Please describe the test kit, what it measures and the basis of the fertiliser recommendation.

There is a huge literature about 'calibration' relations between soil test values and fertiliser requirements. There are very large differences in such relations between soils and environments, unless you are dealing with simple properties such as salinity and acidity. You would be lucky indeed to find an existing set of fertiliser calibrations that suit your purpose. Whatever experiment you do it would be a good idea to take suitable foliar samples and have them tested for a complete suite of nutrients and common mineral toxins so that you can interpret the biomass data.

Paul Milham thank you for the response. The soil test kit that I used is the one that is commonly used in the garden. I already generated the result of the N, P, and K using the kit. Suppose, I wanted to know if there is a recommended equivalent of the generated qualitative data into quantitative data so that I can compute the amount of fertilizer that I will use using the recommended rate of the crop.

The short answer is no. However, you could look up the concept of crop logging. To apply it you would need to guess the 'efficiency' factor for each nutrient.

That is the nature of soil testing in an unknown environment.

Yes, it is possible to convert the qualitative result description generated from a soil test kit into a quantitative equivalent. However, the conversion process depends on the specific soil test kit and the type of measurement being made.

For example, some soil test kits use colorimetric methods to determine the concentration of nutrients in the soil. In these cases, the color of the test solution is compared to a color chart to determine the nutrient concentration. The color chart may provide a range of values or concentrations for each color, allowing the user to estimate the nutrient concentration in their soil sample.

Other soil test kits may use electrical conductivity or pH measurements to determine soil properties. These measurements can be quantified using standard units of measurement, such as millisiemens per centimeter (mS/cm) for electrical conductivity or pH units for soil acidity or alkalinity.

In general, it is recommended to consult the user manual or contact the manufacturer of the soil test kit to determine if a quantitative equivalent is available and how to convert the qualitative result description into a quantitative measurement.

Soil test kit generated soil test values are generally qualitative.Some are quantitative if some instruments are used in the analysis.Even then,the soil test kit generated soil test values may be lower than the regular Soil Testing Lab values.To use the recommendations developed by Agricultural Universities, first quantitative relationships have to be developed using regression models on large volume of data generated by both methods.This task has to be taken up by individual State Agricultural Universities by using more popular rapid soil test kit or kits approved by their Government. It is very difficult to develop quantitative relations between many soil test kits available in the market and regular laboratory soil test values and then use the recommendations developed by the State University.

if and only if the crop response location specific fertilizer trial has done

One of the most important qualitative attributes related to fertilisers application is concerning the soil health;

I think there is several approaches to quantitative it, for example soil CO2 measuring, that's arising from soil biota activities which are an important indicator for soil health.

Or measuring the abundance and species enrichment of soil biota communities.

In our case we didn't do this process, usually, we determined the rate of fertilizers according to two factors, fertilizer soil content, and recommendation applied. But I think doing quantitative is very useful to precisely determine the needs of fertilizer for the crop.

#Basically, Fertilizer recommendations should be site specific and soil test based!

# soil fertility is the totality of physical, chemical and biological fertility of a soil!

# physical fertility can be identified qualitatively from the diagnostic property and materials!

# But quantitative fertilizer recommendations is essentially dependant on the soil analysis result!