Using cereal rye and wheat as cover crops increased the yields of strip-tilled cotton vs. using the same cover crops with conventional tillage, according to recent research by the University of Georgia.
Cover crops and conservation tillage can reduce soil erosion, conserve soil moisture, increase soil organic matter and suppress numerous pests. But there’s been concern about covers tying up too much nitrogen and the timing of its release to the next crop.
A study in Ontario comparing legume and non-legume covers found improved nitrogen availability only following a legume.
However, other research in 2002 showed an accumulation of 55 to 115 pounds of nitrogen per acre in overwintering rye on an irrigated sandy soil, which could be returned to the soil and a following crop.
Materials And Methods
Cover crops were planted Dec. 23, 2009, in randomized complete block design at the University of Georgia Rigdon Farm in Tifton, Ga. Treatments consisted of conventional and strip-till and four cover-crop treatments: crimson clover, cereal rye, wheat and bare soil.
The covers, which were no-till drilled, were seeded at these approximate rates:
- Crimson clover, 14.9 pounds per acre
- Cereal rye, 89 pounds per acre
- Wheat, 118 pounds per acre
Due to the late planting of cover crops, which was a result of weather delays to harvesting the preceding cash crop, cover-crop establishment was poor. Crimson clover plots had to be abandoned in strip-till because of this.
Crimson-clover plots were salvaged in conventional-tillage plots by bringing in residue of crimson clover from another trial and spreading a prescribed amount of material (based on previous year’s data) by hand and incorporating it with tillage.
Cover crops received a burndown application of glyphosate on April 26, 2010, and tillage treatments were established on May 12, 2010. The plots were fertilized on July 26, 2010, with about 20 pounds of nitrogen per acre and about 3.6 pounds of sulfur per acre in the form of 28-0-0-5.
Cover Crop Biomass Breakdown Under Strip-Till
There were no major differences in biomass accumulation for the cotton among the various treatments in either conventional or strip-till. This is likely due a combination of the low residue amounts of the cover crops, aside from crimson clover, and the masking of cover-crop nutrients from the application of sidedress fertilizer in-season.
Similar to most of the other results, there were no differences among treatments in regards to final lint yield.
However, there was a general trend that strip-till plots yielded more than conventional-tillage plots, as seen in all three scenarios where both tillage systems occurred (rye, wheat, no cover).
There were some minor fluctuations in economic differences for adjusted revenue. Adjusted revenue is defined as revenue adjusted for yield, cover crop, tillage and marketing costs.
Gross revenue reflected base cotton prices for the Southeast as of December 2010. Total costs were higher for conventional tillage on a per-acre basis (conventional $239.06 vs. strip-till $216.01), primarily due to costs associated with tillage.
All in all, despite no yield differences, there were several positive results of strip-till vs. conventional tillage.
Although there were no economic advantages to using cover crops vs. having no cover crop in place, there are many documented benefits of growing cover crops. While they often have no inherent monetary value, cover crops can save money in the long run.
Reduced soil erosion on the highly erodible soils of the Southeast is one of the most important reasons, because a large rainfall can wash volumes of priceless soil out of a field and leach nutrients out of the soil profile.