Subsurface drip and overhead irrigation: A comparison of plant boll distribution in upland cotton

Although subsurface drip (SSD) is used as a water-efficient alternative to overhead irrigation in many crops, the effects of SSD on the distribution of bolls on cotton plants (Gossypium hirsutum L.) have not been thoroughly examined. The purpose of this study was to add to the current knowledge about the effects of SSD on cotton yield dynamics. Cultivar DP 488 BG/RR was grown in three studies during 2 yr with irrigation treatments consisting of overhead irrigation (Overhead), a nonirrigated control (Nonirrigated), SSD matched to overhead irrigation amounts and frequency (SSD Matched), and SSD based on soil moisture (SSD Fed) irrigated cotton. The cotton was grown in two locations in 2004 and one location in 2005 in Georgia. Crop height, maturity, and soil moisture status were monitored throughout the growing season in each location. At harvest, a subplot consisting of one harvest row measuring 3 m in length was removed from each plot and handpicked to determine cotton boll distribution in each plot. Irrigation method had a significant impact on boll distribution on the plants, with the overhead irrigation treatment consistently having less cotton near the bottom of the plant and more cotton near the top than either of the SSD methods. We conclude that SSD irrigation decreases early-season fruit loss, resulting in heavier carbohydrate sinks and decreasing overall growth and upper boll filling on the crop.