BLACKVILLE – Don Rackley traveled about 100 miles from his Clinton home for the chance to sink his pocket knife into watermelons so fresh they were still on the vine.

After picking two that weren’t quite ripe, Rackley found the juicy treat he was looking for. The bright red fruit provided the perfect refreshment as the noon sun beat down.

“It’s great if you’re thirsty,” he said.

Rackley was one of more than 150 people who came to Clemson University’s Edisto Research and Education Center on July 10 for the 2008 Watermelon and Vegetable Field Day.

During the free annual event, Clemson Extension area vegetable specialist Gilbert Miller opens his field to the public and discusses his latest research.

For more than 20 years, Miller has worked to understand a fundamental dilemma for growers: the fine line between over watering and allowing the soil to get too dry. Or to put it another way, “How full should we keep our bucket and how deep should it be?” Miller said.

Over watering is just as stressful on the plant as under watering. To understand the correct levels to apply, it’s vital to understand your soil types and when the stress levels occur. Go beyond that stress threshold and a grower likely will lose production, Miller said.

To help make the determination, five years ago Miller started using in-ground sensors to provide a window into the soil.

Sensors supplied by New Jersey-based EarthTec Solutions monitor moisture and nutrient levels vertically and horizontally at depths of 4, 8, 12, 16 and 20 inches. Miller has four treatment plots, one for each sensor array.

One station receives the standard extension recommendations for timing, and amounts of water and liquid fertilizer through drip irrigation. In the other three, Miller deliberately shortchanges the watermelons of nutrients, water or a combination of the two, followed by an overdose.

Miller uses the technology to determine the causes of hollow heart, a condition that makes melons unmarketable. His research also helps growers control costs and produce higher quality crops by saving on fertilizer and water.

For example, by applying the right amount of water, nutrients aren’t washed below the root zone, giving the plant a better chance to thrive.

Solar-powered field stations collect the data, which are transmitted to a server for access via the Internet. From his office, Miller can download the soil moisture and nutrient readings from a series of test plots throughout his watermelon field.

As for Rackley, he left Blackville with the perfect watermelon tucked under his arm. His secret for finding a ripe melon? Look for a yellow patch where the rind is sitting on the soil.

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