It is depending on the soil type and what is being grown.

There is a large gradient between one crop and another, and between soil type and another.

Regards

Dear Mr. Jamal Elfaki

Thank you for your answer but in general what would be the range because im trying to build a system that reads those values colorimetrically in different soil types. so if there was a range what would it be? I believe nitrate is expected to have a range between 0-35 ppm.

The critical level of them N as nitrate in soil solution =50 ppm , P = 5 ppm and K =180 ppm but the are differing among soils ,in additional to the role of environmental factor in limiting them,for example in calcareous soil and the soils which contains 2:1 clay minerals and high Ca and Mg content the critical value of N and K are increasing ,on the other hand if 1:1 clay minerals dominates in the soil the critical value of P will increases since 1:1 clay minerals fix large amount of P in comparing with 2:1 clay minerals .

Dear Prof. Dr. Akram

Thank you for the information.

Levels

The normal background level of nitrates in soil not fertilized or used for commercial crops ranges from 5 to 10 parts per 1 million (ppm). Optimum nitrate level for soil used for corn (Zea mays) production is more than 25 ppm. Nitrate levels between or higher than 25 ppm to 30 ppm are sufficient to grow plants in a vegetable garden.

But it will depend upon several factors like soil type and climatic conditions etc.

Could you please share some scientific papers on this. I am currently working on fertilizer management for smallholder maize production in western Kenya as part of my MSc thesis

The critical value depends on soil type of soils and type of clay minerals chemical for example in calcareous soil:

nitrogen critical level in form of Nitrate = 50 ppm

phosphorus critical level =7 ppm but depending on international measures = 5 ppm.

potassium critical value =180 ppm.

But for phosphorus there is fluctuation in this value depending on environmental condition for example in some studies in India the value is 2 ppm , in iraq the critical level of P determined by on of my MSc student the value was 3ppm but the soil was covered with snow for long time of the experiment

Hi

https://www.canr.msu.edu/foodsystems/uploads/files/soil_test_interpretation.pdf

may be useful.thanks

I would like to know basic rank of my soil according to the result of soil analysis of total NPK, available NPN, OC. Means high, or medium or low in soil nutrient based on the result.

still not clear

quantification is still required

Environmental factor and type or plant cultivar also related to the NPK range.

NPK is in the proportion of 4:2:1 as a ideal condition.

But as we know india comes under the tropical zone of earth....our soil lacks the nitrogen content ....so many time we have to fertilize it with the rich nitrogen fertilizer IKEA uriya...and that's why that ratio change to 8:1:0.5

In actual condition

the critical level is differing depending on environmental condition , soil type, plant type method of extraction:

in general

1- For nitrogen as NO3 =50 ppm

2- For p = 5ppm depending on international value , =7 ppm as Iraqi standard in Indian =2ppm in the results of my MSC student was 3.50 ppm

3- For potassium = 180 ppm

more detailed information in this regard is required and ready to interpret for the researchers