Research Of Tillage-Cropping Systems On Greenhouse Gas Emissions From Permanently Flooded Rice Fields In A Central Sichuan Hilly Area Of Southwest China

CO₂, CH₄ and N₂O are three important greenhouse gases. For the reason of human activities the concentration of CO₂, CH₄ and N₂O have been increasing clearly since the industrial revolution. A study indicates that rice paddy fields are one of the most important biology sources of CO₂, CH4 and N₂O.Therefore, CO₂, CH₄ and N₂O emissions from rice fields are given more attentions in the field of global climate change in recent years.Research of tillage-cropping systems on greenhouse gas (CO₂, CH₄ and N₂O) emissions from three kinds of paddy-rice fields in a central Sichuan hilly area of southwest china from May 2005 to May 2006—in case of jintang in Sichuan province in this dissertation. Have a detailed farmer investigate ,include crop type , tillage ,fertilizer, manure type, irrigation ,output and so on. Mensurate soil pH, N concentration in rainfall, bulk density and so on.Simulate the CO₂, CH₄ and N₂O fluxs from paddy-rice fields by peasants.Research the variations in CO₂, CH₄ and N₂O emissions from rice paddy fields between peasants and experts.Research CO₂, CH₄ and N₂O fluxs from permanently floodedpaddy-rice fields by chang one of the factors in DNDC model.Put forward ways and means to reduce greenhouse gas emissions.The results show that:(1) Research the CO₂, CH₄ and N₂O fluxs from paddy-rice fields by peasants.â‘ CO₂ fluxs from three kinds of paddy-rice fields during the growth period of paddy-rice are similar.CO₂ emissions in not the growth period of paddy-rice were increased after conducting rapeseed-paddy rice fields (RR) and winter wheat-paddy rice fields (RW) systems, which were 5.76 and 6.24 times larger than those of permanently flooded paddy fields (PF). CO₂ emissions in fallow period were 7.58 times larger than the growth period in permanently flooded paddy fields.â‘¡The average CH₄ fluxes from a permanently flooded rice field with a single middle rice crop and flooded with PF were 2.24 kg·hm^-2·d^-1 and 0.512 kg·hm^-2·d^-1 during rice-growing and non-rice growing periods, respectively. The annual CH₄ emission was mainly occurred in the rice growing period, being only 29.27% of the total annual CH₄ flux emitted from the non-rice growing period, though the latter occupied two thirds of a year. The annual average flux of nitrous oxide was 0.014 kg·hm^-2·d^-1 and the N₂O emission also intensive in the rice growing period. However, being only 16.41% of total annual N₂O flux emitted from the non-rice growing period.â‘¢After implementing the rice oil-seed rape rotation (RR) and rice-wheat rotation (RW), the CH₄ emissions were reduced substantially, only 35.64 % and 36.25 % of those of PF, respectively. However, the N₂O emissions were increased after conducting RR and RW systems, which were 2.89 and 3.40 times larger than those of PF.â‘£There was a clear trade-off between CH4 and N₂O emission in paddy fields during the growth period of paddy-rice.⑤The global warming potentials (GWPs) of the CO₂, CH₄ and N₂O emissions under the three tillage-cropping systems were assessed in an integrated way. The results show that the integrated GWPs of the CH₄ and N₂O emissions are in the following sequence: PF＞＞RW＞RR. After introducing rice-wheat or rice oil-seed rape rotation systems into the permanently flooded rice fields, the integrated GWPs of the CH₄ and N₂O emissions were decreased largely. But the results show that the integrated GWPs of the CO₂, CH₄ and N₂O emissions are in the following sequence: RW＞RR＞PF.(2) Variations in CO₂, CH₄ and N₂O emissions from rice paddy fields between peasants and expertsCO₂ fluxs from permanently flooded paddy-rice fields increased 2.08%～3.90 % byuse experts' theoretics. N₂O fluxs from permanently flooded paddy-rice fields increased 49.80 %, 6.83 % and 10.40 % in permanently flooded paddy fields, rapeseed-paddy rice fields and winter wheat-paddy rice fields. CH₄ fluxs from permanently flooded paddy-rice fields reduced 22.38 %, 55.62 % and 55.03 % in permanently flooded paddy fields, rapeseed-paddy rice fields and winter wheat-paddy rice fields.(3) CO₂, CH₄ and N₂O fluxs from permanently flooded paddy-rice fields by chang one of the factors in DNDC model.â‘ The amounts of N₂O flux from permanently flooded paddy-rice fields with the same quantity N account between Urea and ammonium: Urea＞ammonium. There is a linear relationship between N₂O fluxs of Urea and ammonium.N₂O flux from permanently flooded paddy-rice fields increasing with the increase of the N account increased in 100 kg. There is a linear relationship between N₂O fluxs and the amount of nitrogenous fertilizer.â‘¡The Amounts of CH₄ flux from permanently flooded paddy-rice fields with the same quantity C account during different organic manures: farmyard＞＞green≈starw≈liquid animal≈compostThe Amounts of N₂O flux from permanently flooded paddy-rice fields with the same quantity C account during different organic manures: liquid animal＞＞farmyard≈green＞starw≈compost CO₂, CH₄ and N₂O fluxs from permanently flooded paddy-rice fields are increasing with the enhance of the dosage of liquid animal manure.â‘¢CH₄ flux from permanently flooded paddy-rice fields were reduced of 27.57 % because the paddy-fields were basked by the method of experts. And the GWP were reduced of 9.10 %.â‘£CO₂ flux from rice field increasing with the depths of tillage. But CH₄ flux from rice field reducing with the depths of tillage. In the range of 0～10cm under the different depths of tillage, N₂O flux from rice field increasing with the different depths of tillage, there is a linear relationship between N₂O flux and the different depths of tillage. But when the depth of tillage goes to 20cm, N₂O flux from rice field reduced.⑤CO₂, CH₄ and N₂O fluxs from rice field increasing with the increase of temperature, there is a linear relationship between CO₂, CH₄ and N₂O fluxs and temperatures.â‘¥In the range of pH 5-7, N₂O flux from rice field increasing with the soil pH, there is a linear relationship between N₂O flux and pH of soil. In the range of pH 7-9, N₂O flux from rice field reducing with the soil pH, there is a linear relationship between N₂O flux and pH of soil.CO₂ and N₂O fluxs from rice field increasing with the different soil organic C contents, there is a linear relationship between CO₂, N₂O flux and the different soil organic C contents. CO₂, CH₄ and N₂O fluxs from rice field reducing with the soil glutinosity, there is a linear relationship between CO₂, CH4 and N₂O fluxs and soil glutinosity.