Personally, I agree with this approach even in organic agriculture where it's allowed to treat with foliar application of micro-nutrients mixture. There are several products allowed in organic farming, and more over in conventional one.

The scope of using micro-nutrients mixture in foliar application is that the soil test in no more required in case of deficiency appearance at crop level. The leaves are likely to be indicative of more or less advanced nutrient (s) deficiency. Foliar application is more effective and nutrient(s) targeted approach in comparison to organic amendment and soil application. In short term, annual crops are more responsive to soil application than perennial crops, but both of them are responsive to foliar application (except most of monocotyledon).

Boron, molybdenum, iron...are expensive trace elements, so putting them in the soil and waiting for their uptake is quit a waste of time and money, especially if the soil has its own antagonistic effect against some of them.

from scientific point of view, plant nutrition, nutrient supply and budget should be based on soil analysis. however, many farmers in some countries are not analyzing soil frequently as recommended. additionally, they consider macronutrients plant requirements. logically, we should accept the application of micronutrients mixtures. on the other hand, if soil analysis is fulfilled and nutrients requirements  are determined, application of such mixtures should be restricted to avoid toxicity and their side effects. 

Dear Sir, It is more common especially with the farmers growing potato in western part of U.P. in India. Though it is not wise but the greed to get more and more yield farmers are opting all sorts of mixtures of fertilizers and micronutrients for spray and/or soil application. They may get higher yields but  feel scientific way  is to use these micronutrients mixtures is as per soil test basis and that should be followed for efficient and economical use of these costly inputs. Thanks n Regards

I agree to what Dr. S. K. Dubey explained.

Micro nutrients should be applied to crop based on soil test., Sometimes, the symptoms of micro nutrient deficiency are not reflected immediately on the crop but after exposure to relatively longer periods of deficiency in soil, crop develop symptoms; by then it will be late to counter the ill effects of deficiency. So either soil based or foliar application of micro nutrients can be followed for remedial measures.

One view is that we can apply micronutrients through foliar application ,as per the requirement of different crops,irrespective of soil micronutrient status. However in this approach soil micronutrient status may go down and one need to analyze soil nutrient status at certain periodicity and take remedial measure to ensure high crop productivity. Also it may be difficulty to meet full requirements through foliar application.However it may not be justified to apply several micronutrients through soil application without  soil  testing as some micronutrients may accumulate in toxic proportions. I thank all scientists who participated in the discussion so far.

STCR, as a soil application 

It all depends on the water, crop, soil ecology, weather conditions and the phenological stage of the crop. Some micronutrients may become available to the plant by adjusting soil pH, others by simply watering (many micronutrients may be available in water), and others you absolutely cannot wait to apply to the crop and must make foliar application. Of course, the source and derivation of the minerals is also critical. Although soil testing is essential, the crops needs are of dynamic nature thus tissue and petiole analysis are just as crucial. I have found sometimes the need to understand the nutrient content of the final product harvested to be essential, for instance tubers of potatoes and banana fruits. I have no idea what role "greed" plays on this matter. Anyone that farms and utilizes micronutrients deserves my respect since most farmers apply npk blends only. 

I agree with Mr.Hurtado  on two points -there is need for plant analysis especially indicator tissue and also there need for micronutrients in some crops for improving quality  of produce.Thank you for your comments.

A preliminary lab test of the mixtures of micro nutrients is very important because all of them are not compatible to each other. Some researches have shown that combined application of micro nutrients some times gives good results but this all depends upon crops themselves, soil characteristics (especially pH and the status of nutrients being applied) and the climatic factors. Of course application of a nutrients not deficient in a specified situation will not be feasible economically and increase the cost of production. I am of the view that a blind application without any lab test should not be acceptable.   

Most seaweed products which contain an assortment of trace nutrients are applied, I believe, without any consideration of nutrient overload. More rigorous lab testing needed.

Micronutrients can be expensive and on occasions have intended side-effects, so there is no point in using them if unnecessary.  The difficulty, of course, is knowing when they are necessary, unless the deficiency is acute with obvious symptoms.  Soil or foliar testing is also expensive, not always reliable, and results are not always available to farmers in a timely fashion ... and they can require expert interpretation that is not always available. So it is understandable that farmers do their own 'experimentation'. 

The challenge, I believe, is to help farmers make experiments that give useful results. I am a great believer in farmer test-strips, but care needs to be taken in their design, execution and interpretation.

As for seaweed products, they may also contain plant growth regulators, so any responses observed may not be to the nutrients contained.

I thank all the participants in the discussion and especially appreciate the idea of Dr.Cornish to experiment by farmers themselves  to know the perceptible response to micronutrients.

• Seaweed based products do provide a well balanced micronutrient content and certainly provide plenty of plant growth hormones so one must limit the rate or dosage of application. I have seen very sad results of over usage. Remineralization of soils may be in the long run one of the best alternatives on this extremely important subject. On the practical side, opportune and timely tissue analysis as well as water analysis may be the best practical alternative to precisely define micronutrient balances.