Effects of multiple rolling cover crops on their termination, soil water and soil strength

Authors: Kornecki, Ted; Price, Andrew; Raper, Randy; Arriaga, Francisco; Schwab, Eric

Submitted to: International Soil Tillage Research Organization Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/14/2009
Publication Date: 6/14/2009
Citation: Kornecki, T.S., Price, A.J., Raper, R.L., Arriaga, F.J., Schwab, E.B. 2009. Effects of multiple rolling cover crops on their termination, soil water and soil strength. Proceedings of the 18th Triennial International Soil Tillage Research Organization (ISTRO), June 15-19, 2009, Izmir, Turkey. CDROM.

Interpretive Summary: In the southeastern United States, three weeks are typically required after rolling a cover crop to plant a cash crop into residue cover. Although, if abnormal weather does not allow a three-week wait, it may be required to speed up cover crop termination. A common method to enhance cover crop termination process is a supplemental application of herbicides. However, herbicides cannot be used in organic production, thus requiring additional rolling operations. Multiple rolling/crimping operations might cause additional soil compaction, which could be detrimental to water infiltration and crop root development. This study evaluated the effectiveness of a single drum straight bar roller and a two-stage roller in terminating cover crops: a single rye cover, and a mixture of rye, crimson clover, and hairy vetch in multiple rolling operations, and the effect of multiple rolling on volumetric soil water content, soil strength and associated gravimetric moisture content. In 2007 and 2008, three weeks after rolling, both roller designs effectively terminated rye (>90%), which was above the recommended rye termination rate to plant a cash crop. Rolling two or three times did not cause additional soil compaction, and rolled residue kept soil strength significantly lower compared to standing cover crops due to increased termination and thus moisture conservation. Volumetric soil water content after multiple rolling operations was significantly higher compared with standing rye and mixture covers. In the mixture, hairy vetch was actively growing two weeks after rolling, even after three rolling operations and was not effectively terminated by any roller design. Multiple rolling can be beneficial for faster mechanical termination of cover crops such as rye and crimson clover, but may not be adequate for mixtures that include hairy vetch.

Technical Abstract: The impact of multiple rolling rye and mixture (rye, crimson clover and hairy vetch) using two rollers (straight bar, and two-stage) on termination rate, soil strength and soil moisture were evaluated in northern Alabama. In 2007 and 2008 growing seasons, both roller types effectively terminated rye (> 90%) three weeks after rolling, which was above the recommended rye termination rates of 90% to plant a cash crop. In contrast, for the cover crop mixture (rye, crimson clover, and hairy vetch) termination rates were affected by recovered and actively growing hairy vetch during the three weeks of the evaluation period following the rolling operation. In spring of 2007, during a severe drought period, rolled cover crop residue helped to preserve volumetric soil moisture content (7%) up to 2 weeks after rolling compared to standing rye and mixture. Rolling two or three times did not cause soil compaction, and rolled residue kept soil strength (Cone Index) significantly lower compared to standing (untreated) cover crops. This was evident in the 2007 growing season during which a severe drought occurred and elevated soil strength for non-rolled residues, whereas rolled residue covers kept cone index lower and gravimetric soil water higher. Gravimetric soil water content after rolling residue once, twice, or three times was significantly higher compared to standing rye and the untreated mixture covers. In Alabama, multiple rolling can be beneficial for faster mechanical termination of single cover crops such as rye and the mixture (rye and crimson clover,) but not for mixtures which include hairy vetch. Mixtures with hairy vetch, even after three rolling operations exhibited active growth two and three weeks after rolling in both the 2007 and 2008 growing seasons.