氨挥发是农田氮素向环境输出的重要途径,也是我国空气中PM2.5形成的主要因素,给环境和农业生产带来了诸多不利影响。传统的农田氨挥发测定大多依赖酸吸收法,但因采样时间长、劳动量大,难以获取氨挥发日内动态变化规律。基于开放光程可...氨挥发是农田氮素向环境输出的重要途径,也是我国空气中PM2.5形成的主要因素,给环境和农业生产带来了诸多不利影响。传统的农田氨挥发测定大多依赖酸吸收法,但因采样时间长、劳动量大,难以获取氨挥发日内动态变化规律。基于开放光程可调谐二极管激光吸收光谱技术进行田间痕量氨气测定时,测量精度高、选择性好、系统响应速度快,不需要复杂的采样操作,就可以实现激光发射器与反射镜之间数十至数百米的高时间分辨率的氨气浓度原位快速监测。其与微气象反向拉格朗日随机扩散模型相结合(TDLAS-BLS法)是目前农业源氨挥发监测技术领域的研究热点。通过田间试验,分析比较TDLAS-BLS法与微气象水平通量积分法(IHF法)测定的氨挥发速率及氨挥发损失结果,实现对TDLAS-BLS法测定大面积农田氨挥发的可靠性验证。利用监测获取的高时间分辨率数据研究冬小麦追肥期氨挥发日内变化规律及影响因素。结果表明:TDLAS-BLS法和IHF法测定农田氨挥发速率基本一致(斜率为0.97,R2=0.97,n=14),TDLAS-BLS法测定氨挥发速率仅比IHF法低3%,总氨挥发损失仅低6%,证明TDLAS-BLS法可用于冬小麦追肥期大面积农田氨挥发监测中。冬小麦追肥期白天氨浓度明显高于夜间,且受风速波动影响,氨浓度瞬时波动较大。氨挥发速率在追肥后缓慢升高,施肥后第6天出现氨挥发速率峰值8.9 kg N·ha^-1·d^-1,随后逐渐降低,至第15天与背景接近。氨挥发损失主要集中在施肥后的第5~8 d(79~175 h),该时段氨挥发损失占总氨挥发损失的69%。整个监测期间TDLAS-BLS法测定总氨挥发损失为8.8 kg N·ha-1(占施氮量6.3%),较低的损失量与沟施覆土的施肥方式及低温、低光照强度有关。TDLAS-BLS法实现了在线监测大面积农田氨挥发日内变化规律,高时间分辨率数据可更准确地评估气象因素对氨挥发的影响。冬小麦追肥期氨挥发日内波动较大,存在明显的昼高夜低变化规律,与温度、风速、光照有很高的相符性。相关分析表明风速、光照、土壤温度、降水都与氨挥发有显著相关性,异常天气下主导气象因素(如降水)是氨挥发主要控制因素。展开更多
Cropland productivity has been significantly impacted by soil acidification resulted from nitrogen （N） fertilization, especially as a result of excess ammoniacal N input. With decades＇ intensive agricultural cultiv...Cropland productivity has been significantly impacted by soil acidification resulted from nitrogen （N） fertilization, especially as a result of excess ammoniacal N input. With decades＇ intensive agricultural cultivation and heavy chemical N input in the Huang-Huai-Hai Plain, the impact extent of induced proton input on soil pH in the long term was not yet clear. In this study, acidification rates of different soil layers in the soil profile （0-120 cm） were calculated by pH buffer capacity （pHBC） and net input of protons due to chemical N incorporation. Topsoil （0-20 cm） pH changes of a long-term fertilization field （from 1989） were determined to validate the predicted values. The results showed that the acid and alkali buffer capacities varied significantly in the soil profile, averaged 692 and 39.8 mmolc kg-1 pH-1, respectively. A significant （P〈0.05） correlation was found between pHRC and the content of calcium carbonate. Based on the commonly used application rate of urea （500 kg N ha-1 yr-1）, the induced proton input in this region was predicted to be 16.1 kmol ha-1 yr-1, and nitrification and plant uptake of nitrate were the most important mechanisms for proton producing and consuming, respectively. The acidification rate of topsoil （0-20 cm） was estimated to be 0.01 unit pH yr-1 at the assumed N fertilization level. From 1989 to 2009, topsoil pH （0-20 cm） of the long-term fertilization field decreased from 8.65 to 8.50 for the PK （phosphorus, 150 kg P205 ha-1 yr-1; potassium, 300 kg K20 ha-1 yr-1; without N fertilization）, and 8.30 for NPK （nitrogen, 300 kg N ha-1 yr-1; phosphorus, 150 kg P2Os ha-1 yr-1; potassium, 300 kg K20 ha -1 yr-1）, respectively. Therefore, the apparent soil acidification rate induced by N fertilization equaled to 0.01 unit pH yr-1, which can be a reference to the estimated result, considering the effect of atmospheric N deposition, crop biomass, field management and plant uptake of other nutrients and cations. As protons could be consumed by some field practices, such as stubble return and coupled water and nutrient management, soil pH would maintain relatively stable if proper management practices can be adopted in this region.展开更多
