This is an advance summary of a forthcoming article in the Oxford Research Encyclopedia of Environmental Science. Please check back later for the full article.
Agricultural subsurface drainage (“tile” drainage) is an essential water management practice for agricultural systems that has been practiced since ancient times throughout the world. The practice employs ditches and subsurface pipe/tubing to ameliorate conditions of excess water and soil salinity, and to sustain and improve crop production. According to recent estimates by the Food and Agriculture Organization of the United Nations (FAO), approximately 40% of global arable lands lack adequate natural drainage, and only 30% of global drainage needs have been met. Significant advances in materials and technology, particularly over the past 30 to 50 years, have helped agriculture to more effectively address its drainage needs. With these advances, society began to contemplate first, the hydrologic impacts of altered drainage systems, and more recently, their water quality and other environmental effects. The increased global incidence of both marine and freshwater hypoxia over the last three decades has become a research impetus for nutrient movement from agricultural landscapes to surface waters, especially through natural and artificial drainage systems. Universities and other research institutions are building a sizeable body of work on ancillary practices aimed at mitigating and managing unwanted hydrologic and water quality effects of agricultural drainage, while preserving the benefits to agricultural production.