Fertilization
Plant Composition Water composes 90% of plant weight (fresh weight) Dry weight is composed of 17 essential elements: Non-fertilizer elements: Carbon (C) -- 41% of dry weight (DW) Hydrogen (H) -- 6% DW Oxygen (O) -- 42% DW
Plant Composition Dry weight is composed of 17 essential elements: Fertilizer elements: primary macronutrients -- N (4%), P (0.5%), K (4%) secondary macronutrients -- Ca (1%), Mg (0.5%), S (0.5%) micronutrients -- Fe (0.02%), Mn (0.02% ppm), Zn (0.003%), Cu (0.001%), B (0.006%), Mo (0.0002%), Cl (0.1%), Ni (0.0005%)
Fertilization Programming N S? P Ca? K Mg? micros? Post-plant Applications Preplant Incorporation limestone superphosphate micronutrients N & K
Preplant Incorporation Nutrient source Rate per cubic yard Soil-based substrates Soilless substrates For ph regulation and to provide calcium and magnesium Dolomitic limestone 0 to 10 lb 10 to 15 lb Dolomitic limestone (CaCO 3 + MgCO 3 ) also for ph control If no lime is needed: incorporate 5 lb per cubic yard gypsum (CaSO 4 2H 2 O) to supply Ca incorporate 1.5 lb per cubic yard Epsom salts (MgSO 4 7H 2 O) to supply Mg
Preplant Incorporation Nutrient source Rate per cubic yard Soil-based substrates To provide phosphorus and sulfur Soilless substrates Triple superphosphate 1.5 lb 2.25 ( 1 lb)* Gypsum (calcium sulfate) 1.5 lb 1.5 lb (1 lb) Triple superphosphate is granular and does not contain sulfur; no more 0-20-0 superphosphate, though May not want to add full amount of P, especially for plugs* If no P added, then still add Gypsum for S
Phosphorus on Plugs Phosphorus causes stretching in plugs Plugs fertilized with 100 ppm N every 3rd irrigation Supplied 2, 4, 6, and 20 ppm P with each fertilization Lowest P levels did delay salable date (of flats) by 5 days 20-1-20 20-2-20 20-3-20 20-10-20
Preplant Incorporation Rate per cubic yard Nutrient source Soil-based substrates Soilless substrates To provide micronutrients: iron, manganese, zinc, copper, boron, and molybdenum Esmigran 5 lb 5 (2.5 lb)* OR Micromax 1 to 1.5 lb 1 to 1.5 lb (0.5 to 0.75 lb)* Many choices available -- READ THE LABEL!!! Alternative is liquid application (such as with STEM ) soon after planting Note lower rates for plugs*
Preplant Incorporation Nutrient source Rate per cubic yard Soil-based substrates To provide nitrogen and potassium (optional) Soilless substrates Calcium nitrate 1 lb 1 lb ( 1 lb)* Potassium nitrate 1 lb 1 lb (0 lb)* Probably not needed, if liquid feed is to start soon For plugs, there is no benefit from incorporated K*
Preplant Incorporation Nutrient source Rate per cubic yard Soil-based substrates Soilless substrates For ph regulation and to provide calcium and magnesium Dolomitic limestone 0 to 10 lb 10 to 15 lb To provide phosphorus and sulfur Triple superphosphate 1.5 lb 2.25 ( 1 lb)* Gypsum (calcium sulfate) 1.5 lb 1.5 lb (1 lb) To provide micronutrients: iron, manganese, zinc, copper, boron, and molybdenum Esmigran 5 lb 5 lb (2.5 lb)* OR Micromax 1 to 1.5 lb 1 to 1.5 lb (0.5 to 0.75 lb)* To provide nitrogen and potassium (optional) Calcium nitrate 1 lb 1 lb ( 1 lb)* Potassium nitrate 1 lb 1 lb (0 lb)* *Plug substrate recommendations (when different from the general rates) are given parenthetically. Soil-based substrates are not generally used or recommended for plugs.
Substrate ph
Substrate ph Maintaining proper substrate ph will PREVENT most nutrient problems
Substrate ph Maybe it's the pfffffffffff of my substrate Affects nutrient availability Optimum varies with plant species Test, don t guess!!!
Problems Associated With Out of Range Substrate ph Low Toxic: Fe, Mn, Zn, Cu High Deficient: Fe, Mn, Zn, Cu, B Deficient: Ca, Mg Sensitive: NH 4 Leached: PO 4
Nutrient Availability 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 NITROGEN POTASSIUM Soilless Substrates PHOSPHORUS CALCIUM MAGNESIUM IRON MANGANESE BORON ZINC COPPER
General Crops Range 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 NITROGEN POTASSIUM PHOSPHORUS CALCIUM 5.4 to 6.8 IRON MAGNESIUM MANGANESE BORON ZINC COPPER
Forces Affecting Substrate ph Substrate components and amendments Irrigation water alkalinity Fertilizer acidity / basicity Plant species being grown
Potential acidity or basicity and percent of total nitrogen in the ammonium plus urea form for several commercial fertilizers. Potential acidity NH 4 -N Fertilizer* or basicity** (%)*** 21-7-7 1,700 A 90 21-7-7 1,560 A 100 20-9-20 510 A 42 16-17-17 440 A 44 20-10-20 422 A 40 21-0-20 15 A 48 20-0-20 0 69 13-2-13 200 B 11 14-0-14 220 B 8 15-0-15 319 B 13 15.5-0-0 400 B 6 15-0-15 420 B 13 **A = lbs CaCO 3 required to neutralize the acidity in 1 ton of the fertilizer. B = equivalent lbs of CaCO 3 inherent in 1 ton of the fertilizer. ***Is the % of N that is in the NH 4 + urea form; the remainder is NO 3 -N. *Same analyses can have different acidity / basicity and NH 4 content.
