Can Applying a Nonionic Surfactant Increase Soil Water and Nutrient Content and Increase Cotton Boll Density in a Sandy Loam Soil?.

Soil surfactants have the potential to improve water infiltration and distribution and thus optimize water availability and nutrients to roots and conserve water volume. The objective of this study was to evaluate using a nonionic surfactant (SURF) for water conservation and cotton growth. Two field experiments was conducted at Florence, SC on a Goldsboro series soil from May to October 2013 and repeated in 2014 on Noboco series soil. Two cotton varieties (PHY 499WRF and PHY 339WRF), grown as dryland or with irrigation received either no nonionic surfactant (NSURF) or two applications of SURF throughout the season were assigned in a split block experimental design. Soil water content (SWC) measured at 10, 20, 30, and 40 cm were determined throughout each experiment. Soil nutrient status 10:20 cm was determined before and after the experiments were conducted. Boll density and fiber quality were determined at harvest. The main effect of nonionic surfactant application did not influence SWC in both years. However, applying SURF caused a significant SWC increase at the 40 cm depth in June and September in 2013, with no differences determined in 2014. Both varieties receiving SURF had lower boll density, 13 per plant (p=0.0114) compared to untreated soils, 15 per plant (p=0.0123) in 2013, with no differences determined in 2014. Dryland soils had lower pH, potassium and boron and higher phosphorus in 2013 and lower calcium, and potassium, in 2014 compared to irrigated soils.  Applying SURF caused a significant increase in pH and phosphorus in 2013 and calcium in 2014, and a significant decrease in magnesium, and phosphorus in 2014. Generally, SURF did not influence SWC compared to the NSURF soils. This may have been because three times the average rainfall occurred during the 2013 experimental period and two times in 2014. Soil nutrients were not greatly affected, although few significant differences due to SURF were found. Although SURF resulted in lower cotton boll density in 2013, no effects were determined in 2014. The minimal difference in 2013 may not be of practical significance. Further research should focus on drought like conditions and different NSURF application rates and frequencies.