It should be since it is based on plant requirements.  We have used traditional leaf analysis of corn in a study that included organically grown corn (maize) to compare nitrogen uptake in organic and conventional systems.  None of the reviewers questioned that and I would have been surprised if they did.  If interested, the publication is available on my RG site.  Title: "Long-Term Agronomic performance of organic and conventional field crops in the mid-Atlantic region"

https://www.researchgate.net/publication/43270357_Long-Term_Agronomic_Performance_of_Organic_and_Conventional_Field_Crops_in_the_Mid-Atlantic_Region

Article Long‐Term Agronomic Performance of Organic and Conventional ...

Should be ok if you have proper controls

Yes I concur, especially for available nutrients

I appreciate your attention and information. Thank you!

Its OK, leaf analyses is applicable to most of the category of plants; however, if you would like to see the micronutrients and heavy metal accumulation (if any, through organic source) status, then tissue analyses of other plant parts viz. pods, stem, petiole etc. and underground parts for tuber crops may be conducted to have fair idea of nutritional status in plants.

Hi Fabio. In 2006-2007 we looked to some differences in organic vs conventional plastic sheltered vegetables (tomato and green pepper), as well into the field. Although we expect some, there were no significant changes. Soils were ok but bad weather occurred in both years. Moreover, the cellular sap pH into the leaf was observed. I don't have a current document in English but I think you can handle the Romanian one (as a Latin language), into the tables I attach. Regards. S

Leaf analysis is ok because the organic nutrients will be mineralized first before ic anc be absorbed by the plants

I appreciate your attention and information. Thank you!

Hi Sorin Liviu Stefanescu. Thank you for forwarding the document

Although I agree with most of what has been said already, allow me to add a few comments as some colleagues suggested analysing the total plant.

When using plant / tissue analysis as a diagnostic tool – and this I think was the intention according to the original question – a full analysis of the total plant is not called for. However, when used for diagnostic purposes, it’s essential that reference values (critical values) are available, and that the appropriate tissue / organ is sampled at the correct developmental for which the critical values have been developed.

In case such values are not available, a well-fertilised field may be considered as a ‚control‘, although this is not ideal and could lead to misinterpretations due to oversupply with some nutrients.

All these answers referred to the mineral nutrient status only. Additional features (e.g. growth stimulating bacteria, root morphological effects of Azospirillum) often discussed in relation to organic fertilisers like composts etc are not covered. However, as far as consequences of such effects on the nutrient uptake and nutritional status are concerned, they would still be picked up by the leaf / tissue analysis.

The internal needs and nutrient balance of the plants are not supposed to depend on the agricultural system we use or on the origin of the nutrientes (already in mineral form, mineralised, directely absorved or with the intervention of microorganisms). So, and considering most of the remarques already done, my opinion is yes, you can leaf analysys as a diagnostic tool to assess the nutritional  status of plants cultivated in organic farming systems.

Yes, Definitely.

Why not?

Several factors act in determining the productivity of crops, besides the specific type of nutritional management or cultural practice applied. So the standards of critical values of leaf nutrient concentrations should be interpreted critically as they have limited utility when used for different tillage systems (conventional x mineral or organic fertilization and organic fertilization, for example). Do you think a definition of critical levels of leaf disabilities and excess specific for each management system would be needed?

After Reading all contributions, I agree with most of them. The case of esential nutrient could be solved with rutinary analysis. Other question is the composition of plants in trace elements (not nutrients). The adition of Synthesis products (fertilizers, Phitosanitaries, sewage sludge...) can hardly modify the geochemical fingerprint of the soil in the plant. Many publications on this topic can be seen in my profile.

Absolutely Fabio,

However do remember that leaf analysis reports percentage & ppm dry weight and this method of reporting does not take account of the growth induced dilution effect. This is why we prefer to identify ideal nutrient ratios in leaf analysis (see recently published paper on kiwifruit leaf analysis nutrient ratios) .

Recently I compared the leaf nutrient ratios for the top yielding Organic Hayward Kiwifruit with those for the top yielding conventional  and there was virtually no difference.

As João said "The internal needs and nutrient balance of the plants are not supposed to depend on the agricultural system we use or on the origin of the nutrientes" because the needs of plants are the same (or nearly 'cause in organic production, the yields are not the same) so traditional leaf analysis is a good way to assess the nutritional status of plants fertilized, organic or not. But usually, it is combine with soil nutrients balance. Both help to make a good design of the fertilisation application plan.

I thank you for the answers.

Fabio, absolutely, but the most importan is the productivity in kg/ha