Prescription fertilizers trees desert green 2013

Prescription Fertilization of Woody Plants in Desert and Arid Soils

Robert Ll. Morris Emeritus, University of Nevada Email: MorrisR@unce.unr.edu Blog Xtremehorticulture of the Desert Yahoo discussion group: desert_horticulture

Characteristics of desert soils    

Structureless High pH (alkaline) High salts Low organic matter

Plant Nutrients Needed in Large Amounts Carbon Hydrogen Oxygen Nitrogen Phosphorus Potassium Calcium Magnesium Sulfur

Needed in Much Smaller Amounts Iron Manganese Zinc Boron Chlorine Cobalt Molybdenum

Nutrients Needed in Large Amounts Nitrogen Phosphorus Potassium Calcium Magnesium Sulfur

Nitrogen

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Increases leaf and stem growth Darkens green leaf color Increases stored food Can make plants less tolerant of freezing weather Boosts spring recovery and recovery from damage Nitrogen fertilizers typically dissolve easily in water and move with water through the soil profile

Shortage of Nitrogen  

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Slow growth Light green leaf color Thin canopy

Shortage of Nitrogen   

On pines candles are smaller Canopy is not dense Needles at the ends of branches

Nitrogen Too Much?

Rapid growth Dense canopy Dark green leaves Leaf scorch and possible damage Wastes money Environmental pollution

Phosphorus    

Root production Stem strength Flower and seed production Deficient in cold, wet soils

Phosphorus Too Much?

Not Enough?

Moves slowly in the soil Troublemaker Toxicity Wastes money Environmental pollution

Poor growth or performance Disease susceptibility Reduced flowering Poor root development

Phosphorus deficiency Purple coloration in severe deficiency

Potassium ď Ž ď Ž

Landscape plant needs are usually underestimated Stress resistance

Potassium Too Much?

Nothing visual  Wastes money  Not the environmental problem that nitrogen and phosphorus can be 

Not Enough?

Poor tolerance to stress  Disease susceptibility  Poor heat tolerance  Poor cold tolerance

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Nutrients Needed in Smaller Amounts Iron Manganese Zinc Boron Chlorine Cobalt Molybdenum

Desert Soils and Available Nutrients

The Benefits of Decomposing Organics to the Soil   

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Lowers soil pH Adds nutrients Improves soil chemistry Provides natural chelates Preserves soil moisture Increases soil “good guys”

Micronutrients Iron Manganese Zinc

Micronutrients - Iron Found on newest leaves Early stages, leaf yellow with green veins Advanced stages leaf is pure yellow combined with scorch

Micronutrients - Iron

Micronutrients - Iron

Iron Causes:  High soil pH  Soils kept too wet  Rock mulches  High phosphorus  Damage to trunk or stems

Iron Fertilizers and Strategies 

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Add more iron  Iron sulfate Lower the pH  Iron with sulfur Keep iron available to plants  Chelates Organic amendments  Lower soil pH and natural chelates

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Soil applied Foliar applied Injection

What is a Chelate?   

Chelates help make minor elements available to plants Examples are EDTA, DTPA and EDDHA Some chelates perform better in desert soils than others

Desert Soils and the Best Chelate

Micronutrients - Manganese   

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Confused with iron Difficult to identify Leaf veination green like “magic marker” Soil applications, foliar and injection

Micronutrients - Zinc Rosette of leaves on ends of branches  Smaller leaves than normal  Leaf discoloration  Soil applications, foliar and . injection 

What Is the Perfect Fertilizer?

The perfect fertilizer:  Builds a reservoir of nutrients needed by the plant  Replaces nutrients taken from the soil by the tree  Maintains the plant in good health

Are soil tests necessary?

Liebig’s Law of the Minimum Plant growth is limited by the nutrient in least supply.

What is the Perfect Ratio? 

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Ratio (NPK) is determined by type of plant, previous fertilizer applications, soil condition and soil tests if done Generally nitrogen is highest amount followed by potassium and phosphorus lowest Typical ratios: 3-1-2, 3-1-3, 4-1-2, 4-1-3, 4-1-4

What is the Perfect Timing?   

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Single applications late winter/early spring Split applications; ½ late winter, ½ after flowering/fruiting Avoid applications of nitrogen to winter tender plants after August 1 Late fall application

What is the Perfect Amount? ď Ž

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Adjust rates according to growth in previous years and general health of the tree Rates typically 1 - 2 lbs of N per 1000 sq ft under the tree canopy

How to Apply Fertilizers 

Soil applied 

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Foliar applied  

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Place 6 inches deep near sources of water Spray to runoff Use wetting agent to improve foliar uptake

Trunk injection   

Use only when no other option is available Inject in root flares of older trees or as low on trunk as possible Inject with the smallest hole possible

Late Fall Fertilization 

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Apply late enough so that new growth is not encouraged but before leaf drop Builds nitrogen in storage tissue Contributes to early spring greenup/leaf emergence and may eliminate the need for a spring application

Resources ď Ž ď Ž

Blog: Xtremehorticulture of the Desert Yahoo Discussion Group: desert_horticulture