A one-year irrigation termination timing study was initiated to check out the system and gather some preliminary data on cotton production under SDI. A cotton variety trial was also placed under SDI in order to utilize the remainder of the stations. In the former study, irrigation was terminated at zero, 190, and 380 heat units after 5 NAWF under traditional furrow irrigation, on 80-inch drip line centers, and on 40-inch drip line centers. The table below shows the results of that study.
The data show furrow irrigation terminated at 5 NAWF resulted in nearly a 50% yield loss compared with irrigation termination at 380 heat units past 5 NAWF (see table above). By comparison, yield reductions were considerably less for each of the drip line spacings, averaging about 17.5%. On average the 40-inch drip line spacing averaged 14% more yield than that from conventional furrow irrigation. Certainly, delaying irrigation cutoff well past 5 NAWF resulted in substantial yield increases in all three irrigation schemes.
These results show the potential value of SDI in cotton production in the Rolling Plains. However, there are no plans to repeat this study in subsequent years.