Studies on the Influences of Different Planting Patterns on the Emissions of Methane and Nitrous Oxide in the Paddy Field

Xueming TAN,Shan HUANG,Chao XIONG,Qinghua SHI,Xiaohua PAN,Ziming WU

Key Laboratory of Crop Physiology,Ecology and Genetic Breeding,Jiangxi Agricultural University,Ministry of Education,Nanchang 330045,China

Studies on the Influences of Different Planting Patterns on the Emissions of Methane and Nitrous Oxide in the Paddy Field

Xueming TAN,Shan HUANG,Chao XIONG,Qinghua SHI,Xiaohua PAN,Ziming WU*

Key Laboratory of Crop Physiology,Ecology and Genetic Breeding,Jiangxi Agricultural University,Ministry of Education,Nanchang 330045,China

This paper monitors the differences of early rice yield and the emissions of methane and nitrous oxide in the paddy field,based on the different cultivation technologies(high-yield scattered-planting mode,transplanting mode,farmer-planting mode).Results suggested that the rice yield by high-yield scattered-planting mode and transplanting mode was significantly higher than farmer-planting mode,and the increase reached 16.4%and 17.7%.The difference of high-yield scattered-planting mode and transplanting mode was insignificant.The potential contributions of the methane amount by these three patterns to the global contribution were all above 90%.The emission of methane during the growth period by the high-yield scatteredplanting mode was dramatically lower than that by transplanting mode and farmerplanting mode,while the differences between the high-yield transplanting mode and the farmer mode were insignificant.The changes of global temperature increase and the emission of methane were the same.The greenhouse gas intensity of high-yield scattered-planting mode was the lowest,and the farmer-planting mode was the highest.Therefore,the scattered-planting with reasonable fertilizing method is the most essential way to realize high yield of rice and the reducing the greenhouse gas emission as well.

Scattered-cultivation mode,Early rice;Yield;Methane;Nitrous oxide

T he addition of greenhouse gas concentration in the atmosphere is the main reason for global warming.Methane and nitrous oxide are two essential greenhouse gases,which exert significant effects on the climate changes of the earth system[1].The potential of methane and nitrous oxide for temperature rise is 25 times and 298 times that of carbon dioxide,respectively[2],and the concentration rises at a speed of 1%, 0.2%to 0.3%each year[3].Rice is one of the primary crops in the world,accounting for one third of the crop planting area,while the emission of methane and nitrous oxide during the rice production process is one of the sources for greenhouse gas emissions in agriculture[4].The emission of methane and nitrous oxide in the rice field becomes one of the major study fields at the moment.

At present,studies on the emission of methane and nitrous oxide in China and abroad largely concentrate on cultivation,fertilizing,moisture management,and species,etc.[5-8], However,reports on the studies of the greenhouse gas emission in the rice field by different cultivation modes are few[9].Through integrating a series of technologies,such as scattered-planting,artificial transplanting,fertilizing optimization and irrigation,this paper sets up the high-yield low carbon cultivation technology mode,and compares the emission of methane and nitrous oxide in the rice field by different planting patters in order to provide scientific references for the application and studies on the low-carbon cultiva-tion of rice.

Materials and Methods

Materials

The experiment is carried out in the demonstration park of high yield rice cultivation in Yangxi Village,Wenzhen Town,Jingxian County,Jiangxi Province in 2011.The organic substance of soil is 34.2 g/kg,total nitrogen 2.7 g/kg,alkali-hydrolyzable nitrogen 286.0 mg/kg,available phosphorus 31.4 mg/kg,quick-acting potassium 227.9 mg/kg and the pH value of 4.9.The species for test is Super Early Rice Ganxin 203.

Experiment design

This paper supposed three kinds of planting patterns.Firstly,farmers planting pattern:nitrogen 150 kg/hm2, phosphorus 67.5 kg/hm2,and potassium 105 kg/hm2.The cultivation pattern is 19.8 cm×19.8 cm.Each hole has two plants.Except for the mid-term field baking(30 days after transplanting)when the field is dry,the field is filled with water at any other time. Secondly,high-yield scattered-planting mode:nitrogen 180 kg/hm2,phosphorus 105 kg/hm2,and potassium 180 kg/hm2,with transplanting plants when the water is low and irrigating now and then.Thirdly,high-yield transplanting: nitrogen 180 kg/hm2,phosphorus 105 kg/hm2,and potassium 180 kg/hm2. The cultivation pattern is 13.3 cm×23.3 cm.Each hole has two plants,with irrigation now and then.

