化肥减量配施生物炭对植烟土壤氮素淋失的影响

为明确化肥减量和添加生物炭对植烟土壤氮素淋失的影响,采用室内土柱试验,研究了不同施肥处理（常规施肥,化肥减量30%,化肥减量30%+5%生物炭,不施肥）下,褐土、红壤、紫色土中有效氮淋失量变化。结果表明,淋洗前期各形态氮的淋失量较大,随时间推移逐渐减弱。淋失的氮主要为可溶性总氮及硝态氮。与常规施肥相比,化肥减量处理的可溶性总氮、硝态氮、铵态氮淋失量分别减少12.0%~21.8%、8.9%~22.5%、12.7%~25%;化肥减量+生物炭的处理能够明显延缓土壤中氮素淋失出现的时间,可溶性总氮、硝态氮淋失量分别减少26.6%~35.4%、36.5%~59.2%。总之,化肥减量或添加生物炭能减少土壤中可溶性总氮及硝态氮的淋失量。     

广东南雄烟区土壤氮素矿化特征及烟株对氮素的吸收和累积规律

为了探明广东南雄烟区砂泥田、牛肝土和紫色土3种主要植烟土壤的供氮特性及相应土壤中种植烤烟的氮素吸收规律,采用田间试验探讨了烤烟大田生育期植烟土壤氮素矿化特征及烟株对氮素的吸收和积累规律。结果表明:1在烤烟大田生育期中,砂泥田、牛肝土和紫色土3种主要植烟土壤中氮素矿化量随烤烟生育进程的推进而持续增强,总矿化量分别为360.27、327.50和277.82 kg·hm~(-2),且烤烟成熟期氮素矿化量均占总矿化量的60.00%以上;2烟株氮素积累总体上均表现出"缓慢—快速—缓慢"的增长趋势,积累高峰期出现在移栽后45~60 d,总积累量分别为5.36、4.81和4.19 g N·株~(-1);3氮肥利用率分别为34.04%、33.11%和30.53%。因此,在烟草生产实践中可以通过氮肥施用时间前移和少量多次的施氮方法来提高肥料的有效性和利用率,同时避免烤烟生长后期的供氮过量。     

有机肥种类及施用比例对云南洱海烟区植烟土壤氮淋失的影响

为明确有机肥种类对云南洱海烟区植烟土壤氮淋失的减控效果,以及有机肥施用比例与植烟土壤氮淋失关系,以混合型有机肥、生物炭肥、芝麻饼肥为材料进行了室内土柱模拟试验。结果表明：(1)等施氮量且30%有机肥施用条件下,3种有机肥处理硝态氮、铵态氮淋失量和¹⁵N δ值的平均值分别降低29.56%、7.18%和37.83%。(2)生物炭肥处理硝态氮、铵态氮淋失量和¹⁵N δ值分别降低32.59%、9.95%和41.17%,降幅大于混合型有机肥和芝麻饼肥处理。(3)随有机肥施用比例的提高,植烟土壤氮淋失呈下降趋势,有机肥100%施用处理的硝态氮、铵态氮淋失量分别降低51.14%和22.88%。生物炭肥对洱海烟区的植烟土壤氮淋失减控效果较好,有机肥施用比例与植烟土壤氮淋失之间呈线性负相关,提高有机肥施用比例有助于降低洱海烟区的植烟土壤氮淋失污染风险。     

不同肥料配比对南方烟田土壤养分淋溶的影响

为探明大田烤烟基肥施用方式对土壤养分淋溶的影响,通过田间小区试验,对5种不同肥料配比下土壤养分淋溶规律进行了研究。结果表明,烤烟生长期的烟田土壤氮素淋失以硝态氮为主,呈现出先低后高,然后降低的趋势,单施无机肥处理的淋溶量最大,对地下水污染存在潜在危险;铵态氮淋溶量很少,下层土壤淋溶水铵态氮的质量浓度呈现低－高－低的趋势,不同处理间差异明显,施用高比例有机肥有利于减少铵态氮淋溶;土壤淋溶水速效钾动态变化呈现低－高－低的规律,有机、无机肥配施可不同程度减少速效钾的淋失率,单施无机肥对地下水的污染威胁高于其它处理。为减少土壤养分淋溶,在我国南方烤烟基肥施用方式上,提倡20%以上的有机肥与无机肥配施。     

