Environmental and Natural Resource Degradation in Intensive Agriculture in Bangladesh

Bangladeshi agriculture has undergone a substantial intensification. Continued and accelerated agricultural growth will require intensification to continue. There has been rising concern, however, that intensive agriculture may not be sustainable and that it may be damaging to the environment or to other productive sectors. Rising average yields and rising production in Bangladesh have tended to mask evidence of declining productivity. Although data are weak, numerous sources of evidence point to declining productivity. Analysis of official data on yield trends at the district level shows that, despite rising input levels, yields have been declining or stagnant on about two-thirds of the area planted to modern varieties in the boro season in the last decade, and stagnant throughout the country in the aman season. Yield declines are strongly associated with the length of time that intensive production practices have been employed in each district. The results of long-term trials by the Bangladesh Rice Research Institute (BRRI) also indicate that intensive rice cultivation can result in declining yields, even under good management and with full recommended doses of all nutrients being applied. Farmer perceptions also support this conclusion: farmers often claim that yields have been declining and that higher fertilizer applications are necessary to maintain yields. Stagnant or declining yields in the context of rising inputs indicate that land degradation is reducing productivity; if increases in input use had not counteracted the effects of degradation, yields might have fallen even further. This evidence is consistent with patterns of yield change in other Green Revolution countries, many of which have also experienced a slowdown in the rate of growth of production and yield, and with research at the International Rice Research Institute (IRRI). There is considerable debate over the exact causes of declining productivity. In Bangladesh, the most likely cause is nutrient imbalances. High-yielding modern varieties are far more demanding of soil nutrients than much lower yielding local varieties had been, a problem worsened by the increasing prevalence of multiple cropping. Chemical fertilizer use has increased, but not sufficiently to compensate for the higher rates of offtake, and has been offset by decreasing organic content of the soils as a result of reductions in applications of farmyard manure, which is in increasing demand for use as fuel, and increased protection against flooding, which has reduced the deposition of organic matter content from flood waters. In general, applications of nitrogen are adequate but those of other nutrients often are not. Changes in soil physical and chemical properties, such as changing quality and quantity of organic matter and formation of a plowpan, also play a role in declining yields.