Watermelons Bursting and Splitting
The excessive and sudden accumulation of water is readily absorbed by the thirsty melons and they actually engorge themselves to the point where the rind can not keep up and it basically pops from internal pressure.
I recall as a young teen working at a farm stand where we had hundreds of watermelons. The melons were stacked like cannonballs. When more melons came in from the fields we stacked them on top to replace those that sold off. The melons on the bottom lay there soaking in all the rain that puddled around them. In mid summer, a few days after a heavy rain the melons on the bottom started exploding, not popping, but exploding and spitting their seeds out for many yards.
An old woman standing about 10 to 15 feet from one of the stacks when this happened got blasted with red melon pulp and seeds - combined with the sound effect it looked like she got blasted with a shotgun. The image of this poor woman is forever embedded in my mind. Needless to say she got a free watermelon from the top of the stack this time as well as some tomatoes and green beans :>
When melons are deprived of moisture they develop a tighter and harder skin which prevents moisture loss. However, once a sudden moisture surge comes such as a minor deluge or over watering, the skin tries to expand but can't always keep up. As a result, the watermelon bursts.
A less common, but just as plausible reason for watermelons splitting and popping is excessive heat. If your melons pop or crack and they have not been exposed to an erratic water supply, chances are it is during a hot spell.
Water expands under high temperatures, pressure within the watermelon can accumulate when it gets too hot causing the melons to burst. Organic Mulch and temporary shading can help alleviate this issue during extreme hot weather.
Watermelon Pest and Disease Problems Trouble Shooting Watermelon Watermelon. Common Pests and Disease Problems, Nutrient Deficiencies.
Blossom End Rot is caused by temporary insufficiency of water and calcium. The soil may have a calcium imbalance inhibiting the uptake of water. Adding limestone can help if the soil if the pH is below 6.0. It may also occur under high temperatures when the melons are rapidly growing. Recommended treatment Blossom-End Rot Control
Hollow Watermelons - Why ? Watermelons are sometimes hollow in the center. Not a major problem just a little annoying. Melons and related fruits will sometimes form with a hollow interior or 'hollow heart'. The flavor is sometimes not up to par either, now that's a tad more than annoying.
Small Stunted Watermelons - Why ? Every now and again you'll plant watermelons and yes you do get melon, but they're squeamishly small and stunted. There are a number of reason watermelons fail to grow to their anticipated size and at times even fail to ripen at all.
Plant Nutrient Deficiencies Most garden plant issues arise from insect and disease problems, nutrient deficiencies should only be treated when the disease and insect possibilities have first been explored. So long as the soil is relatively fertile and a proper soil pH is maintained Nutrient deficiencies are generally not a major problem.