How to Plant Watermelons Commercially

Plant the watermelon seeds approximately 1 inch deep when the soil is warm enough for them to germinate rapidly. Though the seeds will germinate at around 65 degrees Fahrenheit, the process will be slower than the optimal temperature of 77 degrees Fahrenheit. At this level of warmth, the vines should sprout and be visible after five days.

Deposit plastic mulch, which is an option that can cause the watermelons to harvest up to two weeks earlier. The most common type of plastic mulch is black polyurethane, which can increase the temperature of the soil, thus spurring the plants' growth.

Post beehives every acre to ensure the watermelon flowers are pollinated. The vine bears both male and female flowers, which must be cross-pollinated up to 48 hours after opening. Though honey bees can help transport the male's pollen to the female, wild bees are more aggressive and effective, according to the University of Georgia Cooperative Extension Service's "Commercial Watermelon Production." Once the pollination activity draws to a close, apply pesticide to the watermelon vines.

Manage the soil's pH and fertility with the use of lime and fertilizer. Lime can help balance out the soil's pH, which should hover around 6.0 to 6.5. The soil can be tested with a kit, and lime can be added if the pH is below these levels. Additionally, the typical fertilizers for watermelon are usually high in potassium and phosphorus, which can be added to the soil about once a week.

Water the vines as the soil becomes dry to the touch. For normal soil, the vines can be watered with regular sprinklers, but plastic mulch requires an irrigation system so that the water properly penetrates the mulch and flows into the soil.

Harvest the fruit when it shows signs of maturity. One sign is when the underside of the watermelon, the part that touches the soil, is green. The watermelon should also sound hollow when thumped. Additionally the tendrils, or small curls at the point where the vine touches the melon, should be dry and brown. When these signs are present, the watermelon can be hand-picked and handled carefully to minimize bruising.

Cool the fruit in a refrigerated locker at 40 to 45 degrees Fahrenheit to prolong its shelf life. Watermelons stored at this temperature can last three to four weeks.