Water movement in mulched beds in a rocky soil of Miami-Dade County

Efficient irrigation and fertilizer management for vegetables grown with plasticulture requires an understanding of water movement in mulched beds. Soluble blue dye and controlled irrigation events were used in a dye test conducted on 14 October 2003 on a Krome very gravelly loam soil in Homestead, Fla. The objectives of this study were to visualize the wetting patterns of several drip tapes and provide guidelines for scheduling irrigation. The dye test consisted of preparing mulched beds with different drip tapes, injecting dye, irrigating with a predetermined volume of water (V), digging longitudinal and transverse sections of the beds, and taking measurements of depth (D) and width (W) of the wetted zone, and emitter-to-emitter coverage (L). Drip tape brands were Aqua-Traxx [12-inch emitter spacing (ES); 22 gal/100ft/h], Eurodrip (12-inch ES; 35 gal/100ft/h), Netafim (12-inch ES; 24 gal/100ft/h), Queen Gil (4-inch ES, 33 gal/100ft/h), and T-Tape (8-inch ES, 21 gal/100ft/h). After digging, dye patterns appeared as blue rings under each emitter. Increasing V from 21 to 142 gal/100 ft did not significantly increase D, W, and L. All measurements ranged between 4 and 9 inches. For each drip tape, increasing V significantly increased W, but only within the narrow 4 to 9 inch range. After 2 to 3 hours of irrigation, the dye reached the calcium carbonate bedrock and moved into it thereafter. Hence, the flow rate and emitter spacing had no practical effect on the wetted zone of this rocky soil, possibly because of shallow soil depth (7 to 10 inches) and high soil heterogeneity.