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When should you kill your cover crop? Soil cover vs stored water on the Texas High Plains
The full story behind my Short: Texas A&M AgriLife trials terminated cover crops 8, 6, 4 and 2 weeks before cotton. A late kill was good for cover but drained the most soil moisture; an early kill let the soil recharge. Early results: too soon for firm recommendations.
The short version
On dry land, when you terminate (kill) a cover crop is a trade-off. On the Texas High Plains, the current USDA recommendation is to terminate eight to ten weeks before planting, which lets water return to the soil but leaves little time for the cover crop to grow. Texas A&M AgriLife researchers terminated cover crops at eight, six, four and two weeks before cotton planting. Terminating close to planting was good for biomass and soil protection but depleted soil moisture the most; terminating early enough let soil water recharge before planting. Neither herbage mass nor soil water followed a straight line: soil water was good at eight weeks, lower at six, good again at four and low at two, and it is unclear whether the four-week bump came from the cover crop or irrigation timing. The researchers say it is too early for recommendations (2023 and 2024 were heavily hit by drought) and are working on a decision-support tool using satellite imagery (Texas Water Resources Institute, 20 Oct 2026).
8–10 weekscurrent USDA termination advice before planting on the Texas High Plains [1]
8, 6, 4, 2weeks before cotton planting when cover crops were terminated in the trial [1]
Late killgood for biomass and protection, but depleted soil moisture the most [1]
Too earlyfor recommendations; 2023–24 were heavily hit by drought [1]
What they found
In the Texas High Plains water is scarce and wind can turn dry soil to dust. Cover crops, grown to cover and protect the soil rather than for harvest, help against wind erosion and improve soil health, but they must be terminated before the cash crop is planted, and there is debate about when, to keep enough soil moisture for the next crop [1].
The USDA's current recommendation for the region is to terminate eight to ten weeks before planting. A team including Katie Lewis (Texas A&M AgriLife Research, Lubbock) and Chris Cobos (Texas A&M AgriLife Research and Extension Center, Vernon) compared termination at eight, six, four and two weeks before cotton planting, measuring cover-crop herbage mass (including with multispectral drone imagery and machine learning), soil-water availability, soil carbon and nitrogen cycling, and cotton lint yields [1].
As expected, terminating close to planting was good for biomass and protection but depleted soil moisture the most, while terminating early enough let soil water recharge before planting. Surprisingly, herbage mass rose and fell between timings rather than climbing steadily, possibly due to the crop moving from vegetative to reproductive growth, or drought stress. Soil water was good at eight weeks, lower at six, good again at four and low at two; whether the four-week rise was due to the cover crop or irrigation timing is unclear. The team is analysing 2025 data, a year with a dry winter but plentiful early-season rain [1].
Watch the Short
About this page
These are early trends from TWRI's article; the researchers say it is too early to make recommendations. “My tip” in the Short is my own general takeaway, not advice from the study. Unlike my earlier cover-crop Shorts (letting weeds act as a cover crop in almond orchards, and Iowa's cover-crop insurance discount), this one is about termination timing and soil moisture on dry land. The dust-storm photo (Ransom Canyon, near Lubbock, 2009) is illustrative; the trial photos are from the TWRI article, credited to Texas A&M AgriLife.
The narration is an AI clone of my own voice (Chatterbox), used with my consent.
Why it matters
- Margins. As Chris Cobos puts it, most producers farm hundreds or thousands of acres, so small management decisions can have huge impacts on gross margins [1].
- Check your moisture. My takeaway, not the researchers' recommendation: on dry ground the termination date trades soil cover against stored water, so check soil moisture before you choose.
- Better tools coming. The team plans a decision-support tool using the satellite imagery collected, working with Gurjinder S. Baath at the Blackland Research and Extension Center [1].
Full narration (transcript)
Kill your cover crop too early, it barely protects the soil. Too late, it drinks your water. So when? Texas A&M tested this on the dry Texas High Plains, killing cover crops eight, six, four or two weeks before cotton. The USDA advice there is eight to ten weeks, so rain can refill the soil. But that leaves little time to grow. A late kill was good for cover, but drained the most moisture. An early kill let the soil recharge. And here's where it gets interesting: soil water didn't fall in a straight line. It was good at eight weeks, lower at six, good again at four, then low at two. Was that bump the cover crop, or irrigation timing? It's unclear, and they say it's too early for firm advice. So my tip: on dry ground, the kill date trades soil cover against stored water. Check your soil moisture first. Why it matters: on hundreds or thousands of acres, small calls swing margins. They're building a decision tool from satellite images. For the full story, follow the link in the description.
Sources
- [1] Sells, R. (2026). “When is the Best Time to Terminate a Cover Crop?” Texas Water Resources Institute (TWRI) blog, 20 October 2026. Project supported by USDA NIFA AFRI grant no. 2021-68012-35897. twri.tamu.edu
Credits
Photos: Texas A&M AgriLife / TWRI (article photos), USDA NRCS and Wikimedia Commons: Haboob Ransom Canyon Texas 2009.jpg (Leaflet, CC BY-SA 3.0); Aerial view of the cover-crop termination timing study site (Chris Cobos, Texas A&M AgriLife (via TWRI), press/article photo, credited); Aerial view of the trial plots (Chris Cobos, Texas A&M AgriLife (via TWRI), press/article photo, credited); Cover crop growing in a reduced-tillage field in mid-winter (Texas A&M AgriLife research team (via TWRI), press/article photo, credited); Byers, Texas farmer Tommy Henderson inserts a soil pressure probe in his no-till dryland wheat field to test how loose his soils are and for soil moisture. The full length of this two foot probe easily goes into the soil. (25091239596).jpg (USDA NRCS Texas, Public domain); Drill in a crop field (TWRI article header photo) (Texas A&M AgriLife / TWRI, press/article photo, credited). Sketches and animation: my own. Narration: AI clone of Nasper Mushonga's own voice (Chatterbox TTS by Resemble AI, MIT licence), used with his consent.