水保所知识产出(1956---)知识库

农田生态系统是温室气体（N 2 O、CH 4 和 CO 2 ）重要的排放源，其排放量分
别占全球 N 2 O、CH 4 和 CO 2 总排放的 60%、50% 和 10%。全球干旱和半干旱地
区农田面积占全球农田总面积的 80%，贡献了全球粮食总产量的 60%。我国旱地
约占国土总面积的 70%，干旱半干旱耕地占总耕地面积的 43%，主要分布在西北
地区。我国西北黄土高原为典型的雨养农业区，面积 60 万 km 2 ，其中农田面积
14.58 万 km 2 ，70%属于雨养农业。施氮和轮作是本地区重要的农田管理措施。自
20 世纪 80 年代以来，化肥的投入成为本地区改善土壤肥力和作物产量的重要措
施。但是施氮和轮作对土壤温室气体排放的影响尚不完全清楚。
本研究共分为 2 个田间试验：春玉米连作试验和禾本科-豆科轮作试验。在
春玉米试验中共设置 5 个不同的氮肥处理：对照处理（不施用氮肥处理，N0）；
传统施氮处理（Con）；优化施氮处理（Opt）；优化施氮添加硝化抑制剂处理
（Opt+DCD）；优化施氮使用缓控肥处理（Opt+SR）。在轮作系统中，选取小麦-
小麦-糜子-豌豆轮作系统作为研究对象，研究不同作物轮作次序对土壤呼吸和温
度敏感性的影响。主要获得以下结论：
（1）施氮显著提高了春玉米生长季土壤的累积呼吸量（P<0.05），但是四个
施氮处理之间土壤呼吸无显著差异。与对照相比，施氮处理累积呼吸量 2013 年
提高了 35%，2014 年提高了 54%，但施氮显著降低了土壤呼吸温度敏感性（Q 10 ）
（P<0.05），施氮处理的 Q 10 较对照 2013 年降低了 27%，2014 年降低了 17%。施
氮显著提高了春玉米地上部生物量和根系生物量（P<0.05）。施氮处理根系生物
量较对照处理 2013 年提高了 0.32 倍，2014 年提高了 1.23 倍。施氮对土壤温度
和水分无显著影响，根系生物量是施氮条件下导致土壤呼吸差异的重要生物因素。（2）三个优化施氮处理显著减少了 N 2 O 的年累积排放量，农田温室效应
（Global warming potential，GWP），以及总温室气体排放强度（Greenhouse gas
intensity，GHGI）。与传统的 N 2 O 年累积排放量（1.9 kg N 2 O-N ha –1 ）相比，Opt+DCD
处理 N 2 O 累积排放量下降的最多（48%），其次为 Opt+SR 处理（38%），下降最
少的为 Opt 处理（28%）。施氮和大于 40 mm 降雨事件是 N 2 O 排放的主要控制因
素。其中施氮后 10 天内的排放量占全年排放量的 26%，并与施氮后 10 天内的硝
态氮平均含量呈显著的线性正相关关系。2013 年，由降雨诱导的 N 2 O 排放量占
全年的 6.4%，2014 年为 12.5%。N 2 O 排放因子变化范围为 0.12%0.55%。黄土
高原雨养区农田土壤是大气 CH 4 的弱吸收汇，不同施氮模式对大气 CH 4 的吸收
没有显著的影响。Con，Opt，Opt+DCD 和 Opt+SR 四个处理的 GWP 分别为 788，
536，344，441 kg CO 2 -eq ha −1 。与传统施氮相比，Opt, Opt+DCD 和 Opt+SR 处理
的 GHGI 分别降低了 29%，54%和 42%。
（3）三种优化施氮模式虽然减少了 20%的施氮量，但并没有减少春玉米的
产量，各施氮处理的产量在 2013 年为 9.61−10.46 Mg ha −1 ，2014 年为 11.41-12.23
Mg ha −1 。5 种施氮模式土壤剖面 0−100 cm 和 100−200 cm 的硝态氮残留量分别
介于：33.5−148.9、24.8−92.8 N kg ha −1 之间。与 Con（225.9 N kg ha −1 ）相比，
Opt、Opt+DCD和Opt+SR土壤剖面0−200 cm的硝态氮残留量降幅分别为47.2%、
48.5%和 45.5%。三种优化施氮处理之间硝态氮残留差异不显著（P>0.05）。优化
施氮处理氮肥农学效率和氮肥偏生产力显著大于传统施氮处理。
（4）在小麦-小麦-糜子-豌豆轮作系统中，虽然冬小麦生长阶段土壤呼吸
（1.63 μmol m −2 s −1 ）显著小于糜子（2.40 μmol m −2 s −1 ）和豌豆阶段（2.21 μmol
m −2 s −1 ），但是冬小麦生长阶段的土壤呼吸温度敏感性（2.76）却显著高于糜子（1.85）
和豌豆阶段（1.47）。轮作系统中 Q 10 随着作物生长季的平均温度的升高呈现指数
下降的趋势，当温度超过 15 °C 时，Q 10 趋于稳定（1.8）。此外 Q 10 随着作物生长
季的平均水分的增加而增加，但当土壤水分大于 14.7%时，Q 10 却出现下降的趋
势。在全球变暖的情况下，模拟农业生态系统土壤呼吸时（特别是耐寒作物）必
须考虑作物生长阶段的土壤温度和水分。
关键词：黄土高原；施氮；轮作；CO 2 ；N 2 O；土壤呼吸温度敏感性

Agricultural ecosystem is an important emitter of N 2 O, CH 4 and CO 2 , accounting
for 60%, 50% and 10% of the global N 2 O, CH 4 and CO 2  emissions, respectively. The
rainfed farmland area accounts for 80% of the global farmland area. In China, rainfed
farmland area account for more than 70% of total land area, mainly in the northern and
northwestern regions. The Loess Plateau of northwest China covers more than 600,000
km 2 , consists of typical semiarid and arid areas with rainfed farming, and provides
about 40% of the local food needs. Inherent soil fertility is low in the loess region and
nitrogen (N) levels in all soils are particularly low. Nitrogen fertilization and cropping
rotation are two important management measures to sustain soil productivity in the
rainfed farmland on the Loess Plateau. Since 1980s, chemical fertilizer addition has
been an important measure to improve soil fertility and crop yields in the loess region.
