Effects of cultivating years on soil ecological environment in greenhouse of Shouguang City, Shandong Province

Abstract

Greenhouse farming is one of the important ways to produce vegetables in the world. This technology is characterized by that it may produce high yield of vegetable and would be less affected by the seasons. In addition, it could improve the land-use efficiency and agricultural sustainability in the regions with a large population but not enough arable land. Therefore, it could significantly raise the income of the farmers and was extended quickly in northern China. In China, Shandong province is the major vegetable production region, accounting for nearly 50% in terms of greenhouse area. In recent years, the vegetable production in greenhouse farming system has developed rapidly and brought good economic revenue and social benefits in Shouguang, Shandong Province. Now, Shouguang has been one of the most important vegetable production bases of China and obtained the title “the village of Chinese vegetable”. However, due to the lack of scientific and reasonable fertilization guidance, many problems has also arisen in vegetable production including excessive fertilization nutrient imbalance, and low fertilizer use efficiency, resulting in nutrient accumulation in soil, significant decrease in vegetable quality, and serious deterioration of soil under greenhouse conditions. Thus, the greenhouses for years in some regions are no longer suitable for vegetable production. This situation had brought certain negative impact on the agricultural sustainability, vegetable quality and ecological environment. To examine the effect of different cultivating years on soil ecological environment under the greenhouse conditions, this study was conducted to investigate the differences of soil physical and chemical properties, microflora, and the correlations between cultivating years and soil physic-chemical properties and microbial quantity under the greenhouse conditions. The results showed that with the increase of cultivating years, soil bulk density and pH value were significantly reduced, while the soil porosity, electrical conductivity, soil salt content and organic matter content were significantly increased. The contents of soil total nitrogen and total phosphorus were kept rising. The amounts of total potassium, nitrate nitrogen and available phosphorus in soils increased in the first years, and then followed by a gradual reduction. With the increase of cultivating years, the number of bacteria tended to decrease after a rise in the first years; the number of actinomycetes remained relatively constant after a rapid rise in the first years; only the number of fungi had been continuously increasing. It can be concluded that the large inputs of organic and inorganic fertilizers lead to the soil acidification, nutrient imbalance, a decrease in micro-ecological balance, and significant increases in soil salt content and environmental risk in the greenhouse soils of different cultivating years. Thus, some reasonable and scientific fertilization strategies should be proposed and recommended to the vegetable producers to coordinate the balance between nutrient and energy of soil, improve soil quality and ensure the security of soil ecological environment in greenhouse. Main strategies may include the alteration of the fertilization habit of farmers, reductions in the amounts of nitrogen fertilizers, phosphorus fertilizers and some physiologically acid fertilizers, and properly combined application of organic and inorganic fertilizers.