Effect Of Salt On Soil Electrochemical, Structure And Biological Properties

With the development of facility agriculture and the excessive utilization of chemical fertilizer, the problem of soil salinization is becoming increasingly important. Because of the special environment of greenhouse and unreasonable irrigation and fertilization, soil salt accumulation appears in greenhouse soil and some vegetable field soil, which led to the deterioration of soil quality and the decline of production. Most of the existing relevant research is focusing on the field research, which can not clearly explain the effect of salt on soil properties. The in-room incubation experiment was applied to investigate the effect of salt stress on soil electrochemical properties, soil structure and soil biological properties, in yellow cinnamon soil surrounded Hefei city. In this experiment, a group of the control(CK) and four-level salinity(0.3%, 0.6%, 0.9%, 1.2%) treatment was set up, which was incubated for 90 d at 25 in an incubator. Then discuss the relevant change mechanism ?in order to support the utilization efficiency of greenhouse soil and vegetable field soil.The main results are as follows:(1)Salt had significant effects on soil p H; the higher the salt concentration, the lower the soil pH. Compared to CK, soil p H of 90 d decreased by 0.53 at 1.2% salinity level.(2)Along with the increase of salt concentration, the amount of soil cation exchange capacity decreased. Compared to CK, soil p H of 90 d decreased by 2.5 cmol·kg-1 at 1.2% salinity level. The correlation study showed that soil cation exchange capacity were highly linear with soil p H value under salt stress.(3)In the early days of the cultivation, > 0.5 mm aggregate content in control treatment and 0.3% treatment were higher than the treatment with higher salt concentration. With the extension of incubation time, the micro-aggregates were gradually decreased and the macro-aggregates were gradually increased. The macro-aggregates were also increased along with the increase of the simulated salt concentration.Along with the extension of incubation time, the content of > 0.25 mm aggregates were getting higher, which was mainly because Ca2+ played an important part in the soil. Compared to CK, > 0.25 mm aggregates in 0.6%, 0.9% 1.2% treatment at 90 d increased 11.42%, 21.53% and 31.68% respectively.The change of aggregates mean weight diameter under salt stress was similar to the change of > 0.25 mm aggregates. Along with the extension of incubation time, the mean weight diameter of aggregates was getting higher. Compared to CK, the mean weight diameter of 0.9% and 1.2% treatment at 90 d increased 22.86% and 28.57% respectively.(4)Salt stress had a significant inhibitory effect on soil microorganism. The higher the salt concentration, the lower the soil microbial biomass C and N, during which, the inhibition was the most significant at incubation of 45 d, and respectively got to 65.62% and 57.68% for soil microbial biomass C and N at 1.2% salinity level, compared to CK treatment.The study of soil microbial biomass carbon and nitrogen ratio showed that soil microbial biomass carbon and nitrogen ratio declined along with the salt concentration increased.(5)Salt stress had a significant inhibitory effect on soil enzyme, overall, the activity of enzyme was decreased with the increasing of salt content in experiment soil, in which, that of urease, phosphatase, protease and cellulose inhabitation was relatively notable, especially for cellulose, inhibitory ratio arrived to 62.20% at the level of 1.2% salinity and incubation of 75 d. Correlation analysis indicated that the soil microbial biomass C and N were highly linear with the activities of soil enzymes at same salt content.