Arnold Schumann(UF/IFAS, CREC) Soil Testing for Crop Nutrient Recommendations and Management November 13, 2014 GCREC, FL

Transcription

1 Citrus Responses to Intensive Fertigation Rate and Timing Arnold Schumann(UF/IFAS, CREC) Soil Testing for Crop Nutrient Recommendations and Management November 13, 2014 GCREC, FL

2 Open Hydroponics (OH) Fertigation Frequent fertigation is used to simultaneously apply soluble fertilizer and irrigation water to the grove Scheduling fertigation is therefore complicated by the need to supply both water and nutrient requirements of citrus trees often and in the correct amounts during the growing season Optimally implemented OH fertigation reduces water and nutrient requirements, nitrate leaching, and increases growth rates and yields of trees; all are desirable attributes in HLB-affected groves A Decision Support Program (DSP) was developed to help growers optimize their fertigation systems

3 In Florida citrus, the correct use of OH fertigation relies on horticultural synergies and interactions in a systems approach: Soluble solids (lb/acre) Normalized % gains Orchard architecture 22% Genetics 57% 21% Drip-OH Rootstock (C35) High density (363 trees/acre) Irrigation & Nutrition This component is highly flexible but tree planting costs increase with density

4 Main components of an ACPS in Florida Intensive fertigation (controller, sensors) High Higher planting density (AWS, 2012) Adapted rootstocks ( dwarfing ) Balanced complete nutrition (N-P-K-Ca Mo)

5 Sources of soil fertility and the role of fertigation in Florida Typical agricultural soils Soil solution Readily available FAST SLOW nutrient pool (CEC, fertilizer) N,P,K, Ca, Mg, Fe, Mn, Zn, Cu, B, Mo Slowly available nutrient pool (e.g. OM-N, fixed P) N,P,K, Ca, Mg, Fe, Mn, Zn, Cu, B, Mo VERY LONG TERM Florida s sandy soils Nutrient in soil minerals (e.g. mica, feldspar) P, K, Ca, Mg, Fe, Mn, Zn, Cu, B, Mo Low waterholding capacity Low CEC Low organic matter reserves Predominantly quartz Florida soils in agricultural production benefit from frequent additions of irrigation water and nutrients as fertigation

6 Open hydroponics diminishes the storage role of soil and increases efficiencies Typical agricultural soils Soil solution Readily available FAST SLOW nutrient pool (CEC, fertilizer) Slowly available nutrient pool (e.g. OM-N, fixed P) VERY LONG TERM Nutrient in soil minerals (e.g. mica, feldspar) Low waterholding capacity Low CEC Florida s sandy soils Low organic matter reserves Predominantly quartz Daily drip fertigation Open hydroponics with ACPS (Negligible dependence on soil most efficient) Store water in the ground / reservoir and fertilizer in tanks

7 Lake Alfred: 3 months Drip fertigation 2 drippers/tree ~500 trees/acre

8 Lake Alfred: 1 year

9 Lake Alfred: 2 years Drip fertigation 2 drippers/tree ~500 trees/acre = rapid establishment

10 Lake Placid: 3 years drip fertigation: 18 spaced drip lines OR Microsprinkler fertigation: 7.7 gph 47% HLB+ in March 2014

11 Common threads in these illustrated OH fertigation examples: Increased growth rates and early, high yields Increased water and nutrient use efficiency Minimal reliance on soil for water and nutrient storage = daily fertigation

12 Proper targeting of water and nutrients to the root zone ensures high efficiencies: drip emitters are ideal

13 Upright microsprinkler emitters spray a water pattern that is too large for small trees; only a portion of the wetted zone is occupied by roots

14 Properly designed microsprinkler irrigation systems can achieve similar high efficiencies: target the root zones of trees appropriate for their size e.g. inverted emitters for young trees

15 Inverted microsprinkler emitters spray a water pattern that more efficiently targets the root zone. When trees mature, the emitters are turned upright.

16 Wetted soil pattern: inverted emitter

17 The unique ACPS root system for efficient nutrient uptake Drip emitters Root pad = nutrient filter

18 Drip fertigation develops healthy, dense feeder roots in soil, for precise, direct delivery of nutrients and water

19 Healthy root proliferation can also be achieved in containers, and delivery of nutrients and water with drip OH is very precise

20 Fruit World, CA example 46-acre block: 3 x 7.5 feet = 1,936 trees/acre 1,600 year 4

21 OHS in containers no soil interaction, less pathogens and pests

22 Advanced Citrus Production Systems (ACPS) in Florida High density (363 trees/acre) precocious scion/rootstock ( Hamlin /C35) + open hydroponics (N,P,K, Mo) = 622 boxes/acre in year 4

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25 66% of annual N fertilizer Calculators Daily N requirements Mid-season (June)

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27 Estimate N for bearing, young trees Tree height Fertilizer amount / injection time Irrigation run time

28 DSP irrigation schedules are fine-tuned with soil water sensors 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

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30 OH: Early fruit production, early ripening, high quality after 24 months Conventional methods Advanced drip fertigation methods (OH)

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32 Efficiency gains: 4 to 10x

33 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

34 ACPS experiment: Drip OH, C35 rootstock, 3 years 222 boxes/acre with 363 trees/acre

35 Drip ACPS orange production: year 4 production (no HLB) 622 trees/ac

36 622 trees/ac

37 Fruit yields (boxes/ac) at 5 years b bc c a a a 622 boxes/ac in 4 th year * trees/acre

38 HLB-affected Hamlin yield in year 5: Disease changes everything we know about managing nutrients and irrigation (fertigation) of citrus

39 Summary Intensive fertigation by the OH method reduces reliance on soil for nutrient and water storage / supply Citrus growth and production with the OH method is significantly higher than with conventional production methods. Another good option is nutrient supply with CRF (but expensive) Reduced environmental impacts as measured by reduced nitrate leaching are evidence that the OH fertigation method is a very efficient production method

40 Acknowledgements Kevin Hostler, Laura Waldo Gapway Grove Corp. Griffin Fertilizer, Plant Food Systems, Tiger-Sul, Growers Fertilizer, Harrell s -SCRI