When it comes to watermelons, what you see is not all you get.

The surface area of most plants below ground is far greater than the area we see on the surface. In watermelons the root surface area can be 100 times greater than leaf area above. It’s what Clemson University Plant Physiologist Christina Wells calls “the hidden part of the plant.”

Wells and other Clemson researchers explained the importance of water management and understanding how roots grow to the more than 200 people who attended the 2009 Watermelon Field Day at the Edisto Research and Education Center.

Watermelon roots are shallow, Wells said. They usually grow in the first 12 inches of the soil and spread far from the base. They burn about half the plant’s energy when growing and rely on input from above in the form of water, nutrients and oxygen. Planted too deep, the roots will starve.

“Roots of almost all plants are shallowly distributed,” Wells said. “They breathe and they require oxygen just like we do.”

Extension Vegetable Specialist Gilbert Miller opened his field to the public to discuss the latest research, which this year included presentations by Clemson researchers Hamid Farahani and Anthony Keinath on tactical irrigation and plant-disease control.

The field day featured 30 seedless watermelon and 10 mini-watermelon varieties, including common commercial varieties and potential new melons. Certified Crop Advisor and Pesticide License credits also were offered.

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.

Over-watering is just as stressful on the plant as under-watering. To understand the correct amount to apply, it’s vital to understand soil types and when the stress levels occur, Miller said.

Modern agriculture deploys in-ground sensors, wireless communications and solar technology to provide a window into the soil.

Solar-powered field stations collect data. Miller can download from the Internet the soil-moisture and nutrient readings from a series of test plots throughout his watermelon field.

During this year’s growing season, the region’s rainfall was plentiful, but at times problematic. Growers must carefully monitor their irrigation schedules to prevent over-watering, he said.

But sometimes, you don’t need modern technology to know when there were heavy rains.

“One of the guys who works here at the station swears he saw a 10-inch bass swim out of my field,” Miller said.