizer is taken up, using Y-drops at V3-V4 would be ideal to lay nitrogen near the rootzone and right before the period of rapid uptake. Corn roots remain relatively small at V3 - V4 and often cannot reach the middle of the row.  Sidedressing in the middle of the row (during V3-V4) is not as ideal, but still a better option than placing all of the fertilizer up front. 

Does sidedressing nitrogen always lead to higher yields? That depends; sidedressing nitrogen allows for better nutrient placement and utilization.  The soils aren’t as warm early in the season, which means they haven’t mineralized many nutrients, so having some nitrogen present at V3-V4 keeps the crop fed.   If we experience heavy rain events and nitrogen is leached or denitrified, there is a strong likelihood that sidedress nitrogen will contribute to yield increases. 

For example, corn planted April 13-14.  Emerges, April 28-29.  Plan on that sidedress trip, around May 22.  Call your Agronomy Field Advisor today!

Liquid vs. Urea

There are a few cons to using urea in-season.  To effectively use urea during the growing season, it should be properly incorporated. This can be done with rainfall; a minimum of 0.5 inches is required to accomplish the incorporation and prevent loss of urea.  Urea loss is typically lost to the atmosphere.  Urea can also be difficult to spread evenly across tall corn. Keep in mind that tall corn can act as a funnel or wall, blocking the dispersal rate of urea applied over the top of the plants.  Urea particles typically vary in size, which leads to uneven spread patterns as they "fling" at different rates. UAN, on the other hand, is only 50% urea and is about half as susceptible to ammonia volatilization compared to urea.  UAN can be subsurface injected, eliminating volatilization chances, or surface banded, which still significantly reduces volatilization.  Sidedress applications of UAN are uniform across the acres and reduce the yellow streaking often associated with top-dressing urea.  Of course, using a nitrogen stabilizer at any UAN application should be discussed with your Agronomy Field Advisor.  

Late Season Application - We Can Do It. Is Late Season the Right Time?

The development of “ highboys” and Y-drops has allowed for nitrogen applications later into the growing season, which is ideal for workload and logistics in many cases.  But, is that better for the corn crop? Like everything in agronomy, “it depends” because, in ag, our weather is never the same from one year to the next. We also know that different genetics utilize nitrogen differently. Two advantages of late-season timing are:

  • If your corn crop appears to be strong, you might consider adding a little extra to meet the increased demand.
  • If you fear nitrogen loss because of heavy rains in the early season, later-season applications allow for good placement at a time when moisture can be limited. 

A quick rule of thumb is corn takes up  60% of its nitrogen needs by tassel, and 40% during reproduction. During the period of rapid vegetative growth, corn requires  ~4-8 lbs/N/day to keep on pace, as stated earlier. Nitrogen primarily enters the roots through mass flow.  Mass flow occurs when water entering the roots carries the nitrogen with it, ultimately hitching a free ride. If the forecast shows very little rainfall chances, it does not make much sense to apply extra nitrogen knowing we need mass flow of water for root uptake. This should be a greater consideration the later we progress in the season.  Y-drops, like stated earlier, keep the nitrogen closer to the roots, but they also allow the dew and what little rainfall that does happen to carry it down to the rootzone where it can be used.  Because of this advancement,  you can now purchase sidedress applicators with coulters and y-drop attachments.  

 

 

Conclusion

Today’s hybrids utilize nitrogen much more efficiently than their ancestors, and produce more bushels with the same amount of nitrogen, or less in some cases. Make sure you are feeding corn the way it can best make bushels for you! 

If you have an interest in adding a sidedress application of nitrogen to your corn crop this season, contact your local Agronomy Field Advisor at Liqui-Grow!  We offer different applications and timing to meet your crops’ needs and yield goals.  

UAN vs Urea Sidedress article

 

Liqui_Grow UAN vs Urea Sidedress 2018