Site‐specific effects of winter cover crops on soil water storage

• Published in: Agrosystems, geosciences & environment Vol. 5; no. 1
• Main Authors: Nichols, Virginia A., Moore, E. Britt, Gailans, Stefan, Kaspar, Thomas C., Liebman, Matt
• Format: Journal Article
• Language: English
• Published: Hoboken John Wiley & Sons, Inc 2022; Wiley
• Subjects: Agricultural practices; Agricultural production; Biomass; Bulk density; Cash crops; Corn; Cover crops; Crop planting; Crop production; Crops; Data collection; Drought; Field capacity; Hydrology; Long-term effects; Moisture content; Organic matter; Overwintering; Rye; Secale cereale; Soil properties; Soil texture; Soil water; Soil water storage; Soybeans; Texture; Water content; Water depth; Water shortages; Water storage; Winter
• ISSN: 2639-6696; 2639-6696
• DOI: 10.1002/agg2.20238

Addition of an overwintering cereal rye (Secale cereale L.) cover crop (CC) to midwestern maize (Zea mays L.)‐based systems offers several environmental benefits, but the long‐term effects of this practice on soil hydrological properties are not well understood. We utilized four long‐term (10+ yr) trials (two commercial fields, two research plots) in Iowa that included a replicated winter rye CC and no‐cover treatment in no‐till maize/soybean [Glycine max (L.) Merr.] systems. We took intact 7.62‐cm diam. soil samples from a 10‐to‐18‐cm depth shortly after cash crop planting in the spring. We measured the soil water retention curve using matric potentials ranging from saturation to –500 cmH2O. In addition, we measured organic matter, textural composition, and bulk densities of the soil samples. At the depth sampled, CCs did not meaningfully affect bulk density, water contents at saturation, or air‐entry potentials at any trial, nor increase the percentage of macropores. At two trials, soil water content at field capacity (–100 cmH2O) in the CC treatments was 2.5 vol% (SE: 1.2%; commercial field) and 2.4 vol% (SE: 1.3%; research plot) higher compared with the no‐cover treatments. This increase could meaningfully reduce the amount of water drained from a field after a saturating rain and should be considered when assessing CC impacts on landscape hydrology. The presence or absence of a CC effect on field capacity was not related to CC aboveground biomass production, previous cash crop, or soil texture at the trial sites. Based on our results, a causal model, and previous literature we hypothesize CC root characteristics are key to understanding variable effects of CCs on soil water storage. Our results indicate it is possible for CCs to meaningfully affect soil water storage, but more research is needed on the mechanisms by which these changes occur. Core ideas · Cover crop effects on soil water storage at 10‐to‐18‐cm soil depth were not consistent. · Cover crops increased water held at field capacity in two of four trials. · Cover crops did not affect water held at saturation or increase percentage of macropores. · Causal model suggests cover crop roots may be a key driver of variable results.