I was talking with a friend about Terra Preta, the soil that Amazon Indians manufactured hundreds of years ago. It is a prized soil today and contains a a good quantity of charcoal. I pointed out to him that lump charcoal is biochar and just needs to be broken up. So I am going to use the Sam’s club charcoal pictured for my biochar. It may be a good grow hack to point out you can use lump charcoal as biochar.
But my question is what is a good organic fertilizer to charge the biochar so it doesn’t leach nutrients out of my soil? Apparently soaking biochar for 2 to 4 weeks in a nutrient solution “charges” the biochar and gives the microbes food as well as a place to live.
As a second question, how much biochar should be in soil. The Wikipedia article on Terra Preta said it was about 8 to 10 percent charcoal.