Crop Diversification in the Asia-Pacific region - United Nations in ...

4.1 Crop NutritionA major contribution towards increased yield and sustained production could beachieved by using fertilizers and manures. The actual usage of fertilizers is generally lowerin the developing countries than in developed countries and dangers of overuse, as observedmostly in the highly industrialized countries, has not been a problem. Organic matter usagehas been less in most countries, but its incorporation into the agricultural systems will makethe soils fertile and less degradable. Several problems exist in the use of organic manuressuch as the volume required, time, labour and opportunity costs. Another recentdevelopment is in the development of crop rotations, a strategy towards diversification ofagricultural systems to increase productivity and crop yields. This involves the insertion ofgreen manure cover crops or other legumes in the cropping systems as seen in severalcountries. The popular crop mixes are legumes in maize and other cereals.The consumption of fertilizers in terms of plant nutrients is a reliable indicator ofnutrient usage by different countries in the Region. During 1973-1983 nutrient consumptionincreased from 17 to 35 million metric tonnes. During 1988-1997 further increases havebeen recorded from 47 to 63 million metric tonnes in developing countries of the Region,with an average annual growth rate of 3.7 percent. The countries using the highest rates offertilizer nutrients were China (36 m Mt) and India (16 m Mt). The developed countries ofthe Region (Australia, Japan and New Zealand) also recorded average annual growth rates of9.3 percent.Although the rate of fertilizer used has increased, per hectare usage has been lessimpressive. Many of the developing countries use less than 20 kg nutrients per hectare andthis is regarded as a major reason for low yields. In 1997, the highest rates of fertilizer/hahave been used by the Republic of Korea (471 kg/ha) followed by China (266 kg/ha),Vietnam (218 kg/ha) and Malaysia (158 kg/ha). Among the developed countries of theRegion Japan has used the highest amount of nutrients (366 kg/ha) followed by New Zealand(211 kg/ha).Further analysis of nutrient usage indicates that a large proportion of the fertilizer isused in rice cultivation and insignificant amounts for other field crops. It is necessary toincrease the use of fertilizers and manures to ensure high crop responses to the appliednutrients. It is also necessary to encourage the use of organic fertilizers to renovate soils andimprove their physical and chemical properties and biological activity. Slow release organicfertilizers are also used in some countries where about 80 percent of total nitrogen is presentas organic nitrogen. At normal soil temperatures of around 27 o C, about 60 percent of thisnitrogen is released over the first four months. The losses due to leaching and volatilizationwill be less, hence the efficiency may exceed that of mineral fertilizers in the locations wherethese processes are likely to occur.4.2 Agricultural MechanizationFarm power includes human, animal and mechanical sources. In developingcountries 80 percent of the farm power comes from humans. There is a trend for the shift oflabour from agriculture to industry in most of the developing countries. This has alreadytaken place in the developed countries. This would mean that the few remaining people inagriculture would be required to produce food for more and more people living in urbanareas, showing 7 percent growth per year. Besides, labour costs are escalating, accounting159