氮素指数施肥对杉木无性系苗生长及养分含量的影响

以1年生无性系杉木幼苗为材料,采用温室盆栽方法,设定对照、常规施肥和3个指数施肥共5个处理,施氮总量分别为每株0、0.5、0.5、1.0、2.0 g,施氮20次,间隔为10 d,施氮210 d后,测定杉木的苗高、地径、生物量、叶绿素荧光参数及养分含量.结果表明: 施肥显著促进了杉木无性系的苗高、地径和生物量的增长,以施氮量1.0 g·株^-1的指数施肥处理最佳,分别为59.0 cm、6.0 mm、52.99 g·株^-1;杉木无性系苗木叶绿素荧光参数特征均表现为指数施肥显著大于常规施肥,其中指数施肥的光化学淬灭系数、表观电子传递速率和PSⅡ的有效量子产量均随施氮总量的增加呈先增加后减小的趋势,在施氮量为1.0 g·株^-1时达到最佳,分别为0.89、35.79和0.71.杉木无性系苗木氮含量表现为叶>根>茎.与对照相比,常规施肥根、茎、叶的氮含量分别增加39.6%、16.6%和41.1%,指数施肥根、茎、叶的氮含量分别增加22.6%～81.4%、27.3%～152.6%和73.6%～135.5%.施氮量为1.0和2.0 g·株^-1的指数施肥处理杉木幼苗根、茎和叶氮含量均显著大于常规施肥,而不同器官磷含量和钾含量无显著差异.从苗木生长性状、叶绿素荧光参数特征、植株氮磷钾含量等综合考虑,在本试验条件下,施氮量为1.0 g·株^-1的指数施肥是杉木无系性苗木温室培育的适宜方法.     

长期施锌条件下土壤-植物系统植物营养元素的分布特征

对黄土高原旱地连续17a施用锌肥条件下植物营养元素在土壤-植物系统中的分布特征进行研究,结果表明：长期施用锌肥0～40cm土层土壤的碳、氮元素含量高于对照处理,而40～100cm土层土壤的碳、氮含量低于对照处理;0～100cm土层土壤全磷含量高于对照,而有效磷含量低于对照。施锌冬小麦茎、叶和籽粒中氮含量高于不施锌处理,而壳中氮含量低于对照处理,施锌后氮素在冬小麦茎、叶、籽粒和整个植株中的累积量高于对照,籽粒和茎中磷的含量低于对照,植株中磷的积累量也低于对照。     

苏北滩涂海水灌溉与施氮对籽粒苋生长的影响

为创建海涂海水种、养复合清洁生产模式,首先要探索海水灌溉经济植物的种植条件,为此,在苏北滩涂布置田间小区试验,研究海水灌溉下氮肥与海水对籽粒苋生长的耦合效应。结果表明:1)20%海水灌溉下,施纯氮量120kg.hm-2,植株鲜草和籽粒产量均显著高于施纯氮量60kg.hm-2下的产量,且与施纯氮量180kg.hm-2处理下的产量差异不显著;40%海水灌溉下,施氮120kg.hm-2时籽粒产量最高,但其产量显著低于20%海水灌溉、施纯氮量120kg.hm-2下的产量。2)鲜草产量在淡水灌溉、施纯氮60kg.hm-2下达到最高值,籽粒产量在淡水灌溉,施纯氮180kg.hm-2下达到最高值。但20%海水灌溉、施纯氮120kg.hm-2组合下,籽粒产量和鲜草产量均未与最高产量达显著差异。3)随施氮量的增加,茎、叶中K+含量增加,而根、茎、叶中Na+含量和Cl-含量均先减少后增加。在施氮量为120kg.hm-2范围内,茎K+/Na+随施氮量的增加而升高,施氮量进一步增加,K+/Na+又随之下降。4)20%海水灌溉下,叶片氮素含量在120kg.hm-2处理下达到最高值,在40%海水处理下,氮肥施用对叶片氮素含量影响不显著。...     

