The Best Soil for Watermelons

Soil

• The best soil for growing watermelon is an acidic, well-drained, sandy loam, as recommended by the Oklahoma State University Extension. Heavy soil is not good for growth, as it slows plant development and produces smaller-sized, inferior-quality fruit. Supplemented with the right amount of water and fertilizer, sandy soils lead to the highest-quality fruit. Use windbreaks around sandy soil to minimize possible sandblast damage to seedlings in spring winds.

Water

• After planting in a deep, sandy soil, water with 8 to 10 inches of water, either by rain or through irrigation. Watermelon plants need the most water just after planting, at the time of seedling growth, during the early bloom period and during the 10 days prior to harvesting. Lack of water after planting produces poor seedling growth, water stress at bloom time causes reduced fruit set and lack of water near harvesting reduces fruit size.

Fertilizer

• It is best to conduct a soil test to determine exact soil nutrient levels. On a general note, the recommended fertilizer is 1 lb. of nitrogen, 2 lbs. of phosphorus and 3 lbs. of potassium for every 1,000 square feet, as suggested by the Ohio State University Extension. Lime application is made to bring soil pH to the recommended 6.0 to 6.8.

Planting Recommendations

• If starting seeds indoors, plant seeds in peat pellets or pots about four weeks before the last frost date in the area. Watermelons are highly sensitive to cold temperature and are intolerant of freezing soil. Direct seeding may also be done, but this delays harvest time. Apply black plastic mulch to warm the soil, conserve moisture and reduce weeds.