Date of Award
Doctor of Philosophy (PhD)
Plant and Environmental Science
Khalilian , Ahmad
Farahani , Hamid
Adelberg , Jeff
Hassell , Richard
Watermelon rooting patterns, root dry weight, plant biomass, stomatal resistance, root-to-shoot ratio, fruit yield, and fruit quality were evaluated in field trials during 2008, 2009 and 2010, using three irrigation regimes and three plant types. Plant types included: `Wrigley' grafted on Cucurbita moschata x Cucurbita maxima cv. Chilsung Shintoza; `Wrigley' grafted on Lagenaria siceraria cv. Fr Strong; and `Wrigley' not grafted. The irrigation regimes were: (1) No irrigation (NI) (30 minutes per day for fertigation only); (2) 50% and (3) 15% available water depletion (AWD) in the 0-30 cm soil profile triggered irrigation. Each whole plot contained a Sentek TriSCAN EasyAg 50 multisensor capacitance probe (MCP) for measuring soil volumetric moisture content (VMC). On-site probe calibration showed MCP's with factory calibration were sufficiently accurate and responsive for irrigation scheduling purposes. A Motorola IRRInet Computerized Irrigation Controller received VMC input and triggered irrigation cycles. Root cores were taken at approximately four, eight and twelve weeks after planting (WAP). Core sites were located immediately next to the drip line (Core 1) and 30 cm from the drip line (Core 2). Root measurements were obtained with a WinRHIZO Pro 2009a, b system. Across all sampling dates, root length density (RLD) was not influenced by irrigation treatment or plant type. Grafted plants did not show a greater propensity to extend roots horizontally or vertically. For all the treatments in each year, RLD was significantly greater in the top 30 cm of the soil profile and dropped dramatically below 30 cm. Watermelon roots showed a tendency to grow near the drip line, particularly in sandy soils, but neither as early nor to the extent as reported with other crops. Fruit yield for all plant types was comparable to commercial yields in geographical proximity. `Wrigley' grafted on Chilsung Shintoza RS compared to other plant types showed firmer flesh in all years tested. The 15% AWD treatment
showed significantly higher yield, greater number of fruit and plant biomass when compared to the 50% AWD and NI treatments. The MCP's coupled with short duration irrigation cycles were found to facilitate triggering irrigation at pre-determined set points, reduce water movement below the root zone and simplify automation.
Miller, Gilbert, "SENSOR BASED IRRIGATION EFFECTS ON ROOT DISTRIBUTION AND GROWTH OF GRAFTED AND NON-GRAFTED WATERMELONS" (2012). All Dissertations. 911.