What Will be the global grains yield towards the 21st century? Although there are many different opinions, I believe that the agricultural technology used in the green revolution has a serious problem regarding its long term sustainability, as it must use substantial amounts of chemical materials, and continually develop new varieties to cope with diseases and harmful insects which quickly adapt to the latest agricultural chemicals. 23) However, there is no other way except using this technology for a while to cope with the fast increase in the demand for food during the peak period of population explosion in the developing countries until 2020. So we should modify the green revolution technology to minimize environment destruction until new appropriate technology is established.
Wheat, barley, sorghum and millets have larger area where yield improvement in difficult comparing with rice and maize under current agricultural technological conditions. Thus raising yield of the former grains will be more difflcult. 24) However, some are of the opinion that the significant differences that exist in the grain yield among various countries or regions in the world show the possibility of adopting existing technology and increasing yield through increased use of chemical fertilizer, and at the same time decreasing the environmental damage and soil deterioration, especially in developing countries. 25) The difference in the yield, however, shows not the difference in potentiality in the existing technology, but the restrictions of the natural conditions on the yield in most cases as is clearly seen in the big difference between the yield of wheat in Western Europe and North America. As previously described, the growth rate of grain yield decreased significantly during the eighties, and yield of new high-yield rice varieties has been stagnating or decreasing in Asia. The harvested area of rice, 90% of its production and consumption are concentrated in Asia, has been decreasing as well. A 3% annual increase in rice yield will be needed to cope with the peak of the population explosion until 2020. 26) Although until now, the potential yield of various crops has been raised annually by 1〜2% through the efforts of genetic
