Cover Crops in Conventional Tillage System: Three Years of Impacts on Soil Characteristics and Sweetpotato Yield in North Mississippi

Mississippi production of sweetpotato has increased from 13,000 acres, in 2000 to 24,000 acres, in 2012.  Sweetpotato fields are generally left bare after mechanical harvest, allowing soil erosion and overwintering sites for insect and rodent pests in culled roots. In 2009, studies of cover crops were begun at Mississippi State University’s Pontotoc Branch Experiment Station (Pontotoc, MS) and a grower field in Chickasaw County, MS. Cover crops included brassica, legume, and grass species. At the Pontotoc location each species was planted individually in 2010, while some species were mixed for 2011 and 2012 based on 2010 data.  In all years and locations cover crops were destroyed by mowing then disk incorporated prior to bed formation.  Interactions with year and treatment were observed in soil organic matter at the Pontotoc site ranging from 1.2% to 2.0% for rape and fallow treatments, respectively. Soil nitrate nitrogen levels varied among treatments in all years.  Nitrate nitrogen ranged from 5 to 91 ppm for the Diakon radish and the mustard treatments, respectively.  Total marketable sweetpotato yield ranged from 214 to 741 bu/acre for fallow and Dwarf Essex rape cover crops, respectively.  In all years, sweetpotato yields were comparable between cover crops and fallow treatments at the Pontotoc location.  In 2010, the grower location was limited to brassica cover crops in order to determine their effect on natural reniform nematode levels, however, nematode populations were too low to be meaningful. In 2011 and 2012, legume and grass species were added to complement the trial at the Pontotoc location. In 2010, at the Chickasaw location organic matter was low ranging from 1% to 1.3% for fallow and Diakon radish, respectively. Total marketable yield for all three treatments ranged from 613 to 707 bu/acre for Diakon radish and fallow, respectively.  In 2011 and 2012, organic matter ranged from 1.85% to 2.08% for Diakon radish and ryegrass, respectively. Total marketable yield was influenced by year.  The fallow treatment ranged from 609 to 421 bu/acre in 2011 and 2012 respectively.  It appears that certain cover crops and mixtures can be beneficial for sweetpotato plantings in North Mississippi.