How Much Water do Florida Peaches Need?

Recent Research Suggests that Reducing Irrigation Volume Rates May Not Have Effect on Fruit Yield and Quality

 

Fruit and vegetable growers across the United Sates are facing several challenges to remain profitable and Florida peach growers are not the exception.  State regulations, labor, and optimization of cultural practices are just some of the factors affecting agriculture in Florida.  Optimizing cultural practices, particularly irrigation, is one of the most difficult tasks growers must deal with.  Increasing competition for water between urban areas and farms has attracted the attention of government agencies and researchers, and growers are willing to incorporate techniques to improve irrigation practices.

The University of Florida has released several varieties of subtropical peaches and these varieties are popular because of their adaptability to Florida growing conditions and low-chilling hour requirement.  These characteristics allow Florida peach growers to produce peaches in an early market window between late March and April.  With the early harvest, growers obtain better prices as compared to prices later in the season when there is increased availability of peaches from northern states, such Georgia and South Carolina.  Irrigation recommendations for subtropical peach production in humid conditions are limited.  Using irrigation recommendations from arid climates (e.g., California) can overestimate irrigation water application in Florida, which will invariably result in nutrient leaching in sandy soils.  The purpose of irrigation includes avoiding water stress conditions for the crop and reducing the possible decline in fruit size, quality, and overall marketable yield.

For the past two years, research has been conducted in two locations: Lake Alfred and Plant City, Florida.  Irrigation water rates have been evaluated in order to determine the most appropriate irrigation regime for subtropical peaches.  Four irrigation volume rates have been tested, ranging from 16 gph (e.g., common grower’s practice) to 5.2 gph.  Peach fruit quality and plant growth were measured to identify whether the reduced irrigation volume affected plant growth or fruit quality, or not.  Results collected from August 2014 and July 2016 showed that stem water potential, biomass production, and trunk cross sectional area (TCSA) were not significantly different between irrigation regimes.  These results suggest that irrigation volume may be reduced for peaches without affecting plant growth or increasing water stress to the plant (see Table 1).

Table 1. Plant growth from Aug-2014 to July-2016 (Plant City and Lake Alfred, FL).

Treatment Lake Alfred Plant City
Biomass Wintera

(lb/tree)

Biomass Summerb

(lb/tree)

TCSAc

(in2)

Biomass Wintera

(lb/tree)

Biomass Summerb

(lb/tree)

TCSAc

(in2)

5.2 gph (0.08 in/h) 39.66 45.10 33.75 12.46 30.89 18.27
8 gph (0.09 in/h) 35.60 49.43 36.13 12.19 26.96 20.22
12 gph (0.13 in/h) 35.02 45.63 33.00 15.41 31.71 19.06
16 gph (0.17 in/h) 36.34 48.31 35.49 13.91 30.58 20.40
Significance (P≤0.05) 0.88NS 0.48NS 0.75NS 0.60NS 0.45NS 0.62NS

NSNo significant differences detected (p<0.05)

a Biomass in winter (December) was taken after trees drop the leaves

b Biomass include leaves and was taken on June.

c TCSA was measured in February each year.

 

Fruit yield and quality (total and marketable yield, fruit number and fruit diameter) have shown no significant difference between irrigation regimes (see Tables 2 and 3).  On a commercial operation in the fourth year after establishment, a marketable yield of 60 lb/tree is expected.  This was found in Lake Alfred (mature trees) with all the treatments showing no difference on marketable yield due to reductions on irrigation volumes.  On the other hand, yield in young trees (Plant City) is still increasing to reach maximum production; however, no significant difference is observed on total yield even under the highest reductions in irrigation volume.

 

Although reduction in irrigation application rates have not affect yield and quality of peaches grown in Florida, more research is needed in order to provide more accurate information about irrigation scheduling to the growers.  The recent past two growing seasons and erratic weather (e.g., rainy seasons, warm temperature patterns) have made it very difficult to predict or estimate evapotranspiration rates or chilling hour accumulation.

 

Table 2. Total marketable yield, fruit number, fruit weight, fruit diameter and fruit firmness from Aug-2014 to July-2016 in Lake Alfred Florida.

Treatment Lake Alfred
Total Marketable Yield (lb/tree) Fruit Number (fruits/tree) Fruit weight (oz/fruit) Fruit diameter (in) Fruit firmness (lbf)
5.2 gph (0.08 in/h) 62.55 91 4.76 2.53 6.19
8 gph (0.09 in/h) 61.64 88 5.04 2.59 6.00
12 gph (0.13 in/h) 65.32 96 4.88 2.57 6.11
16 gph (0.17 in/h) 76.05 109 4.94 2.58 6.04
Significance (P≤0.05) 0.30NS 0.24NS 0.52NS 0.54NS 0.87NS

NSNo significant differences detected (p<0.05)

Table 3. Total yield, fruit number per tree, fruit diameter, fruit firmness and fruit weight in Plant City, FL during the 2014-15 harvest season.

Treatment Plant City
Total Yield (lb/tree) Fruit Number (units/tree) Fruit Weight (oz/fruit) Fruit Diameter (in) Fruit Firmness (lbf)
5.2 gph (0.08 in/h) 28.41 194 2.76 2.09 3.88
8 gph (0.09 in/h) 25.40 154 2.59 2.06 4.25
12 gph (0.13 in/h) 27.45 194 2.78 2.10 3.83
16 gph (0.17 in/h) 34.92 223 2.78 2.12 3.95
Significance (P≤0.05) 0.52NS 0.7NS 0.28NS 0.81NS 0.75NS

 

NSNo significant differences detected (p<0.05)

This study is still ongoing, but the preliminary results from the first two years suggest there is plenty room for refinement of the irrigation volume application and scheduling.  Based on the reference water application rate (e.g., 16 gph), this research indicated lower irrigation rates 5.2 to 8.0 gph can be as effective as high irrigation rates.  The refinement of the irrigation water application rates for peaches has great environmental impact with the reduction of water usage and fertilizer loss, in addition to the reduction in overall peach production costs (e.g., fuel and/or electricity), which may increase growers’ profitability.

 

CREDITS

by CARLOS ZAMBRANO-VACAa, MERCY OLMSTEADb, and L. ZOTARELLIc

aGraduate Student, Horticulture Science Department, University of Florida

bFormer Associate Professor and Extension Specialist, Horticulture Science, University of Florida

cssociate Professor, Horticulture Science Department, University of Florida