Organic farming is a form of agriculture that relies on crop rotation, green manure, compost and biological pest control. An organic farmer will still use fertilizers and pesticides, but strictly limits or excludes the use of synthetic fertilizers, pesticides, insecticides, herbicides, and fungicides. The expression, “Feed the soil, not the plant” is a familiar refrain among organic farmers. The organic farmer will also exclude livestock antibiotics, hormones, food additives, human sewage sludge, genetically modified organisms, and nanomaterials. Animals are provided with organic feed and allowed access to fresh air and the outdoors.