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Fertilizer Guidelines
by
Don "Moe" Moeller,
Sales Agronomist
Much of the contained information is from the "WARDguide"
Click here for a pdf printable version
NITROGEN …. (N)
Estimated amounts of Nitrogen available from past legume plants:
Alfalfa .. good stand .. 100 pounds of "N" per acre |
Soybeans .. 40 pounds of "N" per acre |
Alfalfa .. average stand .. 50 pounds of "N" per acre |
Other Beans .. 25 pounds of "N" per acre |
Alfalfa .. poor stand .. 0 pounds of "N" per acre |
Clovers .. 75 pounds of "N" per acre |
Estimated amount of Nitrogen available from manure application:
Beef Feedlot .. 5 pounds of "N" per ton |
Swine .. 8 pounds of "N" per ton |
Dairy .. 8 pounds of "N" per ton |
Slurry .. 17 pounds of "N" per 1000 gallons |
Poultry .. 15 pounds of "N" per ton |
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Figuring Nitrogen need for corn:
Factors to consider when figuring Nitrogen need for corn:
- Corn nitrogen need (factor) is 1.33 pounds of "N" per bushel goal. **
- Subsoil factor 0.3
- Surface-soil ppm (parts per million) .. Surface soil depth is usually to 8 inches.
- Sub-soil depth ppm .. Usually up to 3 foot depth. Note if sub-soil ppm is unknown, as a rule of thumb use 5 ppm for fine textured soils and 2 ppm for sandy soils.
- Nitrogen that may be available from other sources after soil test was taken such as manure or other crop grown.
- The nitrogen requirement for corn is figured by (1) multiplying the crop yield goal by nitrogen requirement, 1.33 ** .
- Calculate the amount of Nitrogen available in the surface-soil by multiplying the ppm from the soil test by both the subsoil factor (0.3), and the soil depth in inches at which the soil samples were taken.
- Calculate the Nitrogen available in the sub-soil by multiplying the ppm from your soil test, (or use the 5 ppm or 2 ppm factors mentioned above if no sub-soil test was made) by both the subsoil factor (0.3) and the soil depth in inches at which the sub-soil test was taken.
- Nitrogen need is then calculated by taking the corn Nitrogen requirement figure and
subtracting the Nitrogen available in the surface-soil, and
subtracting the Nitrogen available in the sub-soil, and also
subtracting the Nitrogen available in the soil from other crops or manure applications.
** (NOTE: Some researchers feel if adequate nitrogen carryover is in the first three feet of soil, then .8# of added N is the figure to use for each bushel of your yield goal)
PHOSPHORUS …. (P2O5)
Each soil test range is an estimate of "sufficiency". Sufficiency is the range of possible yield as determined by the ppm level. The percent sufficiency ranges for phosphorus soil tests are as follows:
Soil Test, Phosphorus ppm |
% Sufficiency (% of expected standard yield |
0 - 5 ppm |
25% - 50% of standard yield could be expected |
6 - 12 ppm |
45% - 80% of standard yield could be expected |
13 - 25 ppm |
70% - 95% of standard yield could be expected |
26 - 50 ppm |
90% - 100% of standard yield could be expected |
51+ ppm |
100% of standard yield could be expected |
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Soil Phosphorus Level, ppm
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|
|
0 - 5 ppm |
6 - 12 ppm |
13 - 25 ppm |
26 - 50 ppm |
51+ ppm |
Standard
yield level |
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|
Pounds of P2O5 needed to add to bring up to standard yield level |
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|
Irr. Corn |
70 - 100 |
45 - 60 |
25 - 40 |
0 - 20 |
0 |
120 bu |
2 lb / 10 bu |
Dryl. Corn |
65 - 90 |
40 - 50 |
20 - 35 |
0 - 20 |
0 |
95 bu |
2 lb / 10 bu |
Corn Silage |
70 - 100 |
45 - 65 |
25 - 45 |
0 - 20 |
0 |
12 ton |
1.5 lb / ton |
Soybean |
50 - 70 |
35 - 45 |
20 - 30 |
0 - 15 |
0 |
35 bu |
5 lb / 10 bu |
Irr. Milo |
60 - 80 |
40 - 55 |
15 - 35 |
0 - 20 |
0 |
100 bu |
2 lb / 10 bu |
Dryl. Milo |
55 - 70 |
35 - 50 |
15 - 30 |
0 - 15 |
0 |
75 bu |
2 lb / 10 bu |
New Alfalfa |
90 - 120 |
60 - 85 |
30 - 55 |
0 - 25 |
0 |
3 ton |
5 lb / ton |
Est. Alfalfa |
90 - 120 |
60 - 85 |
30 - 55 |
0 - 25 |
0 |
4 ton |
5 lb / ton |
Estimated amount of Phosphorus available from manure application:
Manure ……. Pounds of P2O5 |
Manure ……. Pounds of P2O5 |
Beef Feedlot .. 4 pounds / ton |
