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Title: Irrigation capacity impact on limited irrigation management and cropping systems

Author
item SCHNEEKLOTH, JOEL - Colorado State University
item Nielsen, David
item SCHLEGEL, ALAN - Kansas State University

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/15/2012
Publication Date: 2/20/2012
Citation: Schneekloth, J.P., Nielsen, D.C., Schlegel, A. 2012. Irrigation capacity impact on limited irrigation management and cropping systems. Proceedings of the 24th Annual Central Plains Irrigation Conference. pg 68-78. Feb. 21-22, 2012.

Interpretive Summary: A 3-yr study was conducted at Akron, CO to determine an irrigation strategy that would maintain profitable corn production under limited irrigation situations. The study found that irrigating from a well with inadequate capacity would result in decreased yields in years with limited rainfall. Little or no yield reduction was found when irrigations were restricted during vegetative development if irrigations applied during reproductive and grain-filling stages made up for the water withheld early in the season. A 4-yr study was also conducted it Tribune, KS to simulate varying well irrigation well capacities and varying corn seeding rates on corn yield. Corn yields increased with increasing well capacity. The optimum seeding rate was 22,500 seeds per acre when well capacity was 0.15 inches per day or less, but 32,500 when well capacity was 0.20 inches per day. Yield increased linearly with water use, with a slightly greater response seen at Akron compared with Tribune.

Technical Abstract: Irrigation capacity in corn production is an increasingly important issue in the semi-arid Great Plains as irrigation well outputs decrease to the point where fully meeting crop water needs is not possible. Strategies need to be developed that will maximize yields under reduced water application amounts. The objectives of a 3-yr study conducted at Akron, CO were to quantify water use, water stress, and yield of three hybrids of corn varying in relative maturity (99, 101, 103 days to maturity) grown under three irrigation strategies: full irrigation (FI), no irrigation during vegetative development followed by full irrigation during the remainder of the growing season (growth stage limited, GSL), and irrigation during the entire growing season at half of the full irrigation application rate (inadequate capacity, IC). A second study of 4-yr duration was conducted at Tribune, KS with the objective of quantifying the effects of irrigation well capacity and seeding rate on corn grain yield. Crop water use was quantified with periodic measures of soil water with a neutron probe. Water stress was quantified at Akron with weekly measurements of infrared leaf temperatures and stomatal conductance. Both infrared thermometry and stomatal conductance measurements detected the increased water stress developed during the vegetative stage in the GSL treatment and throughout the growing season in the IC treatments. Yield was negatively and linearly correlated with average crop water stress index (CWSI, calculated from infrared leaf temperature measurements). Water use and CWSI were inversely related. Yields were positively and linearly related to water use at both locations. When precipitation was limited, the IC treatment reduced yields to 67% (2010) and 56% (2011) of the yields in the FI and GSL treatments, which were not different from each other. Management strategies and cropping practices that result in fewer acres of an irrigated crop can reduce the potential for severely reduced yields as compared with irrigating the entire cropped area at an inadequate application rate. The optimum seeding rate at Tribune was 22,500 seeds per acre when well capacity was 0.15 inches per day or less, but 32,500 when well capacity was 0.20 inches per day. When well capacities are limited on the entire system, management strategies and cropping practices that result in fewer acres of an irrigated crop can alleviate the potential for severely reduced yields as compared with irrigating the entire system with inadequate capacities.