Dr.Sarwar,the amounts of nutrients in general are small in biochar and the content of micronutriets may still be smaller.The contribution of micronutries through decomposition and mineralization may also be small as the biochar is not expected to decompose in soil like organic manures,rather it should remain in soil for centuries.

Dr. Rao has correctly replied. I can guess role of biochar only through its CEC to bind some mount of micro-nutrients against leaching. Other it does not contain high amounts of nutrients. Again the question is how much biochar could be applied to soils.

Dear Nadeem, the direct effect of biochar on the contribution of available micro-nutrients is not as high as other organic amendments, such as compost and manure. However, the feedstock type and carbonization temperature are among the main factors that may influence the supply of nutrients by biochar. For instance, the nutrient contents of legume and manure based biochars  are higher than hard-wood based biochars. The indirect effect of biochars is, however, significant in terms of retaining both applied and soil nutrients and soil moisture content that would otherwise be lost in different forms. It can also  enhance soil aggregates and soil microbial biomass.

Thus, in addition to its importance in sequestering carbon in the soil and mitigating greenhouse gas emissions, the long-term effects of biochar in terms of improving soil bio-physical and chemical properties is very crucial.  Please find a paper on biochar attached here.

Dr. Getachew ,your comments are interesting. The main problem is we desire to keep the biochar intact in soil for centuries and get benefits of carbon sequestration and climate change. At the same time use it like passive carbon pool,humus and get the benefits of CEC,water holding capacity, aggregation and Microbial biomass(dead bodies of microorganisms). The CEC values reported for biochars are highly variable. Same is the case with water holding capacity. Another question is how inert biochar provides food to microbes.If it provides food to microbes then how it remains in soil for centuries?. Is it desired to prepare biochars from manure or legume straw?. My question to all working on biochar is,do you want to have cake and it too?What proportion of biochar is cake and what proposition is inert?How long we want to keep biochar in soil and get benefits of carbon sequestration?

Dr. Rao, although low temperature(350◦C) biochar has a greater labile fraction of carbon than the high temperature biochar which can be used as an energy source for soil microorganisms its direct effect on provision of food to microbes  is limited. However, its role as a habitat for microbes through its large number of pore spaces is significant. As mentioned above, feedstock type is another factor influencing  the nutrient content of biochar.

Dr.Getachew, I believe that the scientists working on biochars look into the issue of longevity of the material  from low temperature and high temperature biochars in soil.Also for long term carbon sequestration the biochars from woody materials may be better. Again ,we have to think which route is better for agricultural wastes-prepation of compost or biochars?.while preparing biochars a considerable portion, at least 30% of organic matter which When Incorporated in soil serve as labile carbon,is burnt.Further ,when biochar is incorporated in soil it has shown some priming effect,accelerated decomposition of soil organic matter.Can I hypothesize that the microbes by getting anchorage in biochar pores are acting on soil or other added organic materials?I have mentioned a good review article available in European Soil Portal in another question raised by Dr.Ghafoor on biochar role in saline sodic soils.I am providing briefly the reference here

Biochar application to soils-European Soil Portal-Europa eusoils. irc.ec.europa eu7 EUR24099EN

Pedosphere 26(1): 27–38, 2016; doi:10.1016/S1002-0160(15)60019-4

ISSN 1002-0160/CN 32-1315/P; ⃝c 2016 Soil Science Society of China

Published by Elsevier B.V. and Science Press

Conocarpus Biochar Induces Changes in Soil Nutrient Availability

and Tomato Growth Under Saline Irrigation

Adel Rabie A. USMAN1, Mohammad I. AL-WABEL , Yong S. OK,

, Abdulaziz AL-HARBI, Mahmoud WAHB-ALLAH, , Ahmed Hamdy EL-NAGGAR

, Mahtab AHMAD, Abdulelah AL-FARAJ and Abdulrasoul AL-OMRAN1,

See the above paper for subject matter in your question

Dear. Colleagues, the main issue is whether the biochar has sufficient micronutriet concentration to supply to plants.Also whether  the biochar mobilizes micronutriets from soil by supporting Microbial activity in soil.So we need supporting data on those two aspects.

Exactly Dr. Rao, I was plaaning to work on this aspect particularly the role of BioChar in mobilizing micro-nutrients (Zn, Fe) in soil and how will effect the application efficiency of Zn if Zn is applied in combination with Biochar. All this discussion somehow clear my line of action. Thanks to all experts for their participation in this discussion.

Dr.Nadeem best wishes for the initiave.

 Dr.Patil,good paper attached and worth reading.

thanks Dr Rao for the mention of the topic i am doing a research on the same topic i am looking at influence of biochar availability of micro-nutrients