Nutrient Management in Ornamental Production Paul Fisher, Environmental Horticulture Dept. 1 3 5 6
Topics Many factors affect substrate-ph 1. Managing ph and Iron Availability in Containers Lime Substrate Alkalinity Species Acid. Managing Nutrient Level In Containers Petunia Geranium For more detail: HOS 93 (senior) and HOS 693 (grad) Nutrient management for container-grown crops in Fall 015 See Dee Boyle or Amy Alexander to enroll, 1519 Fifield Hall 7 Nitrate NO- 3 Ammonium NH + Fertilizer BASIC Factors (Raise ph) ph balance ACID Factors (Lower ph) 8 Why is substrate-ph important? ph affects Nutrient solubility Uptake by Plant Plant health too much toxicity too little deficiency Low substrate-ph Chlorosis and necrosis in older tissue. Iron/manganese toxicity at low media-ph Excess micronutrient accumulates in tissue below ph 6.0 in iron-efficient species. 9 10 High substrate-ph Chlorosis, often interveinal, in new tissue Iron deficiency at high ph (>6. in iron-inefficient plants) Iron required to produce chlorophyll (green) Low mobility within plant Substrate ph 8.0 7.5 7.0 6.5 6.0 0 10 0 (0% NH N) 17 5 17 (5% NH N) 13 13 (5% NH N) 5.5 5.0 0 5 10 15 0 5 30 0 5 10 15 0 5 30 Days from planting 0 5 10 15 0 5 30 Geranium Impatiens Petunia 11 Argo and Biernbaum, MSU
Why do plants differ in their ph effect? 1. Adaptive response (low P or low Fe) Iron efficiency Exude acid Fe-efficiency adaptive responses sensitivity to iron-deficiency chlorosis (Marschner, 1995) Root zone acidification Fe 3+ reductase Phytosiderophores/phytometallophores Root morphology, ion transfer sites. Dumb response (inherent tendency) Cation/anion balance 13 +Fe -Fe Romheld, 1987 1 Fe-Efficiency adaptive responses Acidification of the rhizosphere (Romheld et al., 198) 15 Pelargonium x hortorum Impatiens walleriana Petunia x hybrida Hydroponic culture Measure acidity basicity Experimental setup Initial Solution Concentrations (mg/l) 0% NH 10% NH 0% NH NH N 0 10 0 NO 3 N 100 90 80 Total N 100 100 100 P 16 16 16 K 117 117 117 Ca 100 100 100 Mg SO S 38 55 67 Fe 1 1 1 Mn 0.5 0.5 0.5 B 0.5 0.5 0.5 Cu 0.1 0.1 0.1 Zn 0.5 0.5 0.5 Mo 0.0 0.0 0.0 16 1:1 relationship between net cation vs anion uptake and ph effect on solution Solution acidity basicity ( = meq acid and + = meq base) 10 8 6 0 0 6 8 10 meq Cations minus meq Anions taken up Cation uptake = ph Anion uptake = ph Pelargonium Impatiens Petunia Regression 17 Solution acidity or basicity ( values = meq acid, + values = meq base) 8 6 0 Species effects 0% NH Solution 0 6 8 Cation minus anion uptake (meq) Pelargonium 0% Impatiens 0% Petunia 0% All species ph Pelargonium = least basic Petunia = most basic 18
Fe-efficient Geranium (Pelargonium x hortorum) Calibrachoa Fe-inefficient Marigold (Tagetes) Petunia Prone to Fe/Mn toxicity below ph 6.0 Recommended ph 6.0-6.6 19 Prone to Fe deficiency above ph 6. Recommended ph 5.-6. 0 ppm iron ppm iron 5 3 1 0 180 150 10 90 (A) Media Iron (B) Tissue Iron Media-pH affects Nutrient solubility Uptake by Plant 1 mg. L -1 Fe-EDTA Chlorophyll ( g.mg -1 ) 60 1.1 0.9 0.7 0.5 0.3 (C) Total Chlorophyll.5 5.0 5.5 6.0 6.5 7.0 Media-pH Plant health Petunia hybrid 1 Impatiens media-ph..7 5.1 6.0 7.0 Inorganic Fe solubility Inorganic Fe solubility Lindsay (1979) ph Highly soluble Fe 3+, Fe + ph 7 Highly insoluble Fe(OH) 3 3 Each ph unit increase leads to 1000x decrease in Fe 3+ solubility.
