The Great Wide Open: Advanced Citrus Production Systems

Florida Citrus Show Extended Content Coverage: The Great Wide Open

During the past two years, the open hydroponics (OH) method of crop production has been intensively studied for proof of concept and adaptation as a new advanced production system (APS) for Florida citrus. The foundation of a successful OH system is based on early, high yields, made possible through 1) intensive fertigation, 2) balanced complete nutrition, and 3) high-density planting. The accelerated growth from optimal balanced nutrition and water relations achieved with precise computerized fertigation is a key component of the APS. When combined with high-density planting, the accelerated growth can potentially cut the time in half to economic production and the return on a new grove investment.

Results from replicated treatments obtained in a replanted 15-acre Hamlin orange block in a commercial grove setting demonstrated during the first year a 60% reduction in irrigation water requirement and an 83% reduction in fertilizer application was possible by using carefully regulated drip fertigation. Despite these input savings, canopy growth of the trees during the same period was 65% greater, resulting in a 9.9-fold increase in efficiency. In the APS treatments, significant reductions in nitrate-nitrogen concentrations were recorded in soil water leachates collected below the root zones of the trees. At no time in the first year did nitrate concentrations exceed the 10 mg/L maximum contaminant level in APS plots, while they frequently exceeded the limit in the conventional control plots. At the end of two years in the field, the APS trees produced their first small fruit crop in December 2010, which was 4.75 times greater than yields from the conventionally grown trees. Fruit quality was already good and passed all the required tests for juice processing (ratios of 16 to 19).

On Trial

The field experiment compares fertigation delivered by microsprinklers with delivery by drip emitters and after 24 months the growth, yield, and fruit quality results of the two systems were similar, but marginally better with the drip system. The drip system is preferred for its high efficiencies, leading to significant savings of water and fertilizer, but has the distinct disadvantage of not being able to protect the crop during winter freezes. Consequently, Florida citrus growers wanting to utilize the high efficiencies of the drip fertigation system also should ensure the crop is protected from freezes — most likely by installing an additional microsprinkler irrigation system for that purpose.
An APS replant configuration currently being researched in the 15-acre experimental Hamlin orange grove near Auburndale relies on two soil sensors placed on at least one “indicator tree.” The shallow water sensor at 0- to 4-inch depth is used to monitor the need for fertigation since it is located in the zone of greatest root proliferation. The second sensor at a depth of 18 inches is required to determine if fertigation or rainfall events cause excessive movement of water and nutrients beyond the main root zone. Thus, both sensors are used simultaneously to determine the optimal fertigation strategy for citrus tree growth and also to avoid leaching nutrient solutions to the groundwater. In this experimental APS, data from the soil sensors is automatically collected with data loggers and transmitted to the office with radio modems and the Internet. The fertigation pump control system also is remotely monitored and controlled by computer software in the office.

One Drop At A Time

From the early results of the field research, steps being taken to adapt and implement the drip fertigation APS for Florida growers can be summarized as follows:
• Keep the soil near field capacity (~zero water tension) with short duration frequent (drip) irrigations to wet the top 18 inches of soil.
• Inject fertilizer with most irrigations (100 to 150 parts per million N) to maintain a solution of readily available balanced nutrition in the root zone.
• If possible, apply the main fertilizer after sunrise and before noon, when photosynthesis and transpiration are at their peak.
• Use a complete, balanced nutrient formula (N, P, K, Ca, Mg, S, Mn, Zn, Fe, Cu, B, Mo, Cl) to maximize growth rates and improve plant fitness/disease resistance.
• Skip fertigation on rainy days, while soil is already near field capacity.
• Flush excess salts from the root zone during the dry season with plain irrigation water (three to four times normal irrigation amount every two weeks).
• Monitor nutrient concentrations in the leaf tissue and make corrections to the nutrient formula and fertilizing intensity as needed.
• Monitor and control insect pests frequently since they are attracted to the rapidly growing new leaf flushes.
Daily delivery of precise amounts of water and nutrients by drip fertigation to the efficient, modified dense root zones of citrus trees is the ultimate goal of the APS. By delivering only the water and nutrients required in a day, we eliminate the need to store fertilizer and water in soil, which is a wasteful but necessary process under conventional cultivation methods. Precise drip fertigation also continuously trains the root systems of the citrus trees to proliferate more vigorously in the small wetted region of soil around each dripper.
For more information and frequent updates on this research, visit

Special thanks to KeyPlex for sponsoring this series on research presentations from the Florida Citrus Show.

