Cover Crops in South Plains Cotton – Not possible, or is it?

Carl Pepper Farm Tour – Spring of 2023

I was scrolling through my LinkedIn this morning (Monday, July 15, 2024) and saw a post by Dr. Joseph Burke that I just had to check out!

Just click on the picture to read the full research paper!

I am going to cut through all the information in the full-text and give you a look at the mini version. Let’s start with the abstract from the first page.

Abstract: By improving soil properties, cover crops can reduce wind erosion and sand damage to emerging cotton (Gossypium hirsutum L.) plants. However, on the Texas High Plains, questions regarding cover crop water use and management factors that affect cotton lint yield are common and limit conservation adoption by regional producers. Studies were conducted near Lamesa, Texas, USA, in 2017–2020 to evaluate cover crop species selection, seeding rate, and termination timing on cover crop biomass production and cotton yield in conventional and no-tillage systems. The no-till systems included two cover crop species, rye (Secale cereale L.) and wheat (Triticum aestivum L.) and were compared to a conventional tillage system. The cover crops were planted at two seeding rates, 34 (30.3 lbs./ac.) and 68 kg ha (60.7 lbs./ac.), and each plot was split into two termination timings: optimum, six to eight weeks prior to the planting of cotton, and late, which was two weeks after the optimum termination. Herbage mass was greater in the rye than the wheat cover crop in three of the four years tested, while the 68 kg ha (60.7 lbs./ac.) seeding rate was greater than the low seeding rate in only one of four years for both rye and wheat. The later termination timing produced more herbage mass than the optimum in all four years. Treatments did not affect cotton plant populations and had a variable effect on yield. In general, cover crop biomass production did not reduce lint production compared to the conventional system.

This last statement, “cover crops did not reduce lint production,” is hugely significant and yet it is exactly what many organic cotton producers have been saying for years!

Temperature and Rainfall data during the study

To continue the “mini version” of the research let’s turn to the Summary and Conclusions on page 9 of the research paper.

The semi-arid Texas High Plains presents challenging early-season conditions for cotton producers. Cover crops can help mitigate erosion and protect cotton seedlings from wind and sand damage without reducing yields compared to conventional practices if managed appropriately. Effective cover crop management is needed to optimize cotton lint yield compared to conventional tillage systems. We focused on three cover crop management practices: species selection, seeding rate, and termination timing. With regard to species selection, rye produced greater herbage mass in three of the four years. The seeding rate had less of an effect on herbage mass; doubling the seeding rate from 34 to 68 kg ha (30.3 – 60.7 lbs./ac.) did not contribute to increased herbage mass. This change in seeding rate only causes an increase in seed costs, and this trend held true for both species and termination timings. Termination timing had the most significant effect on herbage mass, with a two-week delay in termination timing, increasing herbage mass production from 44 to 63%. At the targeted termination time of six to eight weeks before planting, rye and wheat experienced increased growth as they transitioned from vegetative to reproductive growth. This critical period makes termination timing an essential aspect of herbage mass management. Termination timing can also impact the carbon-to-nitrogen ratio, where higher C:N at later growth stages can increase N immobilization. While water availability or allelopathy concerns are cited as risks for cotton germination and emergence when using cover crops, cotton plant populations were not affected in this study.

Cotton lint yields were not impacted by increasing cover crop herbage mass, except in 2018, when greater wheat biomass resulted in decreased lint yield compared to the conventional system. In each year, wheat or rye at a 34 kg ha (30.3 lbs./ac.) seeding rate and optimum termination timing resulted in cotton lint yields not different than the Conventional Treatment. While yield potentials can differ between years depending on precipitation and temperatures, effective cover crop management can help sustain cotton lint yields when compared to conventional treatments. Rye seed tends to cost more than wheat, but it grows more rapidly and could be terminated earlier to allow for increased moisture capture and storage between termination and cotton planting. (below is the final sentence in the paper and summarizes well the entire study)

“This research demonstrates that with effective cover crop management, the implementation of conservation practices can be successful in semi-arid cropping systems.“