Effects of recurrent rolling/crimping operations on cover crop termination, soil moisture, and soil strength for conservation organic systems

Authors: Kornecki, Ted; Arriaga, Francisco; Price, Andrew; Balkcom, Kipling

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2013
Publication Date: 9/1/2013
Citation: Kornecki, T.S., Arriaga, F.J., Price, A.J., Balkcom, K.S. 2013. Effects of recurrent rolling/crimping operations on cover crop termination, soil moisture, and soil strength for conservation organic systems. Applied Engineering in Agriculture. 29(6):841-850.

Interpretive Summary: Mechanical termination of cover crops by rollers/crimpers allows planting cash crops into rolled residue three weeks after rolling. In the Southern US, this period is needed for cover crops to be fully terminated so there is no competition for water and nutrients resources with a cash crop. Depending on year, especially in wet, cooler springs waiting three weeks would push back the cash crop planting too late and potentially affect its growth. In such weather, farmers might apply herbicide as a supplement to rolling/crimping for faster cover crop termination. This option, however, is not allowed in organic production systems, thus repeatable rolling over the same area may be needed. Repeated rolling/crimping might contribute to increased soil compaction, which could have a detrimental effect on cash crop growth. Scientists from the USDA-ARS, National Soil Dynamics conducted a three-year field experiment evaluating recurrent rolling crimping effects on termination rates of single cover crop cereal rye and the mixture (rye, crimson clover and hairy vetch), and measured the associated soil moisture, and soil strength using two different rollers/crimpers. Results from this study showed that rolling two or three times did not increase soil compaction, and rolled residue kept soil strength much lower compared to standing cover crops due to moisture conservation from terminated cover crops. Soil moisture after three rolling operations was significantly higher compared with standing rye and the mixture. Recurrent rolling can be beneficial for faster mechanical termination of single cover crops but may not be adequate for mixtures that include hairy vetch because this legume cover had an ability to recover and re-grow.

Technical Abstract: Rolling/crimping technology has been utilized to mechanically terminate cover crops in conservation agriculture. In the southeastern United States, to eliminate competition for valuable soil moisture, three weeks are typically required after rolling to plant a cash crop into the desiccated cover crop residue. A common method to enhance the cover crop termination process is a supplemental application of herbicides such as glyphosate. However, herbicides cannot be used in organic production, thus additional rolling operations might speed the desiccation process. On the other hand, recurrent rolling/crimping operations could cause additional soil compaction, however, which could be detrimental for water infiltration and crop root development. The objectives of this study were to determine the effectiveness of a single-stage roller with straight bars and a two-stage roller in terminating either rye (Secale cereale L.) or a mixture of rye, crimson clover (Trifolium incarnatum L.), and hairy vetch (Vicia villosa L.) with repeated rolling operations, and the effect of repeated rolling on volumetric soil water content and soil strength. In three growing seasons (2007, 2008, 2009), 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 reduced soil strength significantly lower compared to standing cover crops due to an increased termination rate and associated moisture conservation. Volumetric soil water content after repeated 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. Repeated 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.