| At present,our country has become the first big country raising pigs in the world.Pig farming has become an important thrust to promote the development of pig husbandry,and also one of the important pillar of economic development.In the background of the development of pig industry,a large amount of pig manure is accumulated in soil and applied as organic fertilizer in farmland,which inevitably has a great impact on soil.Tibetan pigs are unique to Tibet and have strong adaptability to the harsh alpine climate and grazing conditions.Under the grazing mode,Tibetan pigs are mostly active in rural fields.However,after the African swine Fever in 2018,a large number of Tibetan pigs died of virus infection,and the Tibetan pig breeding industry suffered a great blow.However,the range of activities of Tibetan pigs is limited to a certain range in semi-shed feeding mode.Therefore,feces and other excrements generated by Tibetan pigs are also accumulated on the soil where Tibetan pigs are active in the semi-shed feeding mode.Farmers gradually apply Tibetan pig feces as an important fertilizer in the field when carrying out agricultural production activities.As a result,Tibetan pig manure has a great impact on soil nutrients,heavy metal content and microbial biomass.Using Tibetan pig manure as raw material of organic manure,this study explored the effects of Tibetan pig manure on soil pH,electrical conductivity,alkali-hydrolyzed nitrogen,available potassium,organic carbon and heavy metals arsenic,cadmium,chromium,lead,copper,nickel,zinc and mercury by applying Tibetan pig manure to the field.Soil samples were collected at the soil layers of 0cm,10cm,20cm,40cm,80cm,150cm and 300cm in the PVC pipe,and the physical and chemical properties and heavy metal content in the soil were measured.The main results obtained in this study were as follows:1.It was found that the pH value of the soil used in the test was above 7,which was alkaline soil.After the application of Tibetan pig manure organic fertilizer,the pH value of the soil was higher than that of the soil without the application of Tibetan pig manure organic fertilizer,especially there was a significant difference between the treatment group with Tibetan pig manure and the treatment group without the addition of Tibetan pig manure.In addition,soil pH values of all treatment groups showed an increasing trend from surface soil to deep soil,indicating that the application of Tibetan pig manure organic fertilizer could improve soil pH and soil salt content.2.It was found that soil electrical conductivity values of the two treatment groups applying Tibetan pig manure organic manure were significantly different from those of the two treatment groups without Tibetan pig manure organic manure.Soil electrical conductivity values of the two treatment groups applying Tibetan pig manure organic manure were significantly higher than those of the two treatment groups without Tibetan pig manure organic manure,indicating that after the application of Tibetan pig manure organic manure,Soil electrical conductivity value increased significantly,indicating that Tibetan pig manure organic fertilizer had a very significant effect on the improvement of soil electrical conductivity.3.The contents of organic carbon,alkali-hydrolyzed nitrogen and available potassium were significantly increased in the surface soil,and the differences in the contents of organic carbon,alkali-hydrolyzed nitrogen and available potassium between the soil with and without application of Tibetan pig manure were gradually reduced with the increase of soil depth,indicating that Tibetan pig manure had no obvious effect on the contents of organic carbon,alkali-hydrolyzed nitrogen and available potassium in the deep soil.However,the content of organic carbon,alkali-hydrolyzed nitrogen and available potassium in surface soil was significantly affected by Tibetan pig manure manure.4.In the experiment,it was found that the contents of arsenic,cadmium,chromium,nickel and mercury in the surface soil were increased after application of Tibetan pig manure.Compared with the soil without application of Tibetan pig manure,the contents of heavy metals as,cadmium,chromium,nickel and mercury in the soil layer from Ocm to 10cm were significantly different.In the soil layer below 20cm,The contents of heavy metals as,cadmium,chromium,nickel and mercury in soil with and without application of Tibetan pig manure showed little difference,indicating that the effects of organic manure from Tibetan pig manure on the contents of heavy metals as,cadmium,chromium,copper,nickel and mercury in soil below 20 cm were not obvious,and the heavy metal content in soil with application of Tibetan pig manure was much lower than the standard value of soil heavy metals stipulated in soil environmental quality standards.It showed that the heavy metal content in soil after application of Tibetan pig manure did not pose a threat to the normal growth and development of soil plants and animals.5.This study found that the content of lead,copper and zinc in soil changed little after the application of Tibetan pig manure with plant stems and leaves as the staple food.Compared with before the application of Tibetan pig manure,the content of lead,copper and zinc in soil had no significant difference except for individual soil layers,indicating that the content of lead,copper and zinc in soil was less affected by the organic manure with plant stems and leaves as the staple food.In summary,this study showed that the application of Tibetan pig manure organic fertilizer had significant effects on soil physicochemical properties and heavy metal content,especially on soil nutrients and heavy metal content in soil suitable for arable layer.This study provided a certain theoretical basis for rational utilization of Tibetan pig manure organic fertilizer in the process of agricultural production. |
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