Field management

Fertilizing method:both the highyield scattered-planting mode and the high-yield transplanting mode apply fertilizers at the rate of 5∶2∶3 of base fertilizer,tiller fertilizer and ear fertilizer.In the farmer-planting mode,base fertilizer,tiller fertilizer and ear fertilizer are applied at the rate of 6∶4∶0.Potash fertilizer is applied at the rate of 7∶3 of tiller fertilizer and ear fertilizer.The phosphate fertilizer is applied as base fertilizer at once.The base fertilizer is applied one day before transplanting. Tiller fertilizer is applied seven days later after transplanting.Ear fertilizer is applied in the early ear tiller period(40 days after transplanting).The nitrogen, phosphorus and potassium fertilizer are urea,fused calcium-magnesium phosphate,and potassium chloride. The experiment is carried out in the high-yield demonstration park.Each cultivation mode covers 0.133 hm2.

Farmer planting pattern breeds the rice seedlings in the wet field,while the high-yield transplanting mode and the high-yield scatted-planting mode breed rice seedlings in a dry field. Breeding rice seedlings in the moist field means that the field is filled with water throughout the entire planting process,while breeding rice seedlings in the dry field means that rice seedlings are sowed on the soft fertile field without much water.There is 30 kg/hm2of hybrid rice seedlings,and 750 per hm2of 561 hole plastic seedling disc.450 kg/hm2of fused calcium-magnesium phosphate,225 kg/hm2of ammonium bicarbonate and 150 kg/hm2of potassium chloride are considered as the base manure. Transplanting is carried out 28 days after breeding the seedlings.

Determination Programs and Methods

Greenhouse gas emissions in the paddy fields

Greenhouse gases were determined and analyzed based on the static chamber and gas chromatography method.Samples of greenhouse gases in the paddy field were collected on the seven and one day before transplanting of plants.Samples in the large field were collected on the 7th, 19th,26th,38th,47thand 56th day after transplanting.There were five repetitive observation stations in every field. The sampling time was between 9:00 and 11:00.Thermograph was used to measure the temperature within the sample collection box and the temperature of soil that was 5 cm deep under the ground.Sealed box was used to collect samples,and the gas chromatograph was used to examine the methane and nitrous oxide emission in the paddy field.The sample collection box was made of stainless steel and plastics.The base was 50 cm long,50 cm wide and 20 cm high.Above the base was a sealed water trough with a depth of 3 cm and a width of 2 cm.The base was buried in the field after transplanting,and was fixed on the sample collection point during its entire growth period.The prolong box was of 50 cm long,50 cm width and 50 cm height,so was the sealed box.The top box and the prolong box are made of stainless steel.The prolong box contains a 12 V axial flow gas mixing fan, a sample collection tube,and heat insulating materials.Fans above the box were opened before collecting the samples to make the gases within the box mix evenly.Samples were collected at 0,5,10 and 15 minutes after covering the box.50 ml hypodermic syringe was used to collect gases from the box that was then transferred into the 0.1 L bag for collecting gas samples through rotating the three-port valve.

Related indicator calculation methods

The gas emission refers to the changes of gas quality within the box within a specific time range.The emission of methane[mg/(m2·h)]and nitrous oxide[μg/(m2·h)]in the paddy field were acquired based on the following formula[10]:

where F is the emission amount [mg/(m2·h)or μg/(m2·h)];dc/dt is the variance ratio of gas within the box as time goes by[ml/(m3·h)or μL/(m3·h)]; H is the actual height of the distance between the top of sample collection box and the water level(m);T is the average temperature within the sample collection box(℃).

In 100 years,the potential for global temperature rise based on carbon dioxide

The intensity of greenhouse gas emission(potential for global temperature rise in each unit of rice)=GWP

Data process

SPSS 11.0 software was applied to analyze the statistics.LSD method was used for comparison and significance tests.

Results and Analyses

Influences of different rice seedling breeding methods on the emission of methane and nitrous oxide

As we can see from Fig.1,the emission of methane in the wet paddy field was distinctly higher than that in the dry paddy field seven days beforethe transplanting and one day before transplanting,and both emissions were above zero,which suggested that the paddy field was emitting methane into the atmosphere.The emission of methane in the dry field was less than zero,which indicated that the dry paddy field was absorbing methane in the atmosphere one day before transporting.

