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Extension Programs in Northeastern Florida Help Growers Produce Quality Strawberries by Improving Water and Nutrient Management1
Robert Hochmuth, David Dinkins, Michael Sweat, and Eric Simonne2The Florida strawberry industry is primarily located in the Plant City area with approximately 6,000 acres. There is scattered acreage in other parts of the state including Bradford County and the surrounding area of northeastern Florida. The Bradford County area was once the main strawberry producing area in the state with 1500 acres of strawberries grown during the period of 1915 to 1920. This rich heritage is still important to Bradford County's economy today. Strawberry acreage in northeastern Florida (Gainesville and north) was estimated at 40 acres in 2003.
Growers in northern Florida have traditionally used plastic mulch culture with overhead irrigation and have depended upon pre-plant fertilization to supply nutrients for the growing season. With heavy rainfall or excessive irrigation, this practice is inefficient and has resulted in nutrient deficiencies at the end of the growing season in part due to nutrient leaching, especially nitrogen. Extension programs in this production area have emphasized teaching growers the benefits of using drip irrigation as a tool for improved water and nutrient management ( Figure 1 ).
On-farm Extension demonstrations throughout the 1990s provided opportunities for growers in the Suwannee Valley area and northeastern Florida to learn how to use drip irrigation for water and fertilizer delivery resulting in increased yield and quality. Drip irrigation is now used by over 95% of the growers in this region of northeastern Florida.
Figure 1. On-farm demonstration of strawberries grown on plastic mulch with drip irrigation. Drip irrigation systems on strawberry farms provide the opportunity to improve nutrient efficiency and reduce crop production costs. Petiole sap-testing programs (Table 1 , Figure 2 ) provided by county Extension agents throughout Florida have taught growers the best nutrient management practices through this technology (Plant Petiole Sap-Testing Guide for Vegetable Crops, UF/IFAS Circular 1144, http://edis.ifas.ufl.edu/CV004). Information was collected during visits with north Florida strawberry growers during the spring fruiting seasons (Feb-May) from 1998-2003 to evaluate various fertilization programs being used (Strawberry Production in Florida, HS736, http://edis.ifas.ufl.edu/CV134 ). Potassium levels were within the ranges in 80% of the samples without drip fertilization, but were within the recommended ranges in 100% of the samples when UF/IFAS drip fertigation recommendations were used. This Extension effort revealed nitrogen management was much more difficult when drip fertigation was not used. The petiole sap tests indicated one pre-plant application of fertilizer was usually insufficient to meet the crop requirement for nitrogen, even when very high rates or some controlled-release nitrogen is used in the pre-plant application. In those crops where drip fertigation was not used, the nitrogen levels in the petiole sap dropped below recommended levels most years. Petiole sap nitrogen levels in March to April frequently fell below 100 ppm if drip fertigation was not used. In years with excessive rainfall, fields with no drip irrigation showed insufficient nitrogen sap levels 90% of the time.
Figure 2. Sap Testing Meter As growers adopted drip irrigation and used recommended fertigation practices (Table 2 ), nitrogen and potassium levels were maintained within the recommended ranges. During the spring harvest season of March-May, plants appeared healthy and vigorous when petiole sap nitrogen levels were 250-500 ppm. ( Figure 3 and Figure 4 ) Plants with less than 200 ppm during that period appeared to have poor color and low vigor.
Figure 3. Healthy strawberry.
Figure 4. Strawberries grown on plastic mulch with drip irrigation. The recommended rate of nitrogen (N) and potassium (K2O) for the main fruiting season is 0.75 lbs/A/day (Strawberry Production in Florida, HS736, http://edis.ifas.ufl.edu/CV134 . Drip fertigation programs at the rate of 0.75 lbs/A/day of nitrogen and K2O were successful in maintaining excellent crop nutrient status. When once-a-week applications of the recommended rates were used, the growers were successful. The various fertilizer sources typically used and weekly amounts applied are shown in Table 3.
This overall Extension program effort has resulted in reductions of water use by 50% on 30 acres of strawberries adopting drip irrigation. In addition, improved fertilizer management programs are reducing fertilizer amounts by at least 20% through more efficient use. Fertigation programs are also improving crop yields and quality by maintaining proper nutrient levels for the duration of the harvest season.
Tables
Table 1. Sufficiency ranges for petiole sap testing for different growth stages of strawberry grown in northern Florida (from Strawberry Production Guide for Florida, HS736, http://edis.ifas.ufl.edu/CV134).
Fresh Petiole Sap Concentration (ppm
Crop Development Stage
NO3-N
K
November, soon after planting 800-900
3000-3500
December, first harvest 600-800
3000-3500
January, main season 600-800
2500-3000
February, main season 300-500
2000-2500
March, main season
200-500
1800-2500
April, late harvest, near end of season 200-500
1500-2000
When petiole sap test falls below sufficiency rates, check irrigation program or increase fertigation by 20% for one week, and re-determine sap nutrient content. Table 2. Daily nitrogen (N) and potassium (K2O) application rates (lbs/A/day) for strawberries grown in northern Florida with or without freeze protection.
With Freeze Protection
Without Freeze Protection
Month Plant Status
N
K2O
Plant Status
N
K2O
October
planting (mid Oct)
0.4
0.4
planting (mid Oct) 0.4
0.4
November vegetative
0.4
0.4
vegatative 0.4
0.4
December fruit set 0.6
0.6
vegetative 0.4
0.4
January 1st picking 0.6
0.6
bloom 0.4
0.4
February fruiting 0.75
0.75
fruit set 0.6
0.6
March fruiting 0.75
0.75
fruiting 0.75
0.75
April fruiting 0.75
0.75
fruiting 0.75
0.75
May fruiting 0.75
0.75
fruiting 0.75
0.75
June fruiting •
•z
fruiting 0.75
0.75
Total for season 145
145
152
152
If 30 lbs per acre of each N and K2O are applied preplant, then injections during the first 4 weeks after planting may be omitted. Adjust rates based on petiole sap test readings.
z Freeze protected strawberry plants seldom fruit in June.
Table 3. Optional strawberry fertigation programs used in northern Florida for the main fruiting season.
Recommended Fertilizer Rate (lbs/A/day)
Amounts of Fertilization Products Injected
Once a Week per Acrez
Premix Option 1
Premix Option 2
Grower Mix
Option 3y
N
K2O
Liquid 7-0-7
Liquid 8-0-8
Ammonium Nitrate 34-0-0
+
Potassium Nitrate 13.5-0-46
0.4
0.4
4.0 gal
3.5 gal
6.0 lbs
+
6.1 lbs
0.6
0.6
6.0 gal
5.2 gal
8.8 lbs
+
9.1 lbs
0.75
0.75
7.5 gal
6.5 gal
11.0 lbs
+
11.4 lbs
z One acre for strawberry is equal to 10,890 linear feed of bed. y Growers would mix these ingredients on their own.
Footnotes
1. This document is HS-956, one of a series of Department of Horticultural Sciences, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Publication date: August 2003. Please visit the EDIS Web site at http://edis.ifas.ufl.edu.2. Robert Hochmuth, multi county extension agent, Suwannee Valley Research and Education Center, David Dinkins, county extension director, Michael Sweat, county extension director, Baker County Extension Service, Eric Simonne, professor, Horticultural Sciences Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611
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U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry Arrington, Dean.
Copyright Information
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