Beyond N-P-K: Chemistry of Soil and Water and How they Effect our Fertilizer Practices

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Beyond N-P-KChemistry of Soil and Water and How
they Effect our Fertilizer Practices

• David Wm. Reed
• Department of Horticultural Sciences
• Texas AM University

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17 Essential Elements
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Supplied Naturally (by H20, O2, CO2) C, H,
O Macronutrients N, P, K, Ca, Mg,
S Micronutrients or Trace Elements Fe, Cu, Mn,
Zn, B, Mo, Cl, Ni
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Where Do All the Nutrients Come From?
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  N P K K Ca Mg S Fe B Other Micro
Incorporated into Soil or Growing Medium - Pre-Planting Incorporated into Soil or Growing Medium - Pre-Planting Incorporated into Soil or Growing Medium - Pre-Planting Incorporated into Soil or Growing Medium - Pre-Planting Incorporated into Soil or Growing Medium - Pre-Planting Incorporated into Soil or Growing Medium - Pre-Planting Incorporated into Soil or Growing Medium - Pre-Planting Incorporated into Soil or Growing Medium - Pre-Planting Incorporated into Soil or Growing Medium - Pre-Planting Incorporated into Soil or Growing Medium - Pre-Planting Incorporated into Soil or Growing Medium - Pre-Planting
complete fertilizer X X X X     ?      
superphosphate   X X   X   X      
dolomitic lime         X X        
gypsum         X   X      
iron sulfate             X X    
micronutrient mix               X X all
Supplied Post-Planting as Granular, Liquid or Slow-Release Application Supplied Post-Planting as Granular, Liquid or Slow-Release Application Supplied Post-Planting as Granular, Liquid or Slow-Release Application Supplied Post-Planting as Granular, Liquid or Slow-Release Application Supplied Post-Planting as Granular, Liquid or Slow-Release Application Supplied Post-Planting as Granular, Liquid or Slow-Release Application Supplied Post-Planting as Granular, Liquid or Slow-Release Application Supplied Post-Planting as Granular, Liquid or Slow-Release Application Supplied Post-Planting as Granular, Liquid or Slow-Release Application Supplied Post-Planting as Granular, Liquid or Slow-Release Application Supplied Post-Planting as Granular, Liquid or Slow-Release Application
complete fertilizer X X X X     ?      
Epsom salt           X X      
soluble micronutr.               X X all
some pesticides               X   Cu,Mn,Zn
irrigation water ppm         gt3-5 gt1     0.3-1.5  
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Water EC, pH Alkalinity
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• Collect water sample
• Meters Used
• pH pH meter
• Soluble Salts or EC conductivity meter
• Alkalinity alkalinity test kit or paper
• Compare reading to Interpretation Table

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Meters Used
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pH
EC
alkalinity kit
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Meters Used
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Combination EC pH Meter
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Water Soluble Salts and EC
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Relative Hazard Relative Hazard Relative Hazard Relative Hazard Relative Hazard Relative Hazard
None Little Moderate Moderate High Severe
Electrical Conductivity dS/m or mmhos/cm dS/m or mmhos/cm dS/m or mmhos/cm dS/m or mmhos/cm dS/m or mmhos/cm dS/m or mmhos/cm
Electrical Conductivity 0.2 lt0.7 0.7-2 2-3 2-3 gt3
 Soluble Salts ppm ppm ppm ppm ppm ppm
 Soluble Salts 140 lt490 490 - 1400 1400 - 2100 1400 - 2100 gt2100
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Water Alkalinity
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Recommended Alkalinity Levels Recommended Alkalinity Levels Recommended Alkalinity Levels Recommended Alkalinity Levels
Minimum Minimum Maximum Maximum
ppm meq/l ppm meq/l
Plugs and/or seedlings 38 0.75 66 1.3
Small pots and shallow flats 38 0.75 86 1.7
4" to 5" pots and deep flats 38 0.75 106 2.1
6 pots and long term crops 63 1.25 131 2.6
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Soil/Media Soluble Salts (EC) pH
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• Collect soil/medium sample below surface
• Extract with water (12 dilution)
• Filter
• Meters Used
• pH pH meter
• Soluble Salts or EC conductivity meter
• Compare reading to Interpretation Table

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Soil/Media pH
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SME SME 12 or 15 Dilution 12 or 15 Dilution  
Extract Slurry Extract Slurry Pour-Through
Optimum pH 5.5 - 6.5 5.4 - 6.2 5.5 - 6.5 5.4 - 6.2 5.5 - 6.5
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Soil/Media Soluble Salts (EC)
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Electrical Conductivity (EC) dS/m or mmho/cm Electrical Conductivity (EC) dS/m or mmho/cm Electrical Conductivity (EC) dS/m or mmho/cm Electrical Conductivity (EC) dS/m or mmho/cm
SME 12 Dilution 15 Dilution Pour-Through
Established plants 2.0-3.0 0.8-1.2 0.3-0.6 3.0-5.0
Seedlings, plugs 1.0-2.0 0.5-0.9 ? ?
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Graphical Tracking pH and EC
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Graphical Tracking of EC
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Selecting a Fertilizer Based on the Form of
Nitrogen
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• Nitrogen exists in two forms
• Ammoniacal (NH4, urea)
• Nitrate (NO3-)
• Nitrogen form used affects
• Type of growth
• Type fertilizer, acid vs. basic
• pH of the soil or growing medium

