Effects Of Long-term Application Of Fertilizer On Wheat Yield And Emission Of The CO₂ And N₂O From Soil In Loess Plateau

Applying of chemical fertilizer and manure can promote the absorption for crop to nutrient and water from soil, and improve soil fertility and crop yield. But unreasonable fertilization method or excessive application of fertilizer increase the emission of CO₂ and N₂O from soil, studying on the emission of greenhouse gas after fertilization is useful to understand the emission amount and emission regularity, and these can provide scientific basis for rational fertilization. Based on the long-term fertilization experiment at the Changwu Agro-ecological experimental station, the objective of this work was to study the effect of fertilization on wheat yield, nutrient uptake characters, CO₂ emission, N₂O emission, soil fertility and water.The results showed that:1. Under different precipitation years, rational fertilization can increase the yield greatly. In drought annual, normal annual and wet annual, fertilizer M increased the yield by 172.43 %, 211.11 % and 262.22 % separately; N, P and M applied together increased production remarkably, in drought annual, normal annual and wet annual, fertilizer NPM increased the yield by 281.74 %,258.89 %,300.00 % separately. The application of organic fertilizer can promote the nutrient absorption significantly, the average of N, P, K uptake were highest in NPM treatment, in wet annual, the N, P, K uptake of wheat seed with M fertilizer are 84.94 %, 84.74 %, 40.55 % higher than NP treatment.2. Soil organic matter in M and NPM treatment were 56.03 % and 51.86 % higher than unfertilized plot, the application of organic fertilizer can promote soil organic matter significantly, and there were no significant difference of total N between M and NPM treatment. Total P and available P in NPM treatment were the highest, they were 16.25 % and 92.69 % higher compared to M treatment, available K of M treatment was the highest and 14.54 % higher than NPM treatment. There was obviously positive correlation between total N and organic matter, soil available P and available K were significantly positively correlated with soil organic matter. Soil water storage in unfertilized and N treatment were higher than others, coefficient of variation of soil water storage in 0⁸0 soil layer was 31 % in different treatments, coefficient of variation of soil water storage was decreasing with the increasing depth, water use efficiency of NPM treatment was the highest, it was 21.23 % and 14.14 % higher compared to NP and M treatment, water use efficiency of M treatment was 1.85 times than unfertilized treatment, and 1.37 times than N treatment.3. Soil organic carbon accumulation with year increasing had different variation trend under different fertilizations, in 2009 the soil organic carbon accumulation of NPM treatment was increased by 81.88 % compared to 1984 when the experiment began, the increasing extent of soil organic carbon accumulatiaon in NPM treatment was the largest. With year increasing, the variation trend of soil organic carbon accumulation in NP and N treatment were not obvious, soil organic carbon accumulation in NPM and M treatment had an obvious rising trend, the application of organic fertilizer can increase soil organic accumulation significantly.4. There were seasonal variability of fluxes of CO₂ emission, under different fertilizer application conditions, the fluxes of CO₂ emission were the lowest in over-wintering stage, and they were below 10 mg CO₂-C·m^-2·h^-1, the fluxes of CO₂ emission in regreen stage was the highest and they were between 0.96 and 117.94 mg CO₂-C·m^-2·h^-1, in regreen stage the fluxes of CO₂ emission of M treatment was the highest, and it was 33.90 mg CO₂-C·m^-2·h^-1. The difference of annual emission of CO₂ between unfertilized and N treatment was not significantly, annual emission of CO₂ of NPM and M treatment were 2301 kg CO₂-C·hm^-2 and 2211 kg CO₂-C·hm^-2, and they were 52.78 % and 48.47 % higher than unfertilized treatment.5. There greater differences in the flux of N₂O emission after fertilization 1 to 20 days, the effect of fertilizer on N₂O emission decreased with the increase of time. The amount of N₂O emission in germination and seeding stage were higher than other stages, the amount of N₂O emission of unfertilized and M treatment had not significant difference in the whole growth stage. Compared to NP and M treatment, the annual emission of N₂O of NPM treatment was increased by 17.09 % and 33.63 % separately, the annual emission of N₂O in M treatment was 0.21 kg N₂O-N·hm^-2, and it was 10.67 % higher than unfertilized treatment. Discharge coefficient of N₂O of NPM treatment was 0.35%, and it was the highest, the discharge coefficient of N₂O of NP and M treatment were 0.28% and 0.22%, all of these were within the normal range of discharge coefficient of N₂O.6. The emission of CO₂ and soil nutrient in NPM and M treatment were increased, the emission of CO₂ in NP treatment was increased, available K in NP treatment was decreased, and the emission of CO₂, total P and available nutrient in N treatment were all decreased. The emission of N₂O and soil nutrient in NPM and NP treatment were increased, the difference of emission of N₂O between M and unfertilized treatment was not significantly, soil nutrient in treatment was greatly increased, the emission of N₂O was greatly increased compared to unfertilized treatment, the effect of N treatment on increasing soil nutrient was not significantly.