Location: Plant Physiology and Genetics Research
2022 Annual Report
Accomplishments
1. Reliable optical leaf area index (LAI) method improves regional LAI estimates. Regional LAI estimates are required to develop and improve modeling tools that aid in monitoring crop conditions and yields at various scales ranging from small regional to global scales. Many methods have been developed to estimate regional LAI using optical remote sensing data; however, it is not clear which methods perform well irrespective of regional differences. An ARS scientist from Maricopa, Arizona, and researchers from the University of Maryland, evaluated existing optical methods under contrasting growing conditions. A physically based PRO-Scattering by Arbitrary Inclined Leaves (PRO-SAIL) inversion approach was found to consistently perform reasonably well irrespective of differences in growing conditions. The results demonstrate the PRO-SAIL inversion approach can be used to produce reliable regional LAI estimates at various spatial scales.
2. PhenoCrop-wheat model provides fine scale winter wheat phenological estimates. Crop growth stages are key factors in determining changes in assimilate partitioning, so it is essential that reliable algorithms are available to characterize crop phenology. An ARS scientist at Maricopa, Arizona, in collaboration with researchers from the University of Maryland tailored the Phenocrop algorithm to estimate crop growth stages of winter wheat. This algorithm allows agronomists and crop modelers to estimate regional crop growth stages at high spatial resolution using satellite imagery. These regional phenology estimates can be used for in-season crop management decisions and for the spatial optimization of crop model parameters.
3. Free-Air C02 Enrichment (FACE) sorghum dataset published. From 1998-1999, ARS researchers from Phoenix, Arizona, (now moved to Maricopa, Arizona,) and the University of Arizona, Tucson, Arizona, along with several other collaborating scientists conducted two FACE experiments on sorghum at ample and limiting levels of water and nitrogen. From these experiments, a comprehensive dataset has been assembled and formatted, which includes management, soils, weather, physiology, phenology, growth, yield, and cyanide data. Using carbon isotopic tracing, carbon flows were measured from the air to the plants to sequestration in the soil. This dataset has now been published, and the data are available for anyone to download, which should be very useful for sorghum crop modelers to validate and improve their sorghum growth models.
4. Net soil carbon storage little affected by sorghum grown under elevated carbon dioxide (CO2). As a part of free-air CO2 enrichment (FACE) experiments on sorghum conducted by ARS researchers at Maricopa, Arizona, measurements of the carbon isotope ratios of the high-CO2-grown plants, the control plants, and soil carbon were determined by cooperating scientists from the University of Arizona. The net new soil carbon enhancement resulting from FACE was 5.8% under ample water and 7.7% under limited water. However, at same time there was a loss of old pre-experiment carbon of about 6%, so the net soil carbon gain was very small. Thus, soil carbon storage under sorghum likely will be little affected by the increasing atmospheric CO2 concentration.
Review Publications
Leavitt, S., Cheng, L., Williams, D., Brooks, T., Kimball, B.A., Pinter Jr., P., Wall, G.W., Ottman, M., Matthias, A., Paul, E., Thompson, T., Adam, N. 2022. Soil organic carbon isotope tracing in sorghum under ambient CO2 and Free-Air CO2 Enrichment (FACE). Land. 11(2). Article 309. https://doi.org/10.3390/land11020309.
Kimball, B.A., Ottman, M.J., Pinter Jr., P.J., Wall, G.W., Leavitt, S.W., Cheng, L., Conley, M.M., La Morte, R.L., Triggs, J.M., Gleadow, R. 2021. Data from the Arizona FACE (Free-Air CO2 Enrichment) experiments on sorghum at ample and limiting levels of water supply. Open Data Journal for Agricultural Research. 7:1-10.
