【作者】 李曼莉；

【导师】 沈其荣； 徐阳春；

【作者基本信息】 南京农业大学 ， 植物营养学， 2003， 硕士

【摘要】 稻田土壤是大气中CH₄和N₂O的主要生物排放源之一。中国是水稻生产大国，稻田对温室效应的影响已成为众人关注的焦点。由于世界范围内的水资源紧缺，水稻旱作已逐渐成为人们研究和推广的重点。土表覆盖旱作水稻是一项崭新的栽培技术，它具有节水、省工、节本等优点。相对于水作稻田而言，水稻旱作栽培后，稻田温室气体排放的种类和数量也相应地有所改变。然而这种栽培方式对温室气体排放的影响尚未见报道。本文通过对不同覆盖处理旱作稻田与水作稻田CH₄和N₂O排放特点进行的比较，旨在阐明水稻旱作栽培对大气环境和温室效应的影响，为该技术的推广提供环境评价依据。 于2001和2002年的5～10月在盐城市郊的江苏沿海地区农科所试验场进行了大田试验。通过连续两年的观察，比较了水稻旱作不同覆盖处理以及水作处理稻田甲烷和氧化亚氮的排放特征。试验中设有盖膜、盖草和裸露3种不同旱作处理和1个常规水作对照，第二年去除旱作裸露处理，增设旱作覆草推荐施肥处理（基肥不施氮肥）。研究结果表明： 常规施肥条件下，水稻生长季旱作各处理稻田的CH₄排放通量显著低于水作处理，而N₂O排放通量显著高于水作处理，旱作各处理间没有显著差异。水作稻田CH₄的排放总量2001年是旱作处理的8～19倍，2002年是旱作处理的5～7倍；而旱作稻田当季N₂O的排放总量2001年是水作稻田的5～6倍，2002年是水作稻田的3～4倍。水作处理稻田CH₄排放通量与生育期密切相关，以2001年分蘖盛期的5.0 mg m^-2 h^-1为最大。氮肥的施用是旱作各处理N₂O排放通量的主控因子，每次施肥后都会出现一个N₂O的排放高峰，最高可达4.394 mg m^-2 h^-1。旱作盖草推荐施肥处理由于基肥不施氮，整个生长季N₂O排放总量显著降低，只有5.565 kg hm^-2，与水作处理稻田的N₂O排放总量(3.742 kg hm^-2)相当。 2001年水作处理的产量(9574.1 kg ha^-1)显著高于旱作各处理的产量(覆膜8518.5 kg ha^-1，盖草8481.5 kg ha^-1，裸露7833.3 kg ha^-1)，而旱作处理间没有显著性差异；2002年的产量除旱作覆草推荐施肥处理(7508.5 kg ha^-1)和旱作覆膜处理(7207.9 kg ha^-1)显著低于常规水作处理(8250 kg ha^-1)外，其余各处理间皆无显著性差异。 在20年的短时间尺度下，2001年旱作各处理稻田产生的CH₄和N₂O对全球温室效应的增温潜势（GWP）与水作处理差异不显著；如果从长远角度看（如500年），由于旱作和水作条件下稻田CH4和N20排放的研究水稻旱作造成土壤NZO的排放增加，反而会导致对温室效应的影响加剧。2002年增设的旱作盖草推荐施肥处理对减少温室效应效果显著，无论在短时间尺度下还是从长远角度看，对全球增温效应都大为减小。 在本试验中，旱作和水作稻田甲烷的排放受化学氮肥施用的影响都不明显。试验表明，氮肥的施肥方式和施肥时期都会影响土壤NZO的排放。氮肥表施的稻田氧化亚氮的排放峰值比穴施的要提前;穗肥后稻田氧化亚氮的排放峰值出现时间比分集肥施用后早，而分集肥后的峰值出现时间又比基肥施用后早。 水作处理搁田后ld左右，稻田甲烷会出现一个排放高峰，此后迅速下降到较低的排放水平;而氧化亚氮的排放从第2d开始逐渐增加，与甲烷的排放互为消长。复水后，稻田甲烷的排放回升速度很慢;而氧化亚氮的排放迅速回落，几乎检测不到。灌溉试验结果表明，田间灌溉对旱作盖草处理的甲烷和氧化亚氮的排放通量都没有显著的影响。 通过单因子分析，气温、土温和降水都不是旱作稻田C场和NZO排放的主控因子，与旱作稻田C执和NZO排放没有明显的相关性。旱作稻田CH;和NZO排放通量的变化趋势可能是多种因素共同作用的结果。更多还原

