How To Calculate Fertilizer Application Rate For Any Crop

Some farmers do not know fertilizers have application rates; most times farmers use the size of their hands as a measure to apply fertilizers to their crops. This is not a good practice for any profit-oriented farmer as fertilizer application has huge economic importance. You will know how to calculate the quantity of fertilizer you need to apply to your farmland as you read through this article.

What is Fertilizer Application Rate

The fertilizer application rate is the amount of fertilizer per unit area (acre, hectare, etc.) or per unit volume. The rate is determined by the desired nutrient concentration and the nutrient release pattern of the fertilizer.

The amount of nutrients that a plant can use is limited by its ability to absorb them. The absorption process begins when water moves through pores in the soil and carries soluble nutrients into the root zone. The rate at which this happens depends on several factors, including soil texture and structure, pH, salinity levels, temperature, and aeration conditions.

Standards Of Fertilizers

Before we delve into learning how to calculate the fertilizer application rate for different crops, it is essential we know the standards of fertilizers. These standards are guides that will aid our calculation as we proceed.

  • The standard size of a bag of fertilizer is fifty (50kg) Kilogram.
  • Fertilizers are recommended in kilogram per hectare
  • One hectare equals 10,000sqm
  • 100kg of any fertilizer goes on one hectare.
  • The ratio of fertilizers, an example is NPK 15:15:15, is the composition of that nutrient element in every 100kg of that fertilizer.

These are the basic standards for applying any fertilizer. Similarly, we need to know the percentage composition of the nutrient element in different types of fertilizers.

Types Of Fertilizers And Nutrient Composition

There are two types of fertilizers, namely:

Single fertilizer: These are the types of fertilizers that supply just a single nutrient element. Examples are urea, which supplies only nitrogen, and muriate of potash, it supplies only potassium.

Compound fertilizers: These are those fertilizers that supply more than one nutrient element. An example is the NPK 15:15:15; it supplies Nitrogen, Potassium, and Phosphorus.

Fertilizers and percentage nutrients

Nitrogenous FertilizersNutrient percentage (%)
Ammonium nitrate34
Ammonium sulphate21
Calcium nitrate15
Calcium ammonium nitrate28
Potassium fertilizersNutrient percentage (%)
Muriate of potash (MOP)62
Sulphate of potash (SOP)50
Phosphatic fertilizersNutrient percentage
Single super phosphate (SSP)22
Triple superphosphate (TSP)48
Fertilizers and percentage nutrients chart

How To Calculate Fertilizer Application Rate

Now, let us calculate the quantity of fertilizer to fertilize your farm.

To calculate fertilizer application rate, first determine how much nitrogen, phosphorus and potassium your soil contains. You can do this by collecting soil samples from different parts of your field and sending them to a laboratory for analysis. If you don’t have access to a lab, there are many home kits available that can help you estimate nutrient levels in your soil.

There is a formula you will use to calculate the quantity of fertilizer required for a particular land size, it is:

Fertilizer application rate formula
Fertilizer application rate formula


  • The recommended rate is the quantity of fertilizer to be applied.
  • The concentration is the nutrient composition of the fertilizer you want to use.

Let us use maize as an example.

If you want to apply fertilizer on a maize plot of a land area, say 350sqm, at a recommended rate of 120kg of Nitrogen, 40kg of phosphorus, and 0kg of potassium.

You can use any of the fertilizers to meet this recommendation. In this context, let us use urea and TSP to satisfy his recommendation.

Mind you, you need to write out some parameters from this fertilizer recommendation.

  • The land area is 350m2
  • Urea has 46% Nitrogen
  • Triple super phosphate has 48% phosphorus.

Using the fertilizer application rate formula, you can calculate the amount of urea and phosphorus needed to satisfy the fertilizer recommendation of the maize plant.

For urea:

Recommended rateKg/Ha) X 100

Concentration (%)

= 120 X 100



This quantity is in hectare (10000 sqm) and your land size is 350m2, hence, you need to adjust the calculation in this simple analogy:

If 266.7kg is required to fertilize 10000 sqm of maize farm, therefore XKg would be required to fertilize 350sqm.

Xkg= 266.7 X 350



Hence, 9.3kg of urea is required to fertilize 350 m2 of maize crop.

For TSP, using the same formula

Recommended rate (Kg/Ha) X 100

Concentration (%)

40 X 100


= 83.9kg of TSP per hectare.

Do not forget you are fertilizing 350sqm; you will adopt the same analogy we did for urea fertilizer.

If 83.9kg of TSP is required to fertilize 10000 sqm of maize, hence, Xkg of TSP will fertilize 350sqm of maize farm.

X=        83.3 x 350


                       X= 2.91kg

Hence, 2.91kg of TSP is needed to supply phosphorus on 350sqm on a maize farm

Generally, to meet the fertilizer requirement on 350sqm of maize farm, you need 9.3kg of urea and 2.91kg of Triple superphosphate (TSP).

This is the general procedure for calculating the fertilizer application rate for any crop. You may want to determine the amount of fertilizer each plant will take.

It is simple…

Firstly, you need to determine the population of plants on your farm; for this example, the population of maize in an area of 350sqm is 233 maize plants. I used this plant population calculator.

Mix the fertilizers thoroughly, 9.3kg of urea and 2.91kg of TSP, making 12.21kg. Divide the amount of fertilizer (12.21kg) by the maize population (233). Hence, you have 0.05kg or 50 grams. Each plant on the plot will take 50 grams of fertilizer.

From this calculation, you can determine the quantity of fertilizer you need for a specific plot and the amount of fertilizer required by each plant on the farm.

Simple, isn’t it?

If you are not still getting it, you can hire the admin to help you with the calculation at an affordable cost.

Economic Importance Of Fertilizer Application.

Fertilizer application is a crucial post-planting operation in agriculture. The application rate of fertilizer can make you earn greatly or run into great losses; it depends on how you determine the fertilizer application rate. Plants need fertilizers at different application rates at different stages of their growth. Each fertilizer has its peculiar application rate. This application rate must be calculated accurately to get the precise quantity of fertilizer needed to fertilize the farmland.

Any activity or operation carried out during the process of crop production has economic importance; fertilizer application is not left out. Applying fertilizers plays a notable role in the economy of crop production; this I found imperative to discuss before the calculation of the application rates of fertilizers, not for any reason but to appreciate the effects or the benefits of applying fertilizers at the right quantity.

#1. Effects of fertilizer on the cost of production

Fertilizers can increase or reduce the cost of your production. One of the goals of production is the reduction of costs; hence, any strategy to achieve that must be adopted. Let us use maize as an example. Assuming the recommended fertilizer rate for maize on a hectare is 3 bags of NPK 15:15:15 using the right application rate; you can end up using 6 bags because you do not know how to calculate the fertilizer application rate for NPK 15:15:15, hence, you have ignorantly increased the cost of your maize production.

#2. Handling of fertilizer

The right application rate for any fertilizer can help you increase the efficiency of handling fertilizers. Using the maize fertilizer recommended rate as an example again, how three (3) bags of fertilizers would be handled is different from how the six (6) bags would be handled, in terms of bulkiness, transportation, and labour required.

#3. Effects of fertilizer on the environment

There is a disease called blue baby syndrome; this disease is caused by the presence of nitrate in the drinking water consumed by pregnant women. Fertilizers need to be applied with modesty; when you overdose the crop, the fertilizer will deplete the soil quality and drain down to contaminate the underground water. Similarly, when you underdose the crops, you have reduced the growth potential of the crop.

You just need to get the calculation of the application rate of fertilizer to make your production profitable and conducive to the environment.

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