Effects Of Long-term Nitrogen And Phosphorus Addition On Soil Carbon, Nitrogen And Phosphorus And Bacterial Characteristics In Loess Plateau

In recent years,with the advance of industrialization,industrial,agriculture,transportation and other industries on the demand for fossil fuel consumption increased dramatically.Agricultural technology increasingly innovation,the inputs of fertilizer,pesticides,organic fertilizer and so on in the farmland soil are increasing.The amount of nitrogen emitted by human beings is constantly increasing.The southeastern part of China is one of the three concentrated areas of the world's nitrogen deposition,gradually expanding to the northwest of our country.There is a close relationship between the farmland ecosystem and the nitrogen deposition.Excessive nitrogen deposition makes the soil of the farmland acidify,which directly affects the soil fertility and microbial activity.Based on the above discussion,this paper explores the characteristics of long-term nitrogen and phosphorus addition to soil chemistry and biology in the typical farmland soils of the northwest farmland-the Changwu Experimental Station of the Chinese Academy of Sciences.In this paper,six different fertilization treatments were used,including Control,N12,N24,P12,P24,N12P12.The basic chemical properties of soil,microbial biomass,soil basal respiration and microbial diversity were measured.By studying the effects of different nitrogen and phosphorus addition on soil basic chemical properties and microbial diversity,some suggestions were given for soil fertility.The following is the conclusion of this paper:In the 0-20cm soil layer,the addition of nitrogen and phosphorus could increase the content of total carbon in the soil compared with nitrogen and phosphorus.The increase was in the range of 1%?8%,when the combination of nitrogen and phosphorus(N12P12)the content of soil total carbon is largest.When adding nitrogen fertilizer solely the content of total carbon in soil was higher than that in single adding phosphate fertilizer.The addition of fertilizers could increase the contents of total nitrogen in the soil,while the content of total nitrogen in the soil was higher than that in the single phosphorus.The higher concentration of nitrogen could promote the accumulation of total nitrogen in the soil,the accumulation of soil total nitrogen was higher in the lower concentration phosphorus.The effect of inorganic phosphorus on soil total carbon and total nitrogen was not obvious.When the phosphorus was transferred to the soil,the contents of total phosphorus and available phosphorus in the soil were improved,and the higher the level of phosphorus concentration,the more obvious the effect on the two.There was a significant difference in soil pH with different fertilization methods in the tested soil test.With the increase of fertilizer concentration,soil pH will decrease.The amount of active organic carbon in the cropland of the Loess Plateau is high,and the addition of fertilizer can improve the microbial biomass,the effect of nitrogen fertilizer on microbial biomass carbon and microbial biomass nitrogen was higher than that of phosphate fertilizer,and the addition of nitrogen and phosphorus at higher concentration level was higher than that of lower concentration.The addition of nitrogen and phosphate could affect the content of NO3-N and NH4-N in soil,especially the addition of nitrogen fertilizer could increase the content of NO3-N in soil.The addition of inorganic fertilizer in soil could improve the content of NH4-N,but the increase is not obvious.Compared with no added chemical fertilizers,the influencing intensity of NO3-N and NH4-N in soil was N24>N12.The addition of nitrogen and phosphorus affects the change of soil microbial biomass P,and the phosphorus fertilizer increased the microbial biomass P,and the microbial biomass P increased with the dosage of phosphate fertilizer.Although the addition of inorganic nitrogen to the soil can also increase the MBP in the soil,the magnitude of this increase is not obvious,and the larger the increase in nitrogen fertilizer,the smaller the increase.The addition of nitrogen and phosphorus promotes soil basal respiration,works best when N12P12,and the effect of phosphate fertilizer on soil basal respiration was higher than that of nitrogen fertilizer.The higher the amount of nitrogen and phosphorus added the stronger basal breathing.Soil pH has the opposite trend of carbon,nitrogen,phosphorus and basal respiration in soil.There was a significant positive correlation between soil total carbon and total nitrogen and MBC,and the correlation coefficient of MBN and basal respiration was larger.There was a significant positive correlation between soil total nitrogen and MBC,and there was a significant positive correlation with MBN and nitrate nitrogen.So the content of soil carbon and nitrogen are closely linked.There was a significant positive correlation between soil total phosphorus and available phosphorus and MBP.Therefore,compared with the soil carbon,nitrogen,soil phosphorus has a certain relative independence.At the similar level of 0.97,the diversity and abundance of soil bacteria were affected by the addition of nitrogen and phosphorus.The diversities of soil bacteria were:N24>CK=P24>P12>N12P12>N12,while the abundances of soil bacteria were:N24>P24>CK>N12P12>N12>P12.The addition of lower nitrogen and phosphorus will reduce the diversity of soil bacteria,and the higher concentration of nitrogen and phosphorus can promote the abundances of soil bacteria.The total sample of the soils of the six sample combinations received 33 phylum,362 genus.But the proportion of dominant bacteria at each level will change due to the addition of nitrogen and phosphorus.At the level of the phylum,the main advantages of this test soil were proteobacteria.acidobacteria.actinobacteria.With the increasing in the level of single-added nitrogen fertilizer increased the proportion of proteobacteria,while with the increasing in the level of single phosphate fertilizer reduced the proportion of proteobacteria.With the increase of the concentration of inorganic nitrogen fertilizer alone,the proportion of acidobacteria was decreased,but the proportion of acidobacteria increased with the concentration of inorganic phosphateadded alone.On the actinobacteria,the addition of other fertilizers would increase the proportion of actinobacteria except for higher concentrations of nitrogen fertilizers.At the level of the genus,the main advantages of this experiment were subgrop-6-norank,bacillus,RB41-norank and nitrobacteria.Phosphorus fertilizer has a positive effect on the proportion of Subgrop-6-norank,and the greater the concentration level is,the more obvious it is.In addition to the addition of higher concentrations of phosphate fertilizer,the other addition of fertilizers make the proportion of RB41-norank reduced.The higher the concentration of nitrogen fertilizer,the greater the proportion of nitrobacteria,however,the increase in the concentration of inorganic phosphorus fertilizer will increase the proportion of nitrobacteria.