The Experimental Study On The Soil Water And Ammonium Nitrogen Transport Characteristics Of Water-biogas Slurry Hole Irrigation

With the rapid development of facility agriculture in our country, the contradiction between supply and demand of agricultural production and fertilizer has become increasingly prominent, leading to the continuous deterioration of agricultural ecological environment.Biogas slurry is the incidental product of biogas project, rich in nutrients and have a high value of use.While hole irrigation is an effective way to water saving irrigation in agricultural production.Taking water- biogas slurry solution as the research object in this paper,on the basis of hole irrigation,indoor simulate infiltration test,study on the effect of soil bulk density, slurry concentration, hole diameter and hole depth four influencing factors on the soil infiltration characteristics of water-biogas slurry hole irrigation and on the distribu- tion characteristics of water and ammonium nitrogen,conclusions of the paper are listed as follow:(1)The infiltration rate and cumulative infiltration of water-biogas slurry hole irrigation reduce with the increase of soil bulk density and concentration of biogas slurry,In which the infiltration rate of CK control treatment is the largest.The infiltration rate of biogas slurry treatment group and CK control treatment were obviously different,the greater concentration of biogas slurry,the more obvious the infiltration rate decreased;the infiltration rate and the cumulative infiltration showed an increasing trend with the increase of the hole diameter,when the hole depth is increased from 5cm to 10 cm, the initial infiltration rate increases 2-3 times.(2)Fitting the dynamic relationship between infiltration rate,cumulative infiltration and time under different treatment conditions by using the Kostiakov infiltration model,the results showed that the two mentioned above had significant correlation with time,R2 reached more than 0.9, and the P in fitting model are less than 0.01,which reach a significant level of difference;empirical infiltration coefficient K is decreased with the increase of soil bulk density, increased with the increase of hole diameter and hole depth,empirical infiltration index α increased with increase of soil bulk density, slurry concentration and the hole diameter, and decreased with increase of hole depth.(3)By measuring the wetted soil moisture content of water-biogas slurry hole irrigation, the results showed that the distribution of the highest area of soil moisture content is more regular, basically distributed in the 2cm of the bottom and horizontal3 cm of the hole. Wetted soil moisture content decreased with the increase of theconcentration of biogas slurry and soil bulk density, and with the increase of biogas slurry concentration, the distribution of soil moisture content tends to be uniform, the sharp decrease tends to decrease gradually. The distribution range of high water content increased gradually with the increase of hole diameter; When the depth of the hole is increased from 5cm to 10 cm, the CK control treatment is more likely to migrate to the lower soil layer.(4)The transfer distribution of ammonium nitrogen content in wetted waterbiogas slurry hole irrigation is basically the same, means that the ammonium nitrogen reached the maximum value near the hole position, with the increase of infiltration distance, the content of ammonium nitrogen in wetted soil decreased rapidly to the original value of soil ammonium nitrogen content, even slightly lower than the original value. While there was a small amplitude increase of the content of ammonium nitrogen in the wetting front position. Therefore, from the hole position the distribution trend of ammonium nitrogen can be divided into three regions, they are high ammonium nitrogen content area near the hole position, the rapid reduction area of ammonium nitrogen content around the high content area and the low content blank area of ammonium nitrogen away from the hole position.(5)The ammonium nitrogen content in wetted soil of water-biogas slurry hole irrigation reduces gradually with increase of the hole diameter, the rapid reduction area of ammonium nitrogen content increased gradually, in high ammonium nitrogen content area, the concentration of ammonium nitrogen increased with the increase of soil bulk density, but the distribution range of ammonium nitrogen content decreased gradually, due to the increase of the hole depth, the vertical migration distance of ammonium nitrogen content increased in the wetted soil, and the vertical migration distance is larger than the transverse distance.(6)Fitting and comparative analysis the change relationship between the content of ammonium nitrogen and soil water content in the longitudinal direction of the wetted soil by using a linear function, cubic polynomial function and power function.It was found that the changing relationship between soil ammonium nitrogen content and soil water content are the highest fitting degree with the function image of three degree polynomial function, the fitting R2 reached more than 0.9.