IMPROVED NUTRIENT MANAGEMENT STRATEGIES IN THE ERA OF HLB Davie Kadyampakeni UF/IFAS CREC
Outline Status of HLB in FL: What we know now Strategies for managing HLB Nutrition studies for managing HLB: Highlights Best management practices for water and nutrients Summary Acknowledgements
Current Status of HLB Citrus accounts for $10 billion in economic activity Pre-HLB 240 million boxes Current 80 million boxes, about 67% reduction in production Production costs up to $2100 per acre due to HLB Significant reduction in production area Declining tree performance, root loss and significant defoliation
Strategies for managing HLB Preventative measures: HLB negative (healthy trees) Frequent irrigation (daily or multiple times a day) e.g. Citrus Under Cover Production System (CUPS); Greenhouse production Regulated deficit irrigation: Proportionate reduction in water use 50 to 75% of ET in the rainy months Partial root zone drying: alternate wetting and drying of the root zone PLUS ASIAN PSYLLID CONTROL!!
Strategies for managing HLB Curative management of HLB positive trees (asymptomatic trees) Daily irrigation plus Asian psyllid control Managing ph to optimum levels for nutrient availability Improved nutrition programs via fertigation Remediation/Management of HLB affected trees (symptomatic trees) Daily irrigation plus Asian psyllid control Managing ph to optimum levels for nutrient availability Fertigation practices
Nutrition studies for managing HLB: Highlights Advanced Citrus Production Systems (ACPS) studies: Two Sites: Immokalee at UF/IFAS, SWFREC, and Lake Alfred (2008 to 2011) Comparison of drip and modified microsprinkler fertigation systems with Conventional grower practices Two ACPS systems: drip (DOHS) and microsprinkler (RM, MOHS), and conventional microsprinkler practice (CMP) Studies from other researchers
ACPS Nutrition Studies Leaf conc. (%) 3.5 3.0 2.5 2.0 1.5 1.0 0.5 N P K Efficiency (cubic m/kg N) 60 50 40 30 20 10 After 1 year After 2.5 years 0.0 CMP DOHS MOHS Fertigation practice Leaf NPK concentration Leaf NPK conc. were in optimum or high range. 0 CMP MOHS DOHS-S DOHS-C35 Fertilization method Nutrient efficiency (m 3 /kg N) CMP needs more fertilizer and water per ha at 1 to 2.5 years than ACPS (Schumann et al. 2010)
ACPS Nutrition Studies (2) N and P accumulation on Immokalee sand Fertigation method CMP Drip RM CMP Drip RM Tissue N (kg ha -1 ) P (kg ha -1 ) Leaves 24.00 49.78 37.10 1.34 1.69 1.48 Fruits 22.40 15.78 29.98 2.68 1.03 2.28 Branches/trunk 20.70 28.38 26.44 4.76 3.80 4.22 Roots 11.60 20.82 20.20 2.85 2.98 2.96 Total 78.70 114.78 113.72 11.64 9.52 10.95 DOHS-Drip open hydroponic system; RM-Microsprinkler open hydroponic system; CMP-conventional microsprinkler practice High N accumulation with ACPS than CMP but P accumulation similar for all practices.
K accumulation (lbs/ac) ACPS Nutrition Studies - Nutrient accumulation (K) 100 80 60 40 20 K accumulation CMP DOHS MOHS Greatest K accumulation in branches, twigs and trunk than other parts K accumulation in CMP>DOHS>MOHS 0 Leaves Fruits Branches Roots Total DOHS-Drip open hydroponic system; MOHS-Microsprinkler open hydroponic system; CMP-conventional microsprinkler practice
ACPS Nutrition Studies - biomass accumulation (3) Conventional practice 24 13 Drip fertigation 31 12 20 38 Microsprinkler OHS 25 16 24 40 Leaves (%) Branches (%) Fruits (%) Roots (%) 21 39 DOHS-Drip open hydroponic system; MOHS-Microsprinkler open hydroponic system; CMP-conventional microsprinkler practice Kadyampakeni et al. 2016. Journal of Plant Nutrition, 39:589-599
ACPS Nutrition Studies (4) Leaf NPK concentration (%) determined in June 2009 at Immokalee. Sufficient NPK concentrations. Drip OHS was effective in enhancing N uptake compared with the other two irrigation methods studied. Leaf P concentration was high (0.17-0.30%) in all treatments Leaf K concentration was within optimum and high ranges (1.2-2.4%) suggesting No significant differences between ACPS and Conventional method.
