Successful adoption of precision farming requires that advanced field diagnostics and application technologies be coupled with science-based decision support systems.
Precision nitrogen and seeding rate management: Developing science-based practices
Issue: The current practice of precision agriculture lacks science-based decision support tools to enable the application of available technology and crop diagnostic capabilities.
Action taken: We conducted field-scale nitrogen application and seeding rate experiments to evaluate wheat performance (yield, protein, nitrogen use efficiency) under precision agricultural practices versus business as usual.
Results: We discovered that growers often divide fields into too many nitrogen management zones with the result that precision nitrogen management may not meet performance expectations. We developed methodology based on long-term, site-specific relative yields within a field that assesses the probability of obtaining a given yield outcome and consequently the field location’s suitability for applying precision technologies. We discovered that low-producing portions of fields are prime locations for substantially reducing nitrogen and seeding rates as compared to current recommendations. These results enable farmers to reduce variable costs associated with fertilizer and seed as well as to improve efficiencies of nitrogen use.
Results published in:
- Brown, T. T. 2015. Variable rate nitrogen and seeding to improve nitrogen use efficiency. Ph.D. Dissertation. Washington State University Department of Crop and Soil Sciences. Taylor, S. E. 2016. Precision nitrogen management: Evaluation and creating management zones using winter wheat performance. M.S. Thesis. Washington State University Department of Crop and Soil Sciences.
- Taylor. S. E., D. R. Huggins, and D. J. Brown. Evaluation of sitespecific nitrogen application in dryland winter wheat. Precision Agriculture. In review.
Barley stem after stripper header harvest. Kernels have been stripped from the head, leaving the rachis intact and hardly damaging the flag leaf.
Stripper header crop residues reduce wind speeds at the soil surface
Issue: Intensive tillage in the low-rainfall production zone of eastern WA results in erosion-prone soils.
Action taken: Long-term research at Ralston, WA, has evaluated novel cropping systems and residue management techniques to reduce soil erosion. We introduced winter triticale, which produces more biomass than winter wheat, as a rotational crop. We harvested it with a stripper header, which resulted in tall crop residues that we then managed with chemical fallow.
Results: During the chemical fallow period, tall residues remained in place and protected the soil from wind, which also allowed for maintenance of seed-zone soil moisture. Average wind speeds at the soil surface in tall triticale residue were onethird of the wind speeds measured over reduced-tillage fallow. These reduced wind speeds can help reduce wind erosion and dangerous dust storm events.
Growers have embraced the stripper header, as it allows them to harvest faster while maintaining crop residues. Since the initiation of this phase of research, stripper headers have been adopted on thousands of acres in Washington’s low-rainfall production zones. Many of the growers who have recently purchased stripper headers are in the process of transitioning to no-till production, which will continue to benefit the sustainability of our cropping systems.
Results published in:
- Port, L. E., F. L. Young, and W. L. Pan. Managing high-residue no-till fallow in the low-rainfall zone of the Pacific Northwest. Crop, Forage & Turfgrass Management. In preparation.
Calculation of nitrogen use efficiency using soil- and plant-derived components and performance criteria established from regional soft white winter wheat fertilizer guide recommendations.
Performance criteria for evaluating site-specific nitrogen management
Issue: Precision nitrogen management often emphasizes the development of prescription maps that are the basis for variablerate nitrogen applications. However, we lack performance criteria to assess if precision applications achieve crop-performance goals.
Action taken: We developed performance criteria including yield, grain protein, and nitrogen use efficiency to classify the within-field performance of wheat, including the results of precision nitrogen management strategies.
Results: We found that performance outcomes that resulted from precision nitrogen applications based on prescription maps varied considerably within management zones. This indicates that nitrogen management prescriptions could be further improved within precision management zones currently used for winter wheat. The performance classes we developed are a useful tool to assess crop outcomes with respect to farming goals and provide a framework for expanding the assessment of other performance goals such as water-use efficiency, revenue, greenhouse gas production, and soil erosion.
Results published in:
- Brown, T. T., D. Huggins, J. R. Reganold, C. K. Keller, and C. E. Kruger. Developing nitrogen use efficiency performance criteria to evaluate site-specific management of winter wheat. Precision Agriculture. In review.