Impact Of Long-term Fertilization On Soil Fertility And Bacterial And Archaeal Communities

The black soil(Mollisol) of northeastern China composes one of the three largest Mollisol areas in the world. It is a very important cormodity grain base in our country since black soil has high SOM(soil organic matter) content, soil nutrients and soil fertility.Black soil areas play an important part in grain security in our country. Fertilization is a very important implement in promoting soil productivity and crop yield. Horever, long-term fertilization degerenated soil quatility gradually with arable layer becoming thinner and SOM content decreased. There have been some researches on the topic of “impacts of long-term fertilization on soil qualities” in recent years. However, their technique and methods are outdated relatively. And they ignored the relationship between soil bacterial and archaeal communities and soil phisochemical characteristics.This paper exploited the 34-year long-term fertilization experiment, aimed to investigate the characteristics of soil bacterial communities shift, and combined with the soil physiochemical characteristics to reveal the main driving factors of soil bacterial and archaeal communities. Five different treatments including CK(without fertilizer), application of recommended doses of NP(nitrogen-phosphorus), NK(nitrogen-potassium), PK(phosphorus-potassium) and NPK(nitrogen-phosphorus-potassium) were sampled. The changes of bacterial communities and soil nutrients were investigated via Miseq pyrosequencing and conventional chemical analysis. Correlation analysis was carried out to reveal the main important factor for determining bacterial community composition. The results are showed as follows:Compared to CK, long-term utilization of nitrogen fertilizer promoted the content of soil nitrogen, NO3-, available nitrogen and SOM, while soil pH decreased. Long-term implement of phosphrous fertilizer promoted the content of available phosphrous with 6.6, 6.6, 8.5 times relatively in NP, PK, NPK treatment compared to unfertilized treatment. While long-term implement of potassium fertilizer promoted the content of available potassium with 30.9%, 29.8%, 50.6% relatively in NP, PK, NPK treatment compared to unfertilized treatment. These results indicated that long-term fertilization increased the contents available nutrints of black soil.Soil catalase activity decreased significantly in fertilized treatment compared with unfertilized control. The activities of soil urease and invertase significantly increased 30.5% and 27.4% relatively in NK treatment, while there are no significant changes in NP, PK, NPK treatment. These results showed that long-term different fertilization decreased the resistivity to H2O2 of black soil, while different utilization of fertilizers had different impacts on soil invertase and urease.Soil crop yield singnificantly increased 116.5%, 59.3%, 48.7%, 154.1% relatively in NP, NK, PK, NPK treatment, and significant distinguishment existed between different fertilization treatments. In addition, NPK treatment owns the highest crop yield and significantly higher than the other four treatments. These results showed that the utilization of chemical fertilizer promoted soil productivity hugely.The quantity of soil bacterial and archaeal singnificantly increased 32.2%, 64.5%, 165.2%, 88.3% relatively in NP, NK, PK, NPK treatment, and significant distinguishment existed between different fertilization treatments. In addition, PK treatment owns the highest copy number and significantly higher than the other four treatments. These results showed that the utilization of chemical fertilizer promoted soil bacterial and archaeal number.Proteobacteria and Acidobacteri are the dominant phyla in 5 different fertilization treatments. Α-diversity showed that balanced fertilization of nitrogen, phosphrous and potassium had the highest bacterial and archaeal diversity and abundance. RDA analysis and Pearson correlation analysis showed that there were close contact between soil phisochemical characteristics and soil bacterial and archaeal communities. All the environment factors contributed 100% variation of soil bacterial and archaeal communities, and pH was the most important one, which contributed 66.5%( P=0.034) variation.In summary, long-term fertilization significantly changed soil phisochemical characteristics, soil enzyme activity, crop yield, soil bacterial and archaeal number and community structures. Balanced fertilization of nitrogen, phosphrous and potassium can effectively promote soil available nutrients, crop yield, and the abundance and diversity of soil bacteria and archaea, which proved to be the best fertilization model of the five. The decrease of soil pH caused by the utilization of nitrogen fertilizer is the main drive of the change of soil bacterial and arhaeal communities. Our research demonstrated the effects of long-term different fertilization on bacterial community shifts, and find out pH was the most important factor for determining bacterial structures. The results may provide a new insight in understanding of the microorganisms of black soil, and will be great meaningful to the rational utilization of fertilizer and agricultural sustainable development.