Maximizing profits via irrigation timing for capacity-constrained cotton production

Cotton producers on the southern High Plains of Texas face reduced seasonal irrigation capacities as groundwater resources from the Ogallala Aquifer decline. Technological advancements have allowed producers to achieve maximal water use efficiencies (>95 %); however, new management strategies are necessary to sustain producer profitability. By determining the optimal timing of irrigation, producers may be able to conserve irrigation water and reduce their pumping expenses. In a field experiment conduced from 2010 to 2013, cotton (Gossypium hirsutum L.) lint yield and profitability were compared across 27 irrigation treatments using a LEPA irrigation system on Pullman Clay/Olton soils. Irrigation was applied during three growing periods determined by growing degree days (GDD_15.6), where P1=emergence to 525 GDD_15.6, P2 = 525–750 GDD_15.6, and P3 > 750 GDD_15.6. Treatments for the experiment included three irrigation capacities of 0, 3.2, and 6.4 mm d⁻¹ in a randomized block design with three replications. Profitability was assessed by calculating gross margin from economic budgets that included the management operations from each year. On average, treatments with an irrigation capacity of 0 mm d⁻¹ in P1 made 6 % less yield, but saved 30 % more water and generated the same profitability as the IC treatments of 3.2 mm d⁻¹. Irrigation during P3 at the 6.4 mm d⁻¹ irrigation capacity (IC) was the most critical for yield potential, generating 114 % more yield than the 0 mm d⁻¹ IC and 27 % more than the 3.2 mm d⁻¹ IC treatments, resulting in a 468 % and 110 % increase in profit, respectively.