Approximately 150,000 acres of sweetpotato (Ipomoea batatas), with a farm gate value of ≈$600 million, were produced in the United States in 2018 [U.S. Department of Agriculture (USDA), National Agriculture Statistics Service (NASS), 2019]. Sweetpotato growers in North Carolina produce ≈66% of U.S. sweetpotato, with the majority of the remaining U.S. acreage in Mississippi, California, Louisiana, Florida, and Arkansas (USDA-NASS, 2019). Sweetpotato is an economically important crop commodity for these states.
Conventional sweetpotato production systems lead to high levels of erosion with an estimated soil loss of 49 t·ha−1 (Bloodworth and Lane, 1994). Severe erosion is caused by the reliance on tillage for crop management and weed control. Before transplanting, the soil is disked and raised beds are formed using a tractor-mounted ripper bedder (Treadwell et al., 2007), followed by an average of three cultivations during the growing season to control weeds, and then the soil is turned over during harvest using a tractor-mounted implement with large disk turning plows (Beam et al., 2018). Tillage is a requirement in current sweetpotato production systems but is detrimental to soil structure and decreases soil organic matter content (Hou et al., 2012).
In other crops, such as cotton (Gossypium hirsutum), corn (Zea mays), and soybean (Glycine max), cover crops are used to reduce reliance on cultivation while increasing soil health. Planting into a rye (Secale cereal) cover crop mulch can increase soil organic matter content (DeLaune et al., 2019; Moore et al., 2014), decrease compaction over the long-term (>10 years) (Blanco-Canqui et al., 2010; DeLaune et al., 2019), and reduce nutrient runoff by increasing water infiltration and soil water storage, and storage of residual nitrate in residue (DaLaune et al., 2019; Hartwig, 1988; Kessavalou and Walters, 1999; Langdale and Leonard, 1983).
High-residue rye cover crop mulch in sweetpotato production has the potential to reduce the need for and impact of tillage. Treadwell et al. (2007) reported similar yield between conventional tillage compared with reduced-tillage sweetpotato grown in a rye mulch system in 2 of 3 years in North Carolina. However, this system-based study had varying nitrogen (N) sources as well as levels of weed interference. Similarly, the use of a wheat (Triticum aestivum) straw mulch reduced weed biomass without a significant effect on sweetpotato yield in an organic production system in Tennessee (Nwosisi et al., 2019).
Along with altered production systems, sweetpotato cultivars with varying canopy architectures have potential to reduce in-season cultivation for weed control. Under season-long weed interference, ‘Carolina Bunch’ (upright architecture) had greater storage root yield than ‘Beauregard’ (prostrate architecture) in 2 of 3 years (Harrison and Jackson, 2011). Additionally, weeds competing with ‘Carolina Bunch’ tended to have less biomass than those competing with ‘Beauregard’, suggesting that upright sweetpotato cultivars could be better suited to compete with weeds (Harrison and Jackson, 2011).
Information in the peer-reviewed literature is limited with respect to high-residue rye cover crop mulch system on otherwise conventionally managed sweetpotato. Thus, studies were conducted to determine the effect of production systems (reduced-tillage, high-residue rye cover crop mulch; conventional no mulch) on soil bulk density and moisture, and growth and storage root yield of sweetpotato cultivars having different vining (upright or prostrate) characteristics.
Beam, S.C., Jennings, K.M., Chaudhari, S., Monks, D.W., Schultheis, J.R. & Waldschmidt, M. 2018 Response of sweetpotato cultivars to linuron rate and application time Weed Technol. 32 6 665 670 https://doi.org/10.1017/wet.2018.68
Blanco-Canqui, H., Stone, L.R., Schlegel, A.J., Benjamin, J.G., Vigil, M.F. & Stahlman, P.W. 2010 Continuous cropping systems reduce near-surface maximum compaction in no-till soils Agron. J. 102 4 1217 1225 https://doi.org/10.2134/agronj2010.0113
Bloodworth, H. & Lane, M. 1994 Sweetpotato response to cover crops and conservation tillage U.S. Dep. Agr., Nat. Res. Conserv. Serv. Tech. Note No. 9.
