Effect Of Long Term Fertilization On The Distribution Of Carbon And Nitrogen In Reddish Paddy Soil

Reddish soil is a major soil type in the rice farming zones of Southern China. Paddy soil is an important wetland ecosystem. In recent years, the structure in reddish paddy soil is damaged seriously and the fertilize of reddish paddy soil decreased significantly under the deterioration of natural environment and human activities, resulting in the sustainable utilization of paddy soil and the quality and quantity of rice reduced seriously.Soil aggregate is an important component of soil structure, and it has an important significance in improving soil fertility and improving soil structure. The distribution of carbon and nitrogen in reddish paddy soil are affected by different kinds of fertilization treatments.Fertilization is an effective method to improve the content of carbon and nitrogen in reddish paddy soil, but excessive fertilization will increase the leaching of soil carbon and nitrogen.The study was established in a 14 years long term field experiment site in reddish paddy soil of Qianyanzhou Ecological Station. The fertilizer species treatments were: Control(CK),straw return(ST), nitrogen, phosphorus and potassium mineral fertilizers(NPK) and pig manure(OM), aiming to study the effect of soil carbon and nitrogen leaching situation under different fertilization in reddish paddy soil, and the distribution of soil carbon and nitrogen contents in bulk and aggregates. Soil solution samples were collected by caly tube and vacuum pump and the soil aggregates by wet sieving method. The main results in our study are as follows:(1) The leaching of dissolve organic carbon(DOC) and ammonium nitrogen(NH4+-N)in reddish paddy soil were higher in the vegetative growth stage than in the reproductive growth stage(P<0.05). In the reddish paddy soil, NH4+-N was the main type of nitrogen in leachate. The leaching amount of NH4+-N was higher in the NPK treatment than other treatments. However, the leaching amount of DOC was highest in the OM treatment in reddish paddy soil.(2) The distributions of NH4+-N, DOC, soil organic carbon(SOC) and total nitrogen(TN)contents were different in reddish paddy soil under different fertilization treatments. The NPK treatment significantly increased TN content, but the SOC content was highest under the OM treatment.(3) The DOC and NH4+-N contents in soil leachate were significantly positive correlated with the SOC and TN contents in reddish paddy soil(P<0.01).(4) The silt and clay was major type of aggregate in reddish paddy soil, which accounted about 1/2.(5) The fertilization treatment of ST, NPK and OM increased the soil organic carbon andtotal nitrogen contents in bulk and three different sizes of aggregates in reddish paddy soil.The effect of OM treatment was more significantly than other treatments.