Don't use poultry manure on melon plants unless you fertilize in the fall, thereby allowing some of the concentrated salts to leach out before spring planting. Melon plants double in size during the hot month of July, and this speedy growth may leave foliage pale. Spray them with a water-soluble fertilizer to give the plants a quick boost. Soil Watermelons need rich, porous soil located in full sun. The pH should be 6 to 6.5.
Taproots can grow an inch per day and eventually reach four feet in length.
Lateral roots may extend even farther than do the vines. Loose soil is necessary for this rampant growth to take place. Also, heavy soils lead to fruit with inferior flavor. Water Lack of water may produce misshapen melons or no fruit at all. But hold back on watering once the melons start to ripen to promote greater sweetness.