Soils, Nutrients and Fertilizers Part I I

Handouts: “Home Garden Soil Testing and Fertilizer Guidelines” MontGuide

Nutrients

• 17 elements essential for plant growth

OxygenCarbonHydrogenNitrogenPhosphorusPotassiumMagnesiumCalciumSulfur

IronBoronChlorineManganeseZincCopperMolybdenumNickel

Carbon, Hydrogen, and Oxygen

• A dried plant is 94% Carbon, Hydrogen, and Oxygen

• Why don’t we ever hear about adding these nutrients to the soil?

CO2H2O

Nitrogen (N)

• Favors vegetative growth such as leaves and shoots

• Good sources:

High N Fertilizers

Blood Meal* Fish Meal* Cottonseed Meal*

* = organic source

Nitrogen Deficiencies

Deficiency : Chlorosis (insufficient chlorophyll) in older plant tissue (Shows up in older leaves)

Phosphorus (P)

• Promotes good seed and fruit ripening, maturation, energy storage/transfer

• Good Sources:

SuperphosphateBone Meal*Diammonium

PhosphateRock Phosphate*

* = organic source

Phosphorus Deficiencies

Deficiency: Older leaves first turn dark green with red/purple between veins. Reduction in growth, poor fruit size and yield.

Potassium (K)

• Stomatal regulation (gas exchange), new tissue growth, root and stem development, hardiness, fruit flavor and fruit color

• Good Sources:

Potassium Chloride

Potash*Cow Manure*

Seaweed Meal*

* = organic source

How about Manure?

Make sure that the manure is fully composted and contains no residual herbicides!

Potassium Deficiency

Deficiency: Mottled chlorosis in older leaves

How about wood ash?

• Not recommended for gardens

– Raises the pH

– High in salts

– No more than a 5-gallon bucket full per 1000 sq.ft.

• Watch the pH levels!

Iron Deficiency

• The soil may have plenty of iron, but due to high soil pH the plants can’t absorb it.

Iron Deficiency = Interveinal Chlorosis

• Highly susceptible plants include raspberry, Amur maple, crabapple, mountain ash, and roses

Be sure you have a real problem and not a pseudodeficiency by virtue of insufficient or excess irrigation

Plant Deficiencies

Healthy leavesShine with a dark green color when adequately fed

Phosphorus DeficiencyLeaves with reddish-purple, particularly on young plants

Potassium DeficiencyDrying along the tips and edges of the lowest leaves

Nitrogen DeficiencyYellowing that starts at the tip and moves along the middle of the leaf

http://landresources.montana.edu/NM/Default.htm

Ultimately, how do you know if you have a nutrient deficiency?

• Soil test to determine if fertilizer is needed

• Keep in mind that some garden soils can actually have TOO MUCH fertility; look for toxicities

• You will only know if you have a deficiency or toxicity by testing!

Soil testing

• Use a tulip bulb planter

• Collect soil from upper 6 inches in about 10 locations

• Mix and send to lab

• See MT200705AG “Home Garden Soil Testing and Fertilizer Guidelines” for details and laboratory addresses

Which Lab to Pick?

Make sure that the lab:

•Makes recommendations

•Makes the recommendations in lbs. per 1000 sq.ft. rather than in acres

•The lab’s turnaround time

Fertilizer Sources

Inorganic?Organic?

Inorganic vs. Organic Fertilizers

Organic

– Bulkier (-)

– Nutrient content low (-)

– Nutrient content difficult to quantify (-)

– Slow release (+)

– Usually supplies organic matter (+)

Inorganic vs. Organic Fertilizers

Manure

(dry)

N (%)* P (%)* K(%)*Per 1000ft2

Chicken 2 to 4.5 4.6 to 6.0 1.2 to 2.4 62

Steer 1 to 2.5 0.9 to 1.6 2.4 to 3.6 115

Dairy 0.6 to 2.1 0.7 to 1.1 2.4 to 3.6 150

Pig 0.5 to 1.0 0.3 to 0.7 0.1 to 2.0 133

Horse 0.3 to 0.6 0.1 to 0.2 0.3 to 1.0 225

* Analysis is approximate

Amount of organic manure needed to add 2 lbs of actual

nitrogen/1000ft2 of garden

Inorganic vs. Organic Fertilizers

Inorganic– No carbon (-)– Easy to store (+)– Higher analysis (+)– Custom formulated (+)– Easy to use (+)– Liquid and solid (+)– Environmental and health

concerns? (-)

Applying Fertilizers

Timing– Preplant

– Postplant

Method– Banding

– Broadcasting

– Sidedressing or Topdressing

How much should you fertilize your garden, flower bed, turfgrass?