文摘氨挥发是农田氮素向环境输出的重要途径,也是我国空气中PM2.5形成的主要因素,给环境和农业生产带来了诸多不利影响。传统的农田氨挥发测定大多依赖酸吸收法,但因采样时间长、劳动量大,难以获取氨挥发日内动态变化规律。基于开放光程可调谐二极管激光吸收光谱技术进行田间痕量氨气测定时,测量精度高、选择性好、系统响应速度快,不需要复杂的采样操作,就可以实现激光发射器与反射镜之间数十至数百米的高时间分辨率的氨气浓度原位快速监测。其与微气象反向拉格朗日随机扩散模型相结合(TDLAS-BLS法)是目前农业源氨挥发监测技术领域的研究热点。通过田间试验,分析比较TDLAS-BLS法与微气象水平通量积分法(IHF法)测定的氨挥发速率及氨挥发损失结果,实现对TDLAS-BLS法测定大面积农田氨挥发的可靠性验证。利用监测获取的高时间分辨率数据研究冬小麦追肥期氨挥发日内变化规律及影响因素。结果表明:TDLAS-BLS法和IHF法测定农田氨挥发速率基本一致(斜率为0.97,R2=0.97,n=14),TDLAS-BLS法测定氨挥发速率仅比IHF法低3%,总氨挥发损失仅低6%,证明TDLAS-BLS法可用于冬小麦追肥期大面积农田氨挥发监测中。冬小麦追肥期白天氨浓度明显高于夜间,且受风速波动影响,氨浓度瞬时波动较大。氨挥发速率在追肥后缓慢升高,施肥后第6天出现氨挥发速率峰值8.9 kg N·ha^-1·d^-1,随后逐渐降低,至第15天与背景接近。氨挥发损失主要集中在施肥后的第5~8 d(79~175 h),该时段氨挥发损失占总氨挥发损失的69%。整个监测期间TDLAS-BLS法测定总氨挥发损失为8.8 kg N·ha-1(占施氮量6.3%),较低的损失量与沟施覆土的施肥方式及低温、低光照强度有关。TDLAS-BLS法实现了在线监测大面积农田氨挥发日内变化规律,高时间分辨率数据可更准确地评估气象因素对氨挥发的影响。冬小麦追肥期氨挥发日内波动较大,存在明显的昼高夜低变化规律,与温度、风速、光照有很高的相符性。相关分析表明风速、光照、土壤温度、降水都与氨挥发有显著相关性,异常天气下主导气象因素(如降水)是氨挥发主要控制因素。
基金financially supported by the National Basic Research Program of China (2011CB100506)the China Agriculture Research System-Wheat (CARS-03-02A)+1 种基金the Knowledge Innovation Program of the Chinese Academy of Sciences (KSCX2-EW-N-08)Research Fund of State Key Laboratory of Soil and Sustainable Agriculture, Nanjing Institute of Soil Science, Chinese Academy of Sciences (Y412201401)
文摘Cropland productivity has been significantly impacted by soil acidification resulted from nitrogen （N） fertilization, especially as a result of excess ammoniacal N input. With decades＇ intensive agricultural cultivation and heavy chemical N input in the Huang-Huai-Hai Plain, the impact extent of induced proton input on soil pH in the long term was not yet clear. In this study, acidification rates of different soil layers in the soil profile （0-120 cm） were calculated by pH buffer capacity （pHBC） and net input of protons due to chemical N incorporation. Topsoil （0-20 cm） pH changes of a long-term fertilization field （from 1989） were determined to validate the predicted values. The results showed that the acid and alkali buffer capacities varied significantly in the soil profile, averaged 692 and 39.8 mmolc kg-1 pH-1, respectively. A significant （P〈0.05） correlation was found between pHRC and the content of calcium carbonate. Based on the commonly used application rate of urea （500 kg N ha-1 yr-1）, the induced proton input in this region was predicted to be 16.1 kmol ha-1 yr-1, and nitrification and plant uptake of nitrate were the most important mechanisms for proton producing and consuming, respectively. The acidification rate of topsoil （0-20 cm） was estimated to be 0.01 unit pH yr-1 at the assumed N fertilization level. From 1989 to 2009, topsoil pH （0-20 cm） of the long-term fertilization field decreased from 8.65 to 8.50 for the PK （phosphorus, 150 kg P205 ha-1 yr-1; potassium, 300 kg K20 ha-1 yr-1; without N fertilization）, and 8.30 for NPK （nitrogen, 300 kg N ha-1 yr-1; phosphorus, 150 kg P2Os ha-1 yr-1; potassium, 300 kg K20 ha -1 yr-1）, respectively. Therefore, the apparent soil acidification rate induced by N fertilization equaled to 0.01 unit pH yr-1, which can be a reference to the estimated result, considering the effect of atmospheric N deposition, crop biomass, field management and plant uptake of other nutrients and cations. As protons could be consumed by some field practices, such as stubble return and coupled water and nutrient management, soil pH would maintain relatively stable if proper management practices can be adopted in this region.
