Many researchers recommending "Biochar"for soil contaminated with heavy metals. Some heavy metals are micronutrients such as Fe, Cu, Zn, Mo etc. If biochar adsorb these micronutrients and make these not available to plant, will have negative effects. If such situation arises, how we can undo the treatment?
If biochar treatment is not reversible, what may be the right way to use biochar to reduce heavy metal related hazard?
Dear Nafees,
As you should know, Biochar is charcoal, and its main characteristic is that its structure is full of micropores that retain nutrients and water. Fot this reason it absorbs nutrients in the soil, cuasing fertilitiy problems in years 1 and 2.
Biochar has an alkaline pH. It is good then for acid soils. Consequentely, it is not suitable for basic soils because it increases the pH even more, blocking nutrients and ultimately reducing fertility, unless accompanied by an acididying amendment.
If this were the case, there are several alternatives to "reduce-reverse" this low pH. It is suggested to add organic fertilizer to avoid negative effects in short term. Second, never forget the use of compost rich in earthworms. They are also good indicators of the quality of the land.
Dear Nafees
It is really interesting.
Biochar increase adoption of any of the nutrients that may be useful for the plant nutrients therefore it is likely to decrease their availability to the plants. I also consider that herbicide efficacy maybe bit reduced in case bio char has been used in that particular field.
Biochar is to be used as an organic amendment , which initially acts as synonymous to organic matter fraction of soil . Biochar does have nutrient filtering ability where heavy metals are no exeption. Unless soils are contaminated with heavy metals , biochar is supposed to cut down the load of heavy metals in soil solution , but again biochar cant be compared with any hyperaccumulator of heavy metals...
Dear Nafees,
As you should know, Biochar is charcoal, and its main characteristic is that its structure is full of micropores that retain nutrients and water. Fot this reason it absorbs nutrients in the soil, cuasing fertilitiy problems in years 1 and 2.
Biochar has an alkaline pH. It is good then for acid soils. Consequentely, it is not suitable for basic soils because it increases the pH even more, blocking nutrients and ultimately reducing fertility, unless accompanied by an acididying amendment.
If this were the case, there are several alternatives to "reduce-reverse" this low pH. It is suggested to add organic fertilizer to avoid negative effects in short term. Second, never forget the use of compost rich in earthworms. They are also good indicators of the quality of the land.
I think the combined use of biochar with other non-pyrolyzed organic amendments (e.g. compost, manure, plant litter etc.) can minimise the adsorption of micronutrients.
Greetings
Good practical question. My assumption is that the setting is a heavy metal contaminated soil. Although some heavy metals are nutrients, but as is mentioned by Dr. Nafees, they are MICRO nutrients, thus are required in low amounts. Therefore, in heavy metal contaminated soils, these micronutrients are in high quantity, and instead of being beneficial, might be at concentration even harmful to the plant. So, in this conditions, biochar eventually will help by lowering their availability.
In normal agricultural soils (not contaminated with heavy metals), one must remember that the whole bulk of the soil is not occupied by biochar! Researches has shown that usually 2-4% biochar will have its beneficial effects. Since micronutrients are required in low amounts by the plant, the roots can absorbe enough of them from soil solution. Thus I don't think that would be a big problem, since crops and trees, does not show micronutrient deficiencies due to biochar application to the soil.
Another observation and conclusions I had with my research works, is that, biochar is a soil amendment, and does not have any particular effect on plant in soil without a problem. Also, although biochar might have some potential to create problems such as increasing pH in calcareouse soils (basic soils), and or even affect soil salinity by increasing it a little bit, however, the other beneficial effects it has on plant growth in problemed soils, most often offsets the possible negative side effects. For example, in all my researches with biochar application in basic soils, the pH increased a little bit, sometimes statistically significant (for example from 8.4 to 8.6). But, although the soil became more basic, but the plant growths were not impaired and we even got incrases in plant growth by proper biochar application rate. The same we have observed with salinity. For example in our experiments, soil EC increased from 8 to 8.4 dS/m, but the final results clearly showed increased plant growth, by biochar application (in fact, better salt tolerance of crop by biochar application).
The suggestions made by Dr. Baltieraa are practical and well worth to try.
Good luck.
The availability of micronutrients is heavily dependent on soil pH.
For avoiding the immobilization from the use of biochar its most unrestricted use is in older red and yellow tropical acid soils.
The more alkaline soils are the soil where immobilization would be most dangerous.
For application in alkaline soils, the char can use lower temperature to produce a slightly acid rather than the alkaline product.
In addition to the alkaline soil condition, the use of sulfur can be employed to acidify the overly acid condition of the soil.
The issue of too much potential toxic metals for biochar could be addressed by testing and sourcing
If crop residues are used and the soil is not heavily contaminated with healvy metals the issues can be avoided.
In areas of heavy metals the biochar which has potential would be kept out of the food production fields.
When we talk about our soil or our plant production there is no one measure and no one practice. As our farmers are aware there are so many details and the ways these are woven together to give a systematic result. Unfortunately, our education and practice is based mostly on an overspecialization the whole systems are not clearly identified and monitored as they might be. We need to put things into priority but not overlooked the holistic nature of the living systems we are part of.
Kindly check https://www.intechopen.com/books/biochar-an-imperative-amendment-for-soil-and-the-environment/biochar-a-sustainable-approach-for-improving-plant-growth-and-soil-properties
Also check https://www.nature.com/articles/s41598-020-69183-9
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