【Abstract】 It is well known that rice field soils are the major sources of atmospheric methane and nitrous oxide (NO2). Since China is the largest producer of rice grain, the contribution of trace gas emissions from rice field soils to the greenhouse effects have become the focus of researches both in agriculture and environment. With the limitation of water resource, worldwide, a number of studies have been conducted in rice planting in aerobic condition, in which the ground cover rice production in aerobic condition is a novel cultivation technique. The characteristics of trace gas fluxes from rice field soils are accordingly changed in aerobic condition compared with those in waterlogged condition.Field experiments were carried out to assess CH4 and N2O emission rate in such two different cultivation systems of rice as traditional waterlogged production and aerobic production with different covers during rice-growing seasons in 2001 and 2002. The experimental field was selected in the suburb of Yancheng city of Jiangsu Province, located at latitude 33 27’N, longitude 120 11 E. The total rainfall during rice-growing season was 484.2 mm in 2001 and 440 mm in 2002. The soil (Halaquepts) had 12.5 g kg-1 of organic matter, 0.8 g kg-1 of total nitrogen and 8.3 of pH in the cultivated layer.There were four treatments, i.e., three treatments designed in aerobic rice production system such as the plots covered with plastic film (F), mulched with crop straw (M) andbare (without any cover)(B) and one treatment in waterlogged rice production (W)(as CK)in 2001. The bare treatment was replaced by the treatment covered with straw mulch using recommendation fertlization(R) in the second trial season (2002), for the results of 2001 showed many advantages of the straw mulching treatment, i.e., saving labour and costs, low-pollution and high yield.The total N2O fluxes in aerobic condition were five to six times higher than those in waterlogged soil, while the total emissions of CH4 in waterlogged soil were eight tonineteen times higher than those in aerobic condition during the rice growing period in 2001. There was no significant difference in the emission rates of methane and nitrous oxide in aerobic condition with traditional fertilization. The methane emission rates during the growing period in waterlogged condition were closely related to the different growing stages. The maximum emission rate of CH4(5.0 mg CR4 m~2 h-1) from waterlogged soil was found in the tillering stage of the rice crop in 2001. Fertilization was the primary factor affecting the N2O emissions in aerobic condition. A peak of the nitrous oxide emission rate was observed after each fertilization during the rice growing stages of all treatments in aerobic condition. Because of no basal fertilization in the treatment R, the total N2O fluxes of this treatment during the entire cultivation period was equal to that in waterlogged condition.In 2001, the rice grain yield of the treatment W was higher than that of the treatments in aerobic condition, while there was no significant difference of the rice grain yield among the treatments in aerobic condition on the significant level of 5%. There was no significant difference of the rice grain yield in 2002 between the different treatments except that the yields of treatment R and F were significantly lower than that of treatment W.In a 20-year time domain, there was no significant difference between the global warming potentials of the three treatments in aerobic condition and that of the treatment W based on the calculation of both N2O and CH4 emissions in the different treatments. But for the long-term period of 500-year, the greenhouse effect would be aggravated by the increased N2O emission from rice field soil in aerobic condition. Calculation of the total global warming potential for these two gases indicated that treatment R would be a preferable fertilization management to mitigate greenhouse gases emission either for the short or for the long-term period.The methane emission rate from ri更多还原