1. Berry, J.K., Delgado, J.A., Khosla, R., Pierce, F.J., Precision conservation for environmental sustainability. Journal of Soil and Water Conservation 2003; 58(6): 332–339. http://www.jswconline.org/content/58/6/332.
2. FAO, (2003), FAO World Agriculture: Towards 2015/2030—An FAO perspective www.fao.org/docrep/005/y4252e/y4252e06.htm.
3. Wheat improves nitrogen use efficiency of maize and soybean-based cropping systems;Gaudin;Agriculture, Ecosystems and Environment,2015