Can you elaborate on your question please?

- What methods are you considering?

- "More reliable" requires a baseline comparison method, so what are you considering to be your standard method?

-When you say boundary-line do you mean a physical boundary of a tree plantation, or an asymptotic line drawn on a graph of nutrient concentration vs yield?

I suspect you will find as many answers as there are crop tree species, as each has it's own range of nutrient requirements at critical points in the annual cycle of flowering, fruiting and senescence.

Dear Ali Mohammed,

To optimize tree nutrition it is critical to get an optimized tree status and then determine the composition at the different growth stages.

Much of the optimized level can be found in composition literature.

I like to focus first on better attention to the soil condition by complete soil testing.

Foliar analysis can be used to see if the analysis is within optimized norms.

The use of remediating foliar applications can be monitored for reaction and testing can confirm the responses.

The recommendations are to start with a complete soil analysis and a soil nutritional balancing plan

Secondly review the literature for optimized foliar values at different phenological stages.

Third perform foliar analysis and pinpoint non optimized levels we are looking for bringing up deficiencies and identifying disbalances.

I would recommend working with most deficient and use foliar application with a observation and repeat analysis to confirm responses.

Target limiting nutrients and monitor the response and confirm it.

I like to target key nutrients under their threshold rather than get too much in diagnostic ratios of nutrients.

This approach has been very effective in my own work with diverse species.

Good luck on your project.

DRIS Analysis

I suggest you (1) CHNS analysis, (2) Flame photometry (k, Na, CA),

(3) SEM edx etc. for estimation of leaf nutrient concentration.

Method of burning. This is the most accurate.

I would recommend the Handbook of Reference Methods for Plant Analysis (Yash P. Kalra, 1998).

The boundary line approach improves the efficiency of plant analysis as it can be better adapted to regional site conditions. You can derive nutrient sufficiency ranges and nutrient relationships without the need for costly and time consuming calibration tests. But it should be considered that it is only valid if there is a cause and response (effect) relationship between two variables like yield and single nutrients.

The content of nitrogen, phosphorus and potassium in plant organs, including its leaves, should be determined by the Kurkayeva method.

If you want to derive critical foliar deficiency concentrations de novo, that is very different from starting with evidence from existing data bases, e.g. Pant Analysis Handbook IV, and refining that information. Such 'sufficiency' levels are typically for 'well-performing' crops, i.e. the size of the gap between the lower end of the sufficiency range, and deficiency, is unknown.

If there are no data for your chosen species, then take guidance from the nearest botanical relative for which data are known. That guidance will likely include sampling guidelines.

My definition of a critical level is that it can only usefully be estimated when all other elements are in sufficient supply. Otherwise one ends up with critical concentrations that are dependent on the status of other nutrients, which confounds the terminology and dilutes the usefulness of the data.

That definition may appear exacting in its prior requirements, but there are sufficiency ranges that apply very widely.

Lastly, in some varieties of cultivated plants differ considerably in their requirement for a particular element, and this seems more often to relate to minor/trace elements.

Last par should read: varieties of some cultivated ......

Circles of trees is best methods of optimum nutrients use efficiency as per recommended dose of particular trees

Consult the handbook " Handbook of Reference Methods for Plant Analysis (Yash P. Kalra, 1998)

Cate and Nelson method

If a nutrient response curve can be generated the foliar analysis at the top yield could be considered the optimized nutrient level.

You could get a good idea by using 0 fertilizer control half dosage full dosage and double doaage to get a yield response curve empirically.

At the optimized yield the foliar analysis would infer optimized nutrient level.

You might use a complete triple 15 with secondaries and micronutrients to get the curve.

You can also employ key nutrients to find threshold and excess levels.

Most people consult the literature and a range of values is given of each crop stage and this can be useful also.

The foliar analysis can be used to target the targeted use of nutrients and to analyze and monitor if remediation measures have been effective.

The color and health of the plant is a good indication of the optimized condition but requires sensitivity and measurements also.

The use of foliar analysis can be complemented with soil analysis and it is important to project goals and monitor responses to treatment.

Here is some litterature that looks at different diagnostic tools.

Parent, L. E., & Dafir, M. (1992). A Theoretical Concept of Compositional Nutrient Diagnosis. Journal of the American Society for Horticultural Science, 117(2), 239‑242.

Parent, S.-É. (2020). Why we should use balances and machine learning to diagnose ionomes. https://doi.org/10.22541/au.157954751.17355951

Parent, L. E., Rozane, D. E., Deus, J. A. L. de, & Natale, W. (2020). Chapter 12 - Diagnosis of nutrient composition in fruit crops : Major developments. In A. K. Srivastava & C. Hu (Éds.), Fruit Crops (p. 145‑156). Elsevier. https://doi.org/10.1016/B978-0-12-818732-6.00012-5

In sugarcane pant, the optimum level of nutrients concentration , 2-3 leaf blade of after first leaf of over head is better for maximum yield.

Consult the leaf concentrations found to be optimal in the literature.

Critical deficiency levels can be targeted by foliar fertilization.

Follow up making measurements of the foliar levels post applications.

Establish your own experiment using levels of fertilization and then taking production levels.

The level of the fertilization which optimizes the production level would be considered the optimized plant state.

Leaf concentration is most reliable of accurate and symptoms of sufficient and insufficient concentrations of essential nutrients. Most of the cereal crops, plant samples taken at younger plant stages