Leave a Reply

Featured Stories

All Vegetables Stories >All Fruits Stories >All Nuts Stories >All Citrus Stories >

The Latest

Crop ProtectionGetting To The Root Of Good Soil Health Requires Some D…
August 21, 2014
Dave Gilliam of Horticultural Alliance says more citrus growers are paying attention to what's happening below the ground in their groves. Read More
Citrus‘Super Cold’ Winter, Sizzling Summer On Tap In 2015…
August 21, 2014
The 223rd edition of the folksy regional forecast manual predicting extremes. Read More
Insect & Disease UpdateMountains Of Data Being Used To Combat Citrus Greening
August 20, 2014
As HLB research evolves, new methods need to be developed to effectively utilize information. Read More
VegetablesAnnual Santa Maria Vegetable Meeting To Cover Progressi…
August 20, 2014
University of California Cooperative Extension will host annual vegetable meeting focusing on nutrient management, plant growth, weed management, and more. Read More
Leafy VegetablesTanimura & Antle Introduces New Lettuce Variety 
August 20, 2014
The California grower now offers George T’s Colossal Romaine Heart, in honor of the company's founder, George Tanimura. Read More
CitrusBorder Crisis Not Helping Farmers
August 19, 2014
As thousands cross into the U.S. seeking refuge, calls for ag labor reform are lost in the uproar. Read More
Cucurbits24 Sweet Watermelon Varieties [Slideshow]
August 19, 2014
Browse the slideshow below for information on 24 watermelon varieties from the nation’s leading seed breeders and distributors. Read More
FruitsHandheld Produce Quality Meter Debuts At 2014 Internati…
August 19, 2014
Researchers to present data measuring dry matter, color, and sugar content of cherries and other product pre- and postharvest. Read More
GrapesNew York State Assists Grape Growers Hit By Harsh Winte…
August 19, 2014
State to open winegrape market to grapes grown outside the state. Read More
FruitsEuropean Fruit And Vegetable Growers Hit By Russian Ban…
August 19, 2014
Angry at European Union/United States sanctions over Ukraine, Russia has banned many food imports. Read More
Apple Grower of the YearGet The Latest News On The Nation’s Apple Crop
August 19, 2014
American and Western Fruit Grower editors will be tweeting in real time this week from the Apple Crop Outlook & Marketing Conference. Read More
OrangesSour Forecast For 2014-2015 Florida Orange Crop
August 18, 2014
Paltry prediction signals lowest output in 50 years. Read More
Crop ProtectionBioConsortia Inc. Bolsters Executive Team
August 18, 2014
Industry veterans Christina Huben and Dr. Susan Turner bring experience to plant biotechnology firm. Read More
Stone Fruit‘Ladderless’ Peach, Nectarine Orchards Explored
August 15, 2014
University of California researchers explore the concept of so-called pedestrian orchards. Read More
CitrusU.S. Sugar Buying South Florida Sugar Cane And Vegetabl…
August 15, 2014
Purported deal worth $100 million to purchase farmland and assets of Knight Management Inc. Read More
CitrusFlorida’s Future Farming Leaders Dig Up Knowledge…
August 15, 2014
Class 3 of FFVA's Emerging Leader Development Program learn a lot from road trip to California's Salinas Valley. Read More
CitrusWater Bond Will Appear On California Ballot
August 14, 2014
Voters will decide if thirsty state will spend $7.5 billion, including $2.7 billion for storage. Read More
BerriesFamiliar Face Settles In As New Florida Strawberry Asso…
August 14, 2014
Kenneth Parker’s deep roots in the community and knowledge of production challenges make a good combination for executive director role. Read More