Crop Residue, Cover Crops Impact on Soil Health Parameters

David Karki

SDSU Extension Agronomy Field Specialist Additional Authors: Anthony Bly

A field of no-till soybeans and corn.

Written collaboratively by David Karki, Anthony Bly, Sandeep Kumar and Shannon Osborne.

Interest in no-till and cover crops has been on the rise among South Dakota (S.D.) crop producers. In 2019, half of S.D. crop ground was under no-till management and about 900,000 acres were planted to cover crops (U S.D.S-NRCS). Growers have indicated that improvement in soil health is one of the main reasons for adopting no-till and cover crops systems.

Growing interest in novel systems always brings new questions or feasibility of such systems. A multi-year study conducted by SDSU and USDA- ARS research team shows that leaving crop residue in the field and adding cover crops can have positive a impact on soil health parameters including soil organic carbon, bulk density, penetration resistance (roots resistance to penetrate deeper in the soil profile), and soil water infiltration.

Study Background

The study site and specific treatments were selected to achieve the objectives of this study. The experiment was conducted at the USDA-ARS laboratory located in Brookings, S.D. on a no-till field rotated to corn and soybean since 2000. The field was divided into two residue treatments- i) all crop residues retained on the field after harvest, and ii) crop residues removed from the field leaving about 6” corn stalks in the field. In 2005, each residue block was divided to include cover crops (and no cover crops) following grain harvest. A mixture of cereal rye and hairy vetch (20 lbs rye + 10 lbs hairy vetch) was planted following corn and hairy vetch alone was planted following soybean. Measurements were collected in the summer during the soybean phase of the rotation from 2014-2016.

Major Observations

  • The soil organic carbon and total nitrogen in top two inches in fields left with crop residue was about 22% and 17% higher than the fields where the crop residue was removed. However, just adding cover crops to the residue treatments did not influence soil organic carbon.
  • In the fields where crop residue was retained after grain harvest, the soil penetration resistance was reduced by 24% and 27% respectively in depths 0-2 inches and 2-6 inches. Adding cover crops also reduced soil penetration resistance significantly at both depths.
  • In most cases, soil bulk density was significantly lower on fields with crop residue and cover crops.
  • Fields with cover crop and crop residue showed significantly higher water retention capacity compared to the fields where the residue was removed and no cover crops.
  • Drastic differences were observed for soil water infiltration rate between fields with and without crop residue and cover crops. Depending on the trial year and treatment, the soil water infiltration rate was observed to be 22.5% to 80% higher in fields with crop residue and cover crops.

Conclusions

Three years of data for this study clearly suggest a positive impact of crop residue and cover crops on soil hydrological properties and overall soil health. More studies similar to this will be helpful to comprehensively understand the long-term effects of no-till, cover crops, crop residue and possibly diverse crop rotations in the Northern Great Plains region.