Hi Karun,

The effect of NPK will also depend upon the type of leaf samples you have considered in your analysis. For instance, the Leaf area index (LAI) plays an important role in radiation capture, crop growth, and yield formation.

Perhaps, the following paper may help you:

https://academic.oup.com/femsec/article/90/1/195/2680501

Article NPK-fertilizer efficiency – A situation analysis for the tropics

cheers

@ Karun, it varies with crop to crop therefore very difficult to generalize. But on an average, N and P concentration is increased with the crop age till critical growth stage. But K concentration is generally higher at the initial stages, later on it declines.

In most of the fruit crops, we have observed N and P increased from pre- anthesis stage to mid fruit development stage and K followed an increasingvtrend untill physiological maturity of fruits. The concentration maxima N , P and K is judged through a stage , it is not affected by their redistribution in developing tissues...

Lemons need more phosphorus than do oranges. Phosphorus deficiency causes low assimilation rate, diminishes vegetative, growth. Potassium is present in all the plant parts but is found in large quantities in leaves and in the growing points. When potassium content of leaves increases the content of many other.

Lemons or acid limes , all plants having seedy fruits need more phosphorous than any other nutrients...

These contents vary according to the stage of growth or development of the plant.

It depends on the growth stage of the crop. Other crops may have high NPK content at flowering stage .......

Considering above comments and my experience with some greenhouse crops like tomato and cucumber, I have experienced that P demand is almost consistent throughout the cropping period, N demand increases slightly increase, while K demands becomes almost double as growth stage advanced, so plant tssue contents do change. Hence, these definitely vary according to the crops, growth stages, and growing behavior of crop (determinate or indeterminate) and so on.

There are number of investigation of on level npk increasing with lower growth of plant while level npk decreasing with highest growth of plant

Generally, the nutrient content of leaves or foliage will be increased with increasing age of the crop and attain maximum level during the active vegetative stage and decrease when the crops attain maturity.

Let me simplify this complex story as much as possible. You asked about 'amount' and if is really what you wanted to know, the amount increases as the biomass increases, while the roots continue to function.

Concentrations are a complex as others have suggested. That is why standard foliar sampling protocols have been developed.

Let me point out a simple perspective about plants growth, biomass and nutrients accumulation (not concentration, which is a relative unit of mass : mass fraction, e.g., g/kg for macro and mg/kg for micronutrients). As long as plant is still growing (either at vegetative or reproductive phenological stages), taking up nutrients and water, there is an increasing of biomass accumulation (dry matter yield), as well as an augmenting nutrient accumulation rate - nutrient uptake rates. On the other hand, considering nutrients concentration/content variation, in the plant tissues - notably in the leaves -, during plant development, generally speaking, nutrients with very low mobility in phloem (e.g., Ca, S, *B, Cu, Fe, Mn, Ni and Zn) tend to increase in the old tissues as function of time course of plant development, while nutrients with high mobility in phloem (N, P, K, Mg, Cl and *Mo) tend to decrease its concentration. *OBS: for a most plant species.

Most plants take up little nutrients when young. The uptake then accelerates at vegetative phase ( near linear growth in uptake), it reaches a peak in the accumulation of NPK in its foliage. The next phase is a decline in the accumulation of the nutrients. It therefore tends to follow the sigmoid curve that is followed by plant growth.