Differences in Biomass Production and Water Use Efficiency among Seven Different Cover Crops in the Wet Winter Seasons of 2016/17 and 2018 in South Carolina

Abstract

Cover crops can protect soil health and increase climate resilience of crop production systems. Agronomic crop producers in the southern USA often demand information on the best cover crops for their locality and cropping system and on the potential impacts of cover crops on stored soil water. The present research evaluated biomass production and water use efficiency (WUE) of single species and multispecies winter cover crops in South Carolina. Overall, a five-species mixture of Austrian winter pea, rye, crimson clover, hairy vetch, and oats and a single species of rye had the greatest biomass production (4600–6480 kg ha−1) at the end of the season (19 April 2017 in season-1 and 10 May 2018 in season-2). The five-species mixture also had the greatest WUE (2184–2232 g m−3). None of the cover crops depleted soil water (in 60 cm depth) greater than a weed-free fallow maintained through herbicide application and a weedy fallow (no herbicide application). Since both the seasons, in which the present study was conducted, received greater than normal rainfall, further studies should verify the applicability of the results in dry years.

Cover cropping and conservation tillage improve soil health in the southeastern United States

“…Decomposition of organic matter from cover crops facilitates soil aggregation and improves soil pore structure (Demir & Işık, 2019). In the Southern Piedmont MLRA of South Carolina, soil water storage 1 mo following cover crop termination was greater with several different cover crops than without cover cropping in 1 of 2 yr (St Aime et al., 2020). Reasons for increased water storage might have been: (a) reduced water evaporation from shading of the soil surface with residues, (b) prevention of heat condution from the atmospheric to soil, and (c) suppression of water vapor movement to the atmosphere from the crop residue layer on the soil surface (St Aime et al., 2020).…”

“…In the Southern Piedmont MLRA of South Carolina, soil water storage 1 mo following cover crop termination was greater with several different cover crops than without cover cropping in 1 of 2 yr (St Aime et al., 2020). Reasons for increased water storage might have been: (a) reduced water evaporation from shading of the soil surface with residues, (b) prevention of heat condution from the atmospheric to soil, and (c) suppression of water vapor movement to the atmosphere from the crop residue layer on the soil surface (St Aime et al., 2020). In the Mississippi Blackland Prairie MLRA, soil bulk density was 0.05 Mg m −3 lower after 5 yr with wheat cover than no cover at depths of 0–5, 5–15, and 15–30 cm (Adeli et al., 2020).…”

“…In summary, several studies indicate that soil physical properties can be improved with various cover crops (Adeli et al., 2020; Peters et al., 2020; St Aime et al., 2020). However, changes may be expressed slowly due to the time required for plant roots and soil biological activity to manifest these changes that most often occur nearest the soil surface.…”

“…Much of the early research on conservation tillage and cover cropping in U.S. agriculture began in the southeastern region. The long summer growing season and relatively mild winter are ideal for both profitable summer cash crop production and protective winter cover cropping (St Aime et al., 2020). Incorporating cover crops into the cropping system increases time of active rooting and protects the soil from rainfall impact.…”

Cover crop mixtures enhance stability but not productivity in a semi‐arid climate

“…Soil water balance estimates (defined here as the soil water content at planting minus the soil water content at harvest) using soil water measurements are often subtracted from inputs to estimate crop water use (St. Aime et al., 2020). Because we did not have VWC measurements for every plot, we considered water use equal to water input, and reasoned this approach would show relative if not absolute differences in WUE across cover crop treatments.…”