Interseeding Cover Crops into Cotton to Improve Fiber Quality, Soil Health, and Farm Profitability

Commodities

Practices

The proposed solution involves actively supporting soil biology and native farm diversity through interseeding cotton with cover crops. This change will provide a sustainable farm transformation by reestablishing the soil, insect and native biocontrol ecosystems that provide ecosystem services like soil structure, pest control, and weed control. This also reduces chemical and soil runoff into waterways and reduces farmer and community exposure to farm chemicals. Post-season cover crops will also be employed to sustain soil biology throughout the year. Here are some of the expected benefits:

1. More plant roots to feed soil biology will lead to greater soil aggregation and nutrient cycling.
2. Increased soil cover will decrease soil surface temperatures, reducing water evaporation and protecting soil microbes from excessive temperatures that kill them. We have seen 40 degree F differences in soil temperatures between bare ground and covers.
3. Enhanced plant diversity will lead to mutual support and greater cotton crop resilience. Conventional monocropping creates a situation where all the cotton plants in the field are seeking the same nutrients at the same growth phases. This creates a situation where plants are competing with one another for resources. Inter-seeding cover crops enriches the plant ecosystem diversity so they can be mutually beneficial to one another by trading nutrients and taking advantage of each specie's strengths. This allows the overall ecosystem to be more resilient and enhances production of all plants, including the cotton crop.
4. Decrease fungal pathogens and increase arbuscular mycorrhizal fungi (AMF) abundance. Past research has shown that diverse cover crops are an important tool for decreasing fungal pathogens and increasing AMF abundance. ( Wooliver R., et. al., Microbial communities and their association with soil health indicators under row cash crop... Front. Microbiol. (2025) )

The cover crops will serve to both crowd out herbicide resistant weeds and protect the soil from wind and water erosion. Interseeded cover crops can reduce soil erosion from fall rains as compared to traditional after-harvest cover crop planting (https://horticulture.oregonstate.edu/system/files/interseeding_cover_crops.pdf) . They also provide habitat for beneficial insects that help keep pathogens and insect pests at bay, reducing the need for expensive herbicide and pesticide applications. Their presence can also increase soil organic matter.

Research has also shown that growing plants from different plant families together can improve the growth of all the plants in the system. Their diverse root structures can improve nutrient cycling and uptake. Studies show that mixed plantings can produce more biomass than single-species plantings, partly due to complementarity, where different species utilize resources in different ways throughout the growing season (University of California, Agricultural and Natural Resources, https://ucanr.edu/blog/uc-master-gardeners-san-mateo-san-francisco-counties/article/better-together-new-science). It is also well known that nitrogen-fixing plants can benefit their neighbors. The Kahle family has seen evidence of this when they observed volunteer soybeans growing in their cotton fields this past year. Multiple plant types also have a variety of different root depths to reduce soil compaction at multiple depths of the field.

Numerous research papers have shown the benefits of interseeding cover crops in cotton. One recent publication showed that a five species cover crop mix increased relative abundance of arbuscular mycorrhizal fungi (Glomeromycota) in the first year, which could be especially important for cotton given that it is a perennial that commonly associates with AMF ( Wooliver R., et. al., Microbial communities and their association with soil health indicators under row cash crop... Front. Microbiol. (2025) ).

Another key benefit of cover crops is that they feed the soil microbiome through their root exudates. They further support microbial life by shading the soil from the sun and keeping soil temperatures livable. A healthy soil microbiome, in turn, provides a multitude of critical ecosystem services. They improve soil structure and give the soil the ability to collect and hold water during rains instead of running off as erosion. This is of critical importance to cotton growers in the South that frequently face the threat of drought. Soil microbes also reduce soil compaction and deliver nutrients to the plant that can only be accessed through microbial partnerships. This means that farmers can apply less fertilizer.

Taken together, the presence of cover crops can produce an upward spiral of benefits for the farmer that include improved soil health, reduced inputs, increased resilience to uncertain weather conditions, increased cash crop quality and quantity, and ultimately increased farm profitability. But, these benefits can only be realized if the proper combination of companion cover crops can be identified and planted at the right time during the cotton season.

In this study, we propose to evaluate two different cover crop mixes at two different planting times in an effort to develop interseeding management practices that will work successfully in the context of Southern cotton growers. We will assess soil health through several different methods during the growing season and also measure cotton yield, quality and profitability. By investigating best management practices, we seek to produce profitable cotton crops while also improving soil health for the next season of production.

The key considerations for successful cotton interseeding are:

• Timing:
  • Interseeding must be done at the right time to allow the cotton plants to establish themselves before introducing the covers. But cover crop planting cannot be so late that the covers are shaded out by the cotton plants before they have a chance to grow.
• Cover crop selection:
  • In this project we will be leveraging the expertise of Green Cover Seed, an industry leading regenerative cover crop seed company, and resources provided from the USDA to optimize the cover crop community. ( https://www.nrcs.usda.gov/sites/default/files/2022-09/InterseedingCCIntoCorn.pdf)
  • Diversity is important and we will select cover crops from a variety of plant families to support the cover crop selection - cost, complementary interactions with cotton, low-growing to stay below cotton height, shade tolerant, potentially could be grazed after cotton harvest, continue to grow into the Fall, support predatory insects, will eventually die off without termination with herbicide, healthy for grazers, insect repellent.
  • Herbicide drift from neighboring farms is a consideration in the selection of the covers.

