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Fertilizer recommendations can be very confusing and it is hard to explain just exactly what the numbers mean, especially in writing, but I am going to make an attempt to do so in as few words as possible.
We’ll use a typical recommendation for a spring application of nitrogen on fescue as an example. That typical recommendation would be 70-30-30 and this is on a per acre basis. Just exactly what does that mean? This means that the blend must supply 70 units of actual nitrogen, 30 units of actual phosphorous and 30 units of actual potash per acre. The first number represents nitrogen. Always. The second number represents phosphorous. Always. The third number represents potash. Always. So when you see a recommendation, you will always know what nutrients the first three numbers represent.
These numbers do not represent the actual amount of material to be applied. What the numbers represent are the actual units of nitrogen, phosphorous and potash required on a per acre basis. The actual pounds of material used is going to depend on the material that is being used.
The four commonly used nitrogen sources and their nitrogen content includes urea at 46 percent nitrogen, ammonium nitrate at 34 percent nitrogen, anhydrous ammonia at 82 percent nitrogen and UAN (urea-ammonium nitrate solution) at 28 percent.
The two most commonly used sources of phosphorous in our area includes diammonium phosphate (DAP) at 46 percent phosphorous. This is a dry material and it’s analysis is 18-46-0. Ammonium polyphosphate is a liquid and it is 34 percent phosphorous and its analysis is 10-34-0. Remember that the first number of a fertilizer analysis is always nitrogen. Based upon this fact then 18-46-0 is 18 percent nitrogen and 10-34-0 is 10 percent nitrogen.
The only commonly used source of potash in our area is 0-0-60. This material is actually potassium chloride which is a salt. This material has no nitrogen or phosphorous in it at all as you can tell by the analysis but it is 60 percent potassium.
The lime recommendation is also sometimes misunderstood for the same reason. Normally, a lime recommendation is made on the basis of effective calcium carbonate or ECC. This recommendation represents the actual pounds of effective calcium carbonate needed per acre to neutralize soil acidity. The actual pounds of liming material to be used is going to depend upon the liming material being used but would nearly always be greater than the pounds ECC needed per acre.
Most ag lime in our area is about 60 percent effective calcium carbonate. Some lime sources can run as high as 97 percent ECC. The ECC of the liming material is determined by the fineness of the material and the calcium carbonate content of the liming material. So in our area the actual lime requirement is going to run about 1.67 times greater than the recommended effective calcium carbonate but this would not be true for a liming material that has a different ECC content than our normal ECC of 60 percent.
By now this should all be as clear as mud. The main point that I wanted to make is that the fertilizer recommendation that I make does not reflect the amount of actual material that is needed. The pounds of actual material needed will be greater than the total of actual nutrients needed and the total amount of fertilizer needed is going to depend upon the nutrient source that is being used. Call me at 724-8233 if you have any questions about this.
Fertilizer recommendations can be very confusing and it is hard to explain just exactly what the numbers mean, especially in writing, but I am going to make an attempt to do so in as few words as possible.
We’ll use a typical recommendation for a spring application of nitrogen on fescue as an example. That typical recommendation would be 70-30-30 and this is on a per acre basis. Just exactly what does that mean? This means that the blend must supply 70 units of actual nitrogen, 30 units of actual phosphorous and 30 units of actual potash per acre. The first number represents nitrogen. Always. The second number represents phosphorous. Always. The third number represents potash. Always. So when you see a recommendation, you will always know what nutrients the first three numbers represent.
These numbers do not represent the actual amount of material to be applied. What the numbers represent are the actual units of nitrogen, phosphorous and potash required on a per acre basis. The actual pounds of material used is going to depend on the material that is being used.
The four commonly used nitrogen sources and their nitrogen content includes urea at 46 percent nitrogen, ammonium nitrate at 34 percent nitrogen, anhydrous ammonia at 82 percent nitrogen and UAN (urea-ammonium nitrate solution) at 28 percent.
The two most commonly used sources of phosphorous in our area includes diammonium phosphate (DAP) at 46 percent phosphorous. This is a dry material and it’s analysis is 18-46-0. Ammonium polyphosphate is a liquid and it is 34 percent phosphorous and its analysis is 10-34-0. Remember that the first number of a fertilizer analysis is always nitrogen. Based upon this fact then 18-46-0 is 18 percent nitrogen and 10-34-0 is 10 percent nitrogen.
The only commonly used source of potash in our area is 0-0-60. This material is actually potassium chloride which is a salt. This material has no nitrogen or phosphorous in it at all as you can tell by the analysis but it is 60 percent potassium.
The lime recommendation is also sometimes misunderstood for the same reason. Normally, a lime recommendation is made on the basis of effective calcium carbonate or ECC. This recommendation represents the actual pounds of effective calcium carbonate needed per acre to neutralize soil acidity. The actual pounds of liming material to be used is going to depend upon the liming material being used but would nearly always be greater than the pounds ECC needed per acre.
Most ag lime in our area is about 60 percent effective calcium carbonate. Some lime sources can run as high as 97 percent ECC. The ECC of the liming material is determined by the fineness of the material and the calcium carbonate content of the liming material. So in our area the actual lime requirement is going to run about 1.67 times greater than the recommended effective calcium carbonate but this would not be true for a liming material that has a different ECC content than our normal ECC of 60 percent.
By now this should all be as clear as mud. The main point that I wanted to make is that the fertilizer recommendation that I make does not reflect the amount of actual material that is needed. The pounds of actual material needed will be greater than the total of actual nutrients needed and the total amount of fertilizer needed is going to depend upon the nutrient source that is being used. Call me at 724-8233 if you have any questions about this.
