Farm Biogas Slurry Irrigation Effects On Bamboo Forest And Soil

Animal feces is one of the main raw materials for biogas fermentation.The use of biogas slurry in agriculture is becoming more and more widely,but mainly in crops as well as fruits and vegetables.In this study,the bamboo,which character as fast-growing,short rotation and fast nutrient consumption,was used as the research object to study the effect of the biogas slurry on the bamboo forest and soil.The test materials was pig biogas slurry from Shipan farm of Yaqian town.Through completely replacing fertilizer sprinkler irrigation bamboo by the biogas slurry,with non-sprayed biogas slurry as control,the purpose of the study was to analyze the changes of soil environmental quality and bamboo yield with the biogas slurry sprinkler years;explore the best sprinkler years of biogas slurry applied in bamboo forest and the environmental carrying capacity of soil against biogas slurry;evaluate the economic and environmental benefits of the "pig-marsh-bamboo" ecological cycle model,and to provide technical guidance for the large-scale farm pollution control and the industrial development of bamboo forest.The main results of the study are as follows:1.Soil Physical and Chemical PropertiesBiogas slurry irrigation can improve soil physical and chemical properties,but the effect on soil bulk density and water content is limited;In soil surface,the soil pH,organic matter,total phosphorus,available phosphorus and available potassium maximum increase compared with the control were:22.12%、54.83%、354.90%、317.25% and 475.00%.In the lower soil,In addition to other available potassium,while the content of other elements was lower than that of surface layer.In consideration of sprinkler uneven or sprinkler own range,the optimal range of the experimental nozzle is 2-3 m.There was a significant positive correlation between soil total nitrogen and total N,total P and available phosphorus,pH and water content and organic matter under different times of sprinkler irrigation.However,the correlations between other indexes were not significant.2.Soil enzymes and soil microbesThe activities of soil urease,sucrase and the total amount of soil microbes were improved in different degree by biogas slurry irrigation,while the values of soil catalase Ure were below 0.1,the activity was almost zero;Both in the surface and in the deep soil,the order of bacteria and fungi amount is: TA> TB> T,while the actinomycetes were less affected by biogas slurry for a short time;In the vertical direction,the soil enzyme activity and microbial biomass in the surface soil were much higher than that in the deep soil;In the horizontal direction,the amount of soil microbes was less farther away from the nozzle.There was a significant correlation between soil urease and sucrase,sucrosease and soil microbes,and the correlation among the other enzymes was not significant.Fungi and actinomycetes were significantly correlated,besides,there was no significant correlation between the remaining soil microbes.3.Soil heavy metal content and pollution riskThe content of Cu,Zn,Pd and Cr in soil sprayed by biogas slurry increased inordinately.Among them,the maximum value of heavy metals in the TA* plots with the longest irrigation period was higher than that in the same year: 325.96%,135.06%,560.83% and 267.44%.The migration characteristics in the vertical direction of soil were obvious except Zn,especially the soil heavy metal Pd.In the horizontal direction,except that Zn content decreased with the distance,there were no significant changes in the rest of other heavy metals;The soil pollution risk elevated with the increase of sprinkler age.Among them,while Zn pollution was serious.Based on the results of risk evaluation under different standard values,it is suggested that bamboo should be primarily produced in the area.4.The impact on bambooCompared with the control,the average DBH and stalk weight of bamboo were significantly increased after spraying by biogas slurry,and the the average diameter of DBH and stalk weight were proportional to sprinkler years;TA,TA* plots of bamboo economic benefits were 4513.36 yuan /mu,5913.69 yuan /mu,which is higher than the control nearly doubled,which enhanced benefits significantly.5.Maximum sprinkler period and environmental carrying capacityBiogas slurry continuous irrigation will increase the risk of heavy metal pollution,especially heavy metal Zn.When the area mainly produce bamboo shoots,the maximum application period of biogas slurry is 3 years,and the soil carrying capacity of biogas slurry is 3t/a.When mainly produce bamboo in this area,the maximum application period of biogas slurry is 35 years,and the soil carrying capacity of biogas slurry is 35 t/a.In summary,the application of biogas slurry improved soil quality and increased the yield of bamboo significantly.Taking into account the impact of heavy metal from biogas slurry,it is recommended that the region be dominated by bamboo production.