Easy Calculate Amount of Fertilizer for a Given Volume
Many a time’s new farmers are confronted with how much of a fertilizer to add to water to make a known PPM strength. There are a number of ways to so calculate. Some are rough measurements and some are very precise computer controlled methods. However, what I use is a small formula for such measurements. The formula is:
Formula for measuring individual fertiliser element in a fertigation solution:
Amount of fertilizer to make one volume = A
Desired concentration ———————— = X
Percentage of required fertilizer ———– = P
Then: A = X / P x K, where K is a constant depending on the units used e.g. K = 75 if units are ounces per gallon; K = 1200 if units are pounds per gallon and K = 10 if units are grams per liter.
Here, before going further in our calculations, let us remember that chemical fertilizers are described as NPK quantities, N being Nitrogen, P being Phosphorous and K being Potassium. A fertilizer mentioned as 20-20-20 NPK means 20% N, 20% P2O5 and 20% K2O. So it means this fertilizer has 20%N, 20% P2O5 and 20% K2O. Further –
%K = % K2O/1.2 and % P = % P2O5/2.3
Therefore, this fertilizer has actually N= 20%, P = 8.7% and K = 16.67%
Shall we do a little calculation – assume we require a concentration of 200 PPM of nitrogen to be given to our crop with a given volume of water. Let us calculate for one liter of water how many gram of this fertilizer to be mixed to get a concentration of 200 PPM of nitrogen. Apply to our equation above
A = 200 /20 (%of N) x 10 = 1 gm. / liter
Now if farmer requires 1000 liters of water to irrigate, he needs 1gm x 1000 = 1000 grams of fertilizer.
The concentration for P or K is also carried out in the same manner taking care to first calculate P% and K%.
If two or more types of fertilisers are being used, then total PPM needs to be added for each of the fertilisers used. As an example if 20-20-20 and 13-0-45 are being used, the concentration of N and K in both would be additive and of P remain same.
Do interact if you have any suggestions or comments or modifications which you are using.
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Why my bottlegourd is wilting
O.K. it would be helpful to have a photo to determine if it is due to disease or pests. meantime as it is winter, helpful to have a 1% spray with a fertiliser having phosphate like 12-61-0.
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great to see your interest. I am presently out of my place and take me sometime due to covid, but hope to reply soon. thanks.
A general way of meeting the fertilizer needs of capsicum has been given in my blog. This is done in two parts. The first is in-bed preparation for plants. The blog suggests 20:25:20 NPK per acre to be realized by giving 80 kg Ammonium Nitrate, 125 kg Super Phosphate and 32 kg Murate of Potash (or 40 kg Sulphate of Potash). The nitrogen should be given in two or three installments and the rest in the beginning. In the second instance, after planting is done, sprays of calcium nitrate and potassium nitrate are given at intervals of 2 to 3 weeks @ 3 gm/ltr.
Please I have stressed that you should first get your soil and water analyzed. And adjust fertilization quantity. Measure pH and e.c. regularly. Modify your sprays if required. Ph range 6 to 6.5.
Please go through the FERTIGATION section on my site for more information.