Swine .. 5 pounds / ton |
Dairy .. 4 pounds / ton |
Slurry .. 13 pounds per 1000 gallons |
Poultry .. 15 pounds / ton |
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POTASSIUM …. (K2O)
Each soil test range is an estimate of "sufficiency". Sufficiency is the range of possible yield as determined by the ppm level. The percent sufficiency ranges for potassium soil tests are as follows:
Soil Test, Potassium ppm |
% Sufficiency (% of expected standard yield |
0 - 40 ppm |
20% - 50% of standard yield could be expected |
41 - 80 ppm |
45% - 80% of standard yield could be expected |
81 - 120 ppm |
70% - 95% of standard yield could be expected |
121 - 200 ppm |
90% - 100% of standard yield could be expected |
200+ ppm |
100% of standard yield could be expected |
Estimated amount of Phosphorus available from manure application:
Manure ……. Pounds of P2O5 |
Manure ……. Pounds of P2O5 |
Beef Feedlot .. 10 pounds / ton |
Swine .. 12 pounds / ton |
Dairy .. 12 pounds / ton |
Slurry .. 34 pounds per 1000 gallons |
Poultry .. 15 pounds / ton |
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Soil Potassium (K2O) Level, ppm
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0 - 40 ppm |
41 - 80 ppm |
81 - 120 ppm |
121 up to 200 ppm |
200 + ppm |
Standard
yield level |
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Pounds of K2O needed to add to bring up to standard yield level |
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Irr. Corn1 |
105 - 180 |
60 - 100 |
35 - 55 |
15 - 30 |
0 |
120 bu |
5 lb / 20 bu |
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Dryl. Corn |
100 - 175 |
55 - 95 |
30 - 50 |
0 - 25 |
0 |
95 bu |
5 lb / 20 bu |
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Corn Silage |
135 - 220 |
80 - 130 |
50 - 70 |
30 - 45 |
0 |
12 ton |
2 lb / ton |
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Soybean |
90 - 145 |
55 - 85 |
30 - 50 |
0 - 25 |
0 |
40 bu |
6 lb / 10 bu |
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Irr. Milo |
75 - 120 |
50 - 70 |
30 - 45 |
15 - 30 |
0 |
100 bu |
5 lb / 20 bu |
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Dryl. Milo |
70 - 115 |
45 - 65 |
25 - 40 |
0 - 20 |
0 |
75 bu |
5 lb / 20 bu |
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New Alfalfa |
130 - 210 |
80 - 125 |
45 - 75 |
25 - 40 |
0 |
3 ton |
6 lb / ton |
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Est. Alfalfa |
130 - 210 |
80 - 125 |
45 - 75 |
25 - 40 |
0 |
4 ton |
6 lb / ton |
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SULFUR (SO4)
- Research has found that organic matter is a good supplier of sulfate-sulfur. It is estimated that approximately three pounds of sulfate-sulfur is released annually from each percent organic matter.
- Irrigation water is also an important source of sulfate-sulfur. Irrigation water should be considered a possible source of Sulfur. Sulfur fertilizer generally does not produce a yield increase on any soil when the irrigation water contains more that 8ppm SO4-S. The possible exception to this is sandy soils.
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0 - 2 ppm |
3 - 4 ppm |
5 - 7 ppm |
8 - 12 ppm |
13+ ppm |
Standard
yield level |
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Pounds of P2O5 needed to add to bring up to standard yield level |
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|
Irr. Corn |
18 - 24 |
11 - 16 |
0 - 9 |
0 |
0 |
150 bu |
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Dryl. Corn |
8 - 15 |
0 - 7 |
0 |
0 |
0 |
95 bu |
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Corn Silage |
18 - 24 |
11 - 16 |
0 - 9 |
0 |
0 |
20 ton |
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Soybean |
12 - 17 |
5 - 10 |
0 |
0 |
0 |
40 bu |
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Irr. Milo |
16 - 21 |
9 - 14 |
0 - 7 |
0 |
0 |
140 bu |
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Dryl. Milo |
4 - 9 |
0 |
0 |
0 |
0 |
75 bu |
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New Alfalfa |
22 - 27 |
14 - 19 |
6 - 11 |
0 |
0 |
5 ton |
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Est. Alfalfa |
35 - 40 |
27 - 32 |
17 - 22 |
0 - 14 |
0 |
7 ton |
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ZINC (Zn)
- Some crops are more responsive to Zinc than others.