• First: Do a soil test and interpret results

• Second: Assess the plant’s growth.

– Not all plants need additional nutrients

• Third: Figure amount of NPK

% NitrogenN

N % Phosphoric acidP2O5

P

% Potassium oxideK2O

K

Math!

Actual Nitrogen

Nitrogen is the most limiting nutrient. Therefore, most calculations are based on % nitrogen

Don’t worry about the P and K at this time, unless deficient

A 100 pound bag of 10-10-10 contains 10 pounds of actual N (10% of 100 = 10) (0.10 x 100 = 10)

A 25 pound bag of ammonium sulfate (21-0-0) contains 5.25 pounds of actual N

(21% of 25 = 5.25) (0.21 x 25 = 5.25) A 50 pound bag of sheep manure (2-1-2) contains 1.0 pound of

actual N (2% of 50 = 1.0) (0.02 x 50 = 1)

Finding the right amount of fertilizer from a recommendation

Recommended Amount/Decimal %

MSU Extension recommends 1 lb. of actual N per 1000 sq.ft. of lawn. You have 34-0-3 fertilizer. How much fertilizer should you apply per 1000 sq.ft.?

1 lb. / .34 = 2.94 lbs

(how much N you need to apply divided by the decimal percentage content of N)

Conclusion: You will need approximately 3 lbs of a 34-0-3 fertilizer to apply 1 lb. of actual N per 1000 sq.ft.

Calculating Fertilizer Applications

Recommendations call for applying 2 lbs of actual N per 1000 sq. ft.

You have a 5000 sq. ft. lawn. How much 12-6-5 should you use?

First: 2 lbs ÷ 0.12 = 16.67 (So, 16.67 lbs will supply 2 lb. of actual N / 1000 sq. ft)

Second: You have 5000 sq. ft., so 16.67 x 5 = 83 lbs. of 12-6-5 will provide 2 lbs of actual N per 5000 sq. ft.

Common Soil Amendments – are they needed?

Amendment Purpose Fact

Coarse Sand Improve

aeration/drainage

Can cause concrete-like

affect in soil with heavy

clay

Sulfur Increase acidity Will only change slightly

and is short lived

Limestone Increase alkalinity Will only change slightly

and is short lived

Gypsum Decreases sodic

conditions

Takes too long and are

short lived, leaches iron

Peat Moss, Compost,

Composted Manure

Increase water and

nutrient-holding capacity

Great amendment. Watch

for herbicide residual

Need to add around 50% by volume of sand!

• Or your soil may become like concrete!

When Should You Amend?

• When your soil needs it

• Fall is the best time to add amendments – if you can find them.

• Finding a good reputable source is very important – Watch for herbicide residual in manure and compost.

Summary

• Soil texture, structure, OM, and CEC affect soil fertility

• Add organic matter (but don’t overdo it!)

• Bacteria and fungi do a lot of the ‘work’ in making nutrients available, but can tie up N

• Do not work soil when it is wet

• It is not recommended to try to change the soil pH

Summary

• There are 17 elements essential for plant growth

• 4 of those (N, P, K and sometimes Fe ) have highest chance of impacting your plants

• By recognizing nutrient deficiency symptoms, and/or soil testing, you can fertilize to optimize plant growth

• Apply amendments (OM!) in the autumn after the growing season has ended

• Make sure that your amendments come from a reputable source

• Make sure that manure is fully composted

End

Next Week Reading assignment: Read Chapter 2 pages 24-48 in the Montana Master Gardener Handbook