Effects of Recurrent Rolling/Crimping Operations on Cover Crop Termination, Soil Moisture, and Soil Strength for Conservation Organic Systems

Abstract

<abstract> <bold><sc>Abstract. </sc></bold>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 is a supplemental application of herbicides such as glyphosate. However, synthetic 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, which could be detrimental for water infiltration and crop root development. The objectives of this experiment were to determine the effectiveness of a single-stage roller with straight bars and a new 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. Cover crop termination dates were selected three weeks before planting date recommendations for vegetables in the northern Alabama region. In three growing seasons (2007, 2008, 2009), three weeks after rolling, both roller designs effectively terminated rye > 90%, which is above the recommended rye termination rate to plant a cash crop. No difference in termination rates were observed between two rollers. Rolling two or three times did not cause additional soil compaction, and rolled residue reduced soil strength compared to standing cover crops due to an improved termination rate and associated moisture conservation. Soil volumetric moisture content (VMC) 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, most likely due to too early growth stage for hairy vetch. 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.