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Studies On Greenhouse Gas Nitrous Oxide Emission And Its Mitigation From Vegetable Field

Posted on:2012-03-17Degree:DoctorType:Dissertation
Country:ChinaCandidate:W H QiuFull Text:PDF
GTID:1113330344452574Subject:Plant Nutrition
Abstract/Summary:PDF Full Text Request
Nitrous oxide (N2O) is an important greenhouse gas, and it can result in greenhouse effect and destruct the ozone layer. Up to now, some researches show that application of nitrogen fertilizer to agricultural system is the major source of N2O in the atmosphere. In China, many researches have been reported on N2O emissions from cereal fields, but not much studies has been done on N2O emissions from vegetable fields, especially in Central China. Therefore, based on the summary of the major sources and factors of N2O emission from soil, indoor incubation, undisturbed lysimeter and field experiments were conducted to study the N2O emission from the Wuhan suburb vegetable soils. The tested soil was Alfisols (yellow-brown soil) and sampled from Wuhan suburb. The vegetables of pepper (Capsicum annuum L.), amaranth (Amaranthus mangostanus L.), radish (Raphanus sativus L.), spinach (Spinacia oleracea L.), lettuce (Lactuca sativa L.) and Chinese cabbage (Brassica Chinensis L.) were planted. The objective of this study was to reveal the effects of nitrogen fertilization on N2O emission from vegetable system, and the relationships between N2O and soil moisture, soil temperature, as well as the mitigation impacts of dicyandiamide (DCD) in reducing N2O emission from grazed grassland in New Zealand and vegetable system in Wuhan suburb, in order to provide the measures of controlling N2O emission in Wuhan suburb vegetable system, and a scientific basis for the sustainable production of vegetables. The main results were as follows.1. Indoor incubation and undisturbed soil monolith lysimeter experiments were conducted to study the effects of nitrogen fertilizer application rates on N2O emission from vegetable soil. Indoor incubation experiment showed that nitrogen fertilization significantly increased N2O emission flux and total N2O emission. The N2O emission increased with the increasing of nitrogen application rate. Total N2O emission from three nitrogen treatments (N0, N1 and N2) were 0.2,6.41,10.40 mg kg-1 soil, respectively. Lysimeter experiment also revealed that nitrogen fertilization significantly increased N2O emission and emission factor (EF) from vegetable system. The average annul total N2O emission were 0.8 kg N ha-1 of N0,1.68 kg N ha-1 of N1,5.44 kg N ha-1 of N2 and 13.51 kg N ha-1 of N3, and the average emission factor of three nitrogen treatments (N1, N2, N3) were 0.36%,0.54% and 1.21%, respectively. In addition, N2O emission from high nitrogen treatments (N2 and N3) had a significant liner relationship with the contents of soil nitrate nitrogen and ammonium nitrogen, but they had no relationships under low level of nitrogen application rates (N0 and N1). Total N2O emission had an exponential relationship with nitrogen fertilizer application rates. The filed trial of nitrogen fertilization verified the above results.2. Undisturbed soil monolith lysimeter and field experiments were conducted to study the N2O emission from different kinds of vegetables. The results of lysimeter experiment showed that the average of daily N2O emission ranked in the order of amaranth, pepper, radish, Chinese cabbage, lettuce and spinach. Except N3 treatment, the average of daily N2O emission from the same vegetables (amaranth and pepper) that planted in two years was similar. The results of field experiment showed that the highest average of daily N2O emission was pepper, which varied from 2.29~55.40 g ha-1d-1, while spinach had the lowest emission, which ranged from 1.43~7.86 g ha-1d-1. The average of daily N2O emission ranked in the order of pepper, radish, Chinese cabbage and spinach.3. Indoor incubation and undisturbed soil monolith lysimeter experiments were conducted to study the effects of soil moisture on N2O emission. The results of incubation experiment revealed that the total N2O emission increased by soil moisture when soil moisture varied from WFPS 35% to WFPS 85%, but the total N2O emission decreased when soil moisture increased to WFPS 110%. The highest total N2O emission occurred when soil moisture was WFPS 85%, while the lowest one occurred when soil moisture was WFPS 35%. Emission factor varied from 0.02~3.11%(N1) and 0.02-2.25%(N2). In addition, the results from lysimeter experiment showed that the higher N2O emission occurred between April and September when most of rainfall occurred, which accounted for 77% of total N2O emission. Meanwhile, there