Commercial-scale recycling of agricultural and municipal wastes into organic soil amendments facilitates safe disposal of waste and reduces environmental contamination. However, phytotoxicity of commercial organic amendments to crops is a major concern to farmers. Consistent with this, commercial chicken manure and Milorganite (recycled from municipal waste) were found to be phytotoxic. Chicken manure aqueous extract contains 10.8 ppm Cu and 0.7 ppm Ni. The level of Cu and Ni in Milorganite is lower. The current study identified an aqueous solution containing 5 ppm Cu, lower than in chicken manure aqueous extract, was highly phytotoxic to mustard seeds germination. Therefore, phytotoxicity of chicken manure is in part due to Cu. An aqueous solution containing 1 ppm Ni was not phytotoxic; whereas 0.125 ppm Ni was phytotoxic when 62.5 ppm Na, which is nontoxic, was added to the solution. Therefore, synergistic effects of chemicals in the organic amendments may induce phytotoxicity.

以商业规模将农业和市政废物回收为有机土壤改良剂，有助于废物的安全处理并减少环境污染。但是，商业有机改良剂对农作物的植物毒性是农民的主要关切。与此相符的是，发现商业鸡粪和Milorganite（从城市垃圾中回收）具有植物毒性。鸡粪水提取物含有10.8 ppm的铜和0.7 ppm的镍。Milorganite中的Cu和Ni含量较低。目前的研究表明，含5 ppm Cu的水溶液比鸡粪水提取物中的含量低，对芥菜种子发芽具有很高的植物毒性。因此，鸡粪的植物毒性部分归因于Cu。含1 ppm Ni的水溶液无植物毒性；而当Na含量为62.5 ppm时，0.125 ppm的镍具有植物毒性，将无毒的溶液添加到溶液中。因此，有机修饰物中化学物质的协同作用可能诱发植物毒性。