Response of carbon and nitrogen contents of winter wheat to long-term fertilization treatments in fluvo-aquic soil

【Objectives】 In order to reveal impact of various fertilization treatments on carbon and nitrogen accumulation in wheat, we analyzed biomass carbon and nitrogen contents at different growth stages of wheatafter 21-year of continuous fertilization management at a Zhengzhou experimental site. 【Methods】 The fertilization treatments included non-fertilization (CK), chemical nitrogen (N), chemical nitrogen and phosphorus (NP), chemical nitrogen and potassium (NK), chemical nitrogen, phosphorus and potassium (NPK), NPK plus organic manure (NPKM), and NPK plus maize stalk (NPKS). The aboveground samples of three quadrats from each plot were randomly collected at the wintering stage, jointing stage, grain filling stage and maturity stage in 2011-2012 winter wheat growing season. The carbon and nitrogen contents of aboveground plant tissue were measured by EuroVector EA3000 Elemental Analyzer. 【Results】 The results show that the above-ground biomass amounts of winter wheat can be improved efficiently under the NPK, NPKM and NPKS treatments, and the amounts at the wintering stage, jointing stage, grain filling stage and maturity stage in the NPKM treatment are 111%, 194%, 238% and 206% higher than those of the CK treatment, respectively. Except the wintering stage, the above-ground biomass amounts at same growth stage are not significantly different among the NPK, NPKM and NPKS treatments, which indicate that compared to the NPK treatment, NPKM and NPKS treatments do not effectively enhance above-ground biomass of winter wheat. The fertilization does not effectively affect the carbon content of aboveground plant tissue. The average of carbon content at the four growth stages is 410 g/kg. The nitrogen contents at the maturity stage of wheat are high under the N (19.4 g/kg) and NK (18.1 g/kg) treatments. The nitrogen content at the maturity stage of wheat under the N treatment is 52% higher than that under the NPKM treatment and 66% higher than that under the NPKS treatment. At different growth stages, the nitrogen contents of aboveground plant tissue are in sequence of wintering stage jointing stage grain filling stage maturity stage. With wheat growth, the carbon content is unchanged while the nitrogen content is decreased gradually, thus C/N ratio of wheat is increased gradually in each treatment. Carbon accumulations in above-ground are affected by above-ground biomass. The nitrogen accumulation amount at the maturity stage of wheat under the NP treatment is significantly higher than those under other treatments, and is about 545 kg/ha. 【Conclusions】The fertilization does not affect the carbon content of wheat, while the fertilization can affect the nitrogen content. Therefore, wheat biomass yield determines the carbon accumulation amount, and the nitrogen content determines C/N ratio. The NPK, NPKM and NPKS treatments significantly enhance the carbon and nitrogen accumulation amounts, thus these treatments are beneficial to enhance carbon and nitrogen accumulation in farmland system and improve soil fertility.