Agronomic and Economic Considerations on Michigan Farms

Agronomic and Economic Considerations on Michigan Farms

MSU Phosphorus and Potassium Fertilizer Recommendations for Field Crops The key ingredients: Soil Test Information Yield Goal Buildup, Maintenance and drawdown

Soil sampling Sample should represent the field Sampling pattern for three separate uniform fields Each sample should be composed of at least 20 cores

Zone delineation (non-uniform) Sand Loam Limed 5 years ago Never limed Formerly 2 fields now all 1 field Muck 3 zones 2 zones 2 zones 15 T/a manure last year No manure 2 zones 3 zones Flat Poorly drained

MSU Phosphorus and Potassium Fertilizer Recommendations for Field Crops The key ingredients: Soil Test Information Yield Goal Buildup, Maintenance and drawdown

Buildup and Maintenance Approach Building up low soil testing soils to a critical level Adding P and K to maintain that level year after year Flexibility to change the rate

Buildup and Maintenance Approach 0 15 30 45 ppm Critical level - Soil test level to achieve economic optimum (95-97% of the maximum yield)

Critical Soil Test P Value The soil test level where you achieve economic optimum yield (95-97% of the maximum yield)

Critical Soil Test P Level Crop Critical P level (ppm) Corn 15 Soybean 15 Wheat 25 Alfalfa 25 The soil test level where you achieve economic optimum yield (95-97% of the maximum yield)

Buildup and Maintenance Approach Buildup and Maintenance Approach 0 15 30 45 ppm Critical level - Soil test level to achieve economic optimum (95-97% of the maximum yield)

Buildup and Maintenance Approach MSU recommended P fertilizer practices Soil Test Level Buildup range (< Critical level) Maintenance range (>critical level) Drawdown range (> maintenance limit) Recommended Fertilizer Rate Apply rates to buildup to critical level plus crop removal rate Only apply crop removal rate only starter P or No Phosphorus

Phosphorus and Potassium Removal Rates (based on the yield goal in soil test) Crop Yield lb P2O5/A removed lb K2O/A removed Corn 180 Bu 67 48 Soybean 45 Bu 36 63 Wheat 75 Bu 47 28 Alfalfa 4 Tons 52 200

MSU Soil Test Lab Report The bar chart closely corresponds to the buildup (below optimum), maintenance (optimum) and drawdown ranges (above optimum).

Soil Test Lab Report The bar chart closely corresponds to the Below optimum (Buildup ) Optimum (Maintenance) Above Optimum (Drawdown) Analysis Recommendation *

Buildup and Maintenance Approach Critical Soil Test K Level Crop Critical K level (ppm) CEC = 10 me/100g Corn 100 Soybean 100 Wheat 100 Alfalfa 100 Potassium is positively charged and attracted to clay or organic matter (Limited losses to environment)

P and K Management Considerations P in soil Many years to build-up and drawdown Applying manure to meet all the N needs of corn leads to over application of P Maintain soil ph range at 6.0-6.8 (Use lime if necessary good return to investment) P and K can be applied in the fall or spring (Fall K fertilizer applications on sandy soils with low organic matter are discouraged)

More information on this approach Special situations will be discussed at the advanced session

18 Essential Plant Nutrients Macronutrients Nitrogen (N), Phosphorus(P), and Potassium(K) Required in large amounts and likely to be deficient Carbon (C), Oxygen (O), and Hydrogen(H) are derived from atmospheric carbon dioxide and soil water Secondary Nutrients Calcium (Ca), Magnesium(Mg) and Sulfur(S) Required in large amounts but less likely to be deficient Micronutrients Manganese (Mn), Zinc (Zn), Boron (B), Copper (Cu), Iron (Fe), and Molybdenum (Mo) Required in trace amounts

A sketch map indicating each soil unit/management zone

What does a soil tests show Physical make-up of the soil Accurately determine available nutrients. Evaluate the probability of deficiencies, excesses or imbalances. Serve as a basis for making fertilizer recommendations. Determine the soil ph.

2. Grid Sampling a Field

A sketch map indicating each soil unit/management zone to be sampled will be helpful. Here are some examples:

Whole Field Sampling pattern for three separate uniform fields Each sample should be composed of at least 20 cores

Grid Systematic sampling Used where nutrients will be applied variably Can be useful if purchase/rent new ground and past history not well known Plus good assessment of nutrient variability Minus expensive

Grid Sample locations have GPS coordinates Sample consists of at least 10 cores composited within a 10 radius of grid point

Buildup and Maintenance Approach Short term strategy or on rented land apply only the maintenance rate (crop removal) and not buildup In the drawdown range, skip any P and K application

Buildup and Maintenance Approach Short term strategy or on rented land Apply P and K first to fields most in need (below critical level) and then allocate the remaining fertilizer to fields with adequate levels Only band application 25-40 lb/a P and K On fields that have the same soil test levels, applying fertilizer at 70% of the recommended rate on all acreage will provide a higher economic return than applying the full rate on 70% of field acres and none on 30% of the acres.

Situation Low testing soil but need to cut down fertilizer. Recommendation 300 lb. Only have 210 lb. (30% reduction) Field Recommended Rate lb/a Application rate lb/a (option 1) Application rate lb/a (option 2) 1 100 70 100 2 100 70 100 3 100 70 10

Fertilizer Grade A bag of 10-10-10 fertilizer contains 10 % nitrogen, 10 % phosphate and 10 % potash A bag of 46-0-0 fertilizer contains 46 % nitrogen, 0 % phosphate and 0 % potash A bag of 0-0-60 fertilizer contains 0 % nitrogen, 0 % phosphate and 60 % potash If the soil test recommendation is for 120 lb/a potassium, then use a 200 lb of potash (0-0-60).

N-P-K Fertilizers Common Fertilizer Grade Nutrient Cost $/ton fertilizer* Urea 46-0-0 N 564 Anhydrous Ammonia 82-0-0 N 785 UAN 28% N 385 Triple Super Phosphate 0-46-0 P205 614 Muriate of Potash 0-0-60 K20 630 Diammonium Phosphate (DAP 18-46-0 N and P 634 Monoammonium Phosphate (MAP) 11-48-0 N and P 704 Ammonium Polyphosphate 10-34-0 N and P 849 Bulk 19-19-19 N, P and K 615 Bulk 6-24-24 N, P and K 627 Bulk 16-35-5 + Zn + S N, P, K, Zn, S 726