广东南雄烟区植烟土壤肥力特征及综合评价

对广东南雄烟区6个基地单元3种主要土壤类型共534个土壤样品的养分指标进行了测定,分析了各类土壤肥力限制因子,并运用主成分分析法确定各土壤养分指标的权重,通过估算土壤肥力综合指标值(IFI)进行综合评价。结果表明:(1)紫色土呈弱碱性,牛肝土呈中性,砂泥土呈较强的酸性;(2)牛肝土和砂泥土速效氮及有机质含量较高,紫色土二者普遍偏低;紫色土和牛肝土速效钾含量丰富,砂泥土普遍缺钾;3种土壤速效磷含量富足;(3)3种土壤不同程度缺乏硼、铜、锌和氯元素,而锰元素含量富足;紫色土不同程度缺乏铁元素;砂泥土不同程度缺乏钙和镁元素;(4)3种土壤综合肥力指标值(IFI)平均为0.577,变异系数为19.25%,雄州(IFI=0.641)和乌迳(IFI=0.655)基地单元土壤综合肥力指标平均值处于"较高"偏下档次,其他基地单元则处于"中等"偏上(0.6IFI0.5)档次;(5)牛肝土土壤肥力(IFI=0.649)处于"较高"偏下档次;砂泥土土壤肥力(IFI=0.574)处于"中等"偏上档次;紫色土土壤肥力(IFI=0.495)处于"中等"偏下档次。     

氮素形态对烟苗根系生长及氮素利用的影响

为探讨不同形态氮素对烟草根系生长和氮素利用的影响,以烤烟品种NC55为材料,在水培条件下,设置相同氮浓度不同铵硝配比的5个处理(T1 NH_4~+-N:NO_3~--N=100:0;T2 NH_4~+-N:NO_3~--N=70:30;T3 NH_4~+-N:NO_3~--N=50:50;T4 NH_4~+-N:NO_3~--N=30:70;T5 NH_4~+-N:NO_3~--N=0:100),研究了不同氮素形态营养下根系形态生理特征及各器官氮素积累分配的差异,结果表明:处理后25d,纯铵态氮处理的烟苗地上部干重和总干重,总根长、根系总表面积、总体积、可溶性糖含量及茎和叶的含氮量、氮积累量与氮分配率均最低;纯硝态氮处理的烟苗根系干重、平均直径与活力及根系含氮量与氮积累量最低。处理20d内,铵硝比50:50的处理根系干重、氮积累量和植株总干重最大。处理后25d,铵硝比70:30的处理根系和地上部干重,根系总体积、总表面积、活力与可溶性糖含量及根系含氮量与氮积累量最高;铵硝比30:70的处理叶片含氮量与氮积累量最高。在2 mmol/L的氮浓度下,单施铵态氮或硝态氮抑制了烟苗生长及对氮素的利用,混施铵态氮和硝态氮促进烟苗的生长发育及对氮素的利用,其中铵硝比70:30促进烟苗根系与地上部的协调生长,铵硝比30:70促进烟苗地上部对氮素的吸收利用。     

粤北始兴烟区植烟土壤养分状况分析

为进一步彰显始兴烟叶浓香型风格,明确始兴烟区土壤养分状况,对始兴烟区156个具有代表性的土壤养分含量进行分析,结果表明:始兴烟区土壤pH 4.62～8.33基本适宜烟叶正常生长发育;有机质、水解氮含量偏高,速效磷含量除有15.4%土壤低于10 mg/kg处于极度缺磷外,其余土壤磷含量丰富;速效钾、有效硼含量普遍缺乏,是影响始兴烟区烟叶质量的主要土壤因子;钙、镁、锌含量丰缺不一。不同土壤类型养分状况差异较大,生产上要根据土壤特性进行合理施肥,可加强该区紫色土优质浓香型特色烟叶的开发,但应注意适当增施腐植酸及硼肥;对其他类型土壤养分应进行有效调节,适当控制牛肝土田、黄泥田、麻沙泥田的氮肥和有机肥施用量,增施钾肥;黄泥田、麻沙泥田应适当增施钙镁肥;同时针对始兴烟区普遍缺硼的问题生产中要适当增施硼肥。     

施氮方式对烤烟氮素吸收积累及品质的影响

试验研究了不同施氮量和基追肥比例对烟株氮素吸收累积、土壤硝态氮、品质及产量的影响。结果表明,不同处理对烤烟生长前期干物质积累量、烟株氮素含量和氮素累积量无明显影响,减少氮肥用量与基肥用量降低了成熟期叶片氮素含量和氮素累积量,减少氮肥用量显著降低了生长前期和后期的土壤硝态氮含量。随施氮量的增加,烤后烟叶还原糖含量、糖碱比表现为下降趋势,而总植物碱、总氮含量表现为增加趋势。相同施氮量基追肥比例为30:70处理的还原糖含量、糖碱比较大,总植物碱含量、总氮含量较小,香气质、余味得分较高。施纯氮90 kg/hm²,基追肥比例为50:50和30:70的处理经济效益明显增加。本试验条件下,兼顾烟叶产量与品质的最佳氮肥运筹模式为施纯氮90 kg/hm²,基追肥比例为30:70。     

有机无机肥不同施用方式对鄂西南植烟土壤有效氮动态的影响

在鄂西南烟区研究了化肥不同施用方式对植烟土壤有效氮时空动态的影响。结果表明,在降雨量较大年份,烟叶移栽后一个月内化学肥料带入的有效氮基本全部损失,有机肥料带入的氮素(有机态氮)则在移栽后45～70 d内在0～20 cm土层内发挥作用;移栽后60 d左右土壤自身有机氮开始矿化加速导致土壤有效氮升高。揭膜可以使化学氮素大量淋失,而全生育期覆膜则使后期土壤有效氮升高。提前施肥可能会使无机肥料氮素转化为有机氮,使氮素淋失的风险大幅度降低。     

贵州省典型植烟土壤氮素矿化研究

为明确贵州省典型植烟土壤的氮素矿化规律,以贵州省典型植烟土壤黄壤、石灰土、紫色土为研究对象,采用Stanford长期好气间歇淋洗培养法,研究了其土壤氮素矿化过程。结果表明,在好气性培养过程中,贵州省典型植烟土壤氮素矿化速率出现快速下降—缓慢下降—趋于稳定的变化过程,矿化速率表现为石灰土>黄壤>紫色土。土壤矿化氮累积量随着培养时间的推进而增加,矿化氮累积量表现为石灰土>黄壤>紫色土。矿化氮累积主要集中在培养的0~63 d,占总矿化氮累积量的78.42%~83.36%。土壤矿化氮量与土壤有机质含量存在显著或极显著的正相关关系,并能与培养时间通过多元回归的方法建立不同类型典型植烟土壤的矿化氮累积量预测模型。     

Unused fertiliser nitrogen in arable soils—its contribution to nitrate leaching

Nitrate present in arable soils in autumn is at risk to leaching during the following winter. To see whether unused nitrogen fertiliser was a major source of this nitrate, ¹⁵N-labelled fertiliser was applied to 11 winter wheat crops at rates of between 47 and 234 kg N ha^?1in spring. The experiments were on three contrasting soil types in south-east England. On average, 17′% of the N from spring-applied labelled fertiliser remained in the 0–23 cm soil layer at harvest (range, 7–36%) but only a small proportion was in inorganic forms (ammonium + nitrate). This was never more than 5 kg N ha^?1and averaged only 1·3% of the fertiliser N applied (range, 0·4–3·6 %). Between 79 and 98% of the inorganic N in soils at harvest was unlabelled, being derived from the mineralisation of organic N rather than from unused fertiliser. The amount of unlabelled N was much greater where wheat was grown after ploughing up grass or grass/clover leys than where it was grown in all-arable rotations. When wheat was grown without N fertiliser, soil inorganic N content at harvest was no lower than in plots given fertiliser at rates up to 234 kg N ha^?1. This work indicates that, for soil growing winter wheat, almost all of the nitrate at risk to leaching over the winter period comes from mineralisation of organic N, not from unused fertiliser applied in spring. Consequently, even a drastic reduction in N fertiliser use would have little effect on nitrate leaching.     

重庆市菜园土壤与蔬菜硝酸盐和亚硝酸盐含量及相关性研究

研究重庆4 个农贸市场市售3大类19 种蔬菜73 个样品中硝酸盐含量及重庆市13 个主要蔬菜基地土壤和蔬菜的硝酸盐、亚硝酸盐含量及相关性。结果表明,重庆市售蔬菜不同种类及同种蔬菜不同部位的硝酸盐含量差异显著。大小顺序为叶菜类（X =1 619.73 mg/kg）＞茄果类（X =1 327.67 mg/kg）＞葱蒜类（X =
1 078.39 mg/kg）;莴苣叶（X=1 567.91 mg/kg）＞莴苣茎（X=1 871.62 mg/kg）。叶菜类全部超过了一级标准,污染指数高达9.09,污染程度最为严重;茄果类和葱蒜类超过一级标准的样本占81.3%和87.5%,污染指数分别高达8.85和6.56。重庆市13 个主要蔬菜基地不同蔬菜以及同种蔬菜不同部位的硝酸盐含量差异也显著,大小顺序为萝卜叶（X=745.97 mg/kg）＞莴苣茎（X=730.88 mg/kg）＞莴苣叶（X=693.32 mg/kg）＞白菜（X=617.63 mg/kg）＞萝卜根（X=575.74 mg/kg）。土壤中NO3－-N含量差异也显著,大小顺序为种植莴苣的土壤（X=75.24 mg/kg）＞种植白菜的土壤（X=47.05 mg/kg）＞种植萝卜的土壤（X=33.42 mg/kg）。蔬菜可食部分的硝酸盐与土壤中的NO3－-N含量呈极显著正相关关系,线性方程y=407.872＋4.796x。供试重庆市13 个主要蔬菜基地土壤及蔬菜可食部分的NO2－-N含量均较低且差异不显著,蔬菜中的亚硝酸盐含量和土壤中的NO2－-N含量也无显著相关性。     

Limitations of using delta 18O for the source identification of nitrate in agricultural soils

The stable isotopic composition (delta 15N and delta 18O) of nitrate was analyzed in two lysimeter field experiments in order to identify the conditions under which the dual isotope approach can be applied to identify the main source of nitrate in agricultural soils. The first field experiment involved six lysimeters beneath fields that had been fertilized for 10 yr with the same type of fertilizer (NH4NO3; delta 15N = +1.2@1000, delta 18O = +18.6@1000). The isotope ratios of NO3- in the leachate (delta 15N approximately 0@1000; delta 18O approximately +2@1000) could not be interpreted in a conventional way with either fertilizer or soil organic nitrogen as main sources. These results provided clear evidence for the microbial immobilization and subsequent mineralization and nitrification to NO3- (mineralization-immobilization turnover concept). This process masked the original oxygen isotope ratio of the fertilizer source during the summer when microbial activity was high. A second experiment involving the application of Ca(NO3)2 to three lysimeters during the winter confirmed that the dual isotope approach remains valid for the source identification of nitrate under conditions of low microbial activity. The study reveals the limitation of the dual isotope approach to characterize nitrate sources under biologically active conditions and the ability to quantify microbial processes when the main sources can be controlled.     

施用石灰和绿肥及生物有机肥后的酸性土壤pH和理化性状动态变化

为明确酸性植烟土壤施用石灰、绿肥和生物有机肥等改土物料组合的效果,研究了酸性土壤单施石灰、石灰+绿肥、石灰+绿肥+生物有机肥等改土物料后土壤pH和土壤理化性状动态变化。结果表明:（1）施用改土物料之后,植烟土壤pH表现为先升后降的阶段性变化,至烤烟移栽60d后逐渐趋于稳定; 单施石灰的植烟土壤容重呈升高趋势,石灰+绿肥、石灰+绿肥+生物有机肥处理的土壤容重呈下降趋势;植烟土壤孔隙度、水分和有机质含量呈“高—低—高”的阶段性变化;植烟土壤碱解氮含量呈“低—高—低—高的阶段性变化;土壤有效磷和速效钾含量呈递增趋势。（2）至烤烟移栽后120d,施用改土物料较对照能提高土壤pH 0.32~1.07个单位,提高碱解氮含量17.1%~25.7%,提高有效磷含量18.2%~70.0%,但降低速效钾含量;石灰+绿肥、石灰+绿肥+生物有机肥处理分别提高土壤有机质含量27.6%和39.3%,提高土壤孔隙度2.02%和3.02%,提高土壤水分7.4%~24.2%,降低土壤容重2.46%和4.10%;单施石灰则会降低土壤有机质含量、土壤孔隙度、土壤水分含量。（3）不同处理以石灰+绿肥+生物有机肥组合对强酸性土壤的改良效果最好,石灰+绿肥次之,单施石灰效果较差。因此,施用石灰时应配施绿肥和生物有机肥,以实现对强酸性土壤的可持续改良。      

Verifiable metamodels for nitrate losses to drains and groundwater in the Corn Belt, USA

Nitrate leaching in the unsaturated zone poses a risk to groundwater, whereas nitrate in tile drainage is conveyed directly to streams. We developed metamodels (MMs) consisting of artificial neural networks to simplify and upscale mechanistic fate and transport models for prediction of nitrate losses by drains and leaching in the Corn Belt, USA. The two final MMs predicted nitrate concentration and flux, respectively, in the shallow subsurface. Because each MM considered both tile drainage and leaching, they represent an integrated approach to vulnerability assessment. The MMs used readily available data comprising farm fertilizer nitrogen (N), weather data, and soil properties as inputs; therefore, they were well suited for regional extrapolation. The MMs effectively related the outputs of the underlying mechanistic model (Root Zone Water Quality Model) to the inputs (R(2) = 0.986 for the nitrate concentration MM). Predicted nitrate concentration was compared with measured nitrate in 38 samples of recently recharged groundwater, yielding a Pearson's r of 0.466 (p = 0.003). Predicted nitrate generally was higher than that measured in groundwater, possibly as a result of the time-lag for modern recharge to reach well screens, denitrification in groundwater, or interception of recharge by tile drains. In a qualitative comparison, predicted nitrate concentration also compared favorably with results from a previous regression model that predicted total N in streams.     

Effect of simulated reclamation on nitrification of ammonium sulphate applied to saline and alkali soils from West Pakistan

Nitrification of ammonium sulphate (100 ppm nitrogen) applied to alkali, saline-alkali, highly saline and moderately saline soils was studied during 12 weeks of incubation before and after simulated reclamation treatments, in which water plus calcium sulphate was used for the two alkali soils and water alone for the two saline soils. Before reclamation there were considerable differences in the pattern of nitrification due to soil type; this was accounted for mainly by the high loss of ammonia by volatilisation (61-96% of the ammonium-nitrogen applied) from the two alkali soils; from 0 to 80% of the nitrogen applied was recovered as nitrate after 12 weeks of incubation. After reclamation the pattern of nitrification was similar for all soils; 58-68% of the applied nitrogen was recovered as nitrate after 12 weeks. The moderately saline soil was the only one to show a lower recovery of applied nitrogen as nitrate after than before reclamation. There was some nitrite accumulation early in incubation in all the original soils, but after reclamation only in the two alkali soils.     

缓释肥配合减氮对烤烟品质和氮素利用的影响

为有效减轻保山烟区因大量施用速效氮肥可能引起的面源污染,研究了缓释肥减氮施用对保山烟区土壤理化性质、烤烟品质和氮素平衡利用的影响。研究结果表明：（1）与不施肥（CK）和单施化肥（T1）相比,缓释肥（T2）及其减氮处理（T3）使团聚体粒径趋于集中,提升了表层土壤速效养分碱解氮、有效磷和速效钾含量;T2与T3相比,速效养分无显著变化;（2）与CK相比,施肥处理增加了烟叶中总糖、还原糖、总氮、烟碱和钾含量;与T2相比,T3降低了总糖、还原糖、总氮、钾和烟碱含量,增加了钾氯比和糖碱比;不同施肥处理间烤烟评吸质量档次差异不显著;（3）T2、T3较T1提高了氮肥农学利用率（RE）、农学效率（AE）和偏生产力（PFP）,T3提高显著（p<0.05）;T3较T1和T2显著降低了氮素表观淋失率（LLR）（p<0.05）;T2、T3氮素稍有盈余,T1氮素稍有亏损。综上所述,缓释肥可以在减氮基础上保持氮素平衡利用和烤烟品质,可考虑在保山烟区推广。     

贵州植烟土壤硫素特征研究与含硫肥料施用探讨

2000年硫素普查结果，全省主要植烟土壤有效硫含量丰富，平均含量40.49mg/kg；各烟区和各土类含硫量差异明显，变幅分别为27.58-49.28mg/kg和31.53-41.75mg/kg。针对贵州土壤硫素特征，结合本省植烟土壤及烟叶的含氯水平，分析了贵州烤烟生产合理施用肥料（硫肥）的可行性及建议。     

南雄烟区生态条件分析

为了明确南雄烟区生态特征,收集了南雄烟区近25年有关气象资料,测定了南雄烟叶主产区300份土壤样品,系统分析了大田期气象条件及主要植烟土壤养分状况。结果表明,南雄烟区还苗期、伸根期气温偏低,降雨量偏多,日照时数偏少;旺长期气温、降雨量和日照时数较适宜;成熟期气温稍偏高,降雨量明显偏多,日照时数较长。紫色土偏碱性,有机质、氮含量较低,磷、钾含量较高;牛肝土田偏酸性,有机质、氮、磷、钾含量均较高;沙泥田呈酸性,有机质、氮、磷含量较高,钾含量偏低。3种植烟土壤类型水溶性氯含量普遍偏低,有效硼、交换性锰和交换性镁含量均处于极缺乏的水平。南雄烟区生态条件总体较适宜,但也存在一定的限制性因子。