Effects Of Fertilization Reforming On The CO₂Flux And The Variation Trend Of Soil Organic Carbon In Paddy Soils With Different Fertilities

Three treatments in a30-year fertilization experiment of paddy soil was adjusted to the following seven treatments:the original high organic material treatment(HOM), the high organic material treatment reforming from the original normal organic material treatment(N-H), the original normal organic material treatment(NOM), the normal organic material treatment reforming from the original chemical fertilizer treatment (C-N), the chemical fertilizer treatment reforming from the original high organic material treatment(H-C), the chemical fertilizer treatment reforming from the original normal organic material treatment(N-C), the original chemical fertilizer treatment(CF). CO2flux of the original and changed treatments during double rice cropping rotation cycle in2012-2013was measured to study the effects of different follow-up fertilization management on CO2flux and variation trend of soil organic carbon (SOC) in red paddy soil with different fertilities. The results clearly showed that the following-up changing of fertilization had obvious impacts on the dynamics of CO2flux. The CO2flux in the soils under long-term organic fertilization treatments decreased after the adjustment from organic fertilization to chemical fertilization. However, the CO2flux in the soils under long-term chemical fertilization treatments increased remarkably after the adjustment from chemical fertilization to organic fertilization. The results also indicated that both organic fertilizer and SOC had important impacts on CO2flux. The amount of organic carbon inputted by organic fertilizers had a significantly positive relationship with the total amount of annual CO2-C flux (p<0.01, n=21), and the inherent SOC content (x) also had a positive relationship with the total amount of annual CO2-C (y)(y=10.96x-68.86, R2=0.74, n=9,p<0.01) in the paddy soils received chemical in2012, while SOC of organinc fertilization treatment has on significant effect on improving CO2flux. The organic material addition amount has no impacts on organic material’s decomposition rate, while the SOC content has clearly effect on its decomposition rate. The fertilization reforming from organic fertilization to chemical fertilization would lead to the loss of SOC in paddy soils due to its mineralization, and the SOC loss increased with the rising of inherent SOC content. The SOC content in the paddy soils under long-term organic fertilization would be consistent with that in the paddy soils under long-term chemical fertilization after the fertilization reforming from organic to chemical fertilization for a certain time. The fertilization reforming from chemical to organic fertilization, or from low organic to high organic fertilization would lead to the SOC accumulation in paddy soils, and the accumulating rate of SOC had a positive relationship with the amount of the inputted organic material. Under same organic fertilization treatment, the apparent decomposition rate of orgamc material applied in the soils with high SOC content was larger than that in the soils with low SOC content, which would result in lower SOC accumulation. So, the paddy soils with different SOC content would have the same SOC level when they received same organic fertilization management for a certain time. As a conclusion, the sustained organic fertilization in red paddy soils with high or low SOC content is essential to maintain or improve the soil organic carbon content in Southern China.