Infiltration characteristics and Philip model fitting analysis of biogas slurry hole-irrigation
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DOI:10.7606/j.issn.1000-7601.2019.01.20
Key Words: biogas slurry hole-irrigation  cumulative infiltration volume  wetted body  Philip infiltration model
Author NameAffiliation
ZHENG Jian China Western Research Center of Energy & Environment, Lanzhou University of Technology, Lanzhou, Gansu 730050, China
Gansu Key Laboratory of Complementary Energy System of Biomass and Solar Energy, Lanzhou, Gansu 730050, China
College of Energy and Power Engineering, Lanzhou University of Technology, Lanzhou, Gansu 730050, China 
ZHANG Yan-ning China Western Research Center of Energy & Environment, Lanzhou University of Technology, Lanzhou, Gansu 730050, China
Gansu Key Laboratory of Complementary Energy System of Biomass and Solar Energy, Lanzhou, Gansu 730050, China
College of Energy and Power Engineering, Lanzhou University of Technology, Lanzhou, Gansu 730050, China 
WANG Yan Gansu Key Laboratory of Complementary Energy System of Biomass and Solar Energy, Lanzhou, Gansu 730050, China
College of Energy and Power Engineering, Lanzhou University of Technology, Lanzhou, Gansu 730050, China 
ZHANG En-ji China Western Research Center of Energy & Environment, Lanzhou University of Technology, Lanzhou, Gansu 730050, China
Gansu Key Laboratory of Complementary Energy System of Biomass and Solar Energy, Lanzhou, Gansu 730050, China
College of Energy and Power Engineering, Lanzhou University of Technology, Lanzhou, Gansu 730050, China 
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Abstract:
      Biogas slurry hole-irrigation technology is a kind of on going integration of water-biogas slurry irrigation method, to explore the soil infiltration characteristics and suitable infiltration model of the conditions of biogas slurry hole-irrigation, effects of biogas slurry ratio(the volume ratios of digestate to water were: 1∶4, 1∶6 and 1∶8), hole diameter(3, 5 and 7 cm), and soil bulk density(1.35, 1.45 g·cm-3) on the soil infiltration characteristics were analyzed through laboratory experiments, and impact factors of infiltration and wetted body under the biogas slurry hole-irrigation were analyzed with the mathematical statistics method. At the same time, using Philip infiltration model analyzed the biogas slurry hole-irrigation cumulative infiltration. The results showed that the cumulative infiltration volume increased with decreasing biogas slurry:water ratio and soil bulk density but increased with increasing the hole diameter. After the infiltration lasted for 180 min, the cumulative infiltration volume in CK treatment were 3.62, 3.12, 2.77 times and 3.47, 2.64, 2.16 times compared to the digestate treatments of 1∶4, 1∶6 and 1∶8 at the soil bulk density of 1.35 g·cm-3 and 1.45 g·cm-3. The shape of the wetting body is an ellipsoid, which changes gradually with increasing the hole diameter, from greater horizontal axis to greater vertical axis. The ratios of horizontal to vertical axis (V/H) were 0.929, 1.081, 1.111 and 0.957, 1.048, 1.064 when the hole diameter were 3, 5 cm and 7 cm at the soil bulk density of 1.35 g·cm-3 and 1.45 g·cm-3. The power function can be used to accurately describe the functional relationship between the maximum wetting distance and time. Meanwhile, the relationship between the cumulative infiltration volume and the soil bulk density, hole diameter, and the biogas slurry ratio can be modeled by the established multiple linear equation perfectly, and the partial regression coefficient test was at significant or very significant level. Philip infiltration model can accurately describe the relationship between the cumulative infiltration and time with a decision coefficient R above 0.98. For the Philip infiltration model, the soil infiltration rate S increased with increasing hole diameter, however, the S decreased with increasing biogas slurry ratio and soil bulk density, the soil stable infiltration rate A with the biogas slurry viscosity and the suspended particles contained in the biogas slurry related. It is suggested that the optimal ratio of biogas liquid, hole diameter, and soil bulk density in agricultural production are 1.35 g·cm-3, 5 cm, 1∶6 and 1.45 g·cm-3, 7 cm ,1∶8, respectively.