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January 2011
Math Anxiety: Fertilizer Calculations
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OU MAY KNOW people who suffer from math anxiety.
They avoid situations where mathematics and calculations are required. However, avoiding math is simply not an option when working with agriculture.
The International Plant Nutrition Institute (IPNI)... in cooperation with university specialists...has recently published a “how-to” workbook that presents commonly used mathematical concepts in agriculture. It begins with simple arithmetic and advances all the way to complex modeling. More details are available at the end of this newsletter. Most of us do not use sophisticated math on a regular basis, but a review of commonly performed calculations will be the subject of this and future INSIGHTS. We’ll start with some of common calculations that are made when dealing with fertilizers.
Fertilizer Notation
Commercial fertilizers are required to show on their label the minimum percentage of nutrients that the manufacturer guarantees to be present. The chemical analysis is composed of at least three numbers separated by dashes. The first number indicates the percent N, the second number indicates the percent P as P2O5, and the third number shows the percent K as K2O based on weight.
The nutrient content of the fertilizer is indicated by these three numbers, but the tradition of using the oxide form of P and K can be a bit confusing and is set in fertilizer law. From the percent N value on the label, it is not obvious if the N is present as nitrate, ammonium, or urea. Similarly, the P in most commercial fertilizers is chemically present as phosphate (PO4), but this number is mathematically converted to P2O5 equivalents for display on the fertilizer label. Potassium fertilizers are never present as K2O, but the K present in the fertilizer is mathematically
Dr. Robert Mikkelsen
Western North America Director
International Plant Nutrition
Institute (IPNI)
4125 Sattui Court
Math Anxiety: Fertilizer Calculations
Y
OU MAY KNOW people who suffer from math anxiety.
They avoid situations where mathematics and calculations are required. However, avoiding math is simply not an option when working with agriculture.
The International Plant Nutrition Institute (IPNI)... in cooperation with university specialists...has recently published a “how-to” workbook that presents commonly used mathematical concepts in agriculture. It begins with simple arithmetic and advances all the way to complex modeling. More details are available at the end of this newsletter. Most of us do not use sophisticated math on a regular basis, but a review of commonly performed calculations will be the subject of this and future INSIGHTS. We’ll start with some of common calculations that are made when dealing with fertilizers.
Fertilizer Notation
Commercial fertilizers are required to show on their label the minimum percentage of nutrients that the manufacturer guarantees to be present. The chemical analysis is composed of at least three numbers separated by dashes. The first number indicates the percent N, the second number indicates the percent P as P2O5, and the third number shows the percent K as K2O based on weight.
The nutrient content of the fertilizer is indicated by these three numbers, but the tradition of using the oxide form of P and K can be a bit confusing and is set in fertilizer law. From the percent N value on the label, it is not obvious if the N is present as nitrate, ammonium, or urea. Similarly, the P in most commercial fertilizers is chemically present as phosphate (PO4), but this number is mathematically converted to P2O5 equivalents for display on the fertilizer label. Potassium fertilizers are never present as K2O, but the K present in the fertilizer is mathematically
Dr. Robert Mikkelsen
Western North America Director
International Plant Nutrition
Institute (IPNI)
4125 Sattui Court