- 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.
|See table below
|Up to 120
|Up to 120
|Up to 120
*Where scab-resistant cultivars are grown, a pH between 6.0 and 6.5 is optimum. Where scab-susceptible cultivars are grown, the pH should be below 5.2 or above 7.2.
**See provisional P recommendation below.
|Total tuber yield goal (cwt/acre)
|Recommended N rate (lbs/acre)
- 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 lb Mn, 3 lb Zn, 4 lb Fe, 3 lb Cu, and 1.5 lb B/A. 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 lb/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
- Band all phosphorus.
- Apply 50% to 70% of N and 50% of K2O at emergence and the remaining N and K at 35 to 40 days after planting.
- Potatoes planted in cool soils might respond to up to 25 lb/ac P2O5applied as starter fertilizer in the furrow with the seed pieces.
- 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.
- 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.
PROVISIONAL RECOMMENDATION: Phosphorus (P)
10/25/22: The following provisional P fertilizer management recommendation for commercial potato production (chipping and table) is effective immediately. It will remain in effect throughout the 2022-23 commercial potato growing season.
- The P fertilizer application rate to potato may be determined independent of a preplant soil test for P. Therefore, P fertilizer may be applied up to the maximum UF/IFAS recommended rate for potato of 120 lbs/acre P2O5 regardless of the soil test P value.
- Footnotes 250, 253, 350, and 356 in UF/IFAS Standardized Nutrient Recommendations for Vegetable Crop Production in Florida still apply, including the P recommendation for cool soils in Footnote 253.
Research Results 10/21/2022
Provisional Phosphorus Recommendations for Commercial Potato Production (chipping and table) – October 2022
Recent potato P rate research results
Kelly Morgan, David Liu, Christian Christensen, Lincoln Zotarelli, Sanjay Shukla, Shinsuke Agehara
Situation: Current UF/IFAS phosphorus (P) fertilizer recommendations for potato are based on Mehlich 3 (M-3) soil test results for extractable soil P. The recommendation is to apply up to 120 lbs/acre of P2O5 to soils with a M-3 P test of ≤ 25 ppm (“low”), up to 100 lbs/acre of P2O5 to soils with M-3 P of 26 – 45 ppm (“medium”), and no P2O5 to soils with M-3 P of > 45 ppm (“high”). Additionally, the recommendations include the optional application of an additional 25 lbs/acre of P2O5 to cold soils as a starter fertilizer.
Research Results: A 3-year (2018-20) potato P rate study was conducted on grower’s fields near Hastings, FL. The study was conducted using fertilizer P rates of 25, 50, and 100 lbs P2O5/acre in a randomized complete block design with four replications. Potato yield increased with each P rate even though the fields tested “high” in M-3 P each year.
In 2022, eight P rate studies were conducted in the Hastings area of northeast Florida, near Balm in west central Florida, and near Immokalee in southeast Florida. These studies used P rates of 0, 45, 90, 135, 180, and 225 lbs P2O5/acre in a similar randomized complete block design with four replications. All studies were conducted on grower’s fields with the exception of three sites grown at the UF/IFAS Hastings Agricultural Extension Center. All sites except one had an initial M-3 P soil test in the “high” range (from 119 to 330 ppm P), approximately 2.5 to 7 times the point at which no fertilizer P is currently recommended. All sites (except for two sites with reduced growth caused by frost and weather-related issues) produced linear responses to increasing P fertilizer applications to the maximum rate of 225 lbs/acre P2O5.
Provisional recommendation: Recent research results have found that potato yield increased with increasing fertilizer P rates in soils with initial M-3 index values above the current UF/IFAS “high” index level indicating further calibration is needed for a recommendation of no fertilizer P application. Therefore, fertilizer P recommendations should not be based on M-3 soil test results until data from additional P studies have been collected. Data collected in 2022 found increases in yield to fertilizer P rates up to 225 lbs/acre P2O5. These data represent production and weather conditions during one growing season, thus they should not be used to alter the currently-recommended maximum UF/IFAS fertilizer P rate until additional studies have been conducted and those data evaluated. Therefore, the maximum fertilizer P rate will remain at 120 lbs/acre P2O5 plus an optional application of 25 lbs/acre P2O5 to cold soils.