What's happening at IRRI
Thursday, April 06, 2017, 01:15pm - 02:15pm
April 6, 2017
1:15pm-2:15pm, Havener Auditorium
"The Nitrogen Dilemma: Good and Bad"
Author: J.K. Ladha
Crop and Environmental Sciences Division
Nitrogen is unique among the major nutrients in that it originates from the atmosphere and its transformations and transport in ecosystems are mediated by the water cycle and biological processes. The atmosphere contains a large, well-mixed biologically unavailable pool of N, of which a small part is converted to biologically available reactive N. Biological N fixation is the primary source of reactive N but, in recent years, chemical N fixation has become important in increasing crop productivity to alleviate the ever-increasing food insecurity. Since the Green Revolution, the application of N fertilizers on “modern crop cultivars” of cereals has boosted food production by about 6.4% per year. Today, fertilizer N supplies 100 Tg year-1 for food production. Of this, 50% is applied to three major cereal crops—maize, rice, and wheat. It is projected that annual total global N use will be around 171 metric t in 2050, assuming that there is no change in nitrogen-use efficiency (NUE). Fertilizer N-recovery efficiency of cereals is 30% to 50%. Surplus N is lost to the environment, causing disruptions in ecosystem functions. Much research has been conducted in the past decades to improve NUE by developing fertilizer management strategies based on better synchronization of supply and crop demand. This presentation will analyze the (1) different sources of N inputs and outputs in global cereal production, (2) effect of long-term addition of synthetic N on soil N storage, (3) NUE of cereals grown across large agroclimatic regions, and (4) agronomic and genetic strategies available to improve NUE and reduce losses.
Havener Auditorium, International Rice Research Institute, Los Baños, 4030 Laguna, Philippines