农田NO排放的实验观测与模式研究

Nitric oxide emissions froma typical wheat rotation system in southeastern China wheat rotation system in southeastern China was characterized for the non-waterlogged period of a rotation cycle. NO.emissions during the period (from March through 1 June were 4 to 6 folds for.the fertilized plots and 1.6 folds for the unfertilized plot larger than those.from November 1 through December.31) Nitric oxide emissions were not not.detected detectable during the winter period from January 1 through late.February)”. Amendment of synthetic fertilizer N significantly enhanced the.NO emission by a factor of 6.5, but the enhancement was significantly.mitigated by 25% through substituting about 15% of the synthetic.fertilizer-N with aerobically fermented crop residues or by 21% through deep.tillage. The NO-N emission factor, defined as the amount of NO-N released.per unit of synthetic fertilizer N input, was determined to be 0.025 kgNO-N.kg-1 of N applied for the non-waterlogged period, which was reduced by 32%.through substituting synthetic fertizer-N with fermented residues or by 24%.through deep tillagefor the SF-DT by 34%. In addition, the NO emission.factor, defined as the amount of NO-N emitted from unit unfertilized area per.day, was observed to be ca. 3.8 gN ha-1 d-1. Approximately 0.55 TgN yr-1 was.likely released as NO from Chinese cultivated lands. A positive correlation.exists between NO emission and soil moisture when surface soil temperature.is > 20oC. The dielurnaliurnal variability in NO emission is characterized.with day-peak, night-peak and irregular patterns, which are in close.association with wheat growth.The diurnal NO emission under the day-peak pattern is correlated with the.simultaneously observed surface soil temperature, while that under the night-peak and.irregular pattern is dependent on soil temperature at 7 ± 2 h and 3 ± 2 h before NO.observation, respectively. The effect of soil temperature on NO emission is well.described by F = α.eβ.T, where F is NO flux, T soil temperature, and α and β empirical.coefficients. The parameter Q10, i.e. the change in NO emission per 10oC soil.temperature, is correlated with the rates of fertilizer-N application. An equation.] 12 / ) - 6 - t sin[( e e e e F T) R /( E k ) T R /( E k a a π τ . . . . . + = , which is oriented from the Arrhenius.equation, is developed to predict diurnal NO emission, where T is the daily average soil.temperature, .T the deviation of soil temperature from the daily average, Ea the.apparent activation energy, R the gas constant, t a given time within the one-day cycle, τ.delayed time for appearance of the diurnal NO emission peak, and k an empirical.coefficient. Based on the results, the authors recommend that intermittent measurement of NO emission from a similar ecosystem would be best taken.around 17:00. The molar ratio of NO/N2O over the non-waterlogged period is > 1,.suggesting that NO emission was mainly derived from nitrification, when soil moisture.content was less than the field capacity. The NO emission factors obtained in this study.is incorporated into IAP-N, a model on regional N cycling. With this model, NO.emission from the agricultural system of the Asian region is estimated.

以太湖地区典型农田类型水稻-小麦/油菜轮作系统为对象，采用全自动连续观测方法同步观测NO排放及相关的环境控制因子，从而定量认识农田NO排放的过程与环境控制机制，并在实验研究基础上建成农田NO排放模式，用以模拟和预测长江三角洲地区农田NO排放。此项研究将为编制10km乘10km分辨率排放清单奠定基础，是“九五”重大基金项目研究内容的必要补充。