Changes of respiration, enzyme activities, pH and EC in greenhouse vegetable soils in Shouguang

The intensive land use under greenhouse conditions resulted in adverse effect on the soil environmental quality, and soil respiration and enzyme activities are sensitive biological indices to reflect this variance. In order to provide the scientific basis of preventing soils from degradation and promoting agriculture sustainable development, soil respiration, enzyme activities, soil pH and EC were studied in the greenhouse vegetable (tomato) soils under different continuous cropping times (1, 5, 8 and 12 year) in Shouguang, Shandong with the open field soil as control. The result indicated that soil respiration intensity and dehydrogenase activity were higher in greenhouse vegetable soils than that in open field soil. Soil respiration intensity and dehydrogenase activity increased at the beginning, then decreased with the continuous cultivation years, then increased again in the soil of 12 year’s continuous cropping. With continuous cultivation, soil urease activity reduced gradually, but catalase activity increased. Soil respiration and all of enzyme activities decreased with soil depths. Soil pH declined with the continuous cropping years while EC increased. Compared with the open field soil, soil pH in 0-20 cm layer under 12 continuous cropping years declined by 1.06 pH unit, however, no notable change was observed in other soil layers. Soil pH of the surface layer in the study area vary from 6.45 to 7.51 and EC values were less than 0.5 mS/cm, which was suitable for crop growth. Soil EC was an important factor affecting soil pH and enzyme activities, consequently, soil EC and catalase activity were proposed as potential indices to reflect the quality of greenhouse vegetable soils.