Productivity and sustainability in intensive agricultural system in the coastal area of lake Dienchi, Yunnan Province, China

Abstract

Since 1979, the collective production team system has been replaced by the farm household responsibility system in China. Farmers were able to improve agricultural intensification to obtain greater annual output and higher profits in the new farm system, which has led to unsustainable agriculture and environmental problem. We assessed the annual nutrient input-output balance in the heavy intensive agricultural systems in the coastal area of Dianchi Lake, one of the most eutrophic lakes in China. The annual nutrient inputs into agricultural systems have drastically increased by the heavy use of chemical fertilizers and manure in multiple cropping fields of vegetables, and concentrate feeds in intensified livestock production systems. However, parts of the nutrient inputs were not used effectively in the agricultural systems and thus the excessive nutrient surplus were emitted into the environment, causing significant environmental problems, such as nitrate contamination of the groundwater and river water. We carried out fi eld experiment based on the result mentioned above and suggested the effective methods showing next that could improve the input–output balance of nutrients without yield loss in the intensive agricultural system. The first method was improvement of input-output balance in multiple cropping fi elds by reducing chemical fertilizer input for leaf vegetables depending on nitrate concentration of the soil without yield loss. The second was improvement of absorption ratio of chemical nitrogen in continuous cropping fields by controlling club root disease （Plasmodiophora brassicae） of cruciferous vegetables by soil solarization. The third was enhancement of the nitrogen cycle in the agricultural system by harvesting common reed planted in constructed wetlands for wastewater treatments, and using harvested common reed as roughage for ruminants.