Conventionally tilled monoculture cropping systems are predominant throughout much of the Southern Great Plains. Texas is no exception, where only about 16 percent of cropped acres are under conservation tillage. In semi-arid environments, soil health promoting practices such as cover crops are not well received due to potential soil moisture use and additional input costs. However, organic producers have been successful in these environments using crop rotation and cover crops under irrigated and dryland agriculture. It has been estimated that around half of Texas producers are open to the idea of organic farming and thousands of farms are already using at least some organic methods. The National Center of Appropriate Technology (NCAT) recommended that assistance to transitioning producers be a priority as well as a greater commitment for university research and extension efforts in organic production in order to accelerate the closing of the gap between consumer demand and the supply of Texas grown organic products. While Texas lags in organic production overall, Texas is the leading producer of organic cotton, peanuts, and rice. Texas growers over 90 percent of organic cotton, 95 percent of organic peanuts and 41 percent of organic rice in the U.S. However, organic management practices are not always considered sustainable as tillage is the primary weed control tool. In addition, full benefits of cover crops may not be realized in organic production systems of West Texas as very low seeding rates coupled with early termination via tillage are common. We have teamed with the Texas Peanut Producers Board and Texas Organic Cotton Marketing Cooperative to identify agronomic production limitations in respective organic systems. In addition, the research team has a long history of working closely with farmers using conservation measures in conventional cropping systems. Our long-term goal is to identify management practices that enhance soil health in organic and conventional agriculture and share successful practices that may be incorporated within respective farming operations to improve soil health and economic viability. Organic and conventional cropping systems varying in intensity of cover crop usage, no tillage, crop rotation, and soil texture have been identified, and soil health assessments will be completed and compared on each, assessing soil physical, chemical, and biological properties as well as potential greenhouse gas emissions. In addition, replicated research trials will be conducted to address key research needs as identified by stakeholders and the research advisory panel. Results from this project will empower both organic and conventional growers to make informed decisions on inputs that will result in effective soil health promoted practices and optimum economic options.
- Identify and quantify the effects of soil health promoting practices in organic and conventional cropping systems in semi-arid regions of Texas via on-farm assessments. More specifically we aim to:
- Formalize partnerships among collaborating entities.
- Identify famers involved in organic agriculture and additional conventional farmers using the following practices: conventional tillage with low crop diversity, conventional tillage with high crop diversity, and no-tillage greater than 10 years.
- Engage all participants in project development and implementation and define historical farming practices and reasons for implementing organic and/or conservation practices.
- Evaluate the impact of cover crops (type and seeding rate), crop rotations, and conservation tillage practices in organic and conventional systems on weed control, ecological services (C sequestration, GHG emissions, and N availability) and stored soil moisture in replicated research trials.
- Research trials will be implemented after identifying key research needs through discussions with a scientific advisory panel composed of our cooperating farmers and stakeholders. Potential experimental factors include: 1) cropping system (organic vs. non-organic); 2) cover crop termination date; 3) cover crop type (rye vs. radish vs. mix of rye, vetch and radish); and, 4) cover crop seeding rate (30 and 90 lb/ac).
- Weed biomass and visual control will be evaluated at planting and at 4-week intervals during each growing season. The Canopeo app will be used to determine the percentage of canopy cover (weeds and cotton) which will then be correlated with soil moisture.
- Soil measurements used to evaluate ecological services will include: soil organic C, total N, nitrate, ammonium, phosphorus, water-extractable C, microbial respiration (3-d CO2), potassium permanganate oxidizable C (POxC), enzyme assays, and living microbial biomass using phospholipid-derived fatty acid (PLFA) analysis. Aggregate stability, infiltration rates, stored soil moisture, and GHG emissions from the soil:atmosphere interface will be determined.
- Cover crop above ground biomass production and C and N content will be determined to evaluate the quantity and quality of C (and N) inputs to the soil. Cotton and peanut crops will be harvested to evaluate the effects of management practices on yield.
- Conduct economic analysis of the proposed production systems to evaluate factors limiting adoption of soil health promoting practices in organic and conventional farming.
- Partial budget analysis will be used to evaluate the costs and returns of alternative farming methods in organic cotton and peanuts.
- Returns above operating and ownership expenses will be calculated for alternative organic prices, and comparisons will be made with conventional cotton and peanut systems.
- Input and feedback from producers and members of the organic industry will be essential for validating the accuracy of the economic analysis.
- Compile and disseminate information to growers, researchers, county agents, natural resource managers, and regional public officials on the production potential, financial viability, and ecological impacts of evaluated cropping systems.
- Stakeholder participation will be key in this project to facilitate dissemination of the results to organic and conventional farmers and other interested groups.
- An active network of University research and Extension personnel and stakeholder organizations is already in place which will enable more rapid dissemination of results.
- Information about the impacts of this project will be presented to local organic and conventional cotton and peanut producers, county extension agents, consultants, chemical industry personnel, policy makers and other interested clientele during the annual field day tours that will be held at Lubbock, Vernon, and on-farm locations.
