Alberto, hope you are not flooded. I meant spraying vinegar on the weed seedlings, not in sufficient quantities to drench the soil. It chemically burns them. It doesn't work so well on older plants. I use it for winter-growing weeds including grasses. As for carbon and oxygen sources - a local soil scientist in a lecture told a group of us to consider adding sugar and 3% hydrogen peroxide to irrigation water for fruit trees and lawns. He said it encouraged growth of beneficial microorganisms. The quantities were small: per irrigated acre / 0.4 hecatare, about 1 cup / 240ml granulated sugar (I know it isn't measured that way in SI but I don't feel like looking up the density of granulated sugar) and 1 pint / 480ml 3% hydrogen peroxide. Leo Martin Phoenix Arizona USA