Two researchers from the Newcastle University and the Swedish University of Agricultural Sciences examined nutrient management on organic farms in their article, “Long-term management of nutrients in organic farming – principles and practice.” The research focuses on the need to replenish soil with nutrients, and the difficulty of managing nutrients without the use of synthetic materials. Nitrogen can be supplied by biological fixation by legumes, but other major and micronutrients rarely meet crop demand in organic fields. Crop rotation is one key element to ensuring nutrient balance, as is the use of on-farm nutrient sources such as manures, composts, and other organic materials. Using methods such as these for balanced nutrient resources will allow organic production to reach or exceed conventional yields. It is also important to prevent nutrient losses through runoff and leaching to ensure soil health while reducing nitrogen pollution.