残膜量对膜孔灌土壤水氮运移特性的影响

为探究土壤残膜量对膜孔灌肥液入渗土壤水氮运移特性的影响,通过室内土箱模拟试验设置0,90,180,360,720 kg/hm~2的5个残膜量水平,分析不同残膜量下膜孔灌肥液入渗累积入渗量、湿润锋运移距离、湿润体特征和水氮分布规律。结果表明:残膜对膜孔灌肥液入渗具有阻渗作用,残膜土累积入渗量较无残膜土减少10.63%～30.77%,Kostiakov模型对残膜土单位膜孔面积累积入渗量与入渗时间有较好地拟合效果;入渗前30 min,不同残膜量的垂直湿润锋运移距离差异不显著,随着入渗时间推进,残膜量与湿润锋运移距离、湿润体体积呈负相关关系。入渗结束时,含残膜土湿润体体积减小18.09%～41.96%。垂直湿润锋距离、湿润体体积与入渗时间均呈显著的幂函数关系,R~2均0.98;除膜孔中心处,相同位置含残膜的土壤含水率低于无残膜,30%高含水率区域减小。湿润体内同一深度土壤NO_3~--N和NH_4~+-N含量随残膜量增加而减小,减小幅度为4.20%～16.27%。研究结果可为残膜土下膜孔灌技术提供理论参考。     

藏东南高寒土坡面细沟水流输沙能力变化特征

为探究高寒土坡面细沟侵蚀过程机理,建立科学的坡面细沟输沙能力因子模型,服务高寒坡面水土流失治理工作,以藏东南高寒土壤为研究对象,采用室内径流放水冲刷试验,探讨不同流量和坡度条件下细沟水流输沙能力特征。结果表明：（1）高寒土坡面细沟水流输沙能力的临界坡长随输沙能力的增加而变短,范围为3.27~8.31 m;坡度在15°~25°时,临界坡长大约稳定在5.0 m;（2）不同坡度下,高寒土细沟水流输沙能力与流量表现为明显的线性正相关关系（T_c=Aq）;小坡度的输沙能力受流量的影响程度大于大坡度;（3）高寒土细沟水流输沙能力与坡度可以用指数方程较好地表示（T_c=-ae^（-S/b）+c）,输沙能力随坡度的增大先快速增大,后逐渐过渡到平稳,当坡度达到15°时增幅平缓;（4）坡面细沟水流输沙能力可以用二元幂函数方程T_c=1697.83S^0.491q^1.043表示。通过本模型与其他模型的比较分析,ANSWERS模型在计算高寒土的坡面细沟水流输沙能力还值得商榷,本试验模型、Lei模型与Gao模型均能较好地模拟高寒区细沟侵蚀输沙能力。     

SWAT模拟耕作方式与盐分对区域土壤氮运移及作物产量影响

耕作方式与土壤盐渍化是影响河套灌区氮素流失及作物产量的重要因素.明确不同耕作方式与盐渍化水平下硝态氮运移量及作物产量的变化,可为制定合理的灌区耕作措施及盐渍化治理方案提供理论依据,对于揭示灌区氮素流失控制及不同作物增产潜力具有重要意义.该研究基于验证后的SWAT(Soil and Water Assessment To...     

Influence of root restriction on two cultivars of summer squash (Cucurbita pepo L.)

Variable root restricting conditions were imposed on summer squash (Cucurbita pepo L.) cultivars ‘Senator’ and Dixie’ using container sizes of 0.35, 2.00, and 7.60 liters. Nondestructive and destructive plant sampling were conducted to evaluate leaf area production, dry weight accumulation and partitioning, crop growth rate and net assimilation rate, and flower and fruit development. Within 10 days after transplanting (DAT), ‘Senator’ exhibited declining leaf area production under increased root restriction, and within 17 DAT leaf area was diminished for both cultivars under increased root restricting conditions. Dry weight accumulation in leaves, stems, roots, and fruit was reduced for both cultivars over time and level of root restriction severity. There was a tendency for greater vegetative growth reductions with ‘Senator’ than with ‘Dixie’ at comparable levels of root restriction. Root‐to‐shoot ratio, timing and duration of flowering, and sex of flowers were not significantly impacted by root restriction level or cultivar. Fruit dry weight was greatest for Dixie’ early on, but by 28 DAT, total fruit dry weight produced did not differ for the cultivars except under the most severe root restricting conditions. Fruit dry weight production was limited for both cultivars as container volume became smaller.     

民勤绿洲不同耕作方式农田表层土壤风蚀规律的风洞模拟研究

[目的]比较分析不同耕作方式下农田表层土壤防风蚀机理和效果,为区域社会经济和生态环境建设提供科学依据。[方法]利用室内风洞及相关配套设备对甘肃民勤绿洲区的免耕、少耕、秋翻和深松农田表层土壤进行风蚀测试,计算风蚀速率及输沙率,研究其风沙运动规律,分析各种耕作农田表层土壤防风蚀情况。[结果]耕作措施对土壤风蚀速率的影响与风速大小相关,风速较小时,不同耕作方式对风速的影响差异不显著,而当风速大于14 m/s后不同耕作农田表层土壤风蚀速率开始出现较明显差异;少耕、秋翻、深松等耕作方式对农田表层土壤风蚀速率和输沙率的影响差异不明显;免耕耕作方式下农田表层土壤风蚀速率和输沙率最低,风速越高,差距越大;风速、耕作以及两者交互作用对农田表层土壤风蚀速率和输沙率有极显著影响。[结论]免耕耕作能有效抵抗农田表层土壤的风蚀,大幅度减少输沙率,表现出极佳的抗风蚀效果。     

