Impact Of Fertilization On The Compoment And Budget Of Black Soil Organic Carbon

Soil organic carbon could change soil physical, chemical and biological properties, improve soil structure, affect the maintenance and improvement of soil fertility, and affect crop yields and qualities. The emission of soil organic carbon was closely linked with the global carbon cycle. So the dynamic of soil organic carbon not only affected the sustainable developments of agro-ecosystem, but also affected sustainable developments of the atmosphere and biosphere. Studies on soil organic carbon helped us properly evaluate soil quality conditions and the global carbon cycle, helped us predict soil evolutionary trend and the climate changes, leading us to reasonably control the development of organic carbon and make positive responses to climate changes.The experiment was carried out to study the effects of long-term fertilization on the distribution of soil organic carbon in black soil in Hailun National Field Research Station under the growing of maize.1)Soil respiration with different fertilization treatments had the same regulation. CO₂-C changed from 43.86 mg m-2 h^-1 to 359.32 mg m-2 h^-1. The rate and cumulation of soil respiration under NPKOM treatment were significantly higher than other treatments. Soil respiration rate, soil cumulation respiration, bulk cumulation respiration, rhizosphere cumulation respiration under NPK treatment were higher than other unbalanced fertilization treatments. Q10 rangd from 1.06 to 2.67, and that in CK was the highest, indicating that fertilization reduced the temperature sensitivity to soil respiration. The trend of R² with quadratiic curve which was used to fit with the relationship between soil respiration and soil moisture was: CK>unbalnced fertilization(PK, NP, NK)>balanced fertilization(NPK, NPKOM),indicating that reasonable application fertilizer could alleviate the impaction of soil moisture on soil respiration.2) Nitrogne fertilizer increased soil organic carbon and total nitrogen, but its effect was less obvious than that of NPKOM. There was significantly positive correlation between soil organic carbon and total nitrogen. The trend of soil organic carbon in density fractions was that: heavy fraction(HF)>free light fraction(free-LF)>occluded light fraction(occluded-LF)(p<0.01). The maximum amount of organic carbon was in HF (23.72 g kg^-1), whereas the average of occluded-LF was only 0.69 g kg^-1. Total nitrogen in HF was much bigger than that of occluded-LF and free-LF (p<0.01). The distributions of soil organic carbon and total nitrogen concentrations in density fractions were the same: free-LF>occluded-LF>HF. Soil organic carbon and total nitrogen concentrations in occluded-LF and HF under NPKOM were bigger than those under other fertilization treatments respectively. The trend of C/N ratios was that: free-LF>occluded-LF>soil >HF. The C/N ratios in HF and soil were lowest under NPKOM treatment, and the highest under CK.3)The concentration of microbial biomass carbon which was effected by long-term fertilization followed the trend: NPKOM>NPK>NP>PK>NK>CK. The concentration of CK was 103.6 g kg^-1. The concentration of NPKOM was 108.02% higher than that of CK, and had reached the significantly difference with CK(p<0.05). Organic fertilizer and N fertilizer could improve microbal quotient, and the effect of organic fertilizer was higher. The trend of water dissolved organic carbon was the same as the microbial biomass carbon, but the concentration of water dissolved organic carbon with PK was higher than that of any other fertilization treatments, so we knew that the N fertilizer could redudce the contentration of water dissolved organic carbon. The concentration of NPKOM was the highest and was 81.8 4 mg kg^-1。Microbial biomass carbon and water dissolved organic carbon had a good correlation with soil respiration4)With the growth of maize, the trend of aboveground biomass was: NPKOM>NPK>NK>NP>CK>PK. Change in underground biomass was: NPKOM>NPK>NK>NP>CK>PK, so we concluded that N and organic fertilizer had an important role in the growth of underground biomass. The trend of maize grain and straw biomass was: organic manure and banlanced chemical fertilizer> nitrogen fertilizer>no nitrogen fertilizer. NPK and NPKOM could significantly improve the grain yield, and reached the significantly difference(p<0.05). The economic coefficients of NPK and NPKOM were higher than other treatments, CK was the lowest, only 0.22. The release of carbon to the atmosphere of each 1 kg grain with the treatment of unbalanced chemical fertilizer was higher than that of balanced fertilizer and without fertilizer, so had a greater impact on the environment.5)The balance of soil organic carbon followed the trend: NPKOM>NPK>NP>NK>0>CK>PK. NPKOM could significantly increase soil organic carbon concentration, which was conducive to the accumulation of soil organic carbon. NPK, NP and NK could promote the growth of plants and increase the content of plant residues due to N fertilizer, so soil organic carbon increased. Withou N fertilizer, CK and PK , made the concentration of soil nitrogen decreased , accelerating mineralization of organic carbon, and reduced biomass, so that soil organic carbon budget was deficient.6) Considering the factors of carbon emissions and biomass, we believed that the organic manure and balanced chemical fertilizer could guarantee maize grain and mitigate the greenhouse effect, which can be used to guide the actual production.