长期秸秆还田下土壤铵态氮的吸附解吸特征

发布时间：2018-04-24 12:29

本文选题：长期秸秆还田 + NH_~+的吸附　；参考：《植物营养与肥料学报》2017年02期

【摘要】：【目的】研究长期秸秆还田对不同轮作区域耕层和亚耕层的土壤铵态氮(NH4+)的吸附、解吸特征差异,通过Langmuir等温吸附方程拟合得到NH4+最大吸附量(qmax)和吸附系数(b),分析长期秸秆还田对不同土壤NH4+的吸附、解吸特征差异及影响因素。【方法】2015年10月水稻收获后,在湖南望城(稻稻轮作)、江西进贤(稻稻轮作)、重庆北碚(稻麦轮作)三个长期定位试验点(25年)采集不施肥(CK)、长期施用化肥(NPK)和长期秸秆还田配施化肥(NPKS)三个处理、0—20 cm和20—40 cm两个土层的土样,进行土壤NH4+的吸附解吸室内试验,吸附试验为添加不同浓度的NH4Cl溶液振荡、离心后,测定滤液NH4+浓度;解吸试验采用吸附试验后的土壤样品,经无水乙醇淋洗至无NH4+后,再加入0.01 mol/L的KCl溶液振荡、离心后测定滤液NH4+浓度。【结果】长期秸秆还田对不同试验点土壤NH4+吸附解吸特征的影响差异较大。处理间的差异主要表现在耕层土壤。当平衡溶液NH4+浓度400 mg/L时,不同试验点耕层和亚耕层处理间差异均不明显;当平衡溶液浓度400 mg/L时,处理间耕层土壤对NH4+吸附表现出差异,其中望城试验点土壤对NH4+的吸附表现为CKNPKNPKS,北碚试验点则表现为CKNPKSNPK,且北碚试验点的紫色土对NH4+的吸附显著高于望城和进贤试验点的红壤性水稻土。进贤试验点不同处理间差异不明显,且土壤对NH4+的吸附量最低。通过相关性分析发现,qmax和土壤p H、阳离子交换量CEC呈显著正相关,而与土壤有机质和全氮含量呈显著负相关;b与土壤性质的相关性与qmax则相反。从土壤对NH4+的解吸曲线来看,耕层和亚耕层土壤对NH4+的解吸在各试验点不同处理间均表现为差异不显著,其中望城和进贤试验点的红壤性水稻土NH4+的最大解吸量高于其吸附量,而北碚试验点的紫色土NH4+的最大解吸量(541.89~742.38 mg/kg)则远低于其吸附量(1003.83~2014.79mg/kg)。【结论】长期秸秆还田对不同土壤NH4+的吸附解吸作用影响不同,对于土壤吸附位点较多且钾离子含量丰富的紫色土而言,长期秸秆还田有利于土壤对氮的吸附;而对于土壤偏酸性的红壤性水稻土而言,长期秸秆还田则可能因为增加了土壤有机质含量而减少了土壤对铵态氮的吸附位点,从而降低了土壤对氮的吸附保持能力。
[Abstract]:[objective] to study the adsorption and desorption characteristics of ammonium nitrogen (NH _ 4) from cultivated and sub-tilling layers of different rotation regions by long-term straw returning to the field. The maximum adsorption capacity of NH4 (Qmax) and adsorption coefficient (BX) were obtained by Langmuir isothermal adsorption equation. The adsorption, desorption characteristics and influencing factors of NH4 in different soils were analyzed. [methods] after rice harvest in October 2015, the adsorption of NH4 in different soils was analyzed. In Wangcheng, Hunan Province (rice and rice rotation, Jiangxi Jinxian (rice and rice rotation), Chongqing Beibei (rice and wheat rotation)) three long-term location test sites (25 years) collected no fertilization, long-term application of chemical fertilizer NPK and long-term straw back to the field. The soil samples of 0-20 cm and 20-40 cm soil layers were treated with NPKS. The adsorption and desorption experiments of NH4 in soil were carried out in laboratory. The adsorption test consisted of adding different concentration of NH4Cl solution oscillating, centrifuging, determining the concentration of NH4 in filtrate, desorption test using soil sample after adsorption test, eluting it to NH4 by anhydrous ethanol. The concentration of NH4 in filtrate was determined after centrifugation. [results] the effect of long-term straw returning to the field on the adsorption and desorption characteristics of soil NH4 in different test sites was significant. The difference between treatments was mainly reflected in the topsoil. When the concentration of NH4 in equilibrium solution was 400 mg/L, there was no significant difference between the topping layer and sub-tilling layer in different test sites, and when the concentration of equilibrium solution was 400 mg/L, the adsorption of NH4 on the topsoil was different between the treatments. The adsorption of NH4 on the soil of Wangcheng experimental site was CKNPKNPKS, and that of Beibei test site was CKNPKSNPK, and the adsorption of NH4 on purple soil in Beibei test site was significantly higher than that in Wangcheng and Jinxian test sites. There was no significant difference among different treatments in Jinxian test site, and the adsorption amount of NH4 to soil was the lowest. Through correlation analysis, it was found that there was a significant positive correlation between Qmax and soil pH, cationic exchange capacity (CEC), but a significant negative correlation between CEC and soil organic matter and total nitrogen content. The correlation between Qmax and soil properties was opposite to that of qmax. According to the desorption curve of soil to NH4, there was no significant difference in NH4 desorption between topsoil and sub-tillage layer, and the maximum desorption amount of NH4 in Wangcheng and Jinxian test sites was higher than that in red soil paddy soil. The maximum desorption capacity of NH4 in purple soil of Beibei test site was 541.89 ~ 742.38 mg / kg), which was much lower than that of 1003.83 mg 路kg ~ (-1) 路kg ~ (-1) ~ (-1) 路kg ~ (-1) 路kg ~ (-1) 路kg ~ (-1) 路kg ~ (-1) 路kg ~ (-1) of NH4 in purple soil. [conclusion] the adsorption and desorption of NH4 in different soils by long-term straw treatment were different. For purple soil with more adsorption sites and rich potassium ion content, long-term straw returning to the field is beneficial to the adsorption of nitrogen, but to the paddy soil of red soil, which is slightly acidic, Long-term straw returning to the field may decrease the adsorption sites of ammonium nitrogen by increasing the content of soil organic matter, thus reducing the adsorption and retention capacity of soil nitrogen.
【作者单位】：华中农业大学资源与环境学院/农业部长江中下游耕地保育重点实验室;湖南省土壤肥料研究所;江西省红壤研究所;西南大学资源环境学院;
【基金】：国家自然科学基金项目(41301319) 湖北省自然科学基金项目(2013CFB203)资助
【分类号】：S158

【相似文献】