Organic farming is another agricultural system that originated early in the 20th century in response to quickly changing farming techniques. Organic farming has been developed by several organic farming associations now. It depends on fertilizers of natural source like compost manure, green manure, and bone meal and puts emphasis on techniques like crop rotation and companion planting. Biological pest management, mixed cropping as well as the boosting of insect predators are all encouraged. Generally, organic standards are made to permit the utilization of naturally occurring compounds while banning or limiting synthetic materials. For example, naturally occurring pesticides like pyrethrin and rotenone are allowed, while artificial pesticides and fertilizers are usually prohibited. Synthetic substances which are permitted include, as an instance, aluminum sulfate, elemental sulfur and Ivermectin. Reasons for advocation of organic farming include benefits in sustainability, openness, self-sufficiency, autonomy/independence, wellness, food safety, and food security.