Advanced ph management

Transcription

1 Advanced management Outline 1. solubility curves, and what they can teach us about management Before we get too far management is not that complex Maintain around , and you will be fine. Paul Fisher, University of Florida. 2. The life cycle of as a young plant crop develops But this is an advanced session, and we will discuss subtleties for nutrition nerds. No apologies (sorry). Paul Fisher and solubility affects Nutrient solubility Uptake by Plant Plant health too much toxicity too little deficiency But it all depends solubility curve: Did you know Based on one mix (peat/bark/sand/vermicultite) and one fertilizer containing STEM (sulfate micronutrients) and dolomitic lime? Why do different nutrients have the reported shape in the curve? ppm Nitrate-N Nitrate is not affected by 1% nitrate-n fertilizer, no plants 9 4 Thanks to QAL, Panama City FL, for analysis 5 Managing nitrate-n is a supply (EC) issue, not a issue 6 Ammonium tends to be nitrified (turned into nitrate) by bacteria at high ppm Nitrogen 1% ammonium-n fertilizer Ammonium-N 5 Nitrate-N Much of the acidity of ammonium can result from microbes 7 Ammonium toxicity with high NH 4 fertilizer, low, cool & wet Phosphorus reacts with calcium at high ppm Phosphate-P Same fertilizer with different lime types Calcium hydroxide Magnesium hydroxide Low P can be an issue at high 8 ppm Potassium Potassium is not affected by, but coconut coir can contribute K Same nutrients with different media types _coir _bark _perlite _vermiculite Media components can sometimes add nutrients 9

2 Increasing Calcium at high is because of the lime source, not solubility ppm Calcium Same fertilizer with different lime types 35 3 Calcium hydroxide 25 Magnesium hydroxide Raising per se will not increase calcium availability 1 Adding calcitic limestone, calcium nitrate, or gypsum increases Ca Magnesium has the same trend as Calcium ppm Magnesium Same fertilizer with different lime types 7 6 Calcium hydroxide 5 Magnesium hydroxide Raising per se will not increase magnesium availability 11 Adding dolomitic limestone, mag nitrate, or mag sulfate increases Mg Turning to micronutrients At low and high micronutrient fertilizer levels, iron-/manganese toxicity is likely in iron-efficient crops Optimum range depends on the crop AND your fertilizer regime 12 If you run high fertilizer, optimum is higher. Lean means lower. 3 ppm N 15 ppm N Substrate components can affect response Adding vermiculite reduced iron/manganese toxicity at low Iron deficiency at high is the most common issue Substrate / 3 perlite ppm Tissue Iron in peat/perlite Substrate- ppm Tissue Iron in peat/perlite/vermiculite Substrate- 7 / 15 perlite/ 15 vermiculite ppm Tissue Manganese in peat/perlite ppm Tissue Manganese in peat/perlite/vermiculite Substrate Substrate Substrate- 15 Iron % of maximum solubility Iron chelate form is very important 1% 8% 6% 4% 2% Chelate forms & effects on iron % EDTA DTPA EDDHA All iron forms effective at low : management is cheapest option Using iron-eddha is very effective at high : insurance 16 At low, there are various iron sources Iron in the pre-plant and post-plant fertilizer Iron in the lime (up to.3%) Iron in the irrigation water (up to 1 ppm) Iron in the peat.3 ppm in water extraction up to 45 ppm in DTPA extraction 17 At low (5.1) all iron forms soluble ppm Iron-EDDHA Iron-EDTA Iron sulfate 18

