Fertilizing
Essential elements Nutrient deficiency symptoms Fertilizer forms Interpreting labels Application techniques
Soil - Macronutrients
Nitrogen (N) Phosphorous (P) Potassium (K) Calcium (Ca) Magnesium (Mg) Sulfur (S)
Soil - Micronutrients Boron (B) Chlorine (Cl) Copper (Cu) Iron (Fe) Manganese (Mn) Molybdenum (Mo) Nickel (Ni) Zinc (Zn)
Nutrient Deficiencies
Lack of either macro or micro nutrients will impede normal plant growth. Not enough in the soil In the soil, but unavailable
Symptoms will appear on different parts of the plant. Interpret these symptoms.
Some common nutrient deficiencies and the symptoms:
Nitrogen deficiency
Older leaves (bottom of plant) begin to yellow. Remainder of plant generally a lighter green than normal.Nitrogen is mobile in the plant and can be
translocated to new, young leaves.Nitrogen can be mobile in the soil.
Phosphorous deficiency
Leaves often dark green. Veins, petioles, and lower surfaces may
become reddish – purple colored. Sparse, distorted foliage.
Phosphorous is mobile in plants.Phosphorous is immobile in the soil.
Potassium deficiency
Marginal and interveinal chlorosis followed by scorching moving inward between the main veins.
Leaf curlingPotassium is highly mobile in plants.Potassium is immobile in the soil.
Iron deficiency
Interveinal Chlorosis: Veins stay green, but area between veins turns yellow.
Common on pin oak, red maple and river birch. Due to high pH soil. Common problem in Iowa, especially on trees planted
where original topsoil has been removed. (New subdivisions)
Iron cannot be translocated.
Organic Fertilizer
Organic fertilizer Derived from plant and animal products.
Blood meal, bone meal, manure & sewage sludge. Organic fert. released slowly – avoids plants from
being burned. Generally more expensive than chemical fert. on the
basis of amount of nutrients supplied. Organic fert can work as a soil amendment at the
same time. Ex. Milorganite
Inorganic Fertilizer
Manufactured chemical fertilizer. Much more concentrated than organic.
Can burn plants with too much fert, especially if using a fast release form.
Less expensive.
Carbon (C) : Nitrogen (N) Ratio
The ratio of carbon atoms to nitrogen atoms.
Soil microorganisms use nitrogen to metabolize (breakdown) carbon.
Certain types of organic matter are very high in carbon:
Sample C:N of various types of organic matter:
Sandy loam (fine) 7:1Humus 10:1
Food scraps 15:1Alfalfa hay 18:1
Grass clippings 19:1Rotted manure 20:1
Sandy loam (coarse) 25:1Vegetable trimmings 25:1
Oak leaves 26:1Leaves, varies from 35:1 to 85:1
Peat moss 58:1Corn stalks 60:1
Straw 80:1Pine needles 60:1 to 110:1Farm manure 90:1Alder sawdust 134:1
Sawdust weathered 3 years 142:1Newspaper 170:1
Douglas fir bark 491:1Sawdust weathered 2 months 625:1
Nitrogen Robbing
Organic matter with excess C:N ratios (or excessive amounts of organic matter) can create problems.
To continue decomposition the soil microorganisms will draw nitrogen out of the soil making it unavailable to plants.
Fertilizer Forms
Liquids Easy application (tank mix or hose end sprayer). Potential to burn plants if mixed too strong, or too
much applied. Soluble Powder
Dissolves readily in water (apply just like liquid). Generally less expensive than liquid.
Fertilizer Forms
GranularMost common and widely used form.Slow release forms available.
Prolongs release of nutrients Decreases burning potential
Fertilizer Labels
AnalysisShows type of nutrients and amount.
Nitrogen – Phosphate – Potash N-P-K10-5-5
Gives the percentage of each in the fertilizer. 10% Nitrogen, 5% Phosphate, 5% Potash Use conversion factors to find % phosphorous and
potassium.
Conversion Factors
To convert phosphate to phosphorous (P):Multiply %phosphate by .44
To convert potash to potassium (K):Multiply %potash by .83
Osmocote fertilizer label
What percentage of the fertilizer is N?19%
What percentage of the fertilizer is phosphate (P2O5)?5%
What percentage of the fertilizer is potash (K2O)?8%
What percentage of the fertilizer is actual phosphorous (P)?5 x .44 = 2.2%
What percentage of the fertilizer is actual potassium (K)?8 x .83 = 6.64%
How long is this fertilizer supposed to last at 70 degrees F.?8-9 months
Does this fertilizer contain any micronutrients?Yes
How many forms of N are in the fertilizer? 3
6.60% Ammoniacal Nitrogen5.70% Nitrate Nitrogen6.70% Urea Nitrogen
Application Methods
Broadcast on the soil surface Most soils supply adequate amounts of nutrients with the exception of N. Effective method for applying N.
Placed in holes in the soil P, K and other nutrients of low solubility benefit from incorporation. Core, punch, or drill holes. 6 inches deep, 2-3 feet apart.
Application methods continued
Injected into the soil under pressure High pressure hydraulic sprayer. 6 inches deep. 150-200 psi pressure.
Sprayed on foliage Placed in holes in tree trunks
Micronutrient implants. Placed in xylem. Holes approx. ½ inch in diameter. Plug holes.
Injected into the trunk Micronutrients. Mauget, Wedgle.
Microinjection:How to use Mauget
Microinjection:Wedgle direct inject system
Fertilizer Math
Remember that a 20 -10 -10 fertilizer, for example, contains only 20% actual N on a weight basis. A useful calculation for determining how many pounds of fertilizer to apply is:
pounds of fertilizer = application rate of the nutrient in pounds
percentage of that nutrient in the analysis
If you want to apply nitrogen at the rate of 2 pounds per 1,000 square feet to an area measuring 300 square feet how many pounds of 20 – 10 – 10 fertilizer should be applied:
pounds of fertilizer = application rate of the nutrient in pounds
percentage of that nutrient in the analysis
pounds of fertilizer = 2 = 10 pounds of fertilizer
.20
10 = x
1,000 300
x = 3 pounds