ph Drift 8.5 8.0 7.5 Alkaline water ph 7.0 6.5 6.0 5.5 5.0 4.5 optimum range + NH 4 fertilizers Time
Substrate ph Regulation ph 7 Desired ph 6 Upper ph decision point 15-0-15 effect and / or water alkalinity effect 20-10-20 effect and / or water acidification effect Successful ph stabilization 5 Initial ph is low due to substrate components Lime effect Lower ph decision point Days 15-0-15 effect and / or water alkalinity effect
Postplant Fertilization NH 4 H 2 PO 4 K Frequency of application K SO 4 CLF versus weekly feed depends on labor and equipment UREA Ca NO 3 NH 4 NO 3 NO 3
Rate of Nitrogen Weekly application range of 240 600 ppm N (1 to 2.5 lbs of 20% N material/100 gallons) Constant feed range of 90 255 ppm N (6 to 17 oz of 20% N material/100 gallons) Categorize crop as very light, light, moderate, or heavy with respect to fertilizer need (Table 9-3) Cut in half for subirrigation systems
Proportion of K O 2 Most do well with 1 N : 1 K O 2 Exceptions include: azalea (3 : 1) elatior begonia ( 2 : 1) foliage plants (1.5 : 1) carnation (1 : 1.5) cyclamen (1 : 2)
Proportion of P O 2 5 Phosphorus may not be needed, if pre-incorporated or soil-based May not know how much is in a commercial substrate Do not know the rate of leaching May be growing long-term crop such as cyclamen Usually add P O equal to one half the N 2 5
Form of Nitrogen Three forms: ammonium - N NH + 4 nitrate - N NO - 3 urea - N CO(NH ) 2 2 Maximum of 40% ammonium-n + urea-n to avoid ammonium toxicity problems, especially if: low ph (<5.5) lower temperatures overly wet substrates
Ammonium Toxicity Lower leaves Margins roll Chlorosis Necrosis Roots Burning
Ion Uptake & ph Uptake of cations lowers substrate ph Uptake of anions raises substrate ph True for any cation / anion uptake process But more N ions are taken up than all others combined, so N has most ph effect
Nitrogen Uptake NO 3 _ OH - H + Water NH 4 + H +
Secondary Macronutrients May need to supply Ca, Mg, and / or S If so, use appropriate fertilizer as in Table 9-5 or alternative source Examine water for Ca, Mg, and S Measure Ca : Mg ratio! 3 : 1 in meq/l 5 : 1 in ppm
Calcium / Magnesium Examine Water Analysis for Potential Problems Alkalinity (meq/l) 3.0 3.0 3.0 Calcium (ppm) 40 54 24 Magnesium (ppm) 12 4 22 Problem? none -Mg -Ca The greater the alkalinity, the greater the concentration of Ca, Mg, and / or Na
Calcium / Magnesium Limestone Regular (calcitic) limestone calcium carbonate Dolomitic limestone calcium carbonate magnesium carbonate
Calcium / Magnesium Epsom salts for Mg 1 lb / 100 gal Single Salts (When all else fails) Applied to substrate Calcium nitrate for Ca 1 lb / 100 gal (200 ppm Ca) Foliar spray
Sulfur Sources Epsom Salts Gypsum Sulfur in fertilizer salts / alkalinity acidification 20 to 30 ppm constant feed is recommended
Calcium, Magnesium, & Sulfur Complete Fertilizers Fertilizer Ca Mg S 20-09-20 - - 1.4 16-17-17-0.9 1.3 20-0-20 6.7 0.2-13-2-13 6.0 3.0-15-0-15 11.0 - -
Micronutrients Most fertilizers have "standard" concentrations of micronutrients Some have none Some have elevated levels Read the labels Availability is ph-related
Fertilizer Selection Selection is based on the system: crop needs desired ph monitoring water quality preplant program (level of P, Ca, Mg, S, and micros)
Fertilizer Formulations Conc. of N and K 2 O (ppm) Fertilzer or salts 50 75 100 250 Acid-residue sources oz per 100 gallons 20-10-20* 3.34 5.0 6.7 16.7 20-9-20* 3.34 5.0 6.7 16.7 ammonium nitrate + potassium nitrate +monoammonium phosphate (20-10-20)* 1.23 1.50 0.54 1.85 2.25 0.81 2.5 3.0 1.1 6.15 7.5 2.7 *These formulations also contain phosphorus (P 2 O 5 ).
Conc. of N and K 2 O (ppm) Fertilzer or salts 50 75 100 250 Basic-residue sources oz per 100 gallons 13-2-13 (-6Ca-3Mg)* 5.13 7.7 10.3 25.65 14-0-14 (-6Ca-3Mg) 4.76 7.14 9.5 23.8 15-0-15 (-9.5Ca-1Mg) 4.45 6.68 8.9 22.25 15-5-15 (-5Ca-2Mg)* 4.45 6.68 8.9 22.25 17-0-17 (-4Ca-2Mg) 3.92 5.88 7.83 19.6 potassium nitrate + calcium nitrate +magnesium nitrate (13-0-13-6Ca-3.3Mg) 1.23 1.50 0.54 1.85 2.25 0.81 2.5 3.0 1.1 6.15 7.5 2.7 *These formulations also contain phosphorus (P 2 O 5 ).