3 At high (7.) iron form matters ppm Iron-EDDHA Calibrachoa, high 7.2 Control ppm Fe-EDDHA At high, increasing micronutrient level can lead to improved growth and appearance ppm iron.5ppm 1ppm 2ppm ( 7.) Iron-EDTA Fe-EDTA FeSO 4 Iron sulfate 19 Adding.5 ppm iron-eddha is a cost-effective method for ironinefficient 2 crops Consider having a separate injector for micronutrients v NPK. Control growth with N or P, maintain color with magnesium and micros. 21 At high, funky things happen with micronutrient reactions. For example, zinc. ppm Zinc Micronutrient form and Zinc solubility It is not always just low iron that is an issue at high EDTA Sulfur 22 Usually an iron drench at high is most effective ppm iron Fe-EDDHA Fe-DTPA Control Calibrachoa 7 (1 days after application, days after planting) But iron is not the only nutrient decreasing at high Effect of on boron solubility ppm Boron Don t ignore management and just add more iron 24 Increasing iron at high can reduce other nutrient levels 2. The life cycle Many factors affect substrate- Lime Substrate Alkalinity Species Acid Petunia Geranium 25 Lime, Root substrate, EC effects Increasing plant and fertilizer effects 26 Nitrate NO- 3 Ammonium NH + Fertilizer 4 BASIC Factors (Raise ) balance ACID Factors (Lower ) 27

4 An example management experiment 29 substrates management during MIST Acid: ammonium Neutral fertilizer ( , 25% NH 4 -N) Acid fertilizer ( , 5% NH 4 -N) NO 3-2 NH ppm N from stick onwards Petunia & Osteos 4 ppm alkalinity water Base: nitrate management during FINISHING Major factors during propagation NO 3 - OH - or HCO 3 - Mist phase Lime reaction Substrate & cation exchange capacity (CEC) Electrical conductivity (EC) Water quality Finishing phase Lime residual Alkalinity Nitrogen form & concentration Plant Species LIME: How does lime react? Equilibrium LIME: Increasing lime rate increases to a maximum level LIME: Not all lime reacts. What is left is residual lime. 8 How quickly lime reacts depends on: size, chemical form, temperature, moisture Equilibrium depends on: lime acid neutralizing value, lime rate (lb/yd 3 or kg/m 3 ), substrate and buffering Initial of the substrate components Substrate- after 14 days Lime rate (lb/yd 3 peat) 35 36

5 LIME: Residual lime buffers drop later in the crop LIME: Chemistry LIME: Particle size Lime chemistry Uses Lime size Uses Impatiens Acid (high ammonium) fertilizer Substrate- Weeks Residual No residual 37 Hydrated (Ca(OH) 2 ) Calcitic carbonate (CaCO 3 ) Dolomitic carbonate (CaMg(CO 3 ) 2 ) Very fast reacting/no residual. Short term crops such as plugs. Fast acting if fine s. Otherwise slow. Supplies Ca. Fast acting if fine s. Otherwise slow. Supplies Ca, Mg. 38 Fine calcitic or dolomitic carbonate lime (most s pass 2 mesh, <.75 mm) Coarse calcitic or dolomitic carbonate lime (most s bigger than 1 mesh,.15 mm) Fast reacting/low residual Short to medium term crops such as plugs. Mainly provides initial correction. Slow reacting/provides residual buffering Medium to long term crops such as nursery. Slow to correct initial. 39 Testing Lime Rates and Reactivity Do a wet out test with each new batch of peat or if you change your lime source Measure substrate- at, 1, 2, 4, 8 weeks depending on crop length SUBSTRATE: Components vary in their lime requirement Typical Lime Component range requirement Vermiculite 7.5 to 9 None SUBSTRATE: Different peat sources vary in lime requirement Plant a crop and track over time, or make up a small batch and keep moist in an open bag or pot Compost 6 to 8 Little to none Perlite, pumice, volcanic rock, sand 6.5 to 7.5 None For short term crops (less than 3 months) should reach the target level within 1 week of planting Coconut fiber (coir) 5.5 to 6.5 None Bark 4.5 to 6 Moderate Blond peat Brown peat Humus 4 3 to 5 High 41 Slightly decomposed Well decomposed Typically higher lime requirement Highly decomposed 42 SUBSTRATE: Cation Exchange Capacity, Base Saturation, and Lime Requirement (A) High Base Saturation Ca ++ K + (B) Blond (C) Decomposed High CEC 43 SUBSTRATE: Interactions with lime Acidic components such as peat ( 3 to 4) need to be neutralized by lime Neutral components such as perlite and coconut coir ( 6 to 7) do not need lime Substrates with acidic components (and more lime) tend to have more buffering 44 Your substrate choice affects liming Example: a 7% peat/3% perlite substrate Is acidic, and is neutralized by lime Not all the lime reacts, which provides buffering Lime also provides Ca and Mg Perlite is inert Example: a 1% Coconut coir substrate Near neutral, so no lime needed Very little buffering to change Check salts (Na, K, Cl). May need leaching. Best as an amendment mixed with other components 45