According to Fig.2,the emissions of nitrous oxide in both wet and dry paddy fields were above zero,and the emission in the wet paddy field was significantly smaller than that in the dry field,which revealed that both paddy fields were emitting nitrous oxide.On the day before transplanting, with the field losing water,the emission of nitrous oxide in the wet paddy field increased,while that in the dry paddy field declined,and the difference during the processing period was significant.

Influences of different planting patterns on the emission of methane and nitrous oxide

According to Fig.3,as time went by,the emission of methane under different cultivation patterns at first increased,and then declined rapidly until the 38 days after transplanting when the field stopped emitting methane. The emissions of methane under each processing pattern on the seventh day after transplanting were similar.When the total emission of methane in the paddy field reached the maximum,the methane emitted by the high-yield transplanting mode also reached the peak,while the amount by other two patterns were almost the same,and the emission amount of three cultivation modes differed little 35 days after the transplanting.

As was shown in Fig.4,as time flew,the emission of nitrous oxide under different processing methods at first increased,and then declined before rising again,and at last decreased.There were two peaks.The first peak was on the 19 days after transplanting when the emission of nitrous oxide by the farmer-planting mode was the largest,which was followed by that of high-yield scatteredplanting mode,and the minimum of high-yield transplanting mode.The second peak appeared on the 38th day after transplanting when the emission of nitrous oxide by high-yield transplanting mode was the highest, and the values were similar between farmers planting mode and the highyield scattered-planting mode.The emission of nitrous oxide on the 55thday after transplanting was as follows: high-yield transplanting mode＞highyield scattered-planting mode＞farm-ers-planting mode.

Table 1 Rice output and factors for its output structure under different planting modes

Table 2 Influences of CH4and N2O emission,global temperature rise potential and greenhouse gas emission under different planting patterns

The early rice output and the emission of methane and nitrous oxide under different cultivation modes

The rice output by high-yield scattered planting mode and the highyield transplanting mode was much higher than that of farmers-planting mode,with an increase span of 16.4% and 17.7%,while the output was similar between the scattered-planting and transplanting mode(Table 1).The effective earing amount by high-yield scattered-planting mode and highyield transplanting mode was notably higher than that of farmer-planting mode,and there was no difference among each earing particle,fruit rate and particle weight.

The emission of methane at the mature stage by high-yield scatteredplanting mode was lower than that by high-yield transplanting mode and farmer-planting mode,with the last two forms emitting similar amount of methane(Table 2).The emissions of nitrous oxide under three different modes were almost the same.The global temperature rise under different planting modes showed similar tendency as the methane emission. The greenhouse gas emission intensity was the minimum by high-yield scattered-planting mode,while that of farmers-planting mode was the highest.

Discussions

Methane in the soil comes from the reduction reaction of H2/CO2and fermentation of CH3COOH.The emission of methane in the paddy field is influenced by the comprehensive influences of soil factor,temperature, farmland management,and rice species[5,11].The nitrous oxide in the soil is produced from the nitrification of microorganism in the soil and anti-nitrification[4].This paper found that the emission of methane in the wet paddy field was significantly higher than that in the dry field,while the emission of nitrous oxide in the wet paddy field was lower than that in the dry field, which proved that different field management resulted in variations in greenhouse gas emissions.Therefore, the reduction of methane emission in the seedling period is an essential way to weaken the greenhouse effect in the ripe stage of rice.Studies revealed that the rice is the main way to emit methane in the paddy field[12].Applying nitrogen can increase the emission of nitrous oxide,while the amount of nitrous oxide at the time when the water was declining accounted for 87.5%to 98.6%of the total nitrous oxide emission when the rice was growing[13-15]. With abundant water,the available nitrogen in the soil affected the emission of nitrous oxide during the rice growth period.The shorter intervals between fertilizing and field baking,the less nitrogen absorbed by crops.It is obvious that the more nitrogen in the soil,the more possibilities of nitrogen transforming into nitrous oxide[12].In this study,the peak of methane emission by three cultivation modes came at the tiller period,which proved that the methane emission was influenced by the amount of plants[11].The peak of methane emission by high-yield transplanting mode was the highest, so the inefficient tiller amount was also the largest[14].It remains to be studies whether the high intensity of rice transporting more O2into the root leads to methane oxidation.The first peak of nitrous oxide emission came after applying tiller fertilizer,and the second peak appeared during the field-baking period.However,the first peak of nitrous oxide emission by farmer-planting mode was higher than that of high-yield transplanting and scattered-planting method,which might because that the farmers applied more tiller fertilizer.How much nitrogen in the soil being transformed into nitrous oxide was restricted by the moisture amount,and the baking of moisture ameliorated the oxygen supply in the soil,which was beneficial to the nitrification and anti-nitrification.

