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ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Agroecosystems Management Research » Research » Publications at this Location » Publication #358456

Research Project: Agroecosystem Benefits from the Development and Application of New Management Technologies in Agricultural Watersheds

Location: Agroecosystems Management Research

Title: Technique to determine water uptake in organic plots

item Logsdon, Sally
item Cambardella, Cynthia
item Prueger, John

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/27/2019
Publication Date: 7/18/2019
Citation: Logsdon, S.D., Cambardella, C.A., Prueger, J.H. 2019. Technique to determine water uptake in organic plots. Agronomy Journal. 111(4):1940-1945.

Interpretive Summary: Methods to determine crop water use may be difficult to implement on numerous research plots. This study used plant cover from photographs along with soil and micrometeorological data to calculate plant water use. The relationship between calculated seasonal crop water use and amount of crop dry matter was similar to published values for oat straw and alfalfa hay; however, the calculated crop water use for soybean or corn was less than that expected based on published relationships between seasonal crop water use and grain yield. This is useful information for scientists who study crop water use and for those who advice crop managers.

Technical Abstract: Methods to determine crop water use may be difficult to implement on numerous research plots. The purpose of this study was to calculate Priestley-Taylor evapotranspiration (ET) from measured input and to assess uncertainty. Input data included net radiation, air temperature, barometric pressure, green ground cover, total ground cover, the ratio of crop to total green cover, soil texture class and clay content for each soil layer, and periodic water content measurements with depth (daily for soil surface). The relationship between seasonal water use and yield was similar to literature values for alfalfa (Medicago sativa L.) and oat (Avena sativa L.) dry matter, but was lower than literature values for corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] grain yield. Monthly trends in water use reflected the seasonal crop growth. In summary, the proposed technique was useful across multiple plots and cropping treatments, and was more reliable than a water balance approach in areas with lateral and upward flow due to periodic high water tables.