What do we know about heavy metals in soil? What do we know about lead exposure through soil and garden plants? What do we know about cadmium and arsenic in soils? What can I do if I’m at risk for heavy metals in my garden soil? Crimson clover market is growing for a crop with economic and environmental benefit. How to properly incorporate grains into an entire farm. Includes suggestions for rotations on various types of farms. Poisonous plants are a major cause of economic loss to the livestock industry. Two poisonous plants common to Oregon are poison hemlock and Western water hemlock. Ingestion of either by humans or livestock typically results in death.