The available ear amount per unit by high-yield scattered-planting mode and the high-yield transplanting mode was significantly higher than that of farmers-planting mode.There was no distinct difference among other factors.This is largely because farmers usually plant scarce rice seedlings in the field,leading to low output.The increase of planting intensity and optimal fertilizing approach are the effective measures for high yield[17].The methane emission is the major contributor for global temperature rice in the paddy field,and the contribution of methane emission by three cultivation modes to the global temperature rise was all above 90%.Therefore,the key of reducing carbon emission lies in the decrease of methane emission[18-19]. The high output of rice by high-yield scattered-planting mode and the low tendency of global warming can realize high yield and reduction of greenhouse gas emission as well.Besides, scattered-planting mode requires less labor forces,so it should be widely applied.

Conclusions

The synchronized observation of early rice yield,methane and nitrous oxide under high-yield scatteredplanting mode,high-yield transplanting mode and farmer-planting mode suggested that the rice yield by high-yield scattered-planting mode and transplanting mode was significantly higher than farmer-planting mode,and the increase reached 16.4%and 17.7%. The difference of high-yield scatteredplanting mode and transplanting mode was insignificant.The potential contributions of the methane amount by these three patterns to the global contribution were all above 90%.The emission of methane during the growth period by the high-yield scatteredplanting mode was dramatically lower than that by transplanting mode and farmer-planting mode,while the differences between the high-yield transplanting mode and the farmer mode were insignificant.The changes of global temperature increase and the emission of methane were the same. The greenhouse gas intensity of highyield scattered-planting mode was the lowest,and the farmer-planting mode was the highest.Therefore,the scattered-planting with reasonable fertilizing method is the most essential way to realize high yield of rice and the reducing the greenhouse gas emission as well.

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Responsible editor:Nana FAN

Responsible proofreader:Xiaoyan WU

不同栽培模式对稻田甲烷和氧化亚氮排放的影响

谭雪明，黄 山，熊 超，石庆华，潘晓华，吴自明*
（作物生理生态与遗传育种教育部重点实验室/江西省作物生理生态与遗传育种重点实验室/江西农业大学，江西南昌330045）

在构建不同栽培技术模式（高产抛栽模式、高产移栽模式、农户模式）的基础上，监测了不同栽培模式下早稻产量及稻田甲烷和氧化亚氮排放的差异。结果表明：高产抛栽模式和高产移栽模式水稻产量均显著高于农户模式，增产幅度分别达到16.4%和17.7%，高产抛栽模式和高产移栽模式产量之间差异不显著。3种模式甲烷排放对全球增温潜势贡献均在90%以上。高产抛栽模式全生育期甲烷排放显著低于高产移栽模式和农户模式，而高产移栽模式和农户模式之间差异不显著，全球增温潜势变化趋势与甲烷排放相同。高产抛栽模式温室气体强度最低，农户模式最高，高产移栽模式居中。因此，在抛栽条件下，配以合理的肥料运筹是同步实现水稻高产和温室气体减排的重要技术途径。

栽培模式；早稻；产量；甲烷；氧化亚氮

国家“十二五”科技支撑计划（2011-BAD16B04）。

谭雪明（1969-），男，江西会昌人，高级实验师，主要从事土壤生态学研究，E-mail：txmfy@163.com。*通讯作者：吴自明，博士，教授，主要从事作物生理与遗传育种研究，E-mail：wuzmjxau@163.com。

2015-03-10

Supported by National"Twelfth Five-Year Plan"of Scientific and Technological Support Plan(No.2011BAD16B04).

*Corresponding author.E-mail:wuzmjxau@163.com

Received:March 10,2015 Accepted:May 1,2015

修回日期2015-05-01