Analysis of amino acid uptake and translocation in Arabidopsis with a low‐cost hydroponic system

In soils, amino acids may be an important source of nitrogen for plants, at least in those where organic matter is not quickly degraded. The physiology of uptake of amino acids by roots was mainly studied in the 70's and 80's, before genes encoding amino acid importers were cloned in the 90's. While two families of amino acid transporters have been identified, yielding a total of about 100 genes, the role of each member is yet to be elucidated. As a tool for studying the role of amino acid transporters from Arabidopsis we set up a new hydroponic system suitable for radioisotope use. This system enables reproducible amino acid uptake by roots and estimation of the transport to the shoots of the amino acid taken up. We show that the rates of glutamine (Gln) uptake by wild‐type roots and transfer to the shoots were linear, and that other tested amino acids were translocated to the shoots with lower efficiency than Gln. A T‐DNA insertion mutant for a Gln exporter was compared to the wild‐type plants. Gln uptake and transfer were similar in both genotypes, showing that the suppression of the exporter did not affect uptake or transfer of amino acids to the shoots. The main advantage of the hydroponic system presented here is that all the materials used to grow Arabidopsis are virtually free and can therefore be discarded, a useful feature when working with radioactivity.     

微咸水冰体融出水质及基于HYDRUS-1D的土壤淋洗特征研究

为揭示微咸水结冰融水时咸淡分离状况及对盐渍土盐分的淋洗效应,通过室内融冰试验研究不同解冻温度(10℃、15℃)和矿化度处理(纯净水、0.5g·L^–1、2 g·L^–1、4 g·L^–1)冰体的融化速度及融出水质,并借助HYDRUS-1D模型,模拟分析了不同处理融出水与微咸水直接入渗对剖面土壤盐分的淋洗效果差异。结果表明：微咸水冰体咸淡分离效果明显,各处理下的微咸水冰体融出淡水体积占比均超75%,矿化度越小融出淡水体积越大;微咸水冰体先咸后淡融出水入渗对盐渍土中的盐分有较好的淋洗效果,优于相同矿化度的微咸水直接入渗处理;10℃处理微咸水冰融出水对盐渍土的淋洗效果要好于15℃处理。研究结果对于探索内陆干旱区地下微咸水资源利用及新的非生育期节水控盐模式具有一定的指导意义。     

土壤优先流运动的活动流场模型分形特征参数计算

活动流场模型分形特征参数控制着优先流的产生和发展,因此准确获得活动流场模型分形特征参数值对提高模型的模拟预测精度具有重要意义。该研究采用染色示踪方法,将优先流流场从流动背景中显示出来,通过数字图像分析和采样分析获得优先流流场和流场内土壤含水率的分布模式,根据活动流场模型本构方程拟合活动流场模型分形特征参数值;针对3种常见的入渗后染色区内土壤含水率分布模式,分别提供了相应的活动流场模型分形特征参数的计算方法。研究结果显示,1）由于入渗后土壤水重分布的影响,活动流场区域和染色区域在整个入渗深度范围并不完全重合,因此仅可选择活动流场与染色区域相重合深度范围内受土壤初始含水率影响较小的数据来拟合活动流场模型分形特征参数值;2）土壤质地对入渗后染色区内土壤含水率的分布模式有显著影响,细质地土壤中入渗后染色区土壤含水率沿入渗方向逐渐减小,粗质地土壤中入渗后染色区土壤含水率沿入渗方向先增大后减小。     

农田耕作措施对近地表风沙运动的影响

我国北方传统耕作模式的犁耕、耙磨及磨平整地措施对农田近地表风沙活动影响显著。通过对春季半干旱沙区农田风沙活动的观测,本文对犁耕、耙磨磨平两种处理下近地表0~60 cm内输沙率和风沙流结构随田块长度的变化规律进行了研究。结果表明,耙磨磨平处理破坏了犁耕在农田地表形成的非可蚀性土块结构,使近地表0~60 cm内输沙率增大,在强沙尘事件中增加幅度可达数10倍。犁耕地表上输沙率随田块长度的增加呈指数关系递增,而耙磨磨平后风沙流发育的饱和路径长度减小,在强沙尘事件中近地表输沙率随田块长度的增加而递减。此外,上风向处犁耕地表低层输沙比例(Q0-10/Q0-60)小于耙磨磨平地表,且随田块长度的增加逐渐增大,而耙磨磨平后风沙流结构随田块长度的变化不大。     

孪井灌区包气带水分运移的数值模拟

为防止盆地低洼处出现盐渍化、节约水资源,用数值模拟和田间中子仪试验相结合的方法,研究了内蒙古孪井灌区包气带的水分运移规律.数学模拟结果与田间实测土壤含水率吻合良好.在此基础上模拟计算出漫灌与喷灌条件下不同灌溉量和不同蒸发量对水分运移的影响以及水分随时间在深度上的分布情况,结果表明1200m/hm2喷灌定额下得农田水分无效消耗最小,从而得出节水高产的喷灌灌溉模式.