ABSTRACT
Winter cover crops (CC) use water, which can have negative, neutral, or
positive effects on soil water storage and supply for the subsequent
summer crop. There is a lack of information on how tillage impacts water
utilization by CC. A plot-scale Long-Term Agro-Ecosystem Research (LTAR)
experiment was initiated in October 2018 at Stoneville, MS, to estimate
crop water use and depletion (net loss) in two CC treatments [no-cover
(NC) and CC (Austrian pea, Pisum sativum L.)] under two tillage
[conventional tillage (CT) vs. no-tillage (NT)] practices in cotton
(Gossypium hirsutum L.) and sorghum (Sorghum bicolor L.)
cropping systems. Soil volumetric water content (VWC, %) was monitored
using capacitance sensors at 12 soil depths to 115 cm. In-field
measurement of VWC was recorded every 30 minutes. In the first year (Dec
2019–May 2020), the total VWC of the 0-45 cm soil profile was similar
for all treatments until mid-March, when CC plots depleted more water
than NC, especially for CT. No effect of CC on VWC was observed in the
45-115 cm profile. The CC did not affect VWC in NT plots. In the second
year (Nov 2020–May 2021), NT (both CC and NC) quickly restored water
depleted by cotton or sorghum (May to October 2020) in the whole 0-115
cm soil profile, whereas, for CT, VWC was not restored in the 45-115 cm
depth until February. The CC-CT depleted more water in 35-55 cm depth in
April and May, relative to NC-NT and CC-NT treatments. The
business-as-usual CT-NC management system consumed soil water
intermediate between NT systems and CC-CT during most of the measurement
period. These results demonstrated that NT-CC can benefit row crop
production systems with minimal use of water and supply water compared
to NC for cotton and sorghum production.