Cover crops after wheat can supply N to next crop

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

Is there a fallow period in your crop rotation after wheat harvest? If so, you have an excellent opportunity to seed various legume cover crop species to supply nitrogen (N) to your following crop. Like biological fertilizer factories, legume cover crops fix nitrogen from the atmosphere and incorporate it into their plant tissue. Upon decomposition, nitrogen from the cover crop is released into the soil where it can be used by the next crop. Here are some results from an experiment in 2011-12 where we planted different types of legume cover crops after wheat harvest at the Penn State Agronomy Research Farm at Rock Springs.

Because there is a month or more of warm summer weather after wheat harvest, summer annual legume cover crop species may have the potential to fix worthwhile quantities of nitrogen before winterkilling. Of the three summer annual cover crop species we planted on August 5, 2011, fava bean accumulated an aboveground biomass nitrogen content of 140 lbs N/ac, soybean accumulated 70 lbs N/ac and sunn hemp only accumulated 35 lbs N/ac prior to winterkill.

Sunn hemp is a tropical legume species and the planting date after wheat harvest in central Pennsylvania did not leave enough growing degree days left in the season to make the cover crop worthwhile. Sunn hemp growth would be greater when planted in southeastern Pennsylvania after wheat harvest in mid-July, or better yet planted in early June as a full season summer cover crop.

The soybean cover crop accumulated a modest but acceptable quantity of N. The best type of soybean to use as a cover crop is typically a forage-type soybean, but seed can be difficult to come by. Instead, we used a maturity group 3.6 grain-type soybean variety seeded at 31 lbs/ac. At this seeding rate the stand was a little bit sparse, so increasing the seeding rate to 50 lbs/ac likely would have boosted the per acre biomass N accumulation.

Fava bean, drilled with a seeding rate of 100 lbs/ac, emerged with the highest N accumulation of the three winterkilled species we tested in 2011. Fava bean thrives in the cooler weather of late summer and early fall and continued to grow through October, several weeks longer than soybean and sunn hemp did.

We also planted a winter-hardy legume cover crop, Medium red clover. By late April 2012, the red clover had accumulated 140 lbs N/ac in its aboveground biomass, a similar amount as the fava bean had accumulated the previous fall.

Following the cover crops, we planted a corn crop and applied rates of nitrogen fertilizer between 0 and 160 lbs N/ac to measure the yield response of the corn to nitrogen fertilizer. We found that red clover supplied the most nitrogen to the corn crop, with a fertilizer equivalency of 160 lbs N/ac. Soybean and fava bean supplied similar quantities of N with a fertilizer equivalency of 100 lbs N/ac. Sunn hemp’s nitrogen contribution to the following corn crop was negligible.

Despite the similar biomass N accumulation of the fava bean and red clover cover crops, red clover was more effective at supplying N to the following corn crop. This is likely because the N release from red clover terminated in the spring was in better synchrony with corn N uptake.  Nitrogen released in early spring from the winter-killed fava bean cover crop may have leached into the subsoil before the corn crop could take it up. Our work to understand the dynamics of N supply from cover crops, particularly how cover crop mixtures might improve efficiency, is continuing and we will keep you up to date on our findings.


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 (0) Leave a comment 

Name
e-Mail (required)
Location

Comment:

characters left


Smooth Wall Grain Bins

Meridian’s SmoothWall bins are the ultimate storage bins, used to handle and store fertilizer, grain, feed and seed, and extend ... Read More

View all Products in this segment

View All Buyers Guides

Feedback Form
Feedback Form