| With the rapid development of livestock breeding industry,manure discharge from livestock breeding has increased rapidly.People pay more and more attention to the impact of livestock manure and urine on soil environment.With the increasing quantity of pig production,the amount of manure produced by raising pigs also increases.The feces and urine produced by raising pigs are characterized by large quantity and strong fluidity,which is easy to pollute the soil environment.However,the manure produced by raising pigs also contains nutrients needed for plant growth.It is very important to properly control the process of pig manure returning to the field for the resource utilization of pig manure and the conservation of soil and water environment.The Qinghai-Tibet Plateau,located in southwest China,is the highest plateau in the world,breeding Tibetan pig,a rare plateau pig species in the world.In order to study the effects of stocking Tibetan pigs on soil quality in the stocking area,this study collected soil(NS)and soil(GS)before and after breeding Tibetan pigs were collected in this study.The changes of soil p H,electrical conductivity,organic matter,alkali-hydrolyzed nitrogen,available phosphorus,available potassium and soil heavy metals were analyzed,and the changes of NS and GS bacterial communities were analyzed using the16 Sr RNA method.The main research results were as follows:(1)The pH value and conductivity content of soil(GS)after breeding Tibetan pigs were increased compared with that before breeding Tibetan pigs,and showed a significant difference(P<0.05),and decreased with the increase of soil depth,indicating that the stocking of Tibetan pigs has a positive effect on the adjustment of soil p H value and the improvement of soil salt content.And it is more obvious in the topsoil.The organic matter content of soil(GS)was slightly lower than that of soil(NS)before pig breeding,showing no significant difference(P>0.05),and decreased with the increase of soil depth,indicating that the effect of stocking Tibetan pigs on soil organic matter was not significant.The contents of alkali-hydrolytic nitrogen,available phosphorus and available potassium in soil(GS)after breeding Tibetan pigs were increased compared with that before breeding Tibetan pigs,and the differences were significant(P<0.05).In surface soil,the contents of GS decreased with the increase of soil depth and showed a decreasing trend,which indicated that stocking Tibetan pigs had a significant effect on increasing soil nutrients.Improving soil quality has positive effect,but the effect on deep soil decreases gradually.(2)The content of arsenic,chromium and nickel in the soil(NS)after pig breeding was slightly increased compared with that before pig breeding,and reached the highest value in the 20 to 25 cm soil layer,but the content was far lower than the national standard for soil environmental quality(GB 15618-2018),and would not cause harm or pollution to the soil environment and plants.The contents of mercury,lead,cadmium,copper and zinc in soil(NS)after breeding Tibetan pigs were lower than those before breeding Tibetan pigs,and showed significant differences(P<0.05).There were significant differences in zinc content in soil layers of 10 to 15 cm and 20 to 25cm(P<0.05).Its content did not exceed the national soil environmental quality standard(GB 15618-2018).Therefore,the effects of Tibetan pig manure on the content of arsenic,chromium and nickel in farmland soil were not obvious.In conclusion,the content of heavy metals in the manure produced by Tibetan pigs is small,which will not cause pollution or harm to the soil environment and plants.(3)The stocking of Tibetan pigs will affect the proportion of bacterial community in shallow soil,thus changing the structure and function of bacterial community in shallow soil,and affecting soil homeostasis and health.Including:The richness and diversity of soil bacterial communities affected by Tibetan pig stocking decreased,resulting in significant changes in the proportion of some bacteria.The proportions of Acidobacteria,Planctomycetes and Verrucomicrobia in GS0 were significantly lower than those in NS0.These bacteria are closely related to the degradation of organic matter,soil nutrients and soil homeostasis.Planctomycetes,Verrucomicrobia,Flavobacterium and Massilia were obviously changed in the soil affected by the grazing of Tibetan pigs,which were closely related to the nitrogen cycle in soil.At the same time,the abundance of Cyanobacteria and Bryobacter decreased,which may affect soil carbon retention ability.The faecal pollution caused by the stocking of Tibetan pigs increased the proportion of certain bacteria groups and genera,such as Firmicutes,Bacteroidetes and Acinetobacter.When soil homeostasis is damaged,the soil will repair itself,and Masseillas and Luteimonas,which have heavy metal resistance,improved soil environment and macromolecular degradation ability,are increased in abundance.The abundance of Verrucomicrobia and Gemmatimonadetes was positively correlated with soil depth. |