6 EC EFFECTS: High and low salts are common at the end of the mist phase Why? Because increases as EC decreases with leaching Leaching with clear water washes out salts and raises = Exchange sites Soil solution Ca ++ Ca EC: Pre-plant salts (especially Calcium) drop Adding fertilizer will drop EC EFFECTS: What should you do about this high /low EC issue? Cation Substrate- Control (water) 5.8 Ammonium 5.5a Potassium 5.5a = Exchange sites Soil solution Magnesium 5.5a Calcium 5.2b 49 5 Avoid excess leaching Fertilizer at end of mist phase 51 WATER QUALITY: effects under mist Which solution will lead to the lowest substrate- under MIST with DI water? Which solution will lead to the lowest substrate- under MIST with well water? 52 Water in pure water has little direct effect on substrate- 53 Increasing EC decreases substrate- (CEC effect) 54

7 2-1-2 Which solution will lead to the lowest substrate- under MIST with well water? Finishing stage (Rooted plants) Major factors during propagation Increasing plant and fertilizer effects Mist phase Lime reaction Substrate & cation exchange capacity (CEC) Electrical conductivity (EC) Water quality Finishing phase Lime residual Alkalinity Nitrogen form & concentration Plant Species Increasing water alkalinity increases substrate Testing species/fertilizer effects 1. Acidic fertilizers do drop substrate- 7.84% ammonium 2% total N = 39% of nitrogen in ammonium form Species Geraniums Impatiens Petunia 7%:3% peat:perlite media Change in Impatiens Hydrated lime (no residual) -1.5 Acidic Basic DI water (no alkalinity) in-diameter azalea pots with saucers Pierre's CCE per metric ton of fertilizer commercial fertilizers 59 High ammonium High nitrate 6 Remember why fertilizers are potentially acidic or basic But species vary with the same fertilizer 1. Petunia.5 Impatiens Iron-efficient Geranium (Pelargonium x hortorum) Change in Pelargonium Marigold (Tagetes) -1.5 Acidic Basic Cations are positively charged and acidic (NH 4+, K +, Ca 2+ ) Anions are negatively charged and basic (NO 3-, SO 4 2-, OH - ) 61 Pierre's CCE per metric ton of fertilizer 62 Prone to Fe/Mn toxicity below 6. Recommended

8 Calibrachoa Iron-inefficient Why do plant species push up or down? (4% NH 4 -N) (25% NH 4 -N) (5% NH 4 -N) We have run experiments with both hydroponics and growing media 7.5 Petunia Root-medium Ryan Dickson Prone to Fe deficiency above 6.4 Recommended Days from planting Geranium Impatiens Petunia 65 Do iron-efficient geraniums take up mostly acidic cations? Do iron-inefficient petunias take up mostly basic anions? 66 Yes. The cation/anion ratio of species matches effect. They are programmed to get into trouble. As Ammonium concentration increases, so does cation/anion uptake. And therefore, drops. We can use this knowledge to improve management Percent Cation/Anion Uptake 12% 115% 11% 15% 1% 95% 9% 85% 8% Cation/Anion Uptake By Species a ab b Pelargonium Impatiens Petunia Plant Species Acidic Basic Percent Cation/Anion Uptake 12% 115% 11% 15% 1% 95% 9% 85% 8% Cation/Anion Uptake By Solution a a b % 1% 2% Percent NH 4 N in Solution (the remainder is NO 3 N) Acidic Basic Uptake of cations such as NH 4+ is acidic Uptake of anions such as NO 3- is basic Nitrogen is most important Geranium is acidic. Impatiens is intermediate. Petunia is basic. We can match nitrogen form & concentration to the crop species and water alkalinity to avoid drift Fertilizer app available at BackPocketGrower.com Fertilizer app available at BackPocketGrower.com In conclusion management is not that complex Maintain around , and you will be fine. Understanding how factors interact will improve your management strategy