Evaluation of winter annual cover crops under multiple residue managements: Impacts on land management, soil water depletion, and cash crop productivity.

Evaluation of winter annual cover crops under multiple residue managements: Impacts on land management, soil water depletion, and cash crop productivity.

Summary

The imminent depletion of the Ogallala Aquifer demands innovative cropping alternatives to prevent dramatic losses of income when water levels are insufficient for irrigated row-crop production in the Southern High Plains. Integrating winter cover crops with summer crops maximizes land productivity and system profitability by improving water infiltration, stabilizing soils, and increasing potential income channels. Even though the benefits of cover crops for nutrient retention and erosion control are well recognized, adoption has been slow because of concerns that cover crops withdraw soil water to the detriment of the summer crop. This small-plot experiment will test the interacting effects of irrigation and tillage management techniques with five cover-crop species on soil water depletion and productivity of the cover and subsequent summer forage crop. The overall aim is to compare the success of residue management schemes in reducing irrigation needs for the water-limited Southern High Plains region.

Data collection will include photographically monitoring ground cover of the cover crops, quantifying plant canopy characteristics and biomass, and monitoring soil water depletion. Research conclusions will be compiled into fact sheets readily available to producers through the Texas Alliance for Water Conservation (TAWC) annual Water College and electronic media, and to be distributed and demonstrated at TAWC and TTU Research Field Days. The impact of this project is two-fold: strengthen rural communities by ensuring the persistence of profitable agriculture in the region, and stabilizing the soil surface from excessive wind erosion and desiccation.

Objectives/Performance Targets

Objectives

1. Compare persistence and productivity of five winter cover crop species under four water and tillage treatment combinations for ability to conserve soil water and promote growth of summer forage.
2. Compare residual effects of cover crops and winter management strategies on the productivity and nutrient status of a subsequent no-till, irrigated summer teff hay crop. Potential effects include nitrogen supplied by legumes, allelopathy from wheat and rye, and depletion of ground water resources.
3. Compile research conclusions into fact sheets readily available to producers through the TAWC outreach program and to be demonstrated at Texas Tech Research Field Days.

Accomplishments/Milestones

1. Plot area was prepared in early September 2015 by:
   1. lightly disking to remove weeds. 
   2. locating underground drip irrigation lines to ensure even distribution within each sub-sub-plot.
2. Winter annual cover crops were planted using a no-till drill on September 17th and 18th 2015. 
3. Soil samples were collected from the top 6″ in six random locations per irrigation x block combination to determine initial water status (September 21st 2015).  
4. Soil access tubes were installed by October 7th 2015. Soil moisture status of each cover crop has been monitored weekly with a capacitance probe. 
5. Irrigation has been applied to supplement rainfall up to no more than 1 inch per month of total water (rain + irrigation) delivery. Irrigation is only applied if volumetric water content decreases below 15%, despite rainfall deficits. Burr medic, fallow (control), and rye have received 2″ of total irrigation since October 2015. Rape-Kale and wheat have received 1.5″, while only 1″ has been applied to the hairy vetch in the same time frame. 
6. Extent of nodulation (for burr medic and hairy vetch, on a 1-5 visual scale) will be recorded in five locations within each plot before harvest. Hairy vetch had four times more total nodules (dryland and irrigated treatments combined) than burr medic. 

Lubbock, TX (March 2016)

Active nodule found on hairy vetch.

Impacts and Contributions/Outcomes

The impact of this project is two-fold: strengthen rural communities by ensuring the persistence of agriculture in the region, and stabilizing the soil surface from excessive wind erosion and desiccation. Cattle production is crucial to the region’s agriculture community (Butler and Muir, 2012). This research can help rejuvenate the region’s ranching heritage but do so by promoting forage-based livestock systems that are potentially more productive and profitable than traditional rangelands, and more water-frugal when integrated into a row-crop dominant ecosystem. Texas plays a major role in agriculture, especially in the beef industry since the state had 12.4% of the nation’s cattle in 2014 (NCBA, 2015). Without the adoption of more sustainable, resource-efficient management practices, agriculture cannot persist on the Southern High Plains.

Preliminary outcomes will be determined once the yield data has been collected from the winter cover crops and residual effect is determined from the summer teff hay crop. 

Collaborators: