Soil Health of a Warm-Season Perennial Pasture Over-seeded with Cool-Season Annuals

View the project final report

Commodities

Practices

• Natural Resources/Environment: soil stabilization, winter annuals
• Soil Management: organic matter, soil chemistry, soil microbiology, soil quality/health

1. The problem addressed was the need to measure and quantify the effects of pasture management on soil health over time.
2. The research approach was two-fold: One cattle producer had used winter annuals and mob grazing on his pastures for eight years. We began soil sampling his fields in 2015 and continued through 2017 to measure the changes or lack thereof in soil health. The majority of expenses for this “site one” were funded by a CIG grant but a small portion of the expenses were funded by the Southern SARE grant. At “site two”, the second cattle producer had three separate pastures that he had subjected to management for 0 years, 4 years and 10 years. This allowed us to compare the effects that use of winter annuals and rotational grazing had on soil health at a given time. This project was entirely funded by the Southern SARE grant.
   The information gathered from these projects was presented to producers and agriculture extension agents at regional, state, and national conferences. Livestock producers could use this information to have some reasonable expectation of what would happen to their soils within 10 years of using winter annuals and rotational or mob grazing.
3. From this research, it was concluded that total carbon and total nitrogen did not change with date of sampling though soil organic matter (SOM) did increase by 6% in site one. Nitrate concentrations decreased by 82% within two years at site one and remained consistent at 2.15 mg kg^-1 at site two. Potential soil microbial enzyme activity increased with increasing years of management (grazing and winter annuals) by 27% and over time by 32% at site one and an average of 70% at site two. Total microbial abundance did not change over time at either site. Soil microbial community structure responded to abiotic conditions (e.g. season and topography) but not to years of management. This pasture management technique of over-seeding a diverse mix of winter annuals may, with time, allow for a steady state of carbon and nitrogen while SOM increases and inorganic nitrogen decreases, and enhance the total soil microbial community and their potential enzyme activity.

1. Determine how long term inclusion of winter annuals in a perennial pasture affect soil health;
2. Compare soil health under earlier stages of similar management strategies.