MSU Fertilizer Recommendations for Field Crops Phosphorus and Potassium
MSU Fertilizer Recommendations for Field Crops Phosphorus and Potassium Michigan’s agronomic, economic and environmental implications Soil Test Interp...
MSU Fertilizer Recommendations for Field Crops Phosphorus and Potassium Michigan’s agronomic, economic and environmental implications Soil Test Interpretation
Agronomic Considerations on Michigan Farms
Economic Considerations on Michigan Farms
Economic Considerations on Michigan Farms 1000 900
Urea
800 Diammonium Phosphate (DAP)
$/Ton
700 600
Monoammonium Phosphate (MAP)
500
Potash
400
Anhydrous Ammonia
300 200 Oct-11
Urea-Ammonium Nitrate (UAN) Nov-11
Dec-11 Month-Year
Jan-12
Feb-12
Environmental Implications on Michigan Farms Potential N and P in the surface water (Great Lakes) and Groundwater
MSU Fertilizer Recommendations
Phosphorus and Potassium The key ingredients: • Buildup and Maintenance Model • Soil Test Information • Yield Goal
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
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
ppm 30 Critical level - Soil test level to achieve economic optimum (95-97% of the maximum yield) 0
15
45
Buildup and Maintenance Approach
Buildup and Maintenance Approach
0
15
30 ppm Critical level - Soil test level to achieve economic optimum (95-97% of the maximum yield)
45
Buildup and Maintenance Approach
Phosphorus and Potassium Crop 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
Buildup and Maintenance Approach
MSU recommended P fertilizer practices Soil Test Level
Recommended Fertilizer Rate
Buildup range (< Critical level)
Apply rates to buildup to critical level plus crop removal rate
Maintenance range (Critical level)
Only apply crop removal rate
Drawdown range
only starter P or No Phosphorus
Buildup and Maintenance Approach
Soil Test Lab Report The bar chart closely corresponds to the
Potassium is positively charged and attracted to clay or organic matter (Limited losses to environment)
Average soil test P levels from Michigan farm Medium P at Soil Test in Michigan fields tested MSU fromLevels 1962- 2007 100
55ppm
50
25
20 07
20 02
19 97
19 92
19 87
19 82
19 77
19 72
19 67
0
19 62
Bray P1 in ppm
75
P CRITICAL LEVELS
Relative Yield (%)
100 90 80 Corn & Soybean Wheat & Alfalfa
70 60 50 0
10
20
30
40
50
Bray P-1 Soil Test Phosphorus (ppm)
60
P and K Management Considerations • P in soil – Many years to build-up and drawdown • P and K can be applied in the fall or spring (Fall K fertilizer applications on sandy soils with low organic matter are discouraged) • 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) • Fertilizer prices MAY continue to increase in 2012 planting season (out of season purchasing options)
Why soil pH is important?
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
