Late-season nitrogen for soybean?

decrease font size  Resize text   increase font size       Printer-friendly version of this article Printer-friendly version of this article

Some South Dakota soybean fields that were planted early and have had sufficient moisture have reached early pod setting stage (R3) and are looking good. What is the potential for increasing soybean yield by adding some late-season N at the pod filling stage? In fact, this is not late for the soybean plant. At early pod set, the soybean plant has reached only 25% of its maximum dry weight and only accumulated about 30% of its total N. The plant will now be rapidly adding pods and filling seed that will require much more nitrogen. When growing conditions are ideal and little stress, there is some evidence that the biological nitrogen fixation that is taking place in the soybean root nodule cannot keep up with the plant’s N needs. 

Applying N at the R3 stage has produced significant, profitable yield increases for irrigated soybean in studies in Nebraska and Kansas. The Kansas study reported six of eight sites that had significant increases (5-10 bu/a) to in-season N applications of 20-40 lb./a. The six responsive sites were generally low in organic matter and available soil nitrogen and had yields above 60-65 bu/a. 

A number of studies from MN, WI, SD, Ill, and IA showed no significant advantage to late N applications for soybean. However, none of these studies had yields above 60 bu/a. Soybean N need can reach almost 300 lb./a for a 65 bu/a yield with about 50-60% of the N coming from nitrogen fixation. The remaining N (120-150 lb./a) must come from either soil inorganic N or mineralization of soil organic matter or breakdown of previous years residue. Supplemental fertilizer N would be needed if the soil cannot meet this N demand. It is assumed that the lack of response from the late-season N studies listed above is because the soil did meet the plant’s N need at these relatively lower yields (<60 bu/a). In addition, surface soils in mid-summer tend to be dry and active uptake of added N is reduced until rainfall is received therefore limiting any yield responses.

For the producer who wants to try some late-N applications for soybean, the following suggestions would be made:

  1. Select fields with excellent yield potential and where soybean has had little stress and growth is exceptional at R3.
  2. Select fields that have adequate soil moisture or are irrigated.
  3. Apply from full bloom (R2) thru beginning pod (R3) stages.
  4. Apply 20 – 40 lbs. of N either as liquid or dry urea.
  5. Preferably, the N should be applied under the soil surface to avoid leaf burn and N volatilization losses.
  6. If applying liquid without injection, use drop nozzles and dribble on soil surface to limit leaf burn.
  7. If treating the whole field, be sure to leave harvest strips where no N is applied so the practice can be economically evaluated.

The chances of an economical yield response will be increased under irrigation and for soils low in organic matter.


Buyers Guide

Doyle Equipment Manufacturing Co.
Doyle Equipment Manufacturing prides themselves as being “The King of the Rotary’s” with their Direct Drive Rotary Blend Systems. With numerous setup possibilities and sizes, ranging from a  more...
A.J. Sackett Sons & Company
Sackett Blend Towers feature the H.I.M, High Intensity Mixer, the next generation of blending and coating technology which supports Precision Fertilizer Blending®. Its unique design allows  more...
R&R Manufacturing Inc.
The R&R Minuteman Blend System is the original proven performer. Fast, precise blending with a compact foot print. Significantly lower horsepower requirement. Low inload height with large  more...
Junge Control Inc.
Junge Control Inc. creates state-of-the-art product blending and measuring solutions that allow you to totally maximize operating efficiency with amazing accuracy and repeatability, superior  more...
Yargus Manufacturing
The flagship blending system for the Layco product line is the fully automated Layco DW System™. The advanced technology of the Layco DW (Declining Weight) system results in a blending  more...
Yargus Manufacturing
The LAYCOTE™ Automated Coating System provides a new level of coating accuracy for a stand-alone coating system or for coating (impregnating) in an automated blending system. The unique  more...
John Deere
The DN345 Drawn Dry Spreader can carry more than 12 tons of fertilizer and 17.5 tons of lime. Designed to operate at field speeds up to 20 MPH with full loads and the G4 spreader uniformly  more...
Force Unlimited
The Pro-Force is a multi-purpose spreader with a wider apron and steeper sides. Our Pro-Force has the most aggressive 30” spinner on the market, and is capable of spreading higher rates of  more...
BBI Spreaders
MagnaSpread 2 & MagnaSpread 3 — With BBI’s patented multi-bin technology, these spreaders operate multiple hoppers guided by independent, variable-rate technology. These models are built on  more...


Comments (1) Leave a comment 

Name
e-Mail (required)
Location

Comment:

characters left

Shane Orr    
Mayville, ND  |  August, 06, 2013 at 10:53 AM

What about a controlled release form of nitrogen like ESN? Could we put down ESN at planting, which is a controlled release, and have release when needed?


Quickveyor

Made of high quality 304 stainless steel, the Quickveyor is one of the strongest trailers on the market. It’s belt ... Read More

View all Products in this segment

View All Buyers Guides

Feedback Form
Feedback Form