| Fertilization can increase soil fertility and crop yield, but excessive fertilization can enhance nitrate leaching and the emissions of greenhouse gases in the cropland, leading to waste of resources and environmental pollution. Based on the long-term fertilization experiment at the Changwu Agro-ecological experimental station in the typical dry-farming area, the objective of this work was to study the effect of fertilization on wheat yield, nitrate leaching, N2O emission, CO2 emission and soil fertility.1. Fertilization can increase the wheat yield significantly. The average yield of wheat was only 1345 kg hm-2 in unfertilized plot from 2006 to 2009, which reached to 1594 kg hm"2 and increased by 18.55% after single application of N fertilizer. The wheat yield was up to 3778 kg hm"2 and 2.37 times as high as that in N treatment when N and P fertilizer were applied together. Appling organic manure can increase more crop yield. The wheat yield of M plot was 3884 kg hm-2 and 2.88 times as high as that in unfertilized plot. When N fertilizer, P fertilizer and manure were applied in combination, the wheat yield was highest and up to 4438 kg hm-2, and 1.14 times as high as that in M treatment.Fertilization can increase height, ear length, spikelet number and grain per spike of winter wheat. The differences of height, ear length, spikelet number and grain per spike of winter wheat were significant in NP or NPM treatments compared with unfertilized plot, but Single application of N or M did not significantly affect height, ear length, grain per spike and 1000-grain weight of winter wheat.N and K uptake rates by wheat were lowest in unfertilized soil, and the average values were 30.93 kg hm"2 and 34.79 kg hm-2 from 2006 to 2009, respectively. N and K uptake rates by wheat increased after fertilization, N uptake rate were the highest (152.55 kg hm-2) in NPM treatment, which was 3.93 times higher than that in unfertilized plot. K uptake rate was the highest (111.22 kg hm-2) in NPM treatment, which was 2.20 times higher than that in unfertilized plot. P uptake rate was the highest (14.62 kg hm-2) when N, P and M were applied in combination, which was the lowest (only 3.99 kg hm-2) in N treatment. N recovery rate was the highest and up to 61.81% in NP plot under different fertilizer application conditions, and it was the lowest (15.17%) in N treatment. The highest value of P recovery rate was found in NP treatment, the average of which was 21.54% from 2006 to 2009. P recovery rates in M and NPM treatments were 4.94% and 4.57%, respectively.2. The increased rate of soil nutrition was the highest after the long-term combined application of N, P and M, and the concentrations of organic matter, total N, total P, available P and available K were increased by 81.88%,115.97%,45.52%,1810.56% and 242.85%, respectively. The increased rate of organic matter, total N, total P and available P were the lowest and increased by 10.02%,33.84%,-2.87% and-49.44% in unfertilized plot, and the increased rate of available K was only-1.56%.3. Excessive N fertilizer application was a main factor for nitrate leaching. NO3--N leached sharply into deep soil in N treatment. NO3--N was not only accumulated in 60～180 cm soil layer, but it also leached below 3 m depth and formed an accumulation peak near 320 cm depth in soil. Residual NO3--N amount was the highest (1498.68 kg hm-2) in 0～400 cm soil layer. NO3--N was accumulated in 20～160 cm soil layer and 160～320 soil layer in the vertical soil profile when N, P and M were applied in combination. NO3--N formed two accumulation zones in the vertical soil profile in NP treatment, but the highest value of NO3--N accumulation peaks were lower than that in N and NPM treatments. NO3--N accumulation were not found in deep soil in unfertilized and M plots, and residual NO3--N amount was the lowest (61.34 kg hm-2) in 0～400 cm soil layer in unfertilized plot. NH4+-N changed irregularly in the vertical soil profiles, the concentration range of which was 10.00 mg kg-1 to 20.00 mg kg-1, and residual amount of NH4+-N in 0～400 cm soil layer was from 650.85 kg hm-2 to 989.73 kg hm-2 under different fertilizer application conditions.From 1999 to 2007, the moving distance of NO3--N was over 100 cm from topsoil to subsoil under different