1. Project Site and General Practices
   1. Ten acre cotton field - Should produce enough cotton to generate an entire bale for each experimental condition so cotton gin can measure yield/quality for each condition.
   2. Cotton planted on a 30" spacing, skip row configuration (every third row is turned off) leaving an alternating 30" then 60" gap every other row.
   3. Cotton stripper used to harvest because this is the type of equipment most used by cotton farmers. We want the outcome of this research to be broadly applicable as possible.
   4. Irrigation will not be used since most farmers do not irrigate and we want our results to be broadly applicable.
   5. Pre-season and post-season cover crops will also be used.
2. Research Design - Three trial conditions will be tested. Each will be planted in multiple, alternating strips such that the combined strips for each condition will constitute ⅓ of the field area.
   1. Test condition 1 - Cotton interseeded with "early" cover crop mix. Cover crops will be planted at 5th true leaf, allowing the cotton to establish prior to introduction of the covers.
   2. Test condition 2 - Cotton interseeded with "late" cover crop mix. Cover crops will be planted at peak cotton bloom, 30 days after the early cover crop planting. This test condition will allow the cotton to reach this critical growth stage before introducing the cover crop. Conversations with cotton agronomists experimenting with cover crops suggests that this may be the optimal planting time.
   3. Test condition 3 (Control) - no interseeded cover crops.
3. Cover crop selection
   1. Green Cover will consult on the cover crop mix to be used. They are a well-respected authority and will also be the cover crop seed supplier. Green Cover seeds are grown in regenerative farm settings and are expected to perform well in the regenerative soils at the Kahle Family Farms.
   2. Considerations - Two different multi-species mixes will be used ("early" mix, and "late" mix). The exact seed combinations and seed treatments will be selected two months prior to cotton planting to allow for seasonal environmental conditions to be taken into account (drought, wet, etc.). The selection criteria will include:
      1. Select species with foliage height below cotton and able to thrive in partial shade of the cotton.
      2. Species from multiple plant families will be included to ensure there is sufficient diversity to support the cotton plants over a wide range of environmental conditions.
      3. Species with root structures at various depths to support soil health and break up soil compaction.
      4. Context appropriate species for the Oklahoma area, soil type, and environmental conditions.
      5. The two mixes used will vary somewhat to produce optimal results given their different planting times.
      6. Support insect populations to encourage predatory insects to manage cotton pests
4. Data collection - five agronomic areas: 1) Soil Nutrients, 2) Plant Health, 3) Soil Health, 4) Cotton Yield and Quality, and 5) ROI. The locations of these measurements will be laid out on a field map prior to season start to avoid sampling biases. Once an area is selected, samples will be drawn randomly from the center of test strips to avoid cross-over effects between the treatments.
   1. Soil Nutrients - measured 1X at the beginning of each season in each test condition
   2. Plant Health - measure cotton sap in each test condition, 2X during the season. First, at the midpoint of the growing season and, second, at the end of the season but prior to cotton senescence.
   3. Soil Health - three different methods will be used
      1. Haney Test (test in triplicate) - provides insight into high-level biological activity in the soil and plant-available nutrients. The Haney test will help measure whether increased biological activity is actually observed.
      2. DNA soil testing (test in triplicate) - DNA soil testing will provide detailed information about the diversity of life in the soil. This is an important innovation in this research project and will provide deep insight into what is happening in the soil as a result of the cover crop introduction.
      3. Overall soil health indicators (test in triplicate) - water infiltration, soil moisture, soil temperature, penetrometer, photos, soil core profile) - the presence of cover crops is predicted to shade and protect the soil, feed soil biology, and improve soil structure. These measurements will indicate whether this hypothesis is correct.
   4. Cotton Quality and Yield
      1. Cotton from each test condition will be harvested separately and measured by raw weight at the farm. It will also be sent separately to the cotton gin where the yield and quality will be measured.
   5. ROI - Record expenses and profits for each test condition over the two seasons to determine ROI.
5. Data Analysis
   1. Three replicates will be collected for the Haney test and the overall soil health indicators (water infiltration, soil moisture, soil temperature, penetrometer reads). This will allow an ANOVA analysis to be performed on these parameters and provide an estimate of the statistical significance of the differences observed between the treatment groups.
   2. There will be three replicates of the DNA sequencing samples for each treatment group. The results will be evaluated using ecological metrics including alpha diversity (abundance of microorganisms within a single sample) and beta diversity (comparison of microbial communities between different samples). Analysis will also be performed to identify the most abundant groups of bacteria, archaea, fungi, and soil invertebrates (microarthropods, worms, etc.) in each sample. A functional analysis of the estimated functional capacity of the microorganisms will be performed and compared across the treatment groups.
   3. Cotton yield and quality - The cotton gin will be asked to assess the cotton quality from three different samples from each of the three test conditions. By requesting replicates of the quality assessment, we will be able to understand the consistency of the analysis. In terms of cotton weight, we expect to get only a single large bale of cotton from each trial condition (each approximately 3 acres). Each bale is expected to weigh roughly 3500-5000lbs).