Submitted to: Proceedings of the Central Plains Irrigation Conference
Publication Type: Proceedings
Publication Acceptance Date: February 16, 2005
Publication Date: February 16, 2005
Citation: Colaizzi, P.D., Evett, S.R., Howell, T.A. 2005. Comparison of spray, LEPA, and SDI for cotton and grain sorghum in the Texas Panhandle. In: Proceedings of the Central Plains Irrigation Conference, February 16-17, 2005, Sterling, Colorado. p. 123-136. Interpretive Summary: Cotton and grain sorghum are typically produced in rotation in the Texas Panhandle, and high yields are possible with irrigation. In the Great Plains, practically all water for irrigation must be pumped from the Ogallala aquifer, a finite and declining freshwater resource. Cotton production is expanding north from the Lubbock area to the Northern Texas Panhandle and Southwestern Kansas as an alternative to corn because both crops have similar revenue potential but cotton only requires about one-half the water as corn; however, the cooler climate imposes some risk for cotton production. In order to stretch irrigation water resources, many producers are considering subsurface drip irrigation (SDI), which is a highly efficient irrigation technology and possible alternative to center pivot sprinkler systems. Center pivot sprinklers are very efficient, but they loose a small amount of water to evaporation (either from water droplets passing through the air or from water on the soil surface). With SDI, water is delivered directly to the plant root zone by plastic tubing beneath the soil surface, so the evaporative loss is eliminated, making SDI (in theory) slightly more efficient than sprinklers. The lack of soil surface evaporation with SDI is also thought to reduce evaporative cooling that would otherwise happen with sprinklers, which may lead to earlier maturity for SDI-irrigated cotton. Some producers to our south claim that they can harvest cotton a week or two earlier under SDI than under center pivot sprinklers. This consideration becomes increasingly critical as cotton moves northward. We compared crop response under SDI and sprinkler systems for three years of grain sorghum and one year of cotton. We also tested the hypothesis that SDI induces earlier maturity in cotton compared to sprinklers. Our single year of cotton data did not support this hypothesis, but we did find that SDI was more efficient than the sprinkler systems for limited irrigation (a.k.a. deficit irrigation, where plant water needs are only partially met, which is typical in our region due to limited irrigation well capacities), but sprinklers were more efficient than SDI for full irrigation (where plant water needs are fully met). Also, cotton fiber quality was slightly better under SDI. We are continuing this experiment for several more seasons, and we plan to measure near-surface soil temperatures and soil water beginning with the 2005 season.
Technical Abstract: Crop responses to MESA (mid-elevation spray applicator), LESA (low-elevation spray applicator), LEPA (low energy precision applicator), and SDI (subsurface drip irrigation) were compared for full and deficit irrigation levels in the Texas Panhandle. Crops included three seasons of grain sorghum and one season of cotton, and crop responses consisted of economic yield, seasonal water use, and water use efficiency (WUE). Irrigation levels were I0, I25, I50, I75, and I100 (where the subscript denotes the percentage of full irrigation, and I0 is dryland). Yield and WUE were greatest for SDI and least for spray at the I25 and I50 levels, and greatest for spray at the I100 level. Yield and WUE trends were not consistent at the I75 level. Seasonal water use was not significantly different in most cases between irrigation methods for a given level. For cotton, the irrigation method did not influence boll maturity rates, but SDI resulted in higher fiber quality at the I25, I50, and I100 levels.