Management intensive grazing of cover crops for soil health and profitability
Open Access
- Author:
- Pant, Divya
- Graduate Program:
- Agronomy
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- February 15, 2022
- Committee Members:
- Erin Connolly, Program Head/Chair
Sjoerd Willem Duiker, Thesis Advisor/Co-Advisor
Ray B. Bryant, Committee Member
Charles M. White, Committee Member - Keywords:
- Management intensive grazing
soil health
cover crop
corn silage
wheat - Abstract:
- Management intensive grazing of cover crops (MIGCC) in continuous no-tillage systems is an opportunity to procure mutual benefits of cover crops for improving soil health and providing forage to livestock. However, soil compaction by grazing animals could also have negative effects on soil structure. Therefore, the research studied impact of management intensive grazing of cover crops on soil physical and biological properties as well as forage production and economic returns. The research was conducted on four farms in southcentral Pennsylvania between 2019 and 2021. The comparison was between the grazed and ungrazed cover crop after small grain or corn silage harvest and between double-cropped soybeans and grazed cover crop after small grain harvest. After small grain or corn silage harvest, cover crops were planted and grazed, and cattle were moved daily with a target of leaving roughly 50% of cover crop biomass for soil protection and soil health management. The first experiment used a randomized full block design with a factorial arrangement of grazing treatment (ungrazed, recently grazed, and grazed 2 weeks earlier) and season (spring or fall) with four farms representing four replication per treatment. Bulk density, aggregate stability, field saturated hydraulic conductivity, soil CO2 burst, organic matter content, and permanganate oxidizable carbon were not significantly impacted by grazing in spring or fall. In the fall, cover crop grazing produced 1916-3746 kg ha-1 forage dry matter, and in the spring, 1425-4349 kg ha-1 forage dry matter. Farmers managed to leave an average of 1534-6717 kg ha-1 of total cover crop biomass (ranging from 47-73 percent) for soil function and protection. In spring 2020/2021, net revenue from grazing cover crops varied from $82 ha-1 to $566 ha-1, and in fall 2019/2020/2021, net revenue ranged from $481 ha-1 to $359 ha-1. In the second experiment, the impacts of grazed cover crops and soybeans on soil health and economic returns were compared using a completely randomized design with a factorial arrangement of treatments (grazed cover crop versus soybean) and years (2019, 2020, and 2021) on two farms, Franklin 1 and Adams 1. For Franklin 1, findings indicated greater field saturated hydraulic conductivity and soil organic matter content in grazed cover crop field than full-season soybean in 2019 and double-cropped soybean in 2021, while no effect was revealed on soil CO2 burst. In 2019, full-season soybeans (94%) outperformed grazed cover crops (85%) in terms of aggregate stability, with no difference between treatments in 2020 and 2021. In 2021, the bulk density of the grazed cover crop was lower than in 2020 and 2019. Similarly, the bulk density of soybean fields in 2021 was lower than in 2019. At Adams 1, when compared to double crop soybean, soil under grazed cover crops had higher permanganate oxidizable carbon in 2021 and enhanced structural stability in 2020 and 2021. Between treatments in 2020 and 2021, no significant differences in bulk density, field saturated hydraulic conductivity, soil CO2 burst, or organic matter content were observed at Adams 1. In 2020 and 2021, partial budget analysis revealed a net positive return of $523.13 ha–1 and $103.38 ha–1 for Adams 1. In 2020 and 2021, however, Franklin 1 had a net return of -$250.40 ha–1 and -$93.28 ha–1. For Adams 1, a complete soybean failure rendered management intense grazing of cover crops more profitable than a double crop soybean. Double crop soybean failure is common on droughty soils or during years with extreme weather like drought or early frost, making grazed cover crops a less risky alternative to double crop soybeans after small grain harvest. The results so far indicate that grazed cover crop results in better soil health and provides farmers a reduced risk compared with double crop soybean, especially on marginal soils. The research suggests that under continuous no-tillage systems, grazing cover crops using management intensive practices can provide additional feed and income to the farmer without detrimental effect on soil health, thereby increasing the motivation to adopt cover crops and their derived conservation benefits.