作 者：
丛日环;张丽;鲁艳红;黄庆海;石孝均;李小坤;任涛;鲁剑巍
单 位：
湖南省土壤肥料研究所;江西省红壤研究所;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;西南大学资源环境学院
关键词：
长期秸秆还田;NH_4~+的吸附–解吸;双季稻轮作;稻麦轮作;土壤pH
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CK>NPK>NPKS,北碚试验点则表现为CK>NPKS>NPK,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。
译 名：
Adsorption-desorption characteristics of soil ammonium under long-term straw returning condition
作 者：
CONG Ri-huan;ZHANG Li;LU Yan-hong;HUANG Qing-hai;SHI Xiao-jun;LI Xiao-kun;REN Tao;LU Jian-wei;Resources and Environment College,Huazhong Agricultural University /Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangte River),Ministry of Agriculture;Soil and Fertilizer Institute of Hunan Province;Research Institute of Red Soil of Jiangxi Province;College of Resources and Environment,Southwest University;
关键词：
long-term straw returning;;NH_4~+ adsorption–desorption;;double rice cropping rotation;;rice–wheat cropping rotation;;soil pH
摘 要：
【Objectives】The experiment was to study the effects of long-term straw incorporation on soil ammonium(NH4+) adsorption-desorption characteristics under the surface and subsurface soil level across different cropping systems. Langmuir equation was used to find the maximum adsorption amount(qmax) and adsorption index(b) in order to explore the NH4+ adsorption-desorption difference among different soil types and the relevant impact factors. 【Methods】Soil samples of 0–20 cm and 20–40 cm depth were taken from the long-term fertilization experiments in Wangcheng(Hunan Province, double rice rotation), Jinxian(Jiangxi Province, double rice rotation), and Beibei(Chongqing City, rice–wheat rotation) after rice/late rice harvest in October, 2015. The treatments included were CK(no fertilization), NPK(chemical fertilizers only) and NPKS(straw returning with chemical fertilization), and soil ammonium N(NH4+) adsorption-desorption experiment using the sampled soils was conducted in the laboratory. For the NH4+ adsorption experiment, different concentrations of NH4 Cl solution were added in the soil samples. After oscillation and centrifugation, the amount of NH4+ adsorption was the NH4+ content in the filtrate. The above soil samples were then eluted by anhydrous ethanol until no NH4+ could be tested. Adding 0.01 mol/L KCl solution with oscillation and centrifugation, and then we analyzed the NH4+ content in the filtrate as NH4+ desorption amount. 【Result】Effects of long-term straw returning on soil N adsorption and desorption characters were different across the three sites. NH4+adsorption difference was mainly detected in the surface soil. There was no difference of NH4+ adsorption among the treatments and soil layers when NH4+ < 400 mg/L in the balanced solution. However, NH4+ adsorption in the surface layer showed difference among the treatment when NH4+ > 400 mg/L in the balanced solution. At Wangcheng site, N adsorption showed as CK > NPK > NPKS. However, at Beibei, N adsorption showed as CK >NPKS > NPK. N adsorption was found significant higher in the purple soil at Beibei than that in the red soil at Wangcheng or Jinxian sites. NH4+ adsorption was not different among the treatments at Jinxian, where was showed the lowest N adsorption among the three sites. Based on the correlation analysis, qmax was showed significant positive correlation with soil p H and soil cation exchange capacity(CEC), but negative correlation with soil organic matter and total nitrogen. Whereas the correlation of b value and soil properties was opposite to qmax.For the NH4+ desorption, there was no significant difference among the samples with different treatment from all three sites. NH4+ desorption was higher than the NH4+ adsorption at Wangcheng and Jinxian, whereas maximum NH4+ desorption(541.89–742.38 mg/kg) was much lower than NH4+ adsorption(1003.83–2014.79 mg/kg) at Beibei. 【Conclusions】Long-term straw returning shows different impact on soil N adsorption-desorption in different soil types. As the straw returning increase the organic matter content and decrease the adsorption point of a soil, the N adsorption will be improved by long-term straw returning in purple soil on which there are more adsorption spots and higher potassium ion content, but that will be reduced in the red soil where the soil p H is lower and soil organic matter content is higher.
