See more from this Session: Management Strategies to Improve Nutrient Use Efficiency: I
In the last 60 years in China, in addition to using organic manure to recycling part of the nutrients in organic wastes, N fertilizer application was started in early 1950s, P fertilizer was added to the fertilization program in 1960s, and K fertilizer and some micronutrients started to be used in 1970s. With time, total nutrient input in inorganic form increased rapidly. By 1993, China became the world largest fertilizer user. In recent year, the total fertilizer nutrient consumption in China accounted for about one third of world total chemical fertilizer consumption. During this process, chemical fertilizer use played an important role in sustained increase in crop production and in improvement of soil fertility and land productivity. At the same time, large tonnage of organic nutrients was not been used properly, also creating negative influence to environment.
Two nationwide fertilizer efficiency studies in early 1960s and 1980s, and the results of International Plant Nutrition Institute (IPNI) cooperative program in China after 2000 indicated that changes of fertilizer use efficiency in China following the law of minimum, the law of diminishing returns, the law of nutrient return, and other principles of plant nutrition. Currently, average agronomic efficiency (AE) of N fertilizer for rice, wheat and maize were 11.5, 10.5 and 9.6 kg grain/kg N, respectively, and the average first crop recovery efficiency of fertilizer N for rice, wheat and maize were 27.2%, 43.8% and 32.4%, respectively. The low N use efficiency in China is due to the high N rate for high yield production and improper use of fertilizers.
Strategy to ensure sustained increase in crop production, to improve soil fertility, to improve land quality and to help the environment, through improved nutrient management and fertilizer use efficiency were discussed, in relation to the highly intensified cropping systems.