Chapter 4 - Nitrogen-Use Efficiency Under Changing Climatic Conditions

Abstract

Resource-use efficiency is a baseline for productive agriculture and proper management of different resources (water, nitrogen, light, and land), and it plays a pivotal role in the accomplishment of this goal. Nitrogen is the most critical input that limits rice productivity. The management of this resource is a significant challenge to most agricultural systems as it can have a significant impact on yield and the environment. The use of applied nitrogen fertilizer to cereals is poor, where only 30–40% is actually used by cereals and the remainder is lost to the environment by surface runoff, soil denitrification, and volatilization. The required amount of nitrogen depends on soil type, variety, climate, method of application, and type of fertilizer. However, supply of the proper amount of nitrogen based on the physiological requirement is the key factor. Poor nutrient management leads to low nutrient-use efficiency and often to large nutrient losses. Poor water management leads to low water-use efficiency and possibly also to low nutrient-use efficiency due to high nutrient leaching losses. Currently, only about half of the applied nitrogen fertilizer is taken up by the crop, depending on crop type and management, while the remainder accumulates in the soil temporarily and/or is lost to the atmosphere via ammonia volatilization and (de)nitrification losses, and/or is lost to groundwater and surface water bodies via leaching, overland flow, and erosion. Globally, nitrogen-use efficiency of crop systems has shown decreasing trends for many continents over the last 50 years, mainly because of increasing nitrogen applications, poor nitrogen management, and the effect of the law of diminishing returns. The implication of decreasing trends of nitrogen-use efficiency suggest that nitrogen losses increase. Nitrogen-use efficiency of a crop plant refers to the relative balance between the amount of fertilizer taken up and then used by the crop versus the amount of fertilizer directly or indirectly applied. In other words, nitrogen-use efficiency looks at the fertilizer input recovery in a production system to classify which plants do this better or worse when compared equally based on production (yield). Nitrogen-use efficiency has been defined by many authors in the context of crop production and the literature contains a number of different definitions depending on whether authors are dealing with agronomic, genetic, or physiological studies first defined nitrogen-use efficiency as grain production per unit of available nitrogen in soil. Nitrogen-use efficiency gives an idea as it delivers a numerical measure of the usefulness of plants to absorb and transform available nitrogen into potential yield under different cropping systems. Nitrogen fertilizer is among the central inputs for cereal production.