Open Hydroponics - Implications for Water and Nutrient Efficiencies and Groundwater Protection under Citrus Production Arnold Schumann, Kevin Hostler, Kirandeep Mann, Laura Waldo (UF/IFAS, CREC) 3rd UF Water Institute Symposium February 15-16, 2012 Gainesville, FL
Introduction Hydroponics- The process of growing plants in sand, gravel, or liquid, with added nutrients but without soil Open Hydroponics (OH)- The process of growing plants in sand, gravel, or soil, with added nutrients and open drainage OH success stories in tree fruit crops Spain, California, Australia, South Africa. Will it work in Florida? Is open drainage environmentally safe? ground water OH research in Florida citrus was prompted by the potential of high early yields, and return on investment to help counteract the effects of HLB disease. Also possible environmental benefits from high efficiency?
Introduction OH research at the CREC: - Compare OH with conventional production system - Compare water delivery drip / microsprinkler - will point-source drip allow precision fertigation? - Growth, fruit yield, quality - Water & nutrient requirements EFFICIENCY - Nitrate leaching potential groundwater protection
Variable rate technology (VRT) - Existing precision fertilization VRT success depends on canopy variability N uptake Only soil under healthy canopy should be fertilized - avoid fertilizing bare soil or weeds
Precision fertilization Row spacing 18 height 100% rate N fertilizer rate =240 lb/ac/y (BMP max) Trunk line Infrared light beams 7 8 Sensors Trunk line 13 height 83% rate 5 6 8 height 66% rate 3 4 1 2 3 height 50% rate 0 height 0% rate
Precision fertilizer application with VRT (at 4.5 mph) (Video clip) (Gapway Groves, Chemical Containers & IFAS) Two rows covered one sided; fertilizer savings: 25-30%
Replant configuration with drip OH - Precision fertigation Water / EC sensor Young citrus tree Sensors: 0-4 depth 18 depth Drip irrigation line Wetted soil and roots Computer control Profile moisture sensor Drip emitters 15 apart Sandy soil
Daily Pulse Irrigation
Selected research results spanning 3 years Hamlin orange trees, Ridge - 16 December 2008 (0 weeks)
Fruit harvested in December 2010 drip OH at 2 years
System comparison, 24 months OH: Early fruit production, early ripening, high quality after 24 months Conventional methods Advanced drip fertigation methods (OH)
OH treatment, 36 months
Soluble solids (lb/acre) 1400 Fruit yields (lb SS/ac) at 3 years 1200 1000 Year 3 Year 2 * trees/acre 800 600 400 200 0
Gapway experiment: Conventional, 36 months
Gapway experiment: Drip OH, C-35 rootstock, 36 months
Efficiency gains: canopy growth @2.5 yrs Table 1. Cumulative water and fertilizer N applied and tree canopy growth during 2.5 years. Water for freeze protection was not included in calculations. Conventional (218 tpa ) Microsprinkler OH (218 tpa) Drip OH (218 tpa) Drip OH (363 tpa) Irrigation water (gal/acre) 133,718* 143,242 103,422 172,211 Fertilizer N (lb/acre) 253 64.3 47.5 79.2 Tree canopy volume 27,523 36,705 41,464 69,043 (feet 3 /acre) Water efficiency (feet 3 /1000 gal) 205.8 (1x) 256.2 (1.24x) 400.9 (1.95x) 400.9 (1.95x) Nitrogen efficiency (feet 3 /lb N) 108.8 (1x) 570.8 (5.2x) 872.9 (8.0x) 872.9 (8.0x) tpa = trees per acre * equivalent to 4.9 acre-inches of irrigation. Water for freeze protection totaled 17.3 acre-inches from 2010 to 2011.
Nitrate-N (mg/l) Environmental benefits reduced [nitrate] in leachate Averages 9.3 mg/l 3.2 mg/l 0.9 mg/l MCL = 10.0 mg/l Methemoglobinemia prevention
The unique OH root system for efficient nutrient uptake Drip emitters Root pad = nutrient filter
Dense, prolific, healthy feeder root system Highly efficient absorptive root pads Nearly direct connection between the roots & the fertigation system (in a reduced soil volume)
Conclusions about OH after 3 years OH reduces time to economic production (-1 to -2 y) Irrigation 95% and N 700% more efficient with drip Microsprinklers are versatile but less efficient Average nitrate leaching reduced 91% with drip OH Efficiency gains will diminish as trees mature
Additional information: CREC.IFAS.UFL.EDU
Acknowledgements Gapway Grove Corp.