N and P fertilizer application conditions. NO3--N was concentrated mainly in 0～160 cm soil layer under no and low N application conditions in the vertical soil profiles. However, NO3--N accumulation peaks were found in 120～140 cm and 240-260 cm soil layers under excessive N application conditions. When the rate of N single application was 90 kg N hm-2 or more per year, NO3--N was accumulated in 80～100 cm soil layer, and part of which had leached into subsoil below 300 cm depth, and residual NO3--N amount was up to 1500.18 kg hm-2 in 0～300 cm soil layer. Applying N alone easily led to NO3--N leaching compared with N and P combined application, and residual NO3--N amount increased significantly with increasing N application rate. There was no effect of P fertilizer on NO3--N leaching at no or low N level. When annual N application rate was increased to 90 kg hm-2 or more, residual NO3--N would decrease with increasing P application rate.There were two accumulation zones of NO3--N in the vertical soil profile after 23-year NPM application under continuous wheat cropping, one at 20～100 cm depth and the other at 140～320 cm depth. However, NO3--N was concentrated mainly in 0～60 cm soil layer under continuous alfalfa cropping, and accumulated slightly in 200～300 cm soil layer. Residual NO3--N amount in alfalfa field was 588.06 kg hm-2 less than that in continuous wheat cropping.4. The fluxes of N2O emission were 0.31～78.66μg N2O-N m-2 h-1 under different fertilizer application conditions. The average flux of N2O emission was the lowest in unfertilized plot and highest in NPM treatment per year. N2O emission fluxes of germination and seeding growth stages increased in N, NP and NPM treatments, and total N2O emission amounts of germination and seeding growth stages were 25～30% of total N2O emission amount in the whole growth year.Total amount of N2O emission was 0.21 kg N2O-N hm-2 in unfertilized soil per year, which did not increase after M application alone. However, Annual amount of N2O emission increased significantly when N fertilizer was applied alone, which was 64% higher than that in unfertilized plot, and the value was up to 0.34 kg N2O-N hm-2. Annual amount of N2O emission in NP treatment was lower than that in N treatment, which was 0.33 kg N2O-N hm-2 and increased by 60% compared with annual amount of N2O emission in unfertilized plot. Annual amount of N2O emission was the highest in NPM treatment and up to 0.37 kg N2O-N hm-2, which was 80% higher than that in unfertilized plot.5. The fluxes of CO2 emission were 0.96～117.94 mg CO2-C m-2 h-1 under different fertilizer application conditions. The annual average flux of CO2 emission was the lowest in unfertilized plot and highest in NPM treatment. The fluxes of CO2 emission in reviving and fallow stages were higher than other growth stages, and the lowest in over-wintering stage.Total amount of CO2 emission was 1391 kg CO2-C hm-2 in unfertilized plot per year, which was up to 1464 kg CO2-C hm-2 and increased by 5.25% after N fertilizer application alone. Annual amount of CO2 emission increased significantly when N and P fertilizers were applied in combination, which was 36.93% higher than that in unfertilized plot. Annual amounts of CO2 emission in M and NPM treatments were 2301 kg CO2-C hm-2 and 2211 kg CO2-C hm-2, which were 53.64% and 46.89% higher than that in unfertilized plot, respectively. In addication, CO2 emission flux was significantly linear correlated with air temperature and ground temperatures of 0 cm,5 cm,10 cm,15 cm,20 cm,40 cm soil lavers.6. Fertilization enhanced the water absorption and utilization of deep soil, and the desiccation of deep soil was found in the 100～260 cm soil layer under different fertilizer application conditions. The water content of soil was the highest in the 100～260 cm soil layer in unfertilized plot, and the average value was 16.29% from 2006 to 2009. The water content of soil was the lowest in the 100～260 cm soil layer in NPM treatment, and the average value was 9.99%. The desiccation of deep soil was found in the 100～260 cm soil layer under the condition of different N and P fertilizer application rates. The differences of moisture storage ranged from-136.5 mm to 5.4 mm in 0～300 soil layer before sowing.
|
PDF Full Text Request