This guideline was developed by the Umpqua Biochar Education Team for an NRCS Conservation Innovation Grant. The plant bioassay we use is a two week germination and growth test using cucumber seeds. The basic procedure is to mix the target material with a plain, peat-based potting soil at the desired rate and plant the same number of seeds in each pot. Trays of pots are placed in a controlled environment and grown for two weeks. At the end of the growth period, we count the number of germinations (a strong indicator of phytotoxicity) and the number of secondary leaves. The number of secondary leaves may indicate different levels of growth promoting hormones, nutrients or other constituents in the target amendment. Then we cut, dry and weigh the biomass of each treatment. The biomass weight will tell us something about nutrients available for growth.