Intensifying Cropping Systems in Semi-Arid Environments to Enhance Soil Health and Profitability

Intensifying Cropping Systems in Semi-Arid Environments to Enhance Soil Health and Profitability

Summary

Four study locations in North Texas have been established to evaluate the effect of cover crops and double crops on profitability, soil health, and soil and water conservation in continuous wheat cropping systems. This was the first year of the study, with initial summer cropping systems established in 2016. Mixed species cover crops are most commonly recommended in the region, which are typically chemically terminated at least one month prior to wheat planting. We hypothesized that double crops could provide similar benefits of cover crops with an opportunity for additional profit. We are comparing traditional wheat cropping systems (summer fallow) with rotational options (canola), cover crop options (mixed species at two different rates and termination timings), and double crop options (mungbeans, cowpeas, pigeon peas, and guar). Success of summer cropping programs varied by location. Legume crops failed at one location due to hot and dry conditions. However, at a nearby location, the summer season was a success due to reception of sporadic precipitation events. Stored soil moisture was not significantly affected by timing of cover crop termination, as soil moisture was similar among treatments by timing of wheat planting. Double crops, with the exception of guar, resulted in lower stored soil moisture at time of wheat planting. By January, stored soil was similar among all treatments. Fall forage production was greater for a cool-season mix versus wheat when planted at the same seed population, although seed costs were 3 times greater for the cool-season mix. Economic enterprise budgets will be developed as cash crop yields are obtained. At one site that has been established since 2015, 2016 wheat yields were not different for wheat following double crops compared to wheat following the same crops that were terminated as cover crops prior to the reproductive stage. Initial project findings were presented at three major regional meetings, each having over 100 attendees.

Objectives/Performance Targets

Objectives

1. Evaluate the effect of intensified cropping systems in a predominantly monoculture wheat producing region that will promote soil health and water conservation while maintaining agronomic profitability and environmental sustainability; and

2. Determine and disseminate the most effective best management systems that promote economic profitability and environmental sustainability while protecting natural resources.

Performance Targets

1) Identify and meet with on-farm collaborators; 2) select on-farm demonstration sites; 3) select treatments for each location; 4) establish cover crop and double crop treatments; 5) measure initial soil parameters; 6) measure soil moisture storage; 7) establish cash crop wheat crops.

Accomplishments/Milestones

Producers initially identified at the pre-proposal phase were eager to continue with project involvement and on-farm demonstrations. Three producers were identified in three counties: Archer, Wichita, and Wilbarger, in which research demonstration sites were ultimately placed. At time of selection, each site was cropped to winter wheat. These three sites complemented the university site located at the Texas A&M AgriLife Research and Extension Center at Vernon (Vernon site). Above normal precipitation during may delayed wheat harvest, and led to abandonment at the Archer County location due to lodging of wheat and heavy infestation of broadleaf weeds. Hence, this site was shredded prior to summer planting. Each location had the following treatments: 1) continuous wheat with fallow summer; 2) wheat/canola rotation with fallow summer; and continuous wheat with 3) mixed species cover crop planted at 15 lb/ac and terminated at 55-70 days; 4) mixed species cover crop planted at 20 lb/ac and terminated at 55-70 days; 5) mixed species cover crop planted at 15 lb/ac and terminated at 75-90 days; 6) mixed species cover crop planted at 20 lb/ac and terminated at 75-90 days; 7) broadleaf mixed species cover crop planted at 20 lb/ac and terminated at 55-70 days; 8) guar; and 9) mungbeans. The Wilbarger and Wichita Country also had black-eyed cowpeas and the Archer and Wichita County sites had pigeon peas. The guar, mungbeans, cowpeas, and pigeon peas were planted as double crops. All of these treatments are evaluated at the Vernon site, with each treatment evaluated as a cover crop and a double crop. The mixed species cover crops include mungbeans, guar, cowpeas, forage sorghum, pearl millet, proso millet, foxtail millet, buckwheat, and sunflower. The broadleaf mix consisted of cowpeas, mungbeans, guar, buckwheat, and sunflower. Soil samples were collected at each location (sampled by block) for nutrient content, organic C, and microbial properties using PLFA analysis.

