Producers are likely familiar with timing of limited irrigation to maximize yield in grain crops, e.g. immediately prior to tassel/silk in corn and boot stage in grain sorghum. These strategies work toward maximizing the most variable yield component and the one typically most sensitive to stress -- kernels per ear row in corn and kernels per head in grain sorghum. While lint quality and lint per boll can vary due to management, bolls per acre is the important yield component in cotton production (Figure 1).
Assuming good stands are established, early season conditions in Kansas typically are conducive to initiating a large number of squares. However, as the season progresses and stress becomes more prevalent the plant response is to abort squares, thus reducing the plants’ maximum yield potential.
K-State research was initiated in 2011 to investigate timing of irrigation cotton yield and the associated impacts on corn yield when two crops are grown with a shared water supply. Treatments include a range of full-season irrigation scenarios where an inch of water was applied every 5, 7, or 10 days throughout the growing season. This simulates full-season irrigation with a standard quarter-section pivot under the constraint of varying well capacities of 500, 350, and 250 GPM. Additional treatments included a dryland treatment (one irrigation to ensure a good stand) and the application of water at selected time periods to maintain the key yield component of bolls per acre. Targeted timing treatments included:
Under full season irrigation there was no yield advantage to irrigating every 5 days as compared to every 7 days, although either of those strategies increased yields compared to irrigation every 10 days. The largest gain in yield per unit of irrigation applied occurred with the targeted timings. Lint yields increased 82% over dryland yields with the application of 1” of water at match-head square (MHS). Application of additional irrigation at bloom did not increase yields.
Producers can maximize cotton yields by ensuring irrigation occurs at or immediately prior to MHS to maintain the bolls-per-acre yield component. Data from this study indicates that a high level of water use efficiency can be attained by targeting small amounts of irrigation at critical time periods.
Lucas Haag, Northwest Area Crops and Soils Specialist
Joshua Morris, Stevens County Research and Extension ANR Agent
Stu Duncan, Northeast Area Crops and Soils Specialist
Gary Cramer, Agronomist-In-Charge, South Central Experiment Field