Daigh, A.L., Helmers, M.J., Kladivko, E., Zhou, X., Goeken, R., Cavdini, J., Barker, D. & Sawyer, J. 2014 Soil water during the drought of 2012 as affected by rye cover crops in fields in Iowa and Indiana J. Soil Water Conserv. 69 6 564 573 https://doi.org/10.2489/jswc.69.6.564
DeLaune, P.B., Mubvumba, P., Lewis, K.L. & Keeling, J.W. 2019 Rye cover crop impacts soil properties in a long-term cotton system Soil Sci. Soc. Amer. J. 83 5 1451 1458 https://doi.org/10.2136/sssaj2019.03.0069
Harrison, H.F. & Jackson, D.M. 2011 Response of two sweet potato cultivars to weed interference Crop Prot. 30 10 1291 1296 https://doi.org/10.1016/j.cropro.2011.05.002
Hou, X., Li, R., Jia, Z., Han, Q., Wang, W. & Yang, B. 2012 Effects of rotational tillage practices on soil properties, winter wheat yields and water-use efficiency in semi-arid areas of north-west China Field Crops Res. 129 7 13 https://doi.org/10.1016/j.fcr.2011.12.021
Kessavalou, A. & Walters, D.T. 1999 Winter rye cover crop following soybean under conservation tillage: Residual soil nitrate Agron. J. 91 4 643 649 https://doi.org/10.2134/agronj1999.91 4643x
Langdale, G.W. & Leonard, R.A. 1983 Nutrient cycling in agricultural ecosystems: Nutrient and sediment losses associated with conventional and reduced tillage agricultural practices Univ. Georgia College Agric. Spec. Publ. No. 23.
Moore, E.B., Wiedenhoeft, M.H., Kaspar, T.C. & Cambardella, C.A. 2014 Rye cover crop effects on soil quality in no-till corn silage–soybean cropping systems Soil Sci. Soc. Amer. J. 78 3 968 976 https://doi.org/10.2136/sssaj2013.09.0401
Nwosisi, S., Nandwani, D. & Hui, D. 2019 Mulch treatment effect on weed biomass and yields of organic sweetpotato cultivars Agronomy 9 4 190 (abstr.), https://doi.org/10.3390/agronomy9040190
Seavers, G.P. & Wright, K.G. 2002 Crop canopy development and structure influence weed suppression Weed Res. 39 4 319 328 https://doi.org/10.1046/j.1365-3180.1999.00148.x
Smith, A.N., Reberg-Horton, S.C., Place, G.T., Meijer, A.D., Arellano, C. & Mueller, J.P. 2011 Rolled rye mulch for weed suppression in organic no-tillage soybeans Weed Sci. 59 2 224 231 https://doi.org/10.1614/WS-D-10-00112.1
Smith, S.C., Jennings, K.M., Monks, D.W., Chaudhari, S., Schultheis, J.R. & Reberg-Horton, S.C. 2020 Critical timing of palmer amaranth (Amaranthus palmeri) removal in sweetpotato Weed Technol. 34 4 1 19 https://doi.org/10.1017/wet.2020.1
Treadwell, D.D., Creamer, N.G., Schultheis, J.R. & Hoyt, G.D. 2007 Cover crop management affects weeds and yield in organically managed sweetpotato systems Weed Technol. 21 4 1039 1048 https://doi.org/10.1614/WT-07-005.1
U.S. Department of Agriculture, National Agricultural Statistics Service 2019 NASS—quick stats 2 Nov. 2020. <https://data.nal.usda.gov/dataset/nass-quick-stats>
U.S. Department of Agriculture, Agriculture Marketing Service 2019 Sweetpotato grades and standards 2 Nov. 2020. <https://www.ams.usda.gov/grades-standards/sweetpotatoes-grades-and-standards>
U.S. Department of Agriculture, Natural Resource Conservation Service 2008 Soil bulk density/moisture/aeration 2 Nov. 2020. <https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_053260.pdf>
Yencho, G.C., Pecota, K.V., Schultheis, J.R., VanEsbroeck, Z., Holmes, G.J., Little, B.E., Thornton, A.C. & Truong, V. 2008 ‘Covington’ sweetpotato HortScience 43 6 1911 1914 https://doi.org/10.21273/HORTSCI.43.6.1911
Yenish, J.P., Worsham, A.D. & York, A.C. 1996 Cover crops for herbicide replacement in no-tillage corn (Zea mays) Weed Technol. 10 4 815 821 https://doi.org/10.1017/S0890037X00040859