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Soil Lab – Taking samples and fertilizer application rates ANSC 110 – Pasture Management October 12, 2010
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Taking the samples The top 2-3 inches is the most important to the plants Root location Pasture fertilization practices Use of a soil probe (auger or tube) Sample in the fall (or spring if not able to do fall) Sample every 2-3 years
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Soil Testing Take at least 15-20 sample cores per pasture or paddock If you have a large pasture and it has different soil characteristics, sample those separately No sample should represent more than 15-20 acres Transverse each field in zig-zag pattern Sample parts of field that appear different in soil or crop Avoid sampling areas that were recently fertilized, obvious dung/urine areas, or areas adjacent to roads
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PASTUREslope water
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Soil Testing Collect soil in clean bucket Break up lumps Mix well, take out a subsample (about ½-pound) Place in soil sample box Label the box!!! Manure application? Legumes in pasture? Crop to be fertilized (i.e., grass type) Field information
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Soil Testing Labs A & L Eastern Agricultural Labs – Richmond, VA Agri Analysis, Inc. – Leola, PA Brookside Labs, Inc. – New Knoxville, OH PA Agricultural Analytical Serv. – Penn State Spectrum Analytic, Inc. – Washington Ct. House, OH Univ. Delaware Soil Testing – Newark, DE Waters Agricultural Labs, Inc. – Camille, GA
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Calculating Fertilizer Rates Fertilizers are listed as N- P 2 O 5 - K 2 O Recommendations are given as: N P 2 O 5 K 2 O
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Fertilization Examples Multiply rate of desired nutrient by 100 and divide by the percentage in the fertilizer Recommended rate of N is 80 lb/acre Using 46-0-0 (Urea) Equation: (80 x 100) / 46 = 174 lb/acre
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Fertilization Examples Recommended rate of P 2 O 5 is 40 lb/acre Using 12-51-0 (Monammonium Phosphate) Equation: (40 x 100) / 51 = 78 lb/acre
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Fertilization Examples Recommended rate of K 2 O is 15 lb/acre Using 0-0-60 (Potassium Chloride - crystalline) Equation: (15 x 100) / 60 = 25 lb/acre
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Fertilization Example – Price Per Unit Cost of fertilizer is related to plant nutrient content Compare prices on cost per pound of “actual” nutrient, not price per ton of fertilizer Divide percentage of nutrient by 100 and multiply by 2,000 lb. (1 ton)
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Fertilization Example – Price Per Unit Example: Urea (46-0-0) costs $253/ton, what is the cost per pound of nitrogen? Equation: Nitrogen in 1 ton of Urea (46-0-0) (46/100) x 2,000 = 920 lb. Cost per lb. of Nitrogen $253 / 920 lbs = $0.275
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Fertilization Example – Price Per Unit Example (Based on 12-51-0 at $403/ton) What is the cost of P 2 O 5 in 12-51-0? Calculate nitrogen cost first (12/100) x 2,000 = 240lbs. 240lbs. X $0.275 = $66 (value of nitrogen)
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Fertilization Example – Price Per Unit Example (Based on 12-51-0 at $403/ton) Cost of phosphate $403-$66 = $337 Phosphate in one ton of 12-51-0 (51/100) x 2,000 = 1020 lb. Cost per lb. of phosphate $337 / 1020 lbs = $0.33
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