Abstract:The different soil bulk density levels (1.35g/cm3, 1.40g/cm3, 1.45g/cm3 and 1.50g/cm3) were constructed by indoor manual configuration. The experiment of water and fertilizer infiltration was carried out in the soil bin. The effects of soil bulk density on cumulative infiltration, wetting front migration, soil moisture, NH+4-N and NO-3-N transport were investigated. An empirical model was created, in which the cumulative infiltration amount and the wetting front migration distance were the dependent variables, and the bulk density and infiltration time were independent variables. Results showed that the soil bulk density had a significant effect on the cumulative infiltration, the migration distance of wetting front and the distribution and transformation of moisture and nitrogen in the soil. With the decrease of soil bulk density, the cumulative infiltration, wetting front migration, moisture in the body, NH+4-N and NO-3-N contents showed an increasing trend. The greater the soil bulk density was, the smaller the infiltration coefficient K became. The greater the soil bulk density was, the greater the infiltration index α became. At the same time, the average value, the change amount and the conversion rates of NH+4-N and NO-3-N in wetted body were increased with the increase of soil bulk density. The closer the distance to the emitter was, the higher the contents of NH+4-N and NO-3-N became. The distribution of NH+4-N in the moist body was mostly concentrated in the vicinity of the emitter. With the redistribution, the content of NH+4-N in the wetted soil and the conversion rate were decreased gradually, and the transformation amount was increased gradually. After the redistribution for 3d, 5d, 10d, 15d and 20d, with the end of irrigation time as the benchmark, the decline order was 2.34%, 11.41%, 34.22%, 59.06% and 73.75%, respectively. The distributions of NO-3-N in the soil were similar to water. After the redistribution for 3d, 5d, 10d, 15d and 20d, with the end of irrigation time as the benchmark, the NO-3-N content increase order was 0.76%， 60.12%, 156.95%, 204.68% and 180.51%, respectively. The soil bulk density had a significant effect on the distribution and transformation of moisture and nitrogen in the soil.
