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 www.crec.ifas.ufl.edu.

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

Food SafetyUSDA Issues Updates To Food Safety Modernization Act
September 19, 2014
Water testing, definition of applicable farms based on produce sales among clarifications to proposed rules. Read More
GrapesThird Straight Record Crop For Washington Grapes
September 19, 2014
Numbers expected to climb as more vines planted in the state. Read More
GrapesFrench Winegrowers Face Higher Labor Costs
September 19, 2014
French wineries may come under added financial pressure as the government considers imposing social charges on wages paid to harvest workers with short-term contracts. Read More
IrrigationCalifornia Boosts Local Water Control
September 19, 2014
Governor Jerry Brown signs historic legislation to strengthen local management and monitoring of critical groundwater basins. Read More
VegetablesSakata Seed America Shows Heart Through Charitable Prog…
September 19, 2014
Company’s corporate giving mission bears fruit for the American Heart Association. Read More
Insect & Disease UpdateAdditional Aid Coming For Florida Citrus Growers Gouged…
September 17, 2014
Through USDA’s Tree Assistance Program, eligible growers can cash in on cost share for diseased tree removal and replanting. Read More
FruitsFlorida Fruit & Vegetable Association Seeks Fresh A…
September 17, 2014
New partnership bolsters Fresh From Florida program. Read More
CitrusFDA Announces Cooperative Agreement To Implement Nation…
September 17, 2014
Agreement will provide information to help plan and carry out the produce safety rule in partnership with state regulatory agencies. Read More
NutsAchieving A Super-Premium Walnut Crop
September 17, 2014
What are the best ways to get high quality walnuts that are light in color and fully developed? Read these 8 harvest best practices to find out. Read More
NutsAlmond Growers Highly Dependent On Groundwater
September 17, 2014
Fully 87% of large growers use groundwater to irrigate their trees. Read More
NutsWarm Winter And Drought Casting Doubt On Pistachio Harv…
September 17, 2014
Though Rabobank report says that one billion pounds still attainable by 2019. Read More
Crop ProtectionBagrada Bug On The Move In California
September 16, 2014
Find out more on management tactics and what counties are impacted by this invasive pest. Read More
Cucurbits14 Stand-Out Melon Varieties [Slideshow]
September 15, 2014
Browse the slideshow below for information on these exceptional melon varieties from the nation’s leading seed breeders and distributors. Read More
Grower Achievement AwardView Highlights From The 2014 United Fresh Washington P…
September 15, 2014
Browse this slideshow to view photos from the 2014 United Fresh Washington Public Policy Conference, including pictures of this year’s Grower Read More
Apples & PearsCanneries Hope To Encourage Growers To Grow Pears For P…
September 15, 2014
Higher wholesale prices offered as means to boost canning pear acres. Read More
FruitsDeadline Nearing For Noninsured Crop Disaster Assistanc…
September 15, 2014
Fruit growers who suffered losses due to frost or freeze in 2012 could be eligible for assistance through USDA’S Farm Service Agency. Read More
BerriesBotrytis Gray Mold Pressure Increasing With Humid Weath…
September 15, 2014
Michigan State University researcher offers tips to reduce the spread of spores. Read More
Fruits5 Mistakes You May Be Making With Your Orchard’s …
September 15, 2014
These deadly sins may be hurting your customers’ experience — and costing you money. Read More