Effects Of Irrigation Intensity Of Biogas Slurry On Soil And Plant Nutrient And Heavy Metal Content

Biogas slurry is rich in nutrients and heavy metals,which excessive used will cause the accumulation of nutrients and heavy metals in the soil,and even bring the problem of quality and safety of agricultural products.Due to the lack of corresponding research,the suitable irrigation level for farmland is not clear at present.In order to investigate the accumulation of nutrients and heavy metals in soil and plants under different irrigation types(different irrigation intensity and plants),in this study,23 different types of cultivated land in Guangxi were selected as the research objects,which the nutrients(TN,TP,AN,AK,AP),heavy metals(TCu,TZn,TPb,TCr,TCd)of the surface soil(0-40 cm)and plant organs(root,stem,leaf,fruit and so on)were analyzed to explore the influence of irrigation intensity and plant type interaction on nutrients and heavy metals in soil and plant.The results showed that:(1)Irrigation of biogas slurry can improve soil nutrient content(0-20 cm)significantly.The average content of soil TN,AN,AK,TP,AP increased by 0.46 g/kg,43.43 mg/kg,106.78 mg/kg,0.70 g/kg and 71.95 mg/kg respectively after irrigated,,and the average increase was 49%,62%,144%,140%and 398%.On the whole,under the condition of II grade(81?160m3/mu),although the increase of soil nutrients content was the largest,the effect of irrigation intensity on nutrient content of quick-acting was not significant.(2)Biogas slurry increased the content of heavy metals in soil significantly,and heavy metals moved towards the 20-40 cm layer obviously.Among the 23 samples,the increased number of Cu,Zn,Pb,Cr,Cd is 20,22,19,16 and 14 respectively,and the average growth of Cu,Zn and Pb were 131%,76%and 23%,respectively.In the 20-40 cm layer,compared with the average CK,the Cu,Zn,Pb,Cr,Cd increased by 105.73%,118.23%,19.43%,58.10%and 47.06%,respectively.(3)Nemero pollution index was used to evaluate all samples.With the increase of the intensity of biogas slurry irrigation,the number of samples of pollution gone up,and increased the pollution level.The samples were clean under Grade I irrigation,there were 2 Zn mild pollution under Grade II irrigation,and 2,6,2 and 4 samples of Cu,Zn,Cr and Cd respectively under Grade ? irrigation.(4)Under the same irrigation intensity,the N,P,K of leafy vegetable and oil plants,and forage heavy metals were higher than those in timber forest and fruit tree.In the plant organs,the amount of nutrient content is leaf>stem,root>fruit,and the content of heavy metals is root>leaf,stem>fruit.(5)The heavy metals of plants are different,elephantgrass has the strongest enrichment ability.The enrichment factor of grass leaf is higher than banana leaves as much as 35.7 times.(6)The contents of heavy metals irrigated with biogas slurry,water spinach,citrus,grapefruit and pear were all above the national standard.Water spinach,pear Pcomplex>3,have were polluted seriously;elephant grass is basically clean.Under the type of elephant grass + group flower,its carrying capacity is 24?30 head pig/mu(3.4 tons pig manure/mu).