Concentration (mg/kg) ACPS Nutrition Studies (5) 3 2.5 2 1.5 1 0.5 0 Irrigated Non-irrigated Irrigated Non-irrigated Ammonium N Nitrate N Conventional practice Drip OHS Microsprinkler OHS Greater inorganic N in irrigated than non-irrigated zones Better N contents in irrigated zones of ACPS than Conventional. Ammonium and nitrate distribution in the irrigated and non-irrigated zone
Concentration (mg/kg) ACPS Nutrition Studies (6) 90 80 70 60 50 40 30 20 10 0 Greater P in irrigated than nonirrigated zones Soil P contents in irrigated zones of Drip greater than Conventional. Mehlich 1 P Irrigated Mehlich 1 P Non-irrigated Soil P distribution in the irrigated and non-irrigated zones
ACPS Nutrition Studies (6) Within row (cm) 30 25 20 15 10 5 0 T D 0 5 10 15 20 25 30 Cross-row (cm) Lateral ammonium-n (mg/kg) distribution in July 2010 at the Lake Alfred site using drip fertigation. 0.4 0.5 0.6 0.7 0.8 0.9 Higher NPK conc. in irrigated vs. non-irrigated zones of drip fertigation. D=area below dripper, T=tree
ACPS Nutrition Studies (7) Canopy volume (m 3 ) 2.5 2.0 1.5 1.0 0.5 DOHS-Swingle CMP MOHS DOHS-C35 ACPS fertigation had greater tree size than conventional practice 0.0 11/1/09 1/1/10 3/1/10 5/1/10 7/1/10 Date Canopy volume as a function of fertilization practice at the Lake Alfred site
ACPS Nutrition Studies (8) Lateral RLD (cm cm -3 ) distribution using CMP Lateral RLD (cm cm -3 ) distribution using DOHS 30 30 D 25 25 Within row (cm) 20 15 10 5 0 T M 0 10 20 30 40 0.07 0.08 0.09 0.10 0.11 Within row (cm) 20 15 10 5 0 D T 0 10 20 30 40 0.15 0.20 0.25 0.30 Cross-row (cm) Cross-row (cm) T=tree, M=microsprinkler Roots uniformly distributed around the tree T=tree, D=dripper, Roots concentrated below the drippers
ACPS Nutrition Studies (9) 30 Positions in the irrigated zones of showed higher root density than non-irrigated zones M=microsprinkler T=tree Within row (cm) 25 20 15 10 5 0 T M 0 10 20 30 40 0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22 0.24 Cross-row (cm) Lateral root density (cm cm -3 ) distribution using ACPS microsprinkler
Studies from other researchers in Citrus The combination of foliar-applied mineral nutrients and non-nutrient elements, excellent psyllid management and improvements to ground-applied fertilizer programs (e.g., use of Ca(NO 3 ) 2, B) do maintain or increase total yields (Spann and Schumann, 2009; 2012). Factors (e.g., soil ph) interact with HLB management practices (Spann and Schumann, 2012; Graham and Morgan, 2017). Good horticultural practices, focused on minimizing plant stress nutrient deficiencies, drought, and maximized productivity (Spann and Schumann, 2009; 2012
Studies from other researchers in Citrus (2) Maximum yield of mature citrus achieved by 3 applications/yr of MnSO4 at 43-100 mm/l spray (Morgan et al. 2016). Conflicting results with Zn, B and K where concave relationships for canopy volume were found for MnSO 4 and ZnSO 4 without KNO 3 and Mn 3 (PO 3 ) 2, Zn 3 (PO 3 ) 2, B and MgSO 4 with KNO 3 (Morgan et al. 2016). Recommendations for nutrition of HLB affected trees need to be developed.
Summary from Nutrition Studies ACPS practices could be adapted to grower practices for vigorous tree growth, greater water use, greater root density, and nutrient accumulation. Good nutrient and water management through ACPS improve biomass accumulation and canopy development N accumulation greater with ACPS than grower practice, but N and K comparable
Summary from Nutrition Studies ACPS resulted in reduced nutrient leaching in the root zone. Additional work on: NPK rates in greenhouses for young citrus Performance of rough lemon under different N sources and micronutrient levels More work needs to be done to establish a suite of recommendations for nutrition of HLB affected trees.
Best water and nutrient management practices
BMP considerations for nutrient and water management Use of UF/IFAS recommendations: Nitrogen rate & timing for the growth of young non-bearing trees depending on soil type, fertilizer source and placement, crop load, citrus variety, tree age and irrigation method Use of soil analyses information for fertilizer application: Growers can make informed decisions about the fertilization requirements of citrus trees.
BMP considerations for water and nutrient management (2) Use of tissue analyses for fertilizer application decisions: This helps in assessing nutrition status of trees for macronutrients (e.g. N and K) and micronutrients (e.g. Cu, Mn, Zn, Fe, B) Training of fertilizer applicators: Adequate training of the field operators in the handling, loading and operating of fertilizer spreaders and accurate calibration of equipment.
BMP considerations for water and nutrient management (3) Fertilizer placement near or over the root zone: Accurate placement of fertilizer facilitates uptake and reduces nutrient losses through runoff and leaching. Avoiding fertilization during high water table or flooded conditions: Applying nutrients during wet conditions leads to leaching and lateral flow of nutrients, thus increasing costs of production and posing environmental concerns to surface and groundwater.
BMP considerations for water and nutrient management (4) Use of CRF for mature trees: CRF, @ 90lbs/ac found to be effective with one time application Use of organic amendments: Adding organic amendments to the soil facilitates slow release of nutrients and improves water and nutrient retention. Avoiding fertilizer application between mid-june and mid- September: Applying fertilizer before or during intense rainfall is not advisable on highly erodible soils.
BMP considerations for water and nutrient management (5) Split fertilizer applications: Split fertilizer applications >4 times per year can reduce leaching losses particularly for N and K during excessive rainfall events. Use of fertigation practices: Helps in precise control of nutrient placement in concert with irrigation for optimal water and nutrient uptake.
BMP considerations for water and nutrient management (6) Soil moisture based irrigation scheduling: Use of TDR, tensiometers and other soil moisture measurement devices. This can reduce nutrient leaching beyond the root zone. ET-based irrigation scheduling: Use of weather data to decide when and how much to irrigate. FAWN and other weather data help in using the soil water budget for irrigation.
Take home message for BMPs BMPs critical for reducing: nutrient loads, irrigation water volumes, and production costs.
Acknowledgements Dr. Morgan, UF/IFAS SWFREC Dr. Schumann, UF/IFAS, CREC Grove Space: UF/IFAS SWFREC, Immokalee, FL Gapway Groves, Auburndale, FL