was a liner relationship between N2O emission and soil moisture in the treatment without nitrogen fertilizer application.4. Indoor incubation and undisturbed soil monolith lysimeter experiments were conducted to study the effects of soil temperature on N2O emission. Incubation experiment showed that N2O daily emission increased by the increase of soil temperature and the peak emission occurred at the highest temperature when soil moisture was relatively stable. However, when soil moisture changed a lot in one day, the peak emission of N2O occurred at appropriate soil moisture and relatively high soil temperature, which meant that both soil moisture and temperature affected the daily change of N2O emission in this vegetable system. Lysimeter experiment revealed that the seasonal variation of N2O emission was mainly influenced by soil temperature, and the high emissions of N2O occurred between April and September, corresponding to the warm and wet soil condition. N2O emissions were very low (<64.5μg m-2 h-1) during the late winter to early spring due to the low soil temperature, and the daily N2O emission was around background level when soil temperature was less than 5℃. Meanwhile, there was a liner relationship between N2O emission and soil temperature in no nitrogen applied treatment.5. Undisturbed soil monolith lysimeter was used to investigate the difference of nitrous oxide (N2O) emission from the bare soil with N fertilizer application and the soil with vegetable planted. Results showed that N2O emission from the bare soil exceed those from the soil with vegetable planted. The average N2O emission flux from the bare soil was 193μg m-2 h-1, while it decreased to 60μg m-2 h-1 with the vegetables planted. Meanwhile, total N2O emission from the bare soil with lower nitrogen fertilizer applied (T1,500 kg N ha-1) (9.54 kg ha-1) was greater than that from the soil with higher nitrogen fertilizer applied (T2,750 kg N ha-1) (4.21 kg ha-1) during the experimental period (October 2007-September 2008). In addition, N2O emission factor from the bare soil (1.76%) was more than that from the soil with vegetable planted (0.39%).6. Undisturbed soil monolith lysimeter and field experiments were used to investigate the effects of nitrogen fertilizer on vegetable yield and its relationship with N2O emission. The results showed that the yield of vegetables first increased then decreased by the elevated nitrogen fertilizer rates. But, nitrogen use efficiency decreased by the increasing nitrogen application rates. Nitrogen use efficiency had an exponential relationship with nitrogen fertilizer application rates. In contrast, total N2O emission increased by the elevated nitrogen application rates. The results suggested that there is an opportunity to reduce N fertilizer application rate in this vegetable production system, though which can reduce N2O emissions.7. Undisturbed soil monolith lysimeter experiment was used to study the effectiveness of DCD in reducing N2O emissions under winter and summer seasons in grazed grassland in New Zealand. Results showed that DCD significant decreased N2O emission both in summer and winter seasons. Total N2O-N emissions from urine-N applied at 1000 kg N ha-1 were 7.8 kg N2O-N ha-1 in the summer season and it was much lower than that emitted during the winter season (12.3 kg N2O-N ha-1). The application of DCD reduced summer N2O-N emissions to 4.8 kg N2O-N ha-1 in summer and 3.9 kg N2O-N ha-1 in winter, representing 40% and 69% reductions, respectively. The results demonstrated that N2O emissions from animal urine-N in grazed pastures were much higher in the winter season than that in the summer season, and DCD was more effective in reducing N2O emissions in the high emitting winter season.8. Undisturbed soil monolith lysimeter was used to investigate the effectiveness of DCD in reducing N2O emissions in vegetable system. Results showed that DCD significantly decreased total N2O emission in vegetable system. With nitrogen fertilizer applied, DCD reduced 49.3%,50.9% total N2O emission of cabbage and pepper, respectively. And in without nitrogen applied treatment, DCD also reduced 33.5%,33.4% total N2O emission. In addition, DCD decreased N2O emission factor, the emission factor decreased from 0.15% (without DCD) to 0.07% (with DCD) of cabbage, and 0.99% (without DCD) to 0.52%(with DCD) of pepper. These results demonstrated the potential of using nitrification inhibitors to mitigate N2O emissions both in grazed pasture soils and in vegetable system.
Keywords/Search Tags:Dicyandiamide, Nitrification inhibitor, Nitrous oxide, Soil moisture, Soil temperature, Vegetable system
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