Addition of Cover Crops Enhances No‐Till Potential for Improving Soil Physical Properties

TLDR

Cover crops are proposed to enhance no‑till systems by improving soil physical properties. The authors conducted a 15‑year winter wheat–sorghum rotation on silt loam with four nitrogen rates, applying hairy vetch after wheat in the first cycle and replacing it with sunn hemp and late‑maturing soybean in subsequent cycles to evaluate cumulative effects on soil physical properties and their relationship with soil organic carbon. Sunn hemp reduced near‑surface bulk density by 4 % and tripled infiltration, while both sunn hemp and soybean lowered Proctor maximum bulk density by 5 % without nitrogen, increased mean weight diameter by 80 %, and raised soil organic carbon by 30 % and 20 % respectively, with the carbon gains negatively correlated with bulk density and positively with aggregate stability and infiltration, demonstrating that cover crops improve soil physical properties and SOC.

Abstract

Inclusion of cover crops (CCs) may be a potential strategy to boost no‐till performance by improving soil physical properties. To assess this potential, we utilized a winter wheat ( Triticum aestivum L.)–grain sorghum [ Sorghum bicolor (L.) Moench] rotation, four N rates, and a hairy vetch (HV; Vicia villosa Roth) CC after wheat during the first rotation cycles, which was replaced in subsequent cycles with sunn hemp (SH; Crotalaria juncea L.) and late‐maturing soybean [LMS; Glycine max (L.) Merr.] CCs in no‐till on a silt loam. At the end of 15 yr, we studied the cumulative impacts of CCs on soil physical properties and assessed relationships between soil properties and soil organic C (SOC) concentration. Across N rates, SH reduced near‐surface bulk density (ρ b ) by 4% and increased cumulative infiltration by three times relative to no‐CC plots. Without N application, SH and LMS reduced Proctor maximum ρ b , a parameter of soil compactibility, by 5%, indicating that soils under CCs may be less susceptible to compaction. Cover crops also increased mean weight diameter of aggregates (MWDA) by 80% in the 0‐ to 7.5‐cm depth. The SOC concentration was 30% greater for SH and 20% greater for LMS than for no‐CC plots in the 0‐ to 7.5‐cm depth. The CC‐induced increase in SOC concentration was negatively correlated with Proctor maximum ρ b and positively with MWDA and cumulative infiltration. Overall, addition of CCs to no‐till systems improved soil physical properties, and the CC‐induced change in SOC concentration was correlated with soil physical properties.