Biochar amendment of soil improves resilience to climate change

Because of climate change, insufficient soil moisture may increasingly limit crop productivity in certain regions of the world. This may be particularly consequential for biofuel crops, many of which will likely be grown in drought-prone soils to avoid competition with food crops. Biochar is the byproduct of a biofuel production method called pyrolysis. If pyrolysis becomes more common as some scientists predict, biochar will become more widely available. We asked, therefore, whether the addition of biochar to soils could significantly increase the availability of water to a crop. Biochar made from switchgrass (Panicum virgatum L.) shoots was added at the rate of 1% of dry weight to four soils of varying texture, and available water contents were calculated as the difference between field capacity and permanent wilting point water contents. Biochar addition significantly increased the available water contents of the soils by both increasing the amount of water held at field capacity and allowing plants to draw the soil to a lower water content before wilting. Among the four soils tested, biochar amendment resulted in an additional 0.8-2.7 d of transpiration, which could increase productivity in drought-prone regions or reduce the frequency of irrigation. Biochar amendment of soils may thus be a viable means of mitigating some of the predicted decrease in water availability accompanying climate change that could limit the future productivity of biofuel crops.