|Conflicting evidence on "yield deceleration" |
An FAO expert consultation in Bangkok in 1996 found "numerous cases of stagnant or decreasing yields and productivity" in rice.
In Bangladesh, for instance, trials consisting of three and two rice crops a year with three fertilizer treatments showed yield declines for each treatment over a period of 10 years.
But some temporary decreases are often confused with yield decline. One case in central China was found to be due to unsuitable varieties and inadequate use of organic matter, while in India causes identified ranged from cyclones to the removal of fertilizer subsidies.
To better understand the phenomenon, the consultation recommended systematic studies to quantify deceleration, stagnation and decline processes and delineate affected areas as accurately as possible.