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ARS Home » Plains Area » Bushland, Texas » Conservation and Production Research Laboratory » Soil and Water Management Research » Research » Publications at this Location » Publication #257705
Title: Determination of growth-state specific crop coefficients (Kc) of maize and sorghum

Author
item PICCINNI, GIOVANNI - Monsato Seed Company
item Ko, Jonghan
item MAREK, THOMAS - Texas Agrilife Research
item Howell, Terry

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2009
Publication Date: 8/5/2009
Citation: Piccinni, G., Ko, J., Marek, T., Howell, T.A. 2009. Determination of growth-state specific crop coefficients (Kc) of maize and sorghum. Agricultural Water Management. 96(12):1698-1704.

Interpretive Summary: Corn (Maize) and sorghum are important crops in the Southwestern Texas region known as the Winter Garden. This region uses groundwater from the Edwards Aquifer that is nearly the sole water source for the city of San Antonio. Consequently, improved irrigation water conservation in this region is imperative. In order to achieve greater water conservation, accurate crop water use for irrigated crops, like corn and sorghum are needed to improve irrigation scheduling. Water use from corn and sorghum was measured at Uvalde, Texas, using accurate weighing, monolithic lysimeters that were 1.5 x 2m in area and 2.2 m deep. Crop water use ranged between 441 and 641 mm for corn and between 491 and 533 mm for sorghum. The crop coefficient values (ratio of the crop water use to that of a short, cool-season grass) varied from 0.2 to 1.2 for corn and 0.2 to 1.0 for sorghum. Some of the crop coefficient values corresponded and some did not correspond to those from other published sources both in Texas and world-wide. The development of regionally based and growth-stage specific crop coefficient values for this region will aid irrigation management and provide precise water application information to conserve water.

Technical Abstract: A ratio of crop evapotranspiration (ETC) to reference evapotranspiration (ETO) determines a crop coefficient (Kc) value, which is related to specific crop phenological development to improve transferability of the Kc values. Development of Kc can assist in predicting crop irrigation needs using meteorological data from weather stations. The objective of the research was conducted to determine growth-stage-specific Kc and crop water use for maize (Zea Mays) and sorghum (Sorghum bicolor) at Texas AgriLife Research field in Uvalde, Texas, United States, from 2002 to 2008. Seven lysimeters, weighing about 14 Mg, consisted of undisturbed 1.5 m x 2.0 m x 2.2 m deep soil monoliths. Six lysimeters were located in the center of a 1-ha field beneath a linear-move sprinkler system equipped with low energy precision application (LEPA). A seventh lysimeter was established to measure reference grass ETO. Crop water requirements, Kc determination, and comparison to existing FAO Kc values were determined over a 3-year period for both maize and sorghum. Accumulated seasonal crop water use ranged between 441 and 641 mm for maize and between 491 and 533 mm for sorghum. The Kc values determined during the growing seasons varied from 0.2 to 1.2 for maize and 0.2 to 1.0 for sorghum. Some of the values corresponded and some did not correspond to those from FAO-56 and from the Texas High Plains and elsewhere in other states. We assume that the development of regionally based and growth-stage specific Kc helps in irrigation management and provides precise water applications for this region.