Studies On Ecological Effect Of Applying Plastic Cover Within A Row Among Different Genotypes Of Soybean

Seasonal drought and discontinuity low temperature are the restrictions for Heilongjiang dry farming agriculture.Therefore, it's of great significance to study and spread the technology for drought-relief and increasing soil temperature by applying plastic covering within a wide ridge.The soybean yield comparison trails by using plastic covering technique were carried out in the Science and Technology Demonstration Area of Qixing State Farm in both 2006 and 2007. With dilution method and DGGE, the dynamic micro-organisms and the genetic diversity of microbial community in soybean rhizosphere were tested in 2007. There are two soybean varieties such as Kenfeng15 and Kenfeng16 were used in the two-year field trials. The treatments were included plastic covering, no-plastic covering as a check traetment for both soybean varieties. In order to investigate the mechanism of applying plastic covering in increasing soybean yield, the soil temperature, soil moisture dynamics, microbial diversity in rhizosphere of soybean, the technology of plastic covering within a wide ridge had been studied. The study has provided us a theory basis for the plastic covering technology.The numerical results were as following:1. Better effects on improving soil moisture, soil temperature were conducted by plastic covering in two years which showed: plastic covering treatment could get a better result for decreasing the evaporation of top layer's soil moisture and regulating the distribution of soil moisture; The soil moisture and moisture-use efficiency within 0-20 cm of plastic coving treatment was consistently higher than the Check, increasing the underground water's movement to the top layer which conducted the moisture content within 20cm-30cm soil layer were higher than the Check plot in the early soybean growing stage, and then lower than the check in the late soybean growing stage. The temperatures were significantly higher by plastic covering than the Check. By the plastic covering, the everage dayly temperature was increased by 2.24℃in 0-20cm soil layer than the Check.The soil temperature in 10cm, 15cm, and 20cm soil layers were higher than the Check which increased everage dayly temperature as 0.93℃, 0.89℃, and 0.79℃; the temperature at 20 o'clock was also increased and everage temperature at 20 o'clock were increased in the soil layers such as 5cm, 10cm, 15cm, and 20cm to 0.61℃, 0.99℃, 0.98℃, and 0.91℃. Therefore, it prevented the low temperature hurt for soybean growth in the early stage.2. By plastic covering, the amount of soybean rhizospheric microorganisms were increased than the check. It showed significantly differences on 30thday and 45th day after plastic covering. The amount of soybean rhizospheric bacteria and actinomycetes have been improved with higher temperature and soil moisture by plastic covering than the Check, meanwhile the rhizospheric fungi were restricted and lower than the Check. The differences in both treatments for a mount of soybean rhizospheric microorganisms were disappeared after the plastic covering was uncovered later.3. By plastic covering, the genetic diversity index was getting riched on 30th day and 45th day and 60th day after plastic covering than the Check. The amount of soybean rhizospheric bacteria and varieties have been improved, and that could be identified by Denaturing gradient gel electrophoresis. The analysis results of Cluster analysis for Kenfeng 15 and Kenfeng 16 showed that the soybean rhizospheric bacteria varieties were belonged to the same family, which indicated that the influences of the soybean rhizospheric bacteria varireties by plastic covering were higher than the influeces of soybean varieties. The differences were disappeared after the plastic covering was uncovered later.4. The soybean growth in the early growing season was improved by plastic covering. Comparing to the Check, the plant hight, and stem thickness and plant's dry matter weight of both soybean varieties were increased significantly by plastic covering.In two years'study, it showed the yields of both Kenfeng 15 and Kenfeng 16 by plastic covering were significantely higher than the Check. By the yield components, it is showed the 100-kemels weight of soybean by plastic covering was higher than the Check, which indicated the total amount of soybean dry matter transformed was higher than the Check.