TEXAS A&M AGRILIFE ROLLING PLAINS AGRONOMY PROGRAM

Converting to alternative annual and perennial forage based systems for sustainable grazing in semi-arid environments

PI: Paul DeLaune

Objectives

Objective 1. Determine the effects of cover crop/forage mixes, crop rotation, and perennial forage-based systems on overall production and soil function.

Objective 2. Evaluate over-seeding of annual forages in warm-season and cool-season perennial systems to expand sustainable grazing options and soil function.

Materials and methods

Objective 1. A replicated research trial was planted at the Smith Ranch near Vernon, TX. There are a total of 20 one-acre plots. Treatments include winter wheat based cropping system with 1) summer fallow; 2) summer cover crop planted at 25 lb/ac; 3) summer cover crop planted at 50 lb/ac; 4) rotation of wheat with cool-season cover/forage crop; and 5) summer-dormant tall fescue (Figure 1).

The fescue was planted in fall 2020. Each treatment is replicated 4 times.  A warm-season mixture containing 16% sorghum-sudangrass, 12% pearl millet, 12% forage sorghum, 36% forage cowpea, 12% mungbean, 4% okra, and 8% sunn hemp was planted using a 20′ no-till drill on 7.5 inch spacing at a rate of 25 and 50 lb/ac on June 9, 2022 and July 10, 2023.  Plots were clipped to estimate herbage mass before and after grazing. After grazing, plots were rolled with a roller crimper. A cool-season cover crop mixture consisting of triticale (30 lb/ac), winter wheat (20 lb/ac); Austrian winter pea (10 lb/ac); hairy vetch (5 lb/ac); and sweet clover (5 lb/ac) was planted using a 20′ no-till drill on 7.5 inch spacing on November 10, 2022. Winter wheat was planted at 60 lb/ac using the same drill on November 11, 2022 and November 7, 2023. Wheat was planted to treatments 1-4 in 2023. Wheat was harvested using a small plot combine on May 21, 2023.

Soil samples were collected October 19, 2022 and to a depth of 48 inches and segmented into increments of 0-4, 4-8, 8-12, 12-24, 24-36, and 36-48 inches. Soil samples from 0-4 and 4-8 inches were sent to the University of Missouri Soil Health Laboratory for microbial analysis via PLFA. Remaining soil samples were collected, processed and stored for soil chemical and physical property analysis. In 2023, soil samples were collected at 0-4 and 4-8 inch increments on November 15, 2023.

Objective 2. Due to the Vernon Research and Extension Center being in the direct path of an EF-3 tornado on May 4, 2022, objective 2 was suspended until 2023. Eight treatments are being evaluated, including: 1) winter wheat (60 lb/ac; annual forage control); 2) summer-dormant tall fescue (3) cool-season grass mix consisting of tall fescue, perennial ryegrass, and orchardgrass (Stockmaster); 4) summer-dormant tall fescue + legume (sweetclover, red clover, burr medic, ball clover, and little burr medic); 5) cool-season grass mixture (little barley, Canada wildrye, Indian ricegrass, and tall wheatgrass); 6) legume mixture (sweetclover, red clover, burr medic, ball clover, and little burr medic) ; 7) grass/legume mixture (sweetclover, red clover, burr medic, ball clover, little burr medic, little barley, Canada wildrye, Indian ricegrass, and tall wheatgrass); and 8) annual ryegrass (Figure 2). Plots were planted on October 9, 2023 using a Great Plains no-till cone drill on 7.5-inch row spacing. 

Research results and discussion

April 2022- March 2023

After planting the warm-season cover crop mixture, recorded precipitation totaled 1.31 inches in June and 0.09 inches in July. These dry and hot conditions led to poor growth and stressed conditions.

Through the first of August, grazing of the cover crop did not appear to be viable due to environmental conditions. However, 3.2 inch rainfall on August 22 with additional small rainfall events led to an emerging crop that was suitable for grazing.  In 2022, plots were grazed September 9th-17th.  A total of 8 acres with this study in addition to 4.5 acres of another study within a 35-acre field were accessible to 40 cow-calf pairs over the course of the grazing period with access to adjacent rangeland which had a water source. At time of grazing, only the sorghum-sudangrass was evident in the mixture, as all other species succumbed to the harsh conditions. Total herbage mass was 1,170 lb/ac for the 50 lb/ac planting rate and 1,241 lb/ac for the 25 lb/ac seeding rate. Forage parameters such as C:N ratio, crude protein, NDF and ADF were similar between seeding rates. As seen in other studies in this region and previous years at this site location, lowering seeding rates does not significantly compromise herbage mass production. At this site, warm-season annual grassy weeds are also an issue. Planting a summer cover crop provided competition and appeared to eliminate the annual grasses in plots where summer cover crops were planted (Figure 3).

Initial soil results after the first year of this project are provided in the figure 4. The fall 2022 actually represented the third year of cover crops as the study was initiated in 2020. Plots were also flash grazed in 2020 and 2021. Grazing did not significantly stimulate microbial activity. Water extractable organic carbon trended higher for wheat systems that implemented a summer cover crop or alternated with a cool-season mixture (Figure 4). Surprisingly, the perennial system was similar to the summer fallow treatment. However, this may be due to fair establishment of the fescue with limited growth during the extreme environmental conditions that have been experienced since project initiation. Due to conditions, tall fesuce has not been grazed. Specific fungi and bacteria communities were similar across treatments as well (Figure 4 right), although levels were trending higher for cover crop and cool-season alternative treatments compared to summer fallow. While grazing did not necessarily stimulate microbial activity or increase soil carbon, these parameters were not negatively impacted by grazing. 

Figure 4. Water extractable organic carbon (WEOC; left) and phospholipid fatty acid (PLFA; right).

April 2023- March 2024

Wheat was harvest in May 2023 with similar yields across all treatments. The summer cover crop mixture was planted later than normal due to drought conditions and awaiting a precipitation event to provide adequate moisture to plant. Initial stands of cover crops were fair, but no precipitation was recorded from July 16th to September 11 with temperatures exceeding 100 ^oF for much of that time. No measurable cover crop herbage mass was collected in fall 2023. This is the first year out of seven that cover crops did not produce measurable herbage mass for years that cover crops were planted 2013-2023. Soil samples are currently being processed and analyzed.

Objective 2. No field data to report. Plots were well established and preparations are being made to collect herbage mass at the time of reporting. Annual forages, wheat and annual ryegrass, appear to have produced the greatest biomass. However, the perennial grass forages tall fescue and stockmaster (consisting of fescue, perennial ryegrass, and orchardgrass) established well. The native perennial grasses did not appear to establish as well. 

Join us at the Texas Rolling Plains Field Day on September 19, 2024 to hear more about this project!