Dr. Merilynn Schantz is a Rangeland Research Scientist with the USDA’s Agricultural Research Station in Temple, Texas. In the fourth lecture of USDA’s Grazing Land Management and Soil Carbon series, she considered how grazing strategies affect soil health and plant production. The study covered a ten-year timespan (2014 to 2024) across two pastures in North Central Texas.
Dr. Schantz began by examining the region’s climate, which she described as “very dynamic”. The winters are mild and dry. The summers are hot and humid. Precipitation can vary considerably from year to year, and extreme weather events are becoming more common. North Central Texas experienced mild droughts before the study began and then a severe drought in 2022. Soil sampling was performing annually in November and June at a depth of 5 cm.
Numerous differences between the study’s two pastures added complexity.
- The North Pasture used rotational grazing, a flexible stocking rate, cover crops, and no fertilizer. Cattle stayed in a paddock for 30 days and were moved to a different paddock each month. Some of the paddocks were different sizes.
- The South Pasture used continuous grazing, a fixed stocking rate, foraging oats, and a turkey litter fertilizer. The stocking rate was not considerably higher, but Dr. Schantz expressed an interest in controlling this variable in a future study.
Throughout the first eight years of the study, the North Pasture and the South Pasture had similar levels of plant production. After the severe drought of 2022, however, the rotationally grazed North Pasture had a higher biomass. “Giving the plants an opportunity to increase their root depth,” Dr. Schantz said, “helps them to be more resilient to drought conditions”. Yet she cautioned that more research is still required in this area.
In terms of soil health, the continuously grazed South Pasture had higher levels of phosphorous, a nutrient that stimulates root development. That might seem counter-intuitive since the North Pasture had higher plant growth. Dr. Schantz theorized that this was because the turkey litter that was applied to the South Pasture is a good source of phosphorous. She also noted that high phosphorus levels in soil can cause problems with drinking water.