This paper deals with the application of man-made water weeds in freshwater fish-farming and its biological mechanism. Putting the man-made water weeds in mixed-fish-farming pond can enlarge the superficial area, accerelate organic substances mineralization rate, enrich the nutrient elements in water body, and increase the amounts of algae and heterotrophic-bacteria. It is found that there are more zooplankton in test-pond than in comparative-pond. Since the bait is increased, the fish yield increased by about 15. 6%. 

The population structure of Shanyi village is analyzed, and future population in 2000 is predicted. Land bearing capacity is estimated based on population density and agricultural production. The possible change of labour structure is predicted on the basis of the adjustment of village industrial structure. It is pointed that the key measure for solving surplus labour problem lies on the enhancement of labour’s quality. 

Based on the investigation of population, resource, economy and environmental situation of Shanyi village, 20 indexes have been selected to compose systematic comprehensive benefit assessment index system in three different aspects. The design principle of index system and interrelationship between individual index and systematic benefit are illustrated. This index system has been used to calculate the economic, ecologic and social benefit indexes of the village in the periods of 1982-1984, 1985-1987 and 1988-1990. The achievements of ecologic construction of the village are quantitatively assessed.

The agro-ecological Environmental problems in mountainous area of Guangdong province are analyzed based on the data from scientific investigation. The countermeasures for agro-ecological environmental protection and improvement in this region are also suggested. 

Agricultural development strategy of Youyu County was analysed with the principal components analysis in this paper, productivity and stability of agroecosystem were evaluated. Results showed that ecological and eco nomic efficiency were good.

This paper reported the life cycle of Apple snail and its ecological characters on egg laying, hatching , growth and dormancy. Based on the characters mentioned, the comprehensive technology for high yielding culture consisting of production arrangement, feed sources, cultural density, water management, periodic distributing and catching in breeding seasons and preserving snail over winter etc. was developed. 

In order to exploit the new source of animal protein-Apple snail, a series of food chain research have been carried out using the snail as animal protein feed on mink, chicken, duck, prawn and crab etc. since 1985. The results of feeding trials for various food chains showed that the weight gains and the economic benefit were very significant , and the trasferring efficiency for snail protein was higher than that in domestic fish meal but somewhat lower than that in Peruvian fish meal. All of these display an extensive potential for exploitation. 

The background values of Cu, Zn, Mn, Co and As content of the major soiltypes (Permeable paddy soil, Stagnating soil, Fluiroaquic sandy soil, Stagnating paddy soil, Peratating paddy soil, Waterlogged paddy soil, Dystric fluiroaquic soil, Sandy loam, Coasted saline soil and salinized soil) in Shanghai are studied for the first time. The contents of Cu, Mn, Co and As are highest in the coasted saline soil, followed by the salinized soil, and is lowest in the Sandy loam. Through variance analysis, it is verified that there are differences at different degrees in some elements among the soil types. And its relationship with the organic matter, pH value and lime reaction is also discussed.

This paper indicates that making useful of waste water from silk reeling synthetically in agricultural engineering is available and practicable through the studying of three kinds of models as follows, i. e. planting lotus root -rasing fish, Mlternanthera philoreroides-planting wild rice stony-arrowhead, Alternantheraphiloxeroides-planting wild rice stem -arrowhead-lotus root. Also we analyse the effects of the varities of aquatic plant, air temperature and the field plot keeping apart to the purification of water. 

In this paper, the trace level of organic pollutants wewe analyzed in irrigating wastewater from west Shanyang area. The methods of resin adsorption and GC/MS/DS were used. 79 organic pollutants were indentified from the irrigating waste water. 24 organic pollutants involved in EPA’s priority pollutants were quantified. The potential danger of the trace toxic pollutants in the water to the soil and ecosystem were also discussed. 

High speed development of agriculture needs the input of chemical fertilizer. However, over use of fertilizer will induce man-made pollution, harm directly human’s health and threaten human’s living environment. It is found that maximum suggested fertilzer application rate is not the best method to be adopted. The results of experiments and theoiy inference indicate that even the suggested fertilizer application rate reduce by 20%, the crop yield will not decrease by more than 2%. This result is benefit in increasing fertilizer availability and reducing chemical fertilizer pollution. 

This paper provides theory basis for the paid use of environment and natural resources throughdemonstrating their values from the natural reproduction process, social reproduction process, direct labour and indirect labour. The major cause of the crisis of environment and natural resources is the insufficient realization of their values. The humanity has plundered the "false profit"by sacrificing environment and natural resources in the history of economic development. The steps fo carry out the paid use policy include further study of basic theory, publicity, the establishment of the accounting system of environment and natural resources, gradual transition form imposing tax to levying fee for the use of environment and natural resources. 

The destruction of the ecosystem caused by the exploitation and utilization of natural resources isfundamental and incorrigible sometimes. According to the stipulations of the Law of Environment Protection, the measures to protect ecosystem must be taken when the natural resource is exploited and utilizated. To the project of exploitation, utilization and construction of natural resources, the measures of collecting ecosystem construction compensation of natural resources exploitation construction project should also be taken to keep the balance of ecosystem. In order to adopt the measure mentioned above smoothly, "The Management Mensures of Collecting Ecosystem Construction Compensation of Natural Resourcesa Exploitation Construction Project"should be discussed and formulated as soon as possible, and then it should be reported to the National People’s Congress for approval and defined in the legal form, so that the destruction of the ecosystem caused by the exploitation and utilization of the natural resources can be controlled on the whole,and the balance of ecosystem can be kept.