- Zinc is an immobile plant nutrient; therefore it should be incorporated into the soil.
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0 - .25 ppm |
.26 - .50 ppm |
.51 - 1.00 ppm |
1.01+ ppm |
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Standard
yield level |
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Pounds of Zinc needed to add to bring up to standard yield level |
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Irr. Corn |
8 - 10 |
6 - 8 |
1 - 5 |
0 |
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Dryl. Corn |
8 - 10 |
6 - 8 |
1 - 5 |
0 |
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Corn Silage |
8 - 10 |
6 - 8 |
1 - 5 |
0 |
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Soybean |
8 - 10 |
6 - 8 |
1 - 5 |
0 |
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Irr. Milo |
8 - 10 |
6 - 8 |
1 - 5 |
0 |
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Dryl. Milo |
5 - 7 |
3 - 5 |
0 - 2 |
0 |
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New Alfalfa |
1 - 3 |
0 |
0 |
0 |
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Est. Alfalfa |
1 - 3 |
0 |
0 |
0 |
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IRON
Iron Soil Test, ppm |
Rating |
Comments |
0 - 2.5 ppm |
Low |
Many crops show Iron Chlorosis |
2.6 ppm - 4.5 ppm |
Medium |
Iron sensitive crops such as milo show Chlorosis |
4.6 ppm - 10.0 ppm |
High |
Lawns may show Iron Chlorosis |
10.1+ ppm |
Very High |
Iron is adequate for all crops |
Low Iron soils are ones that usually have a high pH, low organic matter and excess lime. Application of Ferrous (iron) Sulfate or iron chelate may help to correct this problem. Treatment methods include iron compound additions to the starter fertilizer or foliar application.
LIME
- Lime is applied to the soil to reduce acidity. Soil acidity is determined by soil pH, the lower the pH number is, the more a soil may need to be limed.
- Soils higher in clay and organic matter will require higher amounts of lime.
- Lime applications are used to neutralize low pH soils, or move the soil pH factor up to 6.5 / 7.0.
- Two factors affect the neutralizing value of lime. One is calcium carbonate equivalence (CCE) which is the purity or percent calcium carbonate. The other is the fineness of the grind. Limestone ground to pass through a 60-mesh screen is considered 100% effective and limestone that passes through a 8-mess screen is 50% effective.
- The rate of application is determined by dividing the suggested EEC rate per acre by the percent EEC of the lime being applied. The equation is:
Ag Lime Application
(ECC/Acre Recommended) / (% ECC of Ag Lime X 100
- Lime should be applied well enough in advance of planting to insure adequate incorporation.
- The suggested rates of lime are based on neutralizing 8 inches of soil.
- Research in some states indicates the top 2 inches of soil may become very acid after the use of reduced tillage. In some cases, the application of ¼ the lime amount recommended could be applied every two years to maintain the desirable range.
Crop pH ranges:
CROP |
DESIRED Ph range |
Irr. Corn |
5.7 - 8.3 pH |
Dryl. Corn |
5.7 - 8.3pH |
Corn Silage |
5.7 - 8.3 pH |
Soybeans |
6.1 - 8.3 pH |
Irr. Milo |
5.7 - 8.0 pH |
Dryl. Milo |
5.7 - 8.0 pH |
New Alfalfa |
6.1 - 8.3 pH |
Estalished Alfalfa |
6.1 - 8.3 pH |
When soil pH is less then the desired range, the grower should consider liming. (Irrigators should be aware of the calcium and magnesium content of their irrigation water. Many times there is enough “lime” in the water to compensate for the lime need.
Buffer pH |
Tons of EEC* per acre |
Tons of Ag Lime at 60% EEC |
7.0 |
0.4 |
0.7 |
6.9 |
0.4 |
0.7 |
6.8 |
0.9 |
1.5 |
6.7 |
1.4 |
2.3 |
6.6 |
1.8 |
3.0 |
6.5 |
2.3 |
3.8 |
6.4 |
2.7 |
4.5 |
6.3 |
3.2 |
5.3 |
6.2 |
3.6 |
6.0 |
6.1 |
4.1 |
6.8 |
6.0 |
4.5 |
7.5 |
* This amount will bring the soil pH to 6.5 |
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