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Canopy reflectance informs in-season malting barley nitrogen management: an ex-ante classification approach data

Citation

Nelsen, Taylor; Lundy, Mark (2021), Canopy reflectance informs in-season malting barley nitrogen management: an ex-ante classification approach data, Dryad, Dataset, https://doi.org/10.25338/B8633H

Abstract

Malting barley (Hordeum vulgare) requires precise nitrogen (N) fertilizer management to achieve a narrow range of grain protein content (≈9–10.5%) while maintaining yields, but practical tools to accomplish this are lacking. This study hypothesized that canopy reflectance (Normalized Difference Vegetation Index (NDVI)) measured at tillering (Feekes 2–3) and expressed as a sufficiency index (SI), can estimate the likelihood of a site-specific response to in-season N fertilizer in malting barley. Canopy reflectance was measured from plots at tillering with a GreenSeeker and unmanned aerial vehicle (UAV) borne multispectral cameras in trials across heterogeneous California agroecosystems. Field experiments included a range of N fertilizer application rates (0–168 kg N ha-1) and timings (pre-plant, tillering, or evenly split), and resulted in a range of crop N sufficiency/deficiency. NDVI-based SI measurements were categorized into one of three quantitative categories (low, medium, and high) without additional experimental context using Gaussian mixture modeling. Despite that 85% of variation in protein yield was due to site-year, the reflectance-based categories indicated whether N fertilizer applied in-season would increase protein yield (p < 0.01).  Nitrogen application at tillering increased yield and protein for plots in the “low” and “medium” SI categories (45 and 4% for yield and 16 and 12% for protein, respectively) (p < 0.05), while “high” SI plots had neither yield (p = 0.23) nor protein (p = 0.26) increases. Importantly, the broader agronomic conditions of a site primarily determined whether response to in-season N manifested as increased yield or protein.

Usage Notes

The .Rmd file details how the data was analyzed and used in the manuscript. 

Funding

University of California Division of Agriculture and Natural Resources

University of California, Davis Department of Plant Sciences*

California Crop Improvement Association