Project Summaries

12-171GA  Project Manager: E. M. Barnes


John Snider, Guy Collins, amd Jared Whitaker, University of Georgia

Subsurface drip irrigation (SSDI) can be used to achieve excellent yields in cotton in cases where water is a limiting factor. The technology is already used in vegetable production in Georgia, and a few producers are testing the efficacy of using SSDI as an alternative to center pivots in oddly shaped fields that would be unsuitable for center pivot irrigation. Irrigation water is commonly applied using overhead sprinkler irrigation systems, which are currently used on approximately half of Georgia cotton acreage. However, negative impacts on fruit retention and changes in fruit distribution have been observed due to overhead irrigation. Previous work in Georgia has shown that the more compact fruiting due to subsurface drip irrigation (SSDI) management can produce high yield and high quality cotton. However, his research focused on one cultivar, DP488BR, which is no longer on the market. The study was also limited to one irrigation rate for overhead irrigation.

Research conducted during 2011-2012 utilized SSDI at two depths (2 inch and 12 inch), two rates (65% and 100% of the UGA weekly chart recommendations), two irrigation trigger points (-40 cb and -70cb) for both OVHD and SSDI systems, and with two cultivars (the full-season DP1050 B2RF, and shorter-season FM1740 B2F). This research has two objectives: 1) Identify the growth, yield, and fiber characteristics of cotton subjected multiple subsurface drip and overhead irrigation strategies; and 2) comparing growth, maturity characteristics, yield distribution, and quality under subsurface drip irrigation in multiple environments.

Few interactions between varieties and irrigation treatments were observed; therefore the lint yield responses of both varieties are discussed. When pooled over all locations and varieties, we observed that 65% UGA Checkbook recommendations resulted in similar yields to that of the 100% checkbook recommendations. However, the 2012 growing season was abnormally wet as frequent rainfall was observed across the state this year. However, when comparing sensor-based irrigation treatments, initiating irrigation according to the wetter 40 cb trigger resulted in higher yields than the drier 70 cb trigger, regardless of variety sensitivity to water stress. According to this data, maintaining higher soil moisture status on a consistent basis, and avoiding water depletion (even for a short time), resulted in higher yields.

According to the results of the sensor-based treatments, similar yields can be expected between shallow and deep SSDI and Overhead irrigation. Therefore SSDI shows little advantage nor disadvantage in Georgia cotton production, however it can result in significant water savings and certainly has utility in small odd-shaped fields that would otherwise be dryland environments. However, when observing the effects of tape depth in checkbook SSDI, there appeared to be a yield penalty associated with deeper tape when applying higher rates of irrigation (100% checkbook), but this difference was only numerical for the 65 % checkbook irrigation. A similar effect was observed when several treatments were excluded from the analysis to focus only on the effects of tape depth on sensor-based SSDI. In this situation, a yield penalty was observed with the 70 cb treatment was used to irrigate cotton using deep tape.
In conclusion, Subsurface Drip Irrigation is a feasible practice for cotton growers in Georgia. Compared to overhead irrigation, SSDI could potentially save water and pumping costs, by allowing growers to apply more frequent applications with lower irrigation rates. With this practice, growers could easily adjust for rainfall by ceasing irrigation, whereas water may have been wasted on overhead system if significant rain occurs after and irrigation event. Most importantly, these results show that there is no yield penalty associated with SSDI compared to overhead irrigation, enabling growers to irrigate cotton in smaller, odd-shaped fields that would otherwise be non-irrigated environments. Using the results from this research, we now have a better understanding of how to irrigate cotton using subsurface drip irrigation, which would improve cotton growers' sustainability, and their bottom line.


Project Year: 2012

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