Answer: When are you planting the melons? Melons are a warm season crop in the low desert and should be planted Feb 15- March 15 for watermelon and Feb. 15 through July 15 for cantaloupe. They don't do well during the cool season but just about any type will thrive here. As you probably know, Arizona provides melons for much of the country. Try to choose those that will mature in fewer days or that are well adapted to heat.
It sounds as if you are on the right track improving your soil. To improve your soil, incorporate plenty of compost. In sandy soils, compost improves soil fertility, water and nutrient retention. Add a 4-6 inch layer of compost and incorporate it about 12-18 inches deep. You can use manure if it is well-aged (6 months) or you won't be planting until it has lost it's heat and decomposed. Each planting season, add more compost. You may want to incorporate a balanced fertilizer (e.g., 10-10-10) or add organic fertilizers such as fish emulsion, bone meal, and seaweed/kelp. Follow package instructions.
After planting, add a 1-2 inch layer of mulch. Mulch is great to help retain soil moisture, reduce weeds, and as it breaks down it provides nutrients to the soil. Any organic matter can be used as mulch. Try compost, bark, wood chips, straw, or pine needles. As it breaks down, dig it into your soil and add more.
Melons like a consistent supply of soil moisture. The brown spot on the end may be an indication that the plant was stressed for water. Water slowly and deeply, increasing the depth to about 10-12 inches as the plant matures. I hope this info helps.
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