Recurring Rolling/Crimping Effects on Termination Effectiveness of Iron Clay Pea and Pearl Millet Warm-Season Cover Crops

Abstract

Summer cover crop utilization by no-till vegetable farms is essential for continuous soil protection, especially in the southern United States where intense storms are likely to occur in hot and humid summer months. A field experiment was conducted at the National Soil Dynamics Laboratory in Auburn, AL, USA, between the summers of 2015 and 2017 to determine the effectiveness of an experimental roller/crimper in mechanically terminating summer cover crops. Iron clay peas (Vigna unguiculata, L.) planted on a sandy loam and pearl millet (Penninsetum glaucum, L.) planted on clay soil were selected to determine termination rate effectiveness in single, double, and triple rolling/crimping over the same area. Overall, termination rates for both cover crops were higher for rolling three times (71%) compared to rolling once (55%) or twice (63%). However, cover crop termination was inhibited due to rainfalls on the experimental area during the three-week evaluation period. In 2016, drought conditions and high temperatures (32.6 °C) caused biomass reduction, especially for pearl millet, of over 31% to 39% compared to 2017 and 2015. Rolling provided higher soil-water conservation compared with the non-rolled control due the cover crop mulch layer blocking sunlight, keeping the soil surface cooler and preventing water evaporation. Recurrent rolling did not cause soil compaction above the 2.0 MPa level that inhibits root growth, but changes in soil strength were dependent on the soil moisture content.