| Soil salinization is one of the most important abiotic stresses that constrain global growth and crop production.Effective and rapid improvement and development of coastal salinized soils,while promoting economic development,can also take into account the environment and sustainable development,which has important practical significance.Through the existing research and production practices,it is proved that the cultivation of rice is one of the most effective ways to improve the soil in saline soil.However,there is little report on the information on the improvement mechanism.In this study,the coastal saline-alkali land in Jiangsu Province was studied.By studying the plant growth characteristics,soil physical and chemical properties(including soil salinity,soil pH,soil nutrients,soil organic carbon and its components,soil enzyme activity),soil microbes,etc.,of the the bare lands,the Suaeda lands,the rice lands planted for one(planted in spring 2016)and three years(planted in spring 2014),to explore the biological process and mechanism of planting rice to improve the heavy saline-alkaline soil in the coastal area.The main findings are as follows:1.In July,the biomass of the leaves,stems,roots,and the aboveground and underground parts of the three treated plants ranged from low to high:Suaeda<the rice planted for one year<the rice planted for three years,and all were significant differences.In October and November,the biomass of leaves,stems,roots,rice ears,aboveground parts and underground parts of the rice planted for three years was greater than the rice planted for one year in the same period of time,and all except the leaves were significant difference.In terms of water content,the water content of leaves,stems and roots of the two groups of rice in July was significantly higher than that of Suaeda.In October and November,there was no significant difference in water content of each organ in the rice planted for one year and the rice planted for three years in the same period of time.The Na+ and Cl-contents of rice and rice hulls decreased significantly with the increase of planting years.In addition,with the increase of rice planting years,the fullness of rice ears and 1000-grain weight were significantly improved.2.It showed that the soil bulk density of the rice group was significantly lower than that of the control group and the Suaeda group in the topsoil layer(0-20 cm)through the results of soil bulk density in different soil layers.In other soil layers(10-20 cm,20-40 cm,40-60 cm),the order of soil bulk density from large to small is:bare lands>Suaeda lands>rice lands.The planting of rice and the natural growth of Suaeda can significantly increase the total porosity of the topsoil(0-10 cm).In the 0-20 cm soil layer,the order of total porosity from small to large is:bare lands<Suaeda lands<rice lands.In the 20-60 cm soil layer,the order of total porosity from small to large is:rice lands<Suaeda lands<bare lands.In the topsoil layer(0-10 cm),the capillary porosity of the rice groups are significantly higher than that of the bare lands and the Suaeda lands.The order of the capillary porosity from small to large is:bare lands<Suaeda lands<rice lands planted for one year<rice lands planted for three years.In this soil layer,the non-capillary porosity of the rice groups were significantly higher than that of the bare lands and the Suaeda lands.3.The soil salinity of rice lands planted for three years in the topsoil(0-10 cm)was significantly lower than that of the other groups.In the 10-40 cm soil layer,the salt content of the rice groups were significantly lower than that of the bare lands and the Suaeda lands,and the order of salt content from large to small was:bare lands>Suaeda lands>rice lands.The results of soil pH and nutrient content showed that the planting of rice reduced the soil pH to a certain extent,significantly increased the organic matter content,and the total nitrogen and total potassium content also increased to some extent.4.The organic carbon content of rice groups were significantly higher than that of bare lands and Suaeda lands in 0-20 cm soil layer,and there was no significant difference among the four groups of 20-60cm soil layer.The results of organic carbon content indicate that the order of the components in the 0-10 cm soil layer from small to large is:bare lands<Suaeda lands<rice lands planted for one year<rice lands planted for three years.In the 10-20 cm soil layer,the sequence of mineral-bound organic carbon content from small to large is:bare lands<Suaeda lands<rice lands planted for three years<rice lands planted for one year.In addition,the order of the other four components is the same as that of the 0-10 cm soil layer.The ratio of particulate organic carbon to mineral-bound organic carbon from small to large is:bare lands<Suaeda lands<rice lands planted for one year<rice lands planted for three years,and the ratio of rice groups in 10-60 cm soil layer significantly larger than the bare lands and the Suaeda lands.5.The order of catalase activity,urease activity and invertase activity was as follows:rice lands planted for three years>rice lands planted for one year>Suaeda lands>bare lands.In the topsoil(0-10 cm),there are significant differences among the four groups.In the 10-60 cm soil layer,the activities of the three enzymes in the rice groups were significantly higher than those in the bare lands and the Suaeda lands.Alkaline phosphatase activity is lower in the rice lands than in Suaeda lands.6.The composition of soil microbes generally showed a high degree of similarity,but the distribution of the proportion of each door to each door shows a certain difference.There are four main dominant strains of soil,namely Proteobacteria,Chloroflexi,Bacteriodetes and Faimicutes,which are higher than 70%of the total.The results of bacterial(16S rDNA)sequencing showed that the order of species richness from high to low in different treatments was rice lands planted for one year>rice lands planted for three years>Suaeda lands>bare lands.In conclusion,long-term planting of rice in saline-alkali land can not only improve the quality and yield of rice,but also improve soil physical and chemical properties in some ways,such as improving soil physical properties,reducing soil salinity and pH,increasing soil nutrients,enhancing soil enzyme activity,increasing soil microbial community diversity and abundance,etc.,thereby achieving the effect of improving the soil of coastal saline soil.And these provided a scientific basis for explaining the mechanism of planting rice to improve the function of coastal saline soil. |
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