Sustainable development includes farming methods and practices that promote economic efficiency of products, maintain surrounding environement, and protect people's lives. Keeping a stable and increasing profit in sustainable development for farming is important. Natural resources like water, soil, or energy must be used effectively by minimizing wastefulness. Sustainable farming also concentrates on people's, especially farmers', health and income by improving their quality of life.
Sources and more infomation:
Western SARE: http://www.westernsare.org/About-Us/What-is-Sustainable-Agriculture
ASI at UC Davis: http://asi.ucdavis.edu/sarep/about/def