The truth of the matter is biochar is a soil additive requiring extensive research to establish it’s effects on soil over the long haul.
But a sneak preview into it’s physical and chemical structure gives us some understanding.
An adsorbent is a material that is able to ‘suck up’ and attach to substances in water, soil or air and in many ways, biochar lives up to this billing.
High temperature processes in it’s production lead to the development of charged pores capable of adhering to ions and other substances in the soil.
A good thing?
Well…Yes and No!
Yes because this makes it’s use a formidable detoxification strategy ridding the soil of heavy metals and pesticides.
But no because this same adhesive characteristics leads it to ‘sucking up’ nitrates and phosphorus from the soil depriving crops of useful growth nutrients.
Application of such virgin biochar in some soils may lead to suppressed yields making many doubt it’s usefulness as a soil additive.
But over the long haul, when the storage reserves of the ‘sucked up’ nutrients are filled up, the nutrients end up being released back to the soil resulting into increased fertility.
This is one reason why biochar trials need to take some amount of time (at least 3-4 crop seasons) for useful insights to be drawn.
But this is just one reason why understanding biochar is a complex affair.
Different types of soils behave differently to applied biochar.
Being alkaline in nature, virgin biochar is useful in reducing soil acidity but functions poorly in highly alkaline soils.
It’s also known to improve the fertility of nutrient deficient soils but seems to deliver little value to fertile soils with high amounts of organic matter.
Biochar could be blended with other important soil amendments such as compost or manure to boost it’s performance in many soils.
This is called activated biochar.
For example, biochar mixed with compost and aged for a while before being applied to the soil creates not only a mixture rich in nutrients but also allows build up of microbial communities in the biochar pore spaces.
Such a good chemical and microbial balance coupled with biochar’s porosity and good water holding capacity is bound to improve any types of soil over time.
However, a word of caution is it’s always essential to first test these combinations on your garden soil before going large scale.
Blending biochar with such nutrient rich matter helps in building up soil fertility over time because biochar ‘holds onto’ the nutrients preventing fast loss.
Though biochar by itself is deficient of crop nutrients, it’s ability to bind nutrients could be exploited in building up soil fertility over time.
Using biochar in combination with other nutrient rich materials in farming is therefore an area ripe for exploitation.