Determining Optimum Irrigation Termination Periods for Cotton Production in the Texas High Plains

Abstract

HighlightsIrrigation water use efficiency was consistently higher under deficit irrigation as compared to full irrigation.Irrigation water use was always less than the annual allowable pumping limit under deficit irrigation.The first/second week of September was ideal for terminating irrigation under full/deficit irrigation in normal years.Ideal irrigation termination periods in wet/dry years were a week earlier/later than those in normal years.Abstract. Cotton ( L.) production in the Texas High Plains (THP) region relies heavily on irrigation with groundwater from the underlying Ogallala Aquifer. However, rapidly declining groundwater levels in the aquifer and increasing pumping costs pose challenges for sustainability of irrigated cotton production in this region. Adoption of efficient irrigation strategies, such as terminating irrigation at an appropriate time in the growing season, could enable producers to increase irrigation water use efficiency (IWUE) while maintaining desired yield goals. The objective of this study was to determine optimum irrigation termination periods for cotton production in the THP under full and deficit irrigation conditions using the Decision Support System for Agrotechnology Transfer (DSSAT) CROPGRO-Cotton model, which was evaluated in a prior study in the THP using measured data from an IWUE field experiment at Halfway, Texas. The treatment factors in the field experiment included irrigation capacities of 0 mm d-1 (low, L), 3.2 mm d-1 (medium, M), and 6.4 mm d-1 (high, H), applied during the vegetative, reproductive, and maturation growth stages. This study focused on a full irrigation (HHH) treatment and three deficit irrigation (LMH, LHM, and LMM) treatments. Eight irrigation termination dates with a one-week interval between 15 August and 30 September were simulated, and the impact of irrigation termination date on cotton IWUE and seed cotton yield were studied by dividing the 39-year (1978 to 2016) simulation period into dry, normal, and wet years based on the precipitation received from 1 April to the simulated irrigation termination date. Results indicated that the simulated IWUE was consistently higher under the LHM, LMH, and LMM treatments when compared to the HHH treatment. Based on the simulated average seed cotton yield and IWUE, optimum irrigation termination periods for cotton were found to be the first week of September (about 118 days after planting, DAP) for the HHH and LMH treatments and the second week of September (125 DAP) for the LHM and LMM treatments in normal years. In wet years, optimum irrigation termination periods were a week earlier than those in normal years and a week later in dry years for the HHH, LHM, and LMM treatments. For the LMH treatment, the optimum irrigation termination period in wet years was the same as that in normal years and two weeks later in dry years. The results from this study along with field-specific, late-season information will assist THP cotton producers in making appropriate irrigation termination decisions for improving economic productivity of the Ogallala Aquifer and thereby ensuring water security for agriculture. However, the recommendations from this study should be used with caution, as the optimum irrigation termination periods could potentially change with changes in cultivar characteristics, soil type, climate, and, crop management practices. Keywords: CROPGRO-Cotton, Deficit irrigation, DSSAT, Full irrigation, Irrigation water use efficiency, Seed cotton yield.

Forty Years of Increasing Cotton’s Water Productivity and Why the Trend Will Continue

“…After a thorough evaluation based on measured data, crop models serve as useful tools for simulating numerous hypothetical irrigation experiments inexpensively and quickly and assist in on-farm irrigation decision making. In a study at Halfway in the Texas High Plains (THP) region, Ale et al (2020) used the CROPGRO-Cotton module in the Decision Support System Agrotechnology Transfer (DSSAT) Cropping System Model (CSM) to suggest optimum irrigation termination periods for cotton in dry, normal, and wet years.. While early irrigation termination causes yield loss, late termination results in wastage of irrigation water without any yield increase, delayed harvest, and increased pest management costs.…”

“…Increased crop resiliency will come from improved soil health (greater water holding capacity) and improved rainfall infiltration when cover crops are used. Ale et al (2020).…”

Global Water Security: Current Research and Priorities for Action

“…Irrigation termination is an important decision in cotton production, as early termination results in yield loss while late termination leads to loss of valuable irrigation water, delays harvest, and increases pest incidences. In normal-rainfall years, Ale et al (2020) identified the first and second weeks of September (118 and 125 days after planting, respectively) as ideal irrigation termination periods for cotton under full and deficit irrigation, respectively. Terminating irrigation during these periods resulted in higher irrigation water use efficiency (defined as a ratio of the difference in irrigated and dryland yields, and the amount of seasonal irrigation) while maintaining higher crop yields.…”

Assessing the impacts of irrigation termination periods on cotton productivity under strategic deficit irrigation regimes

“…Rapidly declining groundwater levels and restrictions on the use of groundwater for irrigation necessitate the adoption of irrigation management strategies focused on water savings and economic enhancement. Even though cotton is highly adaptable to limited/deficit water conditions 18 – 20 , alternate approaches should be explored to reduce cotton irrigation demand. One such approach could be determining the optimum irrigation termination periods that can ensure efficient utilization and conservation of irrigation water while achieving higher crop yields.…”

“…One such approach could be determining the optimum irrigation termination periods that can ensure efficient utilization and conservation of irrigation water while achieving higher crop yields. Irrigation termination is an important decision as cotton yield and fiber quality are affected by the timing and amount of rainfall and irrigation 20 – 25 . An early irrigation termination could result in a yield loss, while late termination may lead to undesirable vegetative growth, delayed boll maturity, increased pest management and harvest aid costs, as well as decreased irrigation productivity 20 , 26 , 27 .…”