Site Drop-in: Arid environment is setting for Texas A&M team

Eight research institutions across the country are participating in the Dairy Soil & Water Regeneration (DSWR) project. Texas A&M AgriLife Extension specialist Kevin Heflin and his colleagues provided an update on what’s happening there.

Research focus: The Texas A&M AgriLife Research site at Amarillo is focused on developing soil health management strategies to produce high-quality forage sorghum silage in a water-limited environment. The field experiment compares a conventional tillage system without a cover crop to a system that utilizes minimum tillage and wheat as a winter cover crop. On top of these two tillage systems, liquid dairy manure applications (broadcast and injected), evaporative dairy manure solids and commercial nitrogen and phosphorus-based liquid fertilizer are being evaluated.

The overall goal is to understand how tillage practices and the wheat cover crop in combination with fertilizer management impact soil health, greenhouse gas (GHG) emissions, soil moisture, yield and crop water use efficiency.

What’s happening now: Current activities include measuring GHG fluxes and soil water content through the soil profile via a neutron moisture meter. At harvest, we will measure yield to determine treatment effects while also measuring plant height and germination rates. The annual yield and soil moisture results support the water use efficiency estimates. We will also take stalk nitrate samples from the crop just prior to harvest.

General findings to date: Soil chemical, biological and physical health indicators were evaluated during the first two years of the project (2023 and 2024). Many nearby livestock production fields have historically received manure applications exceeding recommended nutrient levels. To address this, the 2023 experiment aimed to reduce excess soil nitrogen and phosphorus by omitting nutrient inputs and implementing only tillage and cover crop treatments. In 2024, all treatments were fully established, including manure and fertilizer applications.

Across treatments, nutrient additions in 2024 resulted in a significant decrease in soil pH (more acidic) and an increase in nitrate concentration. The elevated nitrate levels highlight the need to reassess manure and fertilizer application rates moving forward, particularly for the 2025 season.

In 2024, total soil nitrogen increased significantly, with higher concentrations observed under manure and synthetic fertilizer treatments. Total carbon was consistently greater in the conventional system compared to the soil health management tillage treatment across both years. Bulk density is not showing a statistical difference to date, but the values were higher for 2024 than 2023.

GHG data collected over three years demonstrated clear interannual differences in mean emission rates. This indicates that multiple factors, such as environment, soil health, crop and management practices, influence GHG emissions and underscores the necessity of region-specific and long-term monitoring. No statistically significant differences were detected in methane and carbon dioxide fluxes with respect to tillage systems, nutrient treatments or row versus furrow positions. In contrast, nitrous oxide fluxes were significantly higher under nutrient-treated conditions, in the presence of cover crops and at row positions where plants grew.

Key challenge: Our research site was originally established in a farmer’s field, but was moved to the Texas A&M AgriLife Research Station at Bushland (near Amarillo) and changed to small-plot research with intensive measurements when the farmer decided to no longer participate. Another challenge has been extreme weather events, from 107 degrees Fahrenheit high temperatures in the summer to 20 degrees below zero windchill in the winter months, and sustained winds of 60 mph with gusts at over 80 mph this March and April. Cover crop establishment has also been difficult in our dry climate.

Key success: Setting up a committed and engaged team, and the learning opportunities that took place over the first years of the project, especially on weed control, manure application and equipment challenges, have been keys to success for us. Additionally, improvements in the quality and quantity of GHG measurements have been achieved by our newest and most dedicated team member, Dr. Myeongseong Lee.