I've been reading some articles about biochar. For anyone who in not familiar with biochar, it is organic material (wood, straw, plant residues) that has been heated super hot with almost no oxygen. The result is like a black perlite - a very high carbon material with high internal and external surface area. Added to soil, it's meant to improve water properties, aeration, pH, plant nutrition, drainage. Apparently a version of biochar was used by ancient Amazonian peoples, and persists in the soil to this day. Some people claim big improvements. Research is mixed. USDA on Biochar. Science Direct on Biochar. Garden Myths on Biochar. There's a lot of people out there promoting it, and others saying, wait a minute, not so sure. I don't know. I was thinking about adding biochar to my raised beds. Some have purchased topsoil. Who knows where it originally comes from. The place where I bought it accepts all kinds of yard waste. They said especially sod, they sift it with a 1/2 inch mesh and combine it all together. I imagine that sod was lawn grass and some chemicals might have been used, and some grass roots and leaves might contribute organic matter. Last year I built two beds with it, mixed with home made compost, and it grew great garlic, onions, lettuce, and peppers. My thought now is, the biochar might improve water retention so I don't need to water as much, and also help buffer the pH and even out soil nutrition. But I just don't know. Also, it does cost money. I guess for a one time investment it would be OK. Maybe my Christmas present to myself?