| Soil salinization recently has become an important bottleneck which constrained crop growth, yield increase and agricultural development in arid and semi-arid area. Its physical properties limited agricultural production transforming towards economic development, hence it is extremely urgent and should be put on top priority. PAM, a kind of polymer material has been recognized in soil improvement, water-saving irrigation and water and soil conservation. Though it is very effective in improving physical properties and hydraulic characteristics, preserving water and fertilizer and increasing yield for unsalted soil, research on its application in saline soil has been rarely reported. This thesis makes basic research on physical properties changes, water-saving potential, fertilizer preservation and yield evaluation of saline soil after application of PAM by combing indoor simulation experiments and filed experiments. This is to explore basic application principle of PAM in saline soil, providing some theoretical supports for PAM’s application in saline soil. The preliminary research results are as follows: (1)PAM’s effects on physical properties of saline soilThrough indoor simulation experiment, after applying different amount of PAM in in four saline soil specimens with different physical properties:The higher concentration of PAM, the more increase of soil aggregate. Their soil bulk density reduced, When PAM concentration was 1:10000, the soil bulk density reduced to the lowest level. Their soil porosity increased, but its increase was not always increased with the increase of PAM concentration. When PAM concentration was 1:20000, the soil porosity reached the highest level.Their saturation water content increased and gradually increased with the increase of PAM concentration. Their field capacity increased and gradually increased with the increase of PAM concentration. For abovementioned physical prosperities, salt affected PAM adsorption in soil. Appropriate salt would be conducive to PAM effects in soil, but these effects would weaken if salt was too much. (2) PAM"s effects on saline soil nutrientAccording to analysis of research on nitrogen temporal-spatial distribution after PAM application, the nitrogen in soil without applying PAM infiltrated into soil to different extent under root layer, while that in soil applying PAM was maintained in 0-40cm soil layer and most of it was maintained in 0-20cm under PAM application layer. For fertilizer utilization, efficiency of nitrogen and phosphate fertilizer were improved after applying PAM.(3) PAM’s effects on temporal-spatial distribution of saline soilAccording to analysis of research on temporal-spatial distribution of soil, salt in soil was very easy to move and greatly affected by irrigation water and soil evaporation. Salt in soil without applying PAM fluctuated greatly, especially in 0-20cm soil layer. While salt in soil applying PAM was greatly affected by irrigation water and leached towards deep layer by irrigation. When water in soil decreased, there was not very much accumulation of salt in the surface soil. It was thus very clear that PAM to some extent can significantly prevent salt from moving upward.(4) PAM’s effects on plant growth indicators in saline soilAccording to filed experiment result for indicators, application of PAM can obviously increase its height, stem diameter and leaf size. It turned out that water content in 0-40cm root layer increased, but it was more effective if the PAM was applied in 0-20cm soil layer. Application of PAM can obviously increase soil temperature and reduce soil evaporation. The experiment also found that PAM can better perform its function in saline soil when it was applied together with fertilizer. According to range analysis of orthogonal experiment and multivariate orthogonal regression, all these three factors involved have greatly influenced the yield and influences were fertilized water >PAM concentration. Based on the range analysis, the optimal experiment combination was S2F2P4; therefore, application of PAM can save 10% water with better fertilizer preservation, meeting requirement of experiment. These were about relation of qualitative analysis factors and level. A relational expression eventually was obtained through multivariate analysis of experiment results and regression equation was proved to be valid after significance analysis of it. |
