To put it simply, sustainable agriculture is the production of food, fiber, or other plant or animal products using farming techniques that protect:
• The environment: Sustainable farms produce crops and raise animals without relying on toxic chemical pesticides, synthetic fertilizers or genetically modified seeds.
• Public health: Food production should never come at the expense of human health. Since sustainable crop farms avoid hazardous pesticides, they’re able to grow fruits and vegetables that are safer for consumers. Likewise, sustainable livestock ranchers raise animals without dangerous practices, such as use of non-therapeutic antibiotics or arsenic-based growth promoters.
• Human communities: Sustainable agriculture must be economically viable, providing farmers, and others employed in the food system with a livable wage and safe working conditions. Sustainable farms must also bolster local and regional economies, creating good jobs and building strong communities.
• Animal welfare: Sustainable farmers and ranchers treat animals with care and respect, implementing livestock husbandry practices that protect animals’ health and wellbeing. By raising livestock on pasture, these farmers enable their animals to move freely, engage in instinctive behaviors, consume a natural diet, and avoid the stress and illness associated with confinement.
Source: http://www.sustainabletable.org/246/sustainable-agriculture-the-basics