Study On Energy Flows Through An Agroecosystem Of Lintao County

Taking the agroecosystem of Lintao as study unit, this paper studied the energy flowing in different sub-systems of farming ,animal husbandry, forest, orchard and human being from 1980 to 1999. The ways of energy flow, structure of supplementary energy input, composition of the input and output energy for different sub-systems and energy transformation efficiency were analyzed. The results showed that (1) supplementary energy input, energy transformation efficiency and output energy of farming sub-system were still in low level . The average supplementary energy input was as much as 80.3% of mean level of the whole country in 1979. The energy input of crop field mainly consisted of organic energy which accounted for 64.9% by manure . The structure of energy input (the ratio of organic energy to inorganic energy) reached 2.5262 which was higher than the mean level of the whole country in 1979. The energy transformation efficiency and the energy output were in low level that the average output of grain was as much as 51.1% of mean level of the whole country in 1979. The output energy per hm2 was strikingly related with the input of direct physiology energy, inorganic energy, organic energy, manure, fertilizer and the structure of energy input. The average utilization efficiency of sunshine of farming system, only reached 0.118%, was as much as 33.7% of mean level of the whole country in 1991. Current energy transformation efficiency was still increasing that the average energy input only reached 72% of reasonable energy input scope and energy input in 1999 only reached 87%. Increasing supplementary energy input especially increasing input of manure and fertilizer could greatly increase energy transformation efficiency and energy output. (2) the ratio of energy output to input of forest was high because of poor management and low input . To orchard, the ratio of energy output to input was low. Planting trees and grass in abandoned crop field would promote improvement of ecosystem environment and proportion adjusting of farming, forest and animal husbandry. (3) the ratio of energy output to input which reached 0.4759 and the transformation efficiency of feed which reached 0.52 were high, but the effective product accounted only for 18% to the total energy output of animal husbandry subsystem. Most energy input was consumed by animal. Adjusting structure of animal husbandry to reduce the quantity of animal lived on feed and increase animal quantity which lived on grass could increase the energy output of animal husbandry sub-system. The county could become a base of animal husbandry if took it as an important role and increased energy input to the subsystem because of abundant grass and feed. (4) energy consumed by mankind which mainly composed of fuel accounted for 48.3% to the effective total energy output ofecosystem. The ratio of energy output to input of this subsystem which reached 0.168 was low. The energy output mainly composed of labor energy which accounted for 86.7% to total energy output of human being sub-system. Adjusting the ratio of energy input between farming , forest and animal husbandry system, developing forest and animal husbandry, developing industry and service line to create opportunity for working would greatly improve the ratio of energy output to input of human being sub-system. The agroecosystem of Lintao county was an open system. Every year ,there was 24054.95 x 10 10J product was transported out of the ecosystem. Food produced by this ecosystem couldn't meet the demand of human being because of low productivity. Every year, there was 261219.12 x 10 10J supplementary energy (such as grain, feed, coal, fertilizer, pesticide, oil , tools, machine , etc) which accounted for 29.6% to the total energy output of this ecosystem was brought in the ecosystem to maintain normal working of the ecosystem. The stability indicator of this agroecosystem was 0.51.