Summer crops were planted in late June using a small plot box drill equipped with a cone planter (plots are 12x40 ft). The Archer County site was planted in early July, due to awaiting producer decision to harvest or abandon the previous wheat crop. Cover crops were successfully established at each location, with the exception of the Archer Co. site due to dry surface conditions and poor seed to soil contact, which was a product of heavy residue from shredding previous wheat crop heavily infested with broadleaf weeds. Establishment was very sporadic at this site. In addition, pigeon peas did not establish well at any location. A germ test was ran on seed, which found very poor quality seed. Another seed source was located and two locations were re-planted with poor success due to hot and dry conditions. The variability in our environment was displayed through our research sites. The Wichita and Wilbarger Co sites are within 10 miles of each other. However, many of the legume species at the Wichita Co site failed due to dry and hot conditions in late June through July. The Wilbarger Co. site received 3-4 precipitation events during the same time period and summer crops performed very well at this location. No double crops were harvested at the Wichita Co. site due to failure. Mungbeans, cowpeas, and guar performed very well at the Wilbarger Co. site, although mungbeans and cowpeas were not harvested due to significant wildlife damage right before scheduled harvest.

Neutron probe access tubes were installed at the Wilbarger Co location to measure stored soil moisture. We were interested in determining the impact of cover crop termination timing and double cropping on stored soil moisture, particularly entering the wheat planting season. Although terminating cover crops in mid-August conserved soil moisture initially, there were no differences between cover crops terminated in August versus mid-September. In other studies, we have noted that soil moisture can be rapidly restored under cover crops by cash crop planting if adequate precipitation occurs between cover crop termination and cash crop planting. The double crops resulted in lower total stored soil moisture entering the wheat season with the exception of guar. Cowpeas and mungbeans resulted in an approximate 0.5 inch deficit within the upper 24 inches of the soil profile in early November. By January, stored soil moisture was similar among all treatments.

1601-2016-Annual-Report-Graphs

Figure 1. Stored soil moisture in the upper 24 inches as affected by cover crops and double crops in Wilbarger Co Texas.

Figure 2. Forage production of wheat following various cover crops and a cool-season mix following summer mixed species cover crops

Canola was planted at each location in September. Frequent rains in September and October hindered canola planting across much of the region. We obtained adequate canola stands, although we have suffered wildlife damage at some locations (feral hog, rabbit, and deer). Bentley winter wheat was planted at each location. Due to low wheat prices, producers became interested in forage production and grazing rather than grain wheat. Hence, at the Archer Co location, we decided to terminate all summer crops (treating all as a cover crop) and plant wheat versus a cool-season mixed species cover crop in mid-September. For the mixed summer cover crop treatments (early vs. late terminated), a mixed cool-season cover crop vs. wheat was tested. Wheat was planted at 75 lb/ac, a typical seeding rate for graze and grain wheat. The cool-season mix was planted at the same plant population, which was approximately 956,000 seeds/ac or 63 lb/ac. The cool-season consisted of Austrian winter field peas, hairy vetch, black oats, triticale, barley, and radish. A forage harvester was used to harvest wheat and the cool-season mix, initially in December. The cool-season mix produced more than 4000 lb biomass/ac. Wheat produced about 1500 lb biomass/ac on average. While the cool-season mix produced much more biomass, the cost of seed was much higher as well ($39 vs $11/ac for wheat).

Soil samples were collected at depths of 0-2, 2-4, and 4-6 inches for nutrient analysis and organic C. Samples were also collected at 0-3 inches for PLFA analysis. These samples are currently being processed and interpreted.

Impacts and Contributions/Outcomes

We will be harvesting the first wheat crop after treatment implementation in May 2017. At the Vernon site, where treatments have been in place since summer 2015, 2016 wheat yields did not differ between cover crop vs. double crop options. This indicates that double cropping may be a profitable option, compared to cover crops, when moisture conditions are adequate. A graduate student was recruited to work on the project and is focusing on nutrient cycling, including the microbial processes involved. Initial project findings were presented at the Red River Crops Conference in January 2017 (124 attendees); Texas Soil Health Short Course in February 2017 (240 registered participants); and the Wichita Falls Farm and Ranch Show in March (100+ attendees). A project update was also presented to the Texas SARE Advisory Committee in January.