Plants need fertilizers in different application rate 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.
Some farmers do not know fertilizers have application rates; most times farmers use the size of their hand 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.
Economic Importance Of Fertilizer Application.
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 the 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
Fertilizer 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 the 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 under dose 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.
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, that supplies only nitrogen and muriate of potash, it supplies only potassium.
Compound fertilizers: They 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
Nutrient percentage (%)
Calcium ammonium nitrate
Nutrient percentage (%)
Muriate of potash (MOP)
Sulphate of potash (SOP)
Single super phosphate (SSP)
Triple super phosphate (TSP)
Now, let us calculate the quantity of fertilizer to fertilize your farm.
There is a formula you will use to calculate the quantity of fertilizer required for a particular land size, it is:
Recommended rate (Kg/Ha) X 100
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.
Recommended rateKg/Ha) X 100
= 120 X 100
This quantity is in hectare (10000 sqm) and your land size is 350m2, hence, you need to adjust the calculation 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 350m2 of maize crop.
For TSP, using the same formula
Recommended rate (Kg/Ha) X 100
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 the urea fertilizer.
If 83.9kg of TSP is required to fertilize 10000sqm of maize, hence, Xkg of TSP will fertilize 350sqm of maize farm.
X= 83.3 x 350
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 on 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 maize population (233). Hence, you have 0.05kg or 50gram. Each plant on the plot will take 50grams of the 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.