Soil Surfactant Increases Nutrient Use Efficiency and Yield of Tomato Grown in Sandy Soil

Florida grows 33,600 acres tomatoes  and the total yearly value is more than $520 million; accounting for 65% of the value of the crop in the nation.  Florida tomatoes are grown primarily in sandy soil, which has low water-holding capacity and high nutrient leaching due to its coarse-sized particles. A soil surfactant, however, is a surface-active substance with both hydrophilic (water-loving, polar) and lipophilic (fat-loving, apolar) properties like soaps and detergents.  These amphiphilic properties can significantly improve soil quality, reduce water repellency, and increase the capacity for holding water and nutrients in sandy soil. The objectives of this research were to: 1) evaluate the effect of a surfactant on nutrient use efficiency and 2) assess the yield enhancement of the surfactant on tomatoes grown in sandy soil.  This research was conducted in a hyperthermic, uncoated Typic Quartzipsamments (USDA, 1979) sandy soil in UF/IFAS Plant Science Research and Education Unit, near Citra, FL, in Fall 2012.  Prior to planting, fertilizers (lb/acre) were applied and incorporated into soil: 160 N (as urea), 83 P₂O₅ (as triple superphosphate), and 250 K₂O (as muriate of potash).  There were two surfactant rates: 0 (control) and 30 (treatment) lb/acre (as Stockosorb^® 660).  Tomato (Lycopersicon esculentum Mill. var. ‘Phoenix’) seedlings were planted in 12.5 m² (135 ft²) plots with three replicates and irrigated with drip and plastic mulch.  Nutrient use efficiency (lb/lb) was defined as tomato yield increment per pound of applied nutrients.  The plant size of the treatment was 15% greater in both height and diameter than the control.  Tomato yields of the control and treatment were 99,017 and 57,738 lb/acre, respectively.  The marketable yield of the treatment was 84% greater than that of the control.  Large, medium, and small tomatoes of the treatment were 192%, 102%, and 38% greater than those of the control.  Nutrient use efficiencies of N, P, and K were 252, 485, and 162 and 123, 236, and 79 lb/lb for the treatment and control, respectively.  These results indicate that soil surfactant significantly increases plant growth, yield, and nutrient use efficiency of the tested tomato cultivar.