However, greenhouse gases (GHGs) emission under nitrogen fertilization and cropping
rotation is not yet clear in the rainfed area.
Two cropping systems of continuous spring maize and three-year rotation were
designed to investigate GHGs emission at the State Key Agro-Ecological Experimental
Station in the Loess Plateau (35°12′N, 107°40′E; 1220 m.a.s.l.) in Changwu County,
Shaanxi Province, China. For continuous spring maize cropping system, five treatments
consist of control (CK), conventional N fertilization rate (Con), optimal N fertilization
rate (Opt), optimal N fertilization rate plus nitrification inhibitor (Opt+DCD), and
optimal N fertilization rate with slow release urea (Opt+SR). For three-year rotation
system, i.e., winter wheat, millet, pea, to explore the changes in soil respiration and Q 10
values under each cropping phase. The results were summarized as follows:  1) The cumulative soil CO 2 emissions were 35% for 2013, 54% for 2014 greater
in N treatment than in CK treatment. Though nitrogen fertilization significantly
increased the cumulative soil CO 2 emissions (P<0.05), it did decrease evidently the
temperature sensitivity of soil respiration (P<0.05). The Q 10 values in N treatment were
decreased by 27% and 17% compared with CK treatment in 2013 and 2014,
respectively. Nitrogen fertilization increased significantly aboveground biomass and
root biomass (P<0.05). Root biomass in N treatment was 32% and 123% greater than
that in CK treatment of 2013 and 2014, respectively. Nitrogen fertilization had no
marked influence on soil temperature or moisture. Root biomass was critical biotical
factor for variation of soil respiration under nitrogen fertilization.
(2) Compared to Con, the Opt, Opt+DCD, and Opt+SR treatments resulted in a
significant decrease in annual cumulative N 2 O emission, net greenhouse gas (GWP)
emission, and net greenhouse gas intensity (GWPI). The greatest decrease of annual
N 2 O emissions (48%) occurred in Opt+DCD treatment, followed by Opt+SR (38%)
and Opt (28%). N fertilization and heavy rainfall event (>40 mm) were the main factors
controlling N 2 O emissions. The cumulative N 2 O emissions within 10 days after N
fertilization accounted for 26% of annual N 2 O emissions, and were positively
associated with mean soil NO 3 -N content (P<0.05). The cumulative N 2 O emissions
induced by heavy rainfall accounted for 6.4% of total annual N 2 O emissions in 2013
and 12.5% in 2014, respectively. The urea-derived annual mean N 2 O emission factor
ranged from 0.12%−0.55%. The soil acted as a small sink for atmospheric CH 4. There
was no significant difference in CH 4 uptake among the N fertilization practices.
Compared with Con treatment, GWP was decreased by 31.2%, 52.5% and 45.0% in
Opt, Opt+DCD, Opt+SR treatments in 2013, and by 32.8%, 60.5% and 43.0 in 2014
(P<0.05); and GWPI was decreased by 32.1%, 48.7% and 43.6% in 2013, and 25.4%,
58.7% and 39.7% in 2014, respectively. In conclusion, nitrification inhibitor was the
most effective fertilization practice in the rainfed regions of Loess Plateau.
(3) The three optimized N treatments, which saved 20% of N fertilization against
the current conventional agricultural N fertilization rate, did not significantly decrease
grain yields. The grain ranged from 9.61 to 10.46 Mg ha −1 in 2013 and from 11.41 to
12.23 Mg ha −1 in 2014 in the four nitrogen treatments. Residuals of nitrate nitrogen at  the depth of 0−100 cm and 100−200 cm of five treatments ranged from 33.5 to 148.9
mg kg -1 and 24.8 to 92.8 mg kg -1 , respectively. The highest accumulation of nitrate
nitrogen in profile (0−200 cm) was in the Con treatment (225.9 mg kg −1 ), followed by
47.2%、48.5% and 45.5% of decrease in the Opt, Opt+DCD and Opt+SR treatments
compared to that in the Con treatment, respectively. The residuals of nitrate nitrogen
among Opt, Opt+DCD and Opt+SR treatments had no significant difference. The three
optimized N managements significantly increased the agronomic efficiency of
appliedN and partial factor productivity from applied N compared to Con.
(4) The soil respiration rate was significantly lower in the winter wheat phase (1.63
μmol m −2 s −1 ) than the millet phase (2.40 μmol m −2 s −1 ) and pea phase (2.21 μmol
m −2 s −1 ) from July 2010 to June 2013. However, the Q 10 value was significantly higher
in the wheat phase (2.76) than in the millet phase (1.85) and pea phase (1.47). The
relationship between the Q 10 values and soil temperature followed an exponential
decay function in the rotation system, and the Q 10 value remained stable (1.8) with no
obvious variation when the temperature exceeded 15 °C. The Q 10 value tended to
increase with the increasing soil moisture and declined until the soil moisture reached
a threshold of 14.7%. Our results indicated that under the condition of global warming,
temperature-respiration empirical models should be parameterized according to crop
types in the rotation phases, especially when estimating soil respiration of cold-
resistant crops.
Keywords: Loess Plateau; nitrogen fertilization; rotation; CO 2 ; N 2 O; Q 10