Orth China Plain. The average annual precipitation is 786.3 mm, and the

Orth China Plain. The average annual precipitation is 786.3 mm, and the average annual temperature is 13.6uC, with the minimum (21.5uC) and maximum (27.5uC) monthly temperatures in January and July, respectively. The annual frost-free period is approximately 170?220 days in duration, and the annual sunlight time is 2462.3 hours. The soil is loam with 40 sand, 44 silt and 16 clay. The characteristics of the surface soil (0?0 cm) were measured as follows: pH 6.2; soil bulk density 1.43 g cm23; soil organic matter 1.36 ; soil total Cucurbitacin I chemical information nitrogen 0.13 ; and soil total phosphorous 0.13 . The meteorological data during the experiment are shown in Figure 1.replicates. Each replicate was 35 m long and 4 m wide. After maize was harvested in each plot, straw was returned to the soil by one of the six following tillage operations: HT – disking with a disc harrow to a depth of 12 cm to 15 cm, RT – rototiller plowing to a depth of 10 cm to 15 cm, NT – no tillage, HTS, RTS, and NTS – plowed using a vibrating sub-soil shovel to a depth of 40 cm to 45 cm, The experimental site was cropped with a rotation of winter wheat (Triticum aestivum Linn.) and maize (Zea mays L.). The wheat was sown in mid-4 IBP custom synthesis October immediately after tilling the soil and was harvested at the beginning of June the following year. The maize was sown directly after the wheat harvest and was harvested in early October. During the wheat growth period, fertilizer was used at a rate of 225 kg N ha21, 150 kg ha21 P2O5 and 105 kg ha21 K2O, and 100 kg N ha21 was used as topdressing in the jointing stage with 160 mm of irrigation water. During the maize growth period, 120 kg N ha21, 120 kg ha21 P2O5 and 100 kg ha21 K2O were used as a base fertilizer, and 120 kg N ha21 was used as topdressing in the jointing stage.CH4 and N2O Sampling and MeasurementsCH4 and N2O content was measured using the static chambergas chromatography method [25]. The duration of gas sample collection was based on the diurnal variations in this region: the collection of CH4 occurred from 9:00 a.m. to 10:00 a.m., and N2O was collected between 9:00 a.m. and 12:00 p.m. from October 10, 2007, to May 19, 2009 at approximately 1-month intervals [26]. Both CH4 and N2O were sampled at 5 minutes, 20 minutes and 35 minutes after chamber closing. Simultaneously, the atmospheric temperature, the temperature in the static chamber, the landExperimental DesignThe experiment was designed as HT, RT and NT farming methods that started in 2004. In 2008, each plot was bisected, with one half maintained using the original tillage method as the control and the other half converted to subsoiling, resulting in six treatment plots: HT and HT conversion to subsoiling (HTS); RT and RT conversion to subsoiling (RTS); and NT and NT conversion to subsoiling (NTS) in a split-plot design with threeFigure 1. The atmospheric temperature and precipitation at the experiment site. The data were collected by the agricultural meteorological station approximately 500 m from the experiment field. doi:10.1371/journal.pone.0051206.gTillage Conversion on CH4 and N2O EmissionsFigure 2. A to C CH4 flux variations of H, R, and N after subsoiling in different periods; D to F N2O flux variations of H, R, and N after subsoiling in different periods. a in Fig. 2 is the wheat growth stage of 2007 to 2008; b is the maize growth stage of 2008 to 2009; c is the wheat growth stage of 2008 to 2009. Arrows indicate time of subsoiling. Dotted lines distinguish the growth period o.Orth China Plain. The average annual precipitation is 786.3 mm, and the average annual temperature is 13.6uC, with the minimum (21.5uC) and maximum (27.5uC) monthly temperatures in January and July, respectively. The annual frost-free period is approximately 170?220 days in duration, and the annual sunlight time is 2462.3 hours. The soil is loam with 40 sand, 44 silt and 16 clay. The characteristics of the surface soil (0?0 cm) were measured as follows: pH 6.2; soil bulk density 1.43 g cm23; soil organic matter 1.36 ; soil total nitrogen 0.13 ; and soil total phosphorous 0.13 . The meteorological data during the experiment are shown in Figure 1.replicates. Each replicate was 35 m long and 4 m wide. After maize was harvested in each plot, straw was returned to the soil by one of the six following tillage operations: HT – disking with a disc harrow to a depth of 12 cm to 15 cm, RT – rototiller plowing to a depth of 10 cm to 15 cm, NT – no tillage, HTS, RTS, and NTS – plowed using a vibrating sub-soil shovel to a depth of 40 cm to 45 cm, The experimental site was cropped with a rotation of winter wheat (Triticum aestivum Linn.) and maize (Zea mays L.). The wheat was sown in mid-October immediately after tilling the soil and was harvested at the beginning of June the following year. The maize was sown directly after the wheat harvest and was harvested in early October. During the wheat growth period, fertilizer was used at a rate of 225 kg N ha21, 150 kg ha21 P2O5 and 105 kg ha21 K2O, and 100 kg N ha21 was used as topdressing in the jointing stage with 160 mm of irrigation water. During the maize growth period, 120 kg N ha21, 120 kg ha21 P2O5 and 100 kg ha21 K2O were used as a base fertilizer, and 120 kg N ha21 was used as topdressing in the jointing stage.CH4 and N2O Sampling and MeasurementsCH4 and N2O content was measured using the static chambergas chromatography method [25]. The duration of gas sample collection was based on the diurnal variations in this region: the collection of CH4 occurred from 9:00 a.m. to 10:00 a.m., and N2O was collected between 9:00 a.m. and 12:00 p.m. from October 10, 2007, to May 19, 2009 at approximately 1-month intervals [26]. Both CH4 and N2O were sampled at 5 minutes, 20 minutes and 35 minutes after chamber closing. Simultaneously, the atmospheric temperature, the temperature in the static chamber, the landExperimental DesignThe experiment was designed as HT, RT and NT farming methods that started in 2004. In 2008, each plot was bisected, with one half maintained using the original tillage method as the control and the other half converted to subsoiling, resulting in six treatment plots: HT and HT conversion to subsoiling (HTS); RT and RT conversion to subsoiling (RTS); and NT and NT conversion to subsoiling (NTS) in a split-plot design with threeFigure 1. The atmospheric temperature and precipitation at the experiment site. The data were collected by the agricultural meteorological station approximately 500 m from the experiment field. doi:10.1371/journal.pone.0051206.gTillage Conversion on CH4 and N2O EmissionsFigure 2. A to C CH4 flux variations of H, R, and N after subsoiling in different periods; D to F N2O flux variations of H, R, and N after subsoiling in different periods. a in Fig. 2 is the wheat growth stage of 2007 to 2008; b is the maize growth stage of 2008 to 2009; c is the wheat growth stage of 2008 to 2009. Arrows indicate time of subsoiling. Dotted lines distinguish the growth period o.