Interactions of Nitrogen with Other Nutrients and Water: Effect on Crop Yield and Quality, Nutrient Use Efficiency, Carbon Sequestration, and Environmental Pollution

Nitrogen, which is required in the greatest quantity of all mineral nutrients absorbed by plant roots, is an essential component of protein. The long-term strategy of nitrogen (N) use in agriculture likely will involve increased reliance on fertilizer N, biological N fixation (BNF) by leguminous crops, and wastes (including farm, urban, and industrial wastes) and their efficient management. The amounts of different nutrients absorbed by a crop from soil may vary 10,000-fold, from 200 kg of N ha-1 to less than 20 g of Mo ha-1, and yet rarely do these nutrients work in isolation. As N function in plant growth and nutrition is closely connected to C, the C=N ratio controls N availability. Nutrient interactions have a role to play in determining the course and outcome of two major issues of interest in fertilizer management—namely, balanced fertilizer input and efficient fertilizer use. The N x P (phosphorus) interaction can be termed the single most important nutrient interaction of practical significance. In addition to N, potassium (K) is the major plant nutrient absorbed and removed by crops in the largest amounts among all essential nutrients. Sulfur (S) is the fourth major fertilizer nutrient along with N, P, and K. The deficiency of S has been reported with increasing frequency in the past several years all over the world. Although Ca requirements for plant growth and metabolism are low—it has great significance in balancing levels of other nutrients—including N. Deficiencies of different micronutrients can result in a serious reduction in grain yield and quality of crops, and utilization efficiency of other nutrients and water. These include zinc, copper, manganese, iron, boron, cobalt, and molybdenum. Also, water and N are the most important factors controlling crop growth and grain production.