We will evaluate the impact of organic and conventional production on ecological services by sampling on-farm. The farmers involved in the research aspect of this project represent both organic and conventional production in three counties of the High Plains of Texas: Terry, Dawson, and Swisher County. Soil samples were collected from organic and conventional fields located in Dawson County in 2019; however, fields in Terry and Swisher Counties were not sampled in 2019 due to delayed project funding and farmers not allowing us to enter fields after crop establishment. Terry and Swisher County fields have been identified and will be sampled in 2020 prior to crop planting. Soil parameters to be determined include: soil organic C, total N, nitrate, ammonium, phosphorus, water-extractable C, and living microbial biomass using PLFA analysis. Infiltration rates will also be measured using double ring infiltrometers. Management practices adopted at farms will be recorded.
Replicated research trials were established in 2019 at the Texas A&M AgriLife Research and Extension Centers in Lubbock (Acuff loam) and Vernon (Miles sandy loam). Based upon meetings with organic and conventional cooperating farmers as well as farmers not involved with project, cover crop termination, cover crop seeding rates, soil moisture use, and weed control were identified as key concerns. Experimental factors being evaluated include: 1) cropping system (organic vs. non-organic); 2) cover crop type (rye vs. radish vs. mix); and, 3) cover crop seeding rate (15, 30, and 90 lb/ac). The experimental factors that were established in 2019 are outlined below.
The experimental design will consist of two cropping systems:
1) Organic cotton/peanut rotation;
2) Conventional* cotton/peanut rotation.
*Conventional defined as reduced tillage, non-organic systems.
Organic system treatments will include cover crops of:
- Rye seeded* at 15 lb ac-1 and terminated in late winter (common farmer practice, control);
- Rye seeded at 30 lb ac-1 and terminated mid-spring;
- Rye seeded at 90 lb ac-1 and terminated mid-spring;
- Radish seeded at 10 lb ac-1 and terminated mid-spring;
- Radish seeded at 30 lb ac-1 and terminated mid-spring;
- Rye/vetch mix seeded at 25/5 lb ac-1 and terminated mid-spring;
- Rye/vetch mix seeded at 75/15 lb ac-1 and terminated mid-spring;
- Rye/vetch/radish mix seeded at 25/3/2 lb ac-1 and terminated mid-spring;
- Rye/vetch/radish mix seeded at 75/9/6 lb ac-1 and terminated mid-spring;
*Cover crops were broadcast seeded in late summer (2019) before cotton harvest and will be drilled following peanut harvest (2020). Cover will be mechanically terminated prior to planting peanuts.
Conventional system treatments will include:
- Reduced tillage systems with no cover crop (no-till cotton, reduced till peanut);
- Reduced tillage system with rye drilled after harvest at 30 lb/ac;
- Reduced tillage system with radish drilled after harvest at 10 lb/ac;
- Reduced tillage system with rye/vetch drilled after harvest at 25/5 lb/ac; and,
- Reduced tillage system with rye/vetch/radish drilled after harvest at 25/3/2 lb/ac.
The study was designed as a split-plot with main plots (cropping system) and sub-plots (cover crop treatments) arranged using a randomized complete block design with four replications per treatment combination. Cover crop treatments were randomly assigned to each sub-plot (56 total plots). Each plot is 50 ft x 4 rows on 40-inch row spacing.
Cropping System Management: The study is being conducted under center pivot sprinkler irrigation at Vernon and using furrow irrigation at Lubbock. Irrigation is being applied at deficit levels, approximately at 70-85% crop evapotranspiration replacement. Cotton was planted mid-June in 2019 using a four-row vacuum planter placed on 40 inch spacing. Compost was applied in organic systems at 2 tons/acre (approximately 30 – 60 lb N/acre), and inorganic fertilizer applied in conventional systems based on yield goals and soil test results. Both compost and fertilizer were applied in 2019 prior to planting cotton. Organic (FM 958 variety) and conventional cotton (DP 1908 B3XF variety in Lubbock and PHY 300 variety in Vernon) was planted at 3 seeds ft-1. Organic peanuts will be planted at 5 seeds ft-1 this year (2020) in mid-May following cover crop termination.
Tillage operations are performed as necessary, which is heavily dependent upon weed pressure. A rotary hoe was used for in-row weed management early in the season (within 6 weeks of planting) and sweeps were primarily used for secondary tillage operations. In contrast, the conventional system was managed with herbicides with leading Xtendflex (Lubbock) and Enlist (Vernon) cotton was planted. In addition, harvest aids were used to expedite harvest in the conventional cropping system. Organic cotton was harvested after natural defoliation due to a freezing temperature. A 2-row cotton stripper was used to harvest the middle two rows of cotton plots in 2019, and subsamples were ginned to determine turnout, lint yield and seed yield.
