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Published byFrederick Godfrey McKinney Modified over 2 years ago

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Soil Fertility Inorganic fertilizersInorganic fertilizers –Most developed in the 1940’s –Ammonium nitrate –Superphosphate –Muriate of potash –These are often pure (do not contain micronutrients) –These are often concentrated (therefore they are cheaper to transport and apply)

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Soil Fertility Nitrogen is often the most limiting nutrient in soilsNitrogen is often the most limiting nutrient in soils Nitrogen applied in excess causes reduced flowering and fruiting and greater vegetative (leafy) growthNitrogen applied in excess causes reduced flowering and fruiting and greater vegetative (leafy) growth

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Soil Fertility Fertilizer analysisFertilizer analysis –Percentage (by weight) of the available Nitrogen (as N), Phosphorus (as P 2 O 5 ) and Potassium (as K 2 O) Ex: 5:10:5 5% N 5% N 10% P 5% K 5% K 80% in the bag is inert material!

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Soil Fertility High analysis = N+P+K percentage > 30%High analysis = N+P+K percentage > 30% –Ex: 30 lbs. of N,P,K in a 100 lb. bag of fertilizer –Less costly (don’t pay for a lot of “filler”, but tricky to apply) Low analysis = N+P+K percentage < 30%Low analysis = N+P+K percentage < 30% –more costly due to weight in transport but easier to apply

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Soil Fertility Fertilizer ratioFertilizer ratio –The proportion of the three major elements Ex: 5:10:5 = 1:2:1 ratio

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Soil Fertility N-recommendations: (in lbs./acre)N-recommendations: (in lbs./acre) If the soil test indicates that you need to apply 100 lbs. of N per acre, how many pounds of a 20:10:10 fertilizer would you need?If the soil test indicates that you need to apply 100 lbs. of N per acre, how many pounds of a 20:10:10 fertilizer would you need? 20% X = 100 lbs. 0.20 X = 100 lbs. X = 100 lbs./0.20 X= 500 lbs.

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Soil Fertility Now… you probably don’t have a garden that is an acre in size.Now… you probably don’t have a garden that is an acre in size. Ex: If your garden is 20’ x 20’ = 400 ft 2Ex: If your garden is 20’ x 20’ = 400 ft 2 20’ 20’ Yourgarden plot plot 1 acre = 43,560 ft 2 208.5’ 208.5’

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Soil Fertility 500 lbsX lbs. 43,560ft 2 400 ft 2 43,560 X = 200,000 200,000 200,000 43,560 43,560 X = 4.59 lbs. of fertilizer per 400 sq. feet X =

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Objective: Students will identify how to interpret fertilizer labels.

Objective: Students will identify how to interpret fertilizer labels.

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