排序方式: 共有3条查询结果,搜索用时 15 毫秒
1
1.
Cropping on jhum fallows in north-eartern India is predominantly done for one year in a jhum cycle. If second year cropping
is done, expanse of the forest land required for slashing and burning could be reduced significantly. We tested this hypothesis
in a young (6 yr) and an old (20 yr) jhum fallow. We also evaluated if the productivity during second year cropping could
be alleviated by auxiliary measures such as tilling the soil or application of fertilizers (chemical or farm-yard manure or
both in combination). The results demonstrate that the ecosystem productivity (total dry matter production) and economic yield
(rice grain production) decline with shortening of jhum cycle. Second year cropping causes a further decline in ecosystem
productivity in old jhum field, but not in young jhum field. Economic yield from second year cropping in its traditional form
(without any fertilizer treatment) is not much lower than that in the first year, and can be improved further by manuring
the soil. Tilling of soil improves neither ecosystem productivity nor economic yield. Different fertilization treatments respond
differently; while inorganic manuring enhances ecosystem productivity, a combination of inorganic and organic manuring improves
economic yield 相似文献
2.
Energy and economic efficiencies were evaluated on young (6 year) and old (20 year) jhum fields in Mizoram, north-eastern
India during second year of cropping, and were compared with those in the first year. The effect of auxiliary measures such
as tilling the soil or application of fertilizers (chemical or farm-yard manure or both in combination) was also examined
on energy and economic efficiencies. The results indicated that traditional jhum cultivation is labour intensive and energy
efficient, producing almost 15–20 times of energy invested. Energy and economic efficiencies decline with shortening of jhum
cycle. These efficiencies decline further from first to second year of cropping. Tilling is not useful to improve either energy
or economic efficiency. Fertilizer application, which is though profitable from the point of view of economic efficiency,
is highly energy inefficient. Application of fertilizers during second year cropping can be encouraged. Organic manuring may
be a better option than others to alleviate energy efficiency. However, a combination of organic and inorgamic manuring could
be the best option to enhance economic efficiency. 相似文献
3.
Changes in soil fertility were evaluated on young (6 year) and old (20 year) jhum fields in Mizoram, north-eastern India in
response to various operations involved injhum such as slashing and burning of vegetation, cropping period, and intervening
fallow period between first and second year cropping. The results demonstrate that the soil is richer in nutrients in old
than young field prior to the start of jhum cultivation. Slash burning depletes soil acidity, carbon and nitrogen but elevates
phosphorus and cations. Soil fertility declined during first cropping phase, and further declined during second cropping phase.
After two cropping years, soil fertility of old field was almost at par with that of young field, signifying that the loss
of soil fertility was more in old than young field. A short intervening fallow period between first and second year of cropping
did not show any pronounced improvement in soil fertility, though it provided some biomass for second burning. Tilling caused
maximum loss to soil fertility. The fertilizer treatments ended with comparable or better soil fertility in comparison to
no-treatment plot. There seems to be none of the fertilizer treatments superior over others from the standpoint of ending
soil fertility. The unifying conclusions of this series of investigations support the hypothesis that the second year cropping
holds promise to reduce the demand for forested land for jhum, and lengthen the jhum cycle substantially. 相似文献
1