Cover Crop Management: For cotton systems, organic approved cover crops were broadcast seeded to coincide with the last secondary tillage pass in early September of 2019. Cover crops were broadcast seeded using a hand operated broadcast seeder. For drilled cover crop treatments, cover crops were planted using a 4-m no-till drill within one week after harvest (late November to mid-December). Cover crops will be clipped from a 9 ft2 area prior to termination in 2020 and measured for biomass production and C/N content using a combustion analyzer.
Soil Health and Chemical Assessment: Soil samples were collected before cotton planting in 2019 at research trial locations. Samples will be collected in 2020 following cover crop termination (prior to peanut planting). Samples were collected to a depth of 40 inches and separated into increments of 0-4, 4-8, 8-24, and 24-40 inches to determine C sequestration with depth. Soil samples will be dried at 60°C for 48 hr and sieved to pass a 2-mm screen. Soil organic C, total C, and total N were determined using dry combustion (Elementar Vario Max CN Analyzer). Other measurements were made including potassium permanganate oxidizable C (POxC), 3-d CO2 respiration, phospholipid fatty acid (PLFA), and enzyme assays (β-glucosidase).
Stored Soil Moisture: A neutron moisture meter is being used to monitor stored soil moisture in three of four reps for each cropping system (30 total experimental plots). Aluminum access tubes were placed 4-6 inches from the row in each plot to a depth of 60 inches. Stored soil moisture is being measured at 8-inch depth increments from 0 to 60 inches bi-weekly from March-November and monthly from December-February. The neutron probe readings will be converted to volumetric soil water content with calibration equations determined for the soil type under investigation at the experimental site. Surface moisture content in the top 2 inches will be determined when gas flux data is collected using a portable soil moisture sensor using coaxial impedance dielectric reflectometry (HydraProbe, Stevens Water).
Determination of Greenhouse Gas Emissions (Lewis and DeLaune): Soil gas fluxes concentrations of CO2, N2O, ammonia (NH3), and CH4 will be measured at locations monthly prior to and after terminating cover crops and throughout the target crop growing season and until planting cover crops in conventional and organic systems. A Gasmet DX-4040 Fourier Transform InfraRed-Multicomponent Gas Analyzer (FTIR; Gasmet Technologies Inc., La Prairie, QC, Canada) integrated with a Li-Cor 8100-103 20-cm survey chamber will be utilized to measure trace gas fluxes at the soil:atmosphere interface. Gas concentrations within the closed chamber will be measured every 20 seconds for a 10-min deployment time. Trace gas fluxes will be determined by regressing the change in gas concentration over time and fitting either a linear or nonlinear (quadratic) regression should a curvilinear response be present. Carbon dioxide flux measurements will allow for determining the rate of soil respiration and C mineralization, and thus, the impact of cover crop biomass and plant roots on C dynamics.
Weed Assessment (Keeling and Kimura): Effective weed management is essential for profitable crop production. Without herbicides, limited tillage and cover crops must be managed to minimize weed emergence. Weed biomass and visual control will be evaluated at planting and at 4-week intervals during each growing season. Weed biomass will be collected from three random 9 ft2 spots in each plot and visual control will be determined from the middle two rows of each plot. The Canopeo app (developed by Oklahoma State University) will be used to determine the percentage of canopy cover (weeds and cotton) which will then be correlated with soil moisture. The effects of the five cover crop treatments on weed emergence and growth will be documented. If hand labor is necessary to remove weed escapes, timed hoeing data will be collected as part of the economic analysis for enterprise budgets. Any shifts in weed spectrum within treatments and over the course of the study will be documented.
Analysis of soil samples collected in spring of 2019 are still being analyzed. Current data is limited to β-glucosidase and mineralizable C. Results indicate that microbial activity is similar across systems which is what would be expected since systems had not been implemented. However, there were differences determined among soil depths with the greatest microbial activity in the 0-4” sample depth. These results are in line with expectations, as microbial activity tends to decrease with soil depth. These samples provide baseline data against which to compare future results. Soil moisture and greenhouse gas flux measurements will be collected in 2020 following cover crop termination; data will be included in next report.
Since cover crop treatments had yet to be implemented, yield was averaged across treatments for the organic and conventional systems. At Lubbock, the mean yield for the organic and conventional cotton was 344 lb/ac and 492 lb/ac, respectively. At Vernon, the mean yield for the organic cotton was 607 lb/ac vs. 946 lb/ac for the conventional cotton. Delayed maturity and lack of an applicable harvest aid in organic cotton (along with genetics) were potential reasons for reduced yields.
Project investigators met with farmer cooperators in 2019 to determine major issues related to conservation management in both organic and conventional production systems. The concerns/issues were then used to establish replicated research trials and to develop on farm sampling plans.
Educational & Outreach Activities
Plans are being made to host a series of farmer workshops and field days in fall 2020 and spring 2021, respectively. This will be a collaborative effort of Texas A&M AgriLife Research and Extension, farmer cooperators, and the Soil Health Institute.