Evaluating the Impact of Wheat Straw Amendments on Dryland Organic Wheat Systems

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Commodities

• Agronomic: wheat

Practices

• Crop Production: cropping systems, fallow, nutrient cycling, organic fertilizers
• Education and Training: on-farm/ranch research
• Natural Resources/Environment: carbon sequestration, soil stabilization
• Production Systems: organic agriculture
• Soil Management: composting, organic matter, soil analysis, soil chemistry, soil microbiology, soil physics, soil quality/health

Western dryland organic wheat production accounts for 49% of all organic wheat produced in the United States. These systems are constrained by limited inputs and low precipitation, leading to declines in wheat yields and soil health. Compost is an effective soil amendment resulting in yields two times higher than control plots 24+ years following a single application, but results are inconsistent. Growers are concerned by this inconsistency because the compost prices are high.

Research has shown that in dry years 80% of the benefit realized from the compost amendment is due to improvements in soil physical health, including improved soil water-holding capacity, infiltration rates, penetration and soil aggregation - critical under dryland systems where two years of water produce one crop. Thus growers asked whether applying lower quality amendments such as wheat straw might improve soil physical health at a lower cost than compost, as has been demonstrated with dry-stacked manure. Straw, however, has a much lower nitrogen content than stacked manure or compost. Nitrogen is required by both the wheat and soil microbes. Nitrogen competition and amendment-induced changes in microbial community diversity and populations, could lead to decreases in grain yield and protein content. Therefore, we will also analyze microbial community diversity, respiration and function to better understand the complex C/N dynamics in the soil environment.

This research will contribute to understanding the most cost-effective way for dryland organic wheat farmers to improve soil physical health while maintaining or improving wheat yields and quality.

Research Objectives:

Objective 1: Determine if straw can be used as a suitable replacement for compost while providing the same benefits to soil physical health and crop yield through increased SOM.

Objective 2: Determine the impact of straw on microbial population diversity and microbial substrate use efficiency as a measure of soil biological health.

Educational Objectives:

Objective 1: Adoption of sustainability practices through result sharing and education.

Objective 2: Undergraduate involvement, education, and project presentations.