稻田CH4的排放规律

通过对我国长江中下游地区、西南地区及华中地区这三大主要水稻区稻田CH_4排放的多年测量,描述了稻田CH_4排放的一般规律及特征。稻田CH_4排放的日变化有三种型式,即下午最大值型式、夜间最大值型式以及下午、夜间双峰型式,导致这三种型式的主要原因是CH_4排放路径的日变化;不同品种水稻的不同生理特性、天气条件会通过改变CH_4排放路径的日变化来改变CH_4排放日变化的型式;随着水稻生长,CH_4排放日变化幅度也会随着变化。 早稻与晚稻稻田CH_4排放的季节变化型式不一致。早稻的CH_4排放一般出现三个排放峰值,其中第一个与第三个峰值是由土壤中CH_4的产生率增加引起的,第二个峰值则是由于CH_4排放路径的畅通引起的。四川地区单季稻CH_4排放的季节变化与早稻比较一致,但是没有第一个排放峰值的出现。引起早、晚稻不同季节变化的原因是水稻生长季节中气温的季节变化。灌溉水状态也能够较大程度的影响稻田CH_4的排放的季节变化。 含SO_4~(2-)的肥料能够降低CH_4的排放,但其作用的大小取决于土壤中有机物质(肥)的数量;施尿素、KCl也能够使CH_4排放降低,但它的降低效应没有有机肥使CH_4排放增大的正效应大,这说明有机肥对CH_4排放的影响很大,而在空气中堆腐过的沼渣肥使稻田CH_4的排放大大降低。不同的施肥使

REGULARITY OF METHANE EMISSION FROM RICE PADDY FIELDS

CH₄ emission rates from rice paddy fields have been measured in the past several years over the three main rice culture regions in China, which are middle and lower reaches of Changjiang River, southwest region and middle China region. The regularity and characteristics of CH₄ emission are described in this paper. Three types of diurnal variation of methane emission have been observed, which are afternoon - maximum mode, night -maximum mode and two-peak mode with maxima occured both in the afternoon and at night. The diurnal variation of CH₄ transport efficiency causes these three types of diurnal variation pattern. Different variety of rice plant and weather condition may change the diurnal variation of CH4 transport ,hence affecting the diurnal variation pattern of CH₄ emission. With the growing of rice plants. the varying range of diurnal CH₄ emission rates also changes.The seasonal pattern of CH₄ emission rates from rice paddies for early rice is different from that of late rice. For early rice, CH₄ emission normally shows three maxima. The first and the third are caused by high CH₄ production rates in the paddy soil, and the second is caused by high CH₄ transport efficiency. For late rice. CH₄ emission appears highest shortly after rice is transplanted, and then decreases gradually with rice growing. The seasonal variation pattern of CH₄ emission of single rice in Sichuan province is similar to that of early rice, but without the first peak. Different trend of air temperature can explain the difference in seasonal pattern of methane emission for early and late rice . The status of flooded water may also greatly affect the seasonal variation of methane emission.The fertilizer containing SO₄^2- may reduce CH₄, emission, but its effect depends on the amount of organic matter in the soil. The use of urea and KCl may also lower CH₄ emission. But its reduction effect is smaller than the positive enhencement by organic manure, which indicates the great importance of organic fertilizer. The fermented manure from bio gas pits which has been stored up in the open air may largely reduce methane emission. Different fertilizer treatment can also change temperature effect of CH₄ emission.Different irrigation method has great influence on CH₄ emission. Deep water cover reduces CH₄ emission for early rice, while the opposite is ture for late rice. A 3 - day - interval frequent drainage dose not affect CH₄ emission too much for the whole growing season. The CH₄ emission rate from the field received constant moisture is very low for both early and late rice.Interannual variation of CH₄ emission in all the three regions has been observed. The mean emission rate in middle and lower reaches of Changjiang River is 0. 39mg · m ^-2·d^-1 and 0. 75mg · m^-2 · d^-1 for early and late rice respectively, while in middle China region it is 0. 28mg · m^-2 · d^-1 and 0. 41mg · m^-2 · d^-1 respectively, and for the single rice growing region in Sichuan it is 1. 41mg · m^-2 · d^-1.