不同形态氮在土壤中的转化及对烤烟生长的影响

烤烟吸收不同形态的氮素,对其生长发育和品质形成具有明显的影响[1,2].长期以来,关于铵态氮和硝态氮对烤烟生长和品质的影响,国内外作了大量的研究[3～7],但由于供试土壤及气候条件不同,至今尚无定论.     

华北太行山前平原农田氨挥发损失

我国氮肥用量约占全世界氮肥总用量的三分之一[1],但当季利用率仅为30%～35%左右[2].据报道,石灰性土壤中氨挥发是氮素损失的主要途径之一[3-4],其损失量相当于氮素总损失量的20%～71%[2,5-7 ].进入大气中的氨引起自然土壤和水体的氮素含量升高,产生富营养化[8],导致植物种类更替和部分物种灭绝[9].     

土壤辐照灭菌对土壤中铵态氮和硝态氮行为的影响

拟通过土壤辐照灭菌的方法,研究土壤微生物对硝态氮和铵态氮在土壤中的相互转化、固持及损失的影响,为提高作物氮肥利用率提供理论依据。采用土壤纯培养的方法,通过外源添加~(15)N标记铵态氮肥[(~(15)NH_4)_2SO_4]和硝态氮肥(Na~(15)NO_3),结合γ辐照灭菌的方法,培养30 d后,测定分析了灭菌和未灭菌土壤中总的、来自于肥料的和来自于土壤的铵态氮和硝态氮含量,并定量评价了肥料氮在土壤中的残留、固持和损失情况。结果表明:灭菌显著抑制铵态氮向硝态氮的转化,激发土壤铵态氮的释放,对铵态氮在土壤中的残留、固持和损失没有显著影响;灭菌对土壤硝态氮转化为铵态氮的过程没有影响,降低了硝态氮在土壤中的残留和固持,增加了硝态氮的损失;与外源添加硝态氮相比,外源添加铵态氮促进了土壤自身无机氮的释放,外源添加的铵态氮在土壤中残留低、固持高、损失高。因此,总体来看,灭菌有利于土壤铵态氮的积累,却降低土壤硝态氮的积累。虽然外源铵态氮较外源硝态氮更能激发土壤无机态氮的释放,并更易被土壤固持,但是铵态氮肥较硝态氮肥在土壤中残留少、损失多。     

应用同位素15N研究硝化抑制剂对水稻的增产作用

引言据国内外报道(Goriog Cleve 1962),氮素化肥施入土壤中,有相当一部分从土壤中损失,一般作物只能利用30-50%。施于土壤中氮肥损失的途径主要是氨的挥发,硝态氮的流失,硝态氮在嫌气条件下的反硝化作用,以及亚硝酸盐的化学分解。     

冻融交替对砒砂岩与沙复配土壤氮素的影响

[目的]探讨冻融作用对毛乌素沙地陕北榆林地区砒砂岩与沙复配土壤氮素的影响,对于提升毛乌素沙地土壤肥力具有重要作用。[方法]通过室内培养试验,探讨不同比例砒砂岩与沙复配土壤氮矿化过程对冻融的响应特征。[结果]冻融交替作用对土壤氮的矿化有显著影响,在冻融1周期时,3种比例复配土壤中硝态氮、铵态氮含量增加较快。在冻融2周期后,复配土壤中硝态氮、铵态氮含量均出现下降趋势。冻融5周期,复配土壤中硝态氮、铵态氮含量均开始呈现稳定增加趋势。冻融10周期后,1∶1,1∶2及1∶5复配土壤铵态氮含量分别增加了10%,49%与11%,硝态氮含量分别增加了14%,39%与34%,其中1∶2复配土硝态氮、铵态氮含量较1∶1,1∶5增加显著,对氮素的保持性能较好。[结论]冻融循环促进了土壤有机氮的矿化,有利于土壤中硝态氮、铵态氮的累积,为早春农作物的生长提供足够的氮素。     

灌溉施肥对壤质潮土硝态氮淋溶的影响

在衡水市邓庄乡壤质潮上上进行了以灌水为主处理、氮用量为副处理,各五水平的定位试验。结果表明,氮肥用量是硝态氮淋溶损失的决定因素,冬小麦施氮150kghm-2不发生淋溶,施氮225～300kghm-2则硝态氮的淋溶增强。小麦播前基施氮肥量过高会使冬季发生硝态氮的淋溶。小麦拔节期和灌浆期灌溉一般不会引起硝态氮的淋溶损失;尽管一次灌水1350m3hm-2硝态氮的淋失量不高,但土壤剖面中的硝态氮含量显著比低灌水量的低。为降低硝态氮的损失,应控制一次灌水量不超过1050m3hm-2。雨季降水导致大量硝态氮淋溶损失,防治雨季土壤硝态氮的淋溶损失至关重要。     

水分调节剂DY-ET100对番茄产量、品质及水氮在土壤中扩散的影响

为解决水分在土壤中横向扩散范围小和硝态氮淋溶等问题,以水分调节剂DY-ET100为供试材料,以清水、渴以友为对照,研究和对比了水分调节剂DY-ET100的添加对水分在不同土壤中的扩散情况及对硝态氮淋溶和番茄产量及品质的影响。结果表明,在掺沙和未掺沙黏土中添加水分调节剂DY-ET100较清水处理番茄果实中VC含量分别显著提高12.50%和20.51%;添加DY-ET100的处理使距滴头0～30 cm范围内的水分在土壤中分布更加均匀,滴灌时水分扩散半径较清水和渴以友分别增加22.53%和12.33%;在掺沙和未掺沙黏土中较清水处理硝态氮累积量增加41.21%和18.83%;同时减少硝态氮的淋溶损失量,在掺沙和未掺沙黏土较清水处理硝态氮淋溶损失降低7.53%和8.07%。研究为水分调节剂的使用推广提供了数据支撑。     

酸雨对表面活性剂促进土壤氮素垂向迁移的强化效应

采用模拟淋溶试验,研究了酸雨对表面活性剂十二烷基苯磺酸钠(SDBS)促进土壤氮素垂向迁移的强化效应。结果表明,酸雨淋溶时,SDBS尽管抑制了铵态氮的淋溶损失,但促进了硝态氮的淋溶损失;土壤SDBS含量越高,铵态氮淋溶损失越小,硝态氮淋溶损失越大;土壤SDBS促进了土壤氮素的淋溶损失,且这种损失受酸雨pH值影响较大,酸度越大,土壤全氮、铵态氮、硝态氮的淋失量也越大。     

基于精细管理地区减少氮淋失的管理模型

虽然氮是集约耕作农业系统的重要营养物,但是充分发挥其效率并减少损失非常困难,原因之一是影响土壤残留硝态氮和硝态氮淋失潜力的空间和时间变异性。1999~2001年美国土壤学家Delgado使用氮素淋洗经济分析(NLEAP)模型评价精细管理地区的氮管理效益。氮淋失随管理地区变化,低生产力地区淋失量最大。研究发现生产力是决定硝态氮淋失的重要空间变量,低生产力地区硝态氮淋失量随施肥量增加而增加。除了氮,可以限制产量以减少硝态氮的生长季淋失和土壤残留硝态氮非生长季的有效淋失。基于生产力地区的空间变量施肥比统一施肥的硝态氮淋失量少,且维持最高产量,使用精细管理后第一年可减少硝态氮的淋失率为25%。     

氮肥施用对黄土高原中部雨养农业区土壤硝态氮分布与累积的影响

黄土高原中部雨养农业区春小麦氮肥试验表明,氮肥施用量对土壤硝态氮的移动深度没有影响,但显著影响土壤硝态氮的含量与累积。连续施氮3年后第3季春小麦收获时,0～200cm土壤剖面中累积大量的硝态氮,其中48.96%～81.38%的总累积量和60.49%～122%的当年净累积量存在于0～110cm土层中。在确定春小麦适宜施氮量时应考虑到0～110cm土层中残留硝态氮的累积量。不施氮和氮磷比例为1:1时,连续施氮三年后土壤硝态氮总累积量最低,数量几乎相等;第3季春小麦收获后较播种时,土壤硝态氮发生亏缺。施氮量为52.5 kgN hm-2时土壤硝态氮的三年总累积率和第3季春小麦当年的净累积率居各处理之首(146.55%和138.21%)。合理的氮磷配比可有效减少土壤硝态氮的累积,不合理的氮磷配比下,低施氮量也会造成土壤硝态氮的大量累积。     

土壤含水率与土壤碱度对土壤抗剪强度的影响

土壤含水率和土壤碱度是表征土壤物理化学性质的两个重要参数。通过室内三轴不固结不排水试验，研究了土壤含水率和土壤碱度对土壤抗剪强度的影响。试验处理采用5种土壤碱度(土壤可交换钠百分比ESP=0、5、10、20、40)和4种土壤质量含水率(0.05、0.10、0.20以及饱和含水率0.34)水平。试验结果显示，土壤黏聚力随着土壤含水率的增加基本上呈先增大后减小之趋势；当土壤含水率在0.10附近时黏聚力达到其最大值。土壤内摩擦角随着土壤含水率的增加而线性减小。土壤碱度对土壤黏聚力的影响机理较为复杂，其影响效果随土壤含水率的增加而减小；但土壤碱度对土壤内摩擦角的影响较小。土壤碱度对土壤抗剪强度的影响程度明显地小于土壤含水率对其的影响程度。     

Effect of soil acidification on the soil microflora

The effects of short and long term acidification on a few Alberta soils were studied with respect to bacterial numbers and total soil respiration. Significant reductions in bacterial numbers were observed in both short and long term acidified soils. Total soil activity was severely affected in an acid soil (pH 3.0, longterm) adjacent to a S block. A soil (pH 6.8) 200 m away from this S block when artificially acidified to pH 2.9 significantly reduced soil activity but not as drastically as found in the long term pH 3.0 soil. A garden soil (pH 7.7) which was also acidified to pH 3.2 showed no significant reduction in total soil respiration rate as compared to its unacidified control soil. These acid soils when amended with organic substrates demonstrated that certain physiological groups of organisms were severely inhibited by this acid condition. The importance of examining more than one parameter when assessing the effect of a potential pollutant on soil activity is discussed.     

Effect of soil structure on soil water status

Although the need for research into soil structural features responsible for water loss from soil is recognised, the research has been hampered by the lack of suitable techniques for measuring in situ soil macrostructure. Therefore, in a field experiment, structural parameters obtained from eight differently tilled (loam) soils in winter and spring were correlated with gravimetric soil water content (at 5 and 10-cm depths) and evaporative water loss during daylight hours. Percentage of voids and aggregates of different sizes, mean aggregate size, mean void size and macroporosity percentage were all calculated from structural data obtained from sectioned blocks of soil that were impregnated with paraffin wax in the field.Significant negative correlations were observed between soil water content, and percentage of 4–8 and 8–16-nm voids, mean aggregate size and macroporosity percentage, especially in winter when there are long periods without precipitation. However, inverse relationships were detected between evaporative water loss during daylight hours on selected days and mean aggregate size, mean void size and macroporosity percentage. But evaporative water loss during daylight hours apparently did not influence water content of bare soil with coarse structure at the surface.     

熏蒸处理对土壤微生物及硝化作用的影响

在田间条件下用溴甲烷(68.1g/m2)、威百亩(7.5mL/m2)进行土壤熏蒸,调查两种药剂对土壤微生物及硝化作用的影响。结果表明:两种熏蒸剂对土壤放线菌无抑制作用,对细菌总量影响较小,但亚硝酸细菌受到强烈抑制,土壤的硝化作用受到明显影响;同时,土壤中真菌的数量及种类变化显著。熏蒸后9周,处理区土壤中的微生物基本恢复正常。     

土壤熏蒸剂对土壤硝化、反硝化作用的影响

采用化学分析和变性梯度凝胶电泳(DGGE)技术,以大田威百亩、棉隆、溴甲烷、硫酰氟熏蒸100 d土壤为研究对象,探究土壤熏蒸对土壤硝化活性、反硝化活性及amoA基因型硝化型细菌、nirS基因型反硝化细菌群落结构影响。研究表明,威百亩、棉隆、硫酰氟熏蒸剂处理下,土壤硝化活性与对照无显著差异;而溴甲烷处理的硝化活性比对照降低13.19%,差异显著(P0.05);熏蒸剂之间土壤硝化活性无显著差异。4种熏蒸剂之间以及与对照之间土壤反硝化活性无显著差异。4种熏蒸剂中溴甲烷处理土样amoA型硝化细菌多样性指数、均匀度显著低于对照土样和其他3种熏蒸剂处理土样;而丰富度指数无显著差异。威百亩、棉隆和硫酰氟熏蒸土样之间及与对照之间amoA型硝化细菌3种生态指数无明显差异。4种熏蒸剂处理土壤nirS型反硝化细菌多样性指数、均匀度与对照无显著差异(P0.05);熏蒸剂之间存在显著差异(P0.05)。研究表明,溴甲烷对土壤硝化活性的抑制是通过抑制amoA型硝化细菌的多样性而实现,其他3种熏蒸剂对土壤硝化活性无显著影响。4种熏蒸剂对土壤反硝化活性无显著影响。     

Assessment the effect of homogenized soil on soil hydraulic properties and soil water transport

Soil hydraulic properties play a crucial role in simulating water flow and contaminant transport. Soil hydraulic properties are commonly measured using homogenized soil samples. However, soil structure has a significant effect on the soil ability to retain and to conduct water, particularly in aggregated soils. In order to determine the effect of soil homogenization on soil hydraulic properties and soil water transport, undisturbed soil samples were carefully collected. Five different soil structures were identified: Angular-blocky, Crumble, Angular-blocky (different soil texture), Granular, and subangular-blocky. The soil hydraulic properties were determined for undisturbed and homogenized soil samples for each soil structure. The soil hydraulic properties were used to model soil water transport using HYDRUS-1D.The homogenized soil samples showed a significant increase in wide pores (wCP) and a decrease in narrow pores (nCP). The wCP increased by 95.6, 141.2, 391.6, 3.9, 261.3%, and nCP decreased by 69.5, 10.5, 33.8, 72.7, and 39.3% for homogenized soil samples compared to undisturbed soil samples. The soil water retention curves exhibited a significant decrease in water holding capacity for homogenized soil samples compared with the undisturbed soil samples. The homogenized soil samples showed also a decrease in soil hydraulic conductivity. The simulated results showed that water movement and distribution were affected by soil homogenizing. Moreover, soil homogenizing affected soil hydraulic properties and soil water transport. However, field studies are being needed to find the effect of these differences on water, chemical, and pollutant transport under several scenarios.     

