Watermelon
General Information
- UF/IFAS fertilization and liming recommendations are advisory in nature and emphasize efficient fertilizer use and environmentally sound nutrient management without losses of yield or crop quality.
- It is assumed the nutrients will be supplied from purchased commercial fertilizer and the expected crop yields and quality will be typical of economically viable production.
- Growers should consider UF/IFAS recommendations in the context of their entire management strategy, such as return on investment in fertilizer and the benefits of applying organic soil amendments.
Fertilizer Rates
| Target pH | lbs/acre/cropping season | |||||||
|---|---|---|---|---|---|---|---|---|
| N | P2O5 | K2O | ||||||
| Soil test | Low | Med | High | Low | Med | High | ||
| Watermelon | 6.0 | 150 | 100 | 100 | 0 | 120 | 100 | 0 |
- Indicated fertilizer rates plus the nutrients already in the soil will satisfy the crop nutrient requirement for this cropping season. Excessive fertilization has been shown to reduce vegetable quality.
- On soils that have not been in vegetable production within the past 2 years, or where micronutrients are known to be deficient, apply 5 lbs Mn, 3 lbs Zn, 4 lbs Fe, 3 lbs Cu, and 1.5 lbs B/ac. Use soil testing to monitor micronutrient status every 2 years to avoid micronutrient toxicity, because some micronutrients can build up in the soil. When deciding about micronutrient applications, consider micronutrients added to the crop via fungicides.
- Up to 40 lbs/acre Mg might be needed when soil test is medium or lower in Mg. Mg can be supplied in fertilizer or from dolomitic limestone, when liming is recommended. Calcium concentrations are typically sufficient in most soils used continuously for vegetable production or where the Mehlich-3 Ca index is >300 ppm. Calcium is added during liming activities and from calcium carbonate present in irrigation water drawn from aquifers in Florida. These sources should be considered in the determination of Ca fertilizer needs.
Fertilizer Timing and Placement
For non-mulched crops
- Fertilizer should be applied in split applications to reduce leaching losses and lessen danger of fertilizer burn.
- Broadcast all P2O5 and micronutrients, if any, and 25% to 30% of the N and K2O in the bed at planting.
- Apply remaining N and K2O in sidedress bands during the early part of the growing season.
- Additional, supplemental sidedress applications of 30 lbs N/A and 20 lbs K2O/ac should be applied only if rainfall/irrigation amounts exceed 3 inches within a 3-day period or exceed 4 inches within a 7-day period (leaching rain rule).
For mulched crops
- If irrigation is subsurface, incorporate 10% to 20% of the N and K2O, plus all of the P2O5 and micronutrients, if any, into the bed. Apply the remainder of the N and K2O 2 to 3 inches deep in one or more bands about 6 to 10 inches from the plants.
- For drip irrigation, incorporate 20% to 40% of the N and K2O and all of the P2O5 and micronutrients, if any, into the bed. Apply the remainder of the N and K2O periodically through drip tubes according to the rate of crop growth.
- For management systems where both subsurface and drip irrigation are being used, apply no more than 20% of the N and K2O, plus all of the P2O5 and micronutrients, if any, into the bed. Apply the remainder of the N and K2O periodically through drip tubes according to the rate of crop growth.
- For overhead irrigation, incorporate all of the N, P2O5, K2O and micronutrients, if any, into the bed prior to installation of the plastic mulch.
Transplants may benefit from application of a dilute, soluble starter fertilizer, especially at cool soil temperatures. Starter solution rates of N and P2O5 need not exceed 10 to 15 lbs/acre each.
Fertilizer Sources
- Supply 25% to 50% of the N in the nitrate form if soils were treated with multipurpose fumigants or if the soil temperature will stay below 60°F for up to one week following transplanting or germination.
- 25 to 30% of the N may be supplied from slow-release N sources, such as sulfur-coated urea, polymer-coated fertilizers, or isobutylidene-diurea (IBDU).
Water Management
- Fertilizer and water management are linked. Maximum fertilizer efficiency is achieved only with close attention to water management. Supply only enough irrigation water to satisfy crop requirements. Excess irrigation may result in leaching of N and K, creating possible plant deficiencies.
- For subsurface irrigation, maintain a constant water table between 18 (at planting) and 24 inches (near harvest) below the top of the bed. Monitor water table depth and do not fluctuate to avoid fertilizer loss below the root zone.
- Consult AE259, "Scheduling Tips For Drip Irrigation of Vegetables," AE260, "Principles and Practices of Irrigation Management for Vegetables," and AE500, "How to Determine Run Time and Irrigation Cycles for Drip Irrigation: Tomato and Pepper Examples" for information on injection schedules.
Additional Information
- Fertilizer rates suggested are for the first crop. Squash and cucumber following other crops on the same mulch may not need substantial additional fertilizer. If fertilizer is needed for the second crop, apply fertilizer using a liquid-injection wheel or via drip irrigation. Apply no more than 30 to 40 lb/acre N and/or K2O in any single injection wheel application.
References
CIR 1152 UF/IFAS Standardized Nutrient Recommendations for Vegetable Crop Production in Florida
HS 711 Soil and Fertilizer Management for Vegetable Production in Florida
CV 296 Vegetable Production Handbook: Chapter 2. Fertilizer Management for Vegetable Production in Florida
Other Resources
SL 352 A Summary of N, P, and K Research with Watermelon in Florida
AE 503 Water and Nitrogen BMPs for Tomato and Watermelon: Water Quality and Economics
SL 342 Nutrient Mass Budget--The Case of Florida Watermelon Phosphorus Export