Irrigation strategies that use cutout for optimum boll maturation and yield where growing season duration is limited

Authors: Baumhardt, Roland - Louis; Brauer, David; Schwartz, Robert

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/26/2017
Publication Date: 3/16/2017
Citation: Baumhardt, R.L., Brauer, D.K., Schwartz, R.C. 2017. Irrigation strategies that use cutout for optimum boll maturation and yield where growing season duration is limited. In: Proceedings of 2017 Beltwide Cotton Conference. January 4-6, 2017, Dallas, Texas. p.113-118.

Interpretive Summary: The declining Ogallala Aquifer and pumping restrictions for irrigation have encouraged cotton farming in the Texas Panhandle and western Kansas. This area’s short growing season often impedes maturing of bolls and causes inefficient use of late season irrigations. Irrigation strategies are needed that promote earlier cotton and good fiber quality. ARS scientists from Bushland, Texas measured cotton growth, yield, and lint quality for normal irrigation and a timed deficit irrigation. Compared with normally irrigated cotton, timed deficit irrigation made cotton earlier for the same lint yield, but fiber quality suffered on some soils tested. Findings on timed deficit irrigation for improved cotton earliness permit farmers to optimize production for more efficient water use that conserves the Ogallala Aquifer.

Technical Abstract: Irrigation water availability is decreasing due to declining water sources and greater competition. Many producers must now comply with annual pumping restrictions that may limit overall productivity of crops like corn (Zea mays L.). Cotton [Gossypium hirsutum (L.)] water demand is less than corn, but the limited growing season in the Texas Panhandle and western Kansas often prevents maturing of bolls and inefficient use of late season irrigations. We determined growth and yield of cotton under shelter control of rainfall and irrigated to replace evapotranspiration with the objective of imposing water stress through deficit irrigation to induce “cutout,” cessation of flowering, and reduce late fruit load. We hypothesized that, following a water stress induced cutout, cotton would use assimilate more efficiently to mature bolls and affect fiber quality and yield. Imposing water stress after first flower advanced cutout and significantly (P=0.01) reduced average green bolls per square meter to 14 compared with 33 under full irrigation. The number of open bolls and lint yield did not differ (P=0.05) between the full and cutout irrigation treatments, but varied with soil type. Greater plant assimilate for maturing bolls did not improve fiber uniformity, micronaire, strength, and length under the cutout irrigation strategy. These differences in fiber quality contributed to significantly (P=0.01) reduced price premiums under the cutout irrigation strategy. Possible degradation in water uptake when irrigation resumed or reduced plant canopy for the cutout strategy might explain a 20-30% reduction in water use and fiber quality compared with the full irrigation control.