Abstract
Adequate water, fertilizer, and fumigant management in plasticulture production systems requires an understanding of water movement in mulched beds. Soluble blue dye and controlled irrigation conditions were used to visualize the wetting pattern of several common drip tapes on three Florida sandy soils. On an Orangeburn fine sandy loam near Quincy, Fla., the wetted zone reached the 10-inch-deep impermeable layer between 60 and 120 gal/100 ft (2 to 4 hours at 30 gal/100 ft per hour; 12-inch emitter spacing). With greater irrigation volumes, lateral water movement occurred. On a 15-ft deep Lakeland fine sandy soil near Live Oak, Fla., increasing irrigation volume from 24 to 192 gal/100 ft (1 to 8 hours at 24 gal/ hour per 100 ft; 12-inch emitter spacing) significantly increased depth (D), width (W), and emitter-to-emitter coverage (L) of the water front. The wetting front passed the bottom of the root depth (12 inches) after an irrigation volume of approximately 72 gal/100 ft (3 hours). After 8 hours, W did not exceed 15 inches. Complete emitter-to-emitter coverage was reached after approximately 3-hours irrigation (72 gal/100 ft). Therefore, the highest volume of irrigation water that can be applied in this soil type when no leaching is expected is 72 gal/100 ft (3 hours). On a Boca sand soil with a spodic layer at the 18 inch depth in Hendry County, Fla., the water front reached the impermeable layer after 96 gal/100 ft (4 hours at 24 gal/hour per 100 ft; 18-inch emitter spacing). Lateral, then upwards vertical movement occurred with greater irrigation volumes. In Live Oak, W did not exceed 30% of the bed width, confirming that complete wetting of 32-inch-wide beds cannot be achieved with a single drip tape. The presence of an impermeable layer in Quincy and LaBelle would allow for greater W once the entire profile has been wetted. Using the drip line to deliver fumigants may impact preplant fertilizer movement, thereby requiring an adjustment of the fertility program.