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Selecting a Fertilizer Based on the Form of
Nitrogen
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Form of Nitrogen Influences Type Growth and is Seasonal Form of Nitrogen Influences Type Growth and is Seasonal Form of Nitrogen Influences Type Growth and is Seasonal
Nitrogen Form Type Growth Used For
High Ammoniacal (gt25) lush growth larger leaves longer stems foliage plants flowering plants early warmer summer
High Nitrate (gt75) hardy plant compact growth flowering plants finishing cooler winter
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Selecting a Fertilizer Based on the Form of
Nitrogen
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Form of Nitrogen Influences Soil/Medium pH Form of Nitrogen Influences Soil/Medium pH Form of Nitrogen Influences Soil/Medium pH
Nitrogen Form Type Fertilizer Soil/Medium Reaction
High Ammoniacal (gt25) acid pH decreases becomes more acid
High Nitrate (gt75) basic pH increases becomes more basic
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Selecting a Fertilizer Based on the Form of
Nitrogen
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Acid versus Basic Fertilizers Acid versus Basic Fertilizers Acid versus Basic Fertilizers Acid versus Basic Fertilizers
Fertilizer NH4 Potential Acidity Potential Basicity
21-7-7 acid 100 1560  
20-18-18 73 710  
15-15-15 52 261  
20-0-20 25 40  
20-0-20 69 0 0
15-5-15 28   135
15-0-15 13   319
15.5-0-0 Ca nitrate 6   400
13-0-44 K nitrate 0   460
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Fertilizer Label Lists Potential Acidity
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Label Fertilizer Analysis
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Micronutrients in Acid Vs. Alkaline
Soil(especially heavy metals Fe, Mn, Zn, Cu)
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Selection of Heavy Metal Carriers based on Soil pH Selection of Heavy Metal Carriers based on Soil pH Selection of Heavy Metal Carriers based on Soil pH
Nitrogen Form Acid Soil Alkaline Soil
Sulfates effective not very effective
Chelates effective, but expensive so why use. most effective
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Which Chelate to Use?
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Which Chelate to Use?
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Highest pH Still Effective Chelate
6 lignosulfonate, citrate, HEDTA
6.5 EDTA
7.5 DTPA (330)
any pH EDDHA (138)
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Fertilizer Label Lists Chemicals Used
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Rose Rootstocks Tolerance to Alkaline Soil
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Rose species/cultivar Chlorosis Rating (5green to 1yellow)
R. canina 5.0
R. manettii 4.9
R. odorata 4.8
R. sp. Mexican 4.8
R. fortuniana 4.4
R. multiflora 'Dan Whiteside' 2.7
R. multiflora Brooks 56' 2.7
R. multiflora 74-3 died
R. 'Dr Huey' died
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Rose Rootstocks Tolerance to Alkaline Soil
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EarthKindTM Landscape Roses(http//aggie-horticul
ture.tamu.edu/earthkindrose/index.html)
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EarthKindTM Landscape Roses
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Cultivar Flower Color Flower Type Blooming Period Ht x Wd (feet) Category
Ground Covers Ground Covers Ground Covers Ground Covers Ground Covers Ground Covers
Sea Foam creamy white double April-November 2 x 6 shrub
Dwarf Shrubs Dwarf Shrubs Dwarf Shrubs Dwarf Shrubs Dwarf Shrubs Dwarf Shrubs
Marie Daly Pink semi-double April-November 3 x 3 polyantha
The Fairy light pink double April-November 3 x 4 polyantha
Small Shrubs Small Shrubs Small Shrubs Small Shrubs Small Shrubs Small Shrubs
Caldwell Pink lilac pink double May- November 4 x 4 found
Easy Going yellow double April-November 4 x 4 floribunda
Knock Out cherry red semi-double April-November 4 x 4 shrub
Livin' Easy apricot-orange double April-November 4 x 4 floribunda
Perli d'Or peach pompon April-November 4 x 4 polyantha
Medium Shrubs Medium Shrubs Medium Shrubs Medium Shrubs Medium Shrubs Medium Shrubs
Belinda's Dream Pink double April-November 5 x 5 shrub
Climbing Pinkie pink semi-double April-November 5 x 7 polyantha
Else Poulsen pink semi-double April-November 5 x 5 floribunda
Katy Road Pink pink semi-double April-November 5 x 4 found
Mutabilis Butterfly Rose yellow, pink, crimson single April-November 6 x 6 China
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Belindas Dream(developed by Dr. Robert Basye)
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