节水灌溉对盐渍土盐分调控与土壤微生物区系的影响

河套灌区是我国大型自流灌区之一,盐渍化是该区土壤主要障碍因素之一。目前,河套灌区葵花田生育期灌溉量约为1 100～1 200 m3hm-2,灌溉用水量偏大和地下水位偏高已成为制约当地灌溉农业可持续发展的主要障碍:一方面,水资源浪费严重;另一方     

Tillage effects on soil degradation, soil resilience, soil quality, and sustainability

Soil degradation, decrease in soil's actual and potential productivity owing to land misuse, is a major threat to agricultural sustainability and environmental quality. The problem is particularly severe in the tropics and sub-tropics as a result of high demographic pressure, shortage of prime agricultural land, harsh environments, and resource poor farmers who presumably cannot afford science based recommended inputs. Tillage methods and soil surface management affect sustainable use of soil resources through their influence on soil stability, soil resilience, and soil quality. Soil stability refers to the susceptibility of soil to change under natural or anthropogenic perturbations. In comparison, soil resilience refers to soil's ability to restore its life support processes after being stressed. The term soil quality refers to the soil's capacity to perform its three principal functions e.g. economic productivity, environment regulation, and aesthetic and cultural values. There is a need to develop precise objective and quantitative indices of assessing these attributes of the soil. These indices can only be developed from the data obtained from well designed and properly implemented long-term soil management experiments conducted on major soils in principal ecoregions.     

黑土区土壤侵蚀厚度对土地生产力的影响及其评价

为了研究黑土区土壤侵蚀厚度对土地生产力的影响,采用盆栽试验,人为剥离黑土表层0、5、10、15、20、25和30 cm土壤以模拟侵蚀厚度不同的耕层土壤,分析土壤侵蚀厚度对土壤理化性质、大豆生物性状和水分利用效率等指标的影响。并对TOPSIS(technique for order preference by similarity to ideal solution)模型进行改进,用于评价侵蚀厚度不同的土壤的土地生产力。结果表明:土壤全N、碱解N、全P、速效P、有机质含量和土壤田间持水率均随侵蚀厚度的增加而递减,土壤容重随侵蚀厚度的增加而递增。土壤侵蚀厚度对大豆生长有显著影响,随着侵蚀厚度的增加,大豆减产率呈"S型"曲线递增,产量、耗水量呈"Z型"曲线递减,水分利用效率呈指数曲线关系递减。改进的TOPSIS模型对不同侵蚀厚度下土地生产力的评价结果较为理想,计算的土地生产力指数随土壤侵蚀厚度的变化呈"Z型"曲线,与大豆产量的变化趋势相同,且二者呈指数函数关系,决定系数达0.996,均方根误差为0.65。研究结果可为黑土区土壤侵蚀防治提供理论依据。     

农林复合种植模式对红壤坡地表土水力特性及储水的影响

为探讨红壤坡地不同农林模式表层土壤水力特性差异及其对土体储水量的影响,该文分析了红壤坡地"农-林-草"、"农-林+横坡耕作"、"农-林+顺坡耕作"和"纯林"4种典型农林复合模式表层土壤(0～0.30 m)的土壤水力特征参数,并通过Richards方程数值求解模拟了不同表层土壤水力特性下的土壤含水率动态和土体储水量。结果表明,农林复合模式对表层土壤水力特性有较大影响,"农-林-草"、"农-林+横坡耕作"、"农-林+顺坡耕作"、"纯林"模式的表层土的土壤性质依次表现为:土壤黏性增强(土壤进气值倒数减小)、透水性减弱(饱和水力传导度减小)。饱和水力传导度、土壤进气值倒数与土壤容重的相关系数为-0.98和-0.96。当仅考虑表层土壤水力特性差异时,土体储水能力由强到弱依次为"农-林-草"、"农-林+横坡耕作"或"农-林+顺坡耕作"和"纯林"模式土壤。"农-林-草"模式表层土壤具有在蒸发期减少深层土壤水消耗、在降雨期增加深层土壤水补给的作用,该土壤储水机制为"农-林-草"复合种植模式推广提供了理论基础。