Synthetic chelates Fe solubility and chelation ph 5.1 Petunia 0.5 0.5 1 ppm Iron-EDDHA Most common fertilizers: FeSO, Fe-EDTA (constant) Fe-DTPA, Fe-EDDHA (corrective) Iron-EDTA Iron sulfate (Norvell, 1991) (W.A. Norvell., 1971) 6 ph 6.9 Petunia 0.5 0.5 1 ppm Peat-Lite blended fertilizer ratios Iron-EDDHA Iron-EDTA Iron sulfate 7 8 Calibrachoa, high ph 7. Control 0.5 1.0.0.0 ppm Fe-EDDHA Fe-EDDHA is most effective Fe source at high ph mg.l -1 iron 0 0 80 Fe-EDDHA Fe-EDTA Fe-DTPA FeSO 9 Control Calibrachoa ph 7 (10 days after application, days after planting)
Reading a bag of blended water-soluble fertilizer } } } Fertilizer Formula Nitrogen Form ph Effect Macronutrients Micronutrients Applying Fertilizer Mixing Rates EC Chart } 31 ph effect: Potential Acidity or Basicity NH -N + Formula urea (%) Reaction Highly Acidic Fertilizers 1-7-7 100 % A 1560 Acidic Fertilizers 0-10-0 39 % A 06 Neutral Fertilizers 17-5-17 0 % B 0 Basic Fertilizers 15-0-15 13 % B 0 Tendency of a fertilizer to change ph after it is applied Can not be measured with a ph meter 3 Ammonium Fertilizers Nitrate Fertilizers NO 3 - NH + NO 3 - ph H + ph OH - HCO 3-33 3 Coated Fertilizers Controlled-Released Fertilizers Other names Resin-coated, plastic coated, polymer coated Coated Fertilizers Controlled-Released Fertilizers Other names Resin-coated, plastic coated, polymer coated Water 35 36
Coated Fertilizers Controlled-Released Fertilizers Other names Resin-coated, plastic coated, polymer coated Coated Fertilizers Controlled-Released Fertilizers Other names Resin-coated, plastic coated, polymer coated Salts Salts Salt release based on: 1) Substrate Temperature ) Fertilizer release duration 3) Incorporation Rate 37 38 Pros and cons of controlled-release and water-soluble fertilizers? Water Soluble Good under rain cover (more typically greenhouse) Easy to change concentration over time to suit crop needs Needs targeted delivery to containers (e.g., with drip, hose, or flood) or considerable waste and pollution Easy to leach out if fertilizer level is too high Requires a fertilizer injector Controlled Release Good when rain is not controlled (more typically outdoor nursery) Must predict and match release curve with crop needs Less polluting and wasteful than WSF if irrigating with sprinklers Harder to leach out if fertilizer level is too high Crops can be irrigated with water only, no equipment needed High EC Lower leaves marginal chlorosis and necrosis, leathery or crispy Controlled-release fertilizers can provide a base charge, supplemented with water soluble 39 Low EC Overall pale and stunted. Yellow, purple depending on cultivar Nutrient level (EC) in a pot is like a bank Deposits Water-soluble fertilizer Irrigation water Surface-applied fertilizer Acid injection Sanitizers Withdrawals Uptake by plant Salt layer at top of medium Leaching 1 Starting balance Media components Pre-plant charge
High EC can arise in two ways Low EC can arise in two ways Deposits greater than Withdrawals Deposits less than Withdrawals What is the best concentration of fertilizer to apply? Starting balance Initial nutrient charge is high Starting balance Initial nutrient charge is low 3 The more you leach (withdraw), the more fertilizer you must apply (deposit) Leaching is an important kind of withdrawal and is easy to measure Media-Electroconductivity (ms/cm) after 16 wks 10 8 6 0 100 ppm N 00 ppm N 00 ppm N Optimum EC range 0% 15% 35% 55% Leaching fraction (%) with each fertigation Yelanich and Biernbaum (Michigan State University) 5 6 Example: A grower moves from inefficient overhead sprinklers with 0% leaching to efficient drip irrigation with 10% leaching If you can help ornamental plant growers manage ph and EC issues, you will solve 95% of their problems. How will nutrient level in the substrate change? How should the grower adjust fertilizer rates? 7 8