不同土壤肥力条件下施氮量对小麦氮肥利用和土壤硝态氮含量的影响

在土壤肥力不同的两块高产田上,利用15N示踪技术,研究了高产条件下施氮量对冬小麦氮肥吸收利用、籽粒产量和品质的影响,及小麦生育期间土壤硝态氮含量的变化.结果表明：1.成熟期小麦植株积累的氮素73.32%～87.27%来自土壤,4.51%～9.40%来自基施氮肥,8.22%～17.28%来自追施氮肥;随施氮量增加,植株吸收的土壤氮量减少,吸收的肥料氮量和氮肥在土壤中的残留量显著增加,小麦对肥料氮的吸收率显著降低;小麦对基施氮肥的吸收量、吸收率和基施氮肥在土壤中的残留量、残留率均显著小于追施氮肥,基施氮肥的损失量和损失率显著大于追施氮肥;较高土壤肥力条件下,植株吸收更多的土壤氮素,吸收的肥料氮量较少,土壤中残留的肥料氮量和肥料氮的损失量较高,不同地块肥料氮吸收、残留和损失的差异主要表现在基施氮肥上.2.当施氮量为105 kg/hm2时,收获后0～100cm土体内未发现硝态氮大量累积,随施氮量增加,0～100cm土体内硝态氮含量显著增加;施氮量大于195 kg/hm^2时,小麦生育期间硝态氮呈明显的下移趋势,土壤肥力较高地块,硝态氮下移较早,下移层次深.3.随施氮量增加,小麦氮素吸收效率和氮素利用效率降低,适量施氮有利于提高成熟期小麦植株氮素积累量、籽粒产量和蛋白质含量;施氮量过高籽粒产量和蛋白质含量不再显著增加,甚至降低;较高土壤肥力条件下,获得最高籽粒产量和蛋白质含量所需施氮量较低.     

硫硒配施对茎瘤芥生长和营养效应的研究

以茎瘤芥品种‘涪杂1号’为材料,通过盆栽实验探讨不同浓度的硫(S)、硒(Se)配施处理对茎瘤芥干物质积累、矿质元素吸收及膨大茎营养品质的影响,为生产中合理施用硫、硒肥提供理论依据.结果表明:与对照(S0Se0,未施硫硒肥)相比,增施硫、硒肥处理均能显著提高茎瘤芥的根、膨大茎、叶片和单株干物质产量,并以S50Se1[S/Se=50(mg/kg)/1(mg/kg)]和S100Se1的处理效果较好,其单株干物质产量分别比对照显著增加32.3%和36.2%;不同硫、硒浓度配施处理对茎瘤芥13种矿质元素积累的影响不同,主要显著促进了茎、叶对氮、磷、钾、硫、硒的吸收积累,而对其它元素的影响不显著,其中茎、叶的硒含量以S50Se3处理最高,硫含量以S100Se1处理最高;各硫硒配施处理对膨大茎营养品质的影响不同,其中S50Se1和S50Se3处理能显著提高膨大茎有机硒、总氨基酸和粗蛋白含量,而对维生素C和可溶性糖含量无显著影响.可见,适宜的硫硒配施可以明显促进其对矿质元素的吸收,提高植株干物质积累,有效改善茎瘤芥膨大茎营养品质,且硫硒配施用量以S 50mg/kg、Se 1mg/kg为宜.     

不同品种菠菜叶肉及叶柄中硝态氮累积与硝酸还原酶活性的关系

盆栽试验条件下,菠菜体内的硝态氮含量及硝酸还原酶（NR）活性因品种和部位而异。硝态氮含量以短缩茎中最高,叶和叶柄中次之,根中最低,且根,冠比越大的品种,其整体植株中的硝态氮含量越低;根尤其是侧根NR活性较高;叶肉和叶柄中硝态氮含量均与根中以内、外源硝酸盐为底物的NR活性呈一定的负相关。     

施肥方式和施氮量对欧美108杨人工林土壤氮素垂向运移的影响

在大田试验条件下,研究了施肥方式(滴灌施肥和沟施)和施氮量(单次每株25、50、75 g)对欧美108杨人工林土壤氮素垂向运移动态的影响.结果表明：不同施肥方式和施氮量下,土壤中铵态氮和硝态氮含量均随土层深度的增加而降低;滴灌施肥下铵态氮和硝态氮主要集中在0～40 cm土层,随时间变化呈先升后降的变化趋势,分别于施肥后第5天和第10 天达到最大值（211.1和128.8 mg·kg^-1).沟施下铵态氮和硝态氮主要集中在0～20 cm土层,硝态氮含量随时间呈逐渐增加的变化趋势,于施肥后第20天达到最大值(175.7 mg·kg^-1),但铵态氮随时间无显著变化;滴灌施肥下氮素在土壤中的有效时长约为20 d,而沟施下氮素在土壤中有效时长超过20 d.滴灌施肥下,土壤中铵态氮和硝态氮的含量和运移距离均随施氮量的增加而增加;沟施下,施氮量越高土壤中硝态氮含量越高,但对铵态氮含量无显著影响.滴灌施肥下林地土壤中尿素的水解、硝化速率和运移深度均高于沟施,且施氮量越大,氮素在深层土壤的积累量越高.结合欧美108杨根系和土壤氮素分布特征,滴灌施肥能够为更大的细根分布区提供氮素,更适用于人工林培育.当单次施氮量为每株50 g时,既可保证细根主要分布区内有较高含量的氮分布又不会造成淋溶,肥料利用效率可能更高.     

茭白生育过程中地上各部位内源激素的含量变化

以两个茭白品种为试材,测定了植株茎蘖生育过程中地上各部位主要激素及肉质茎膨大过程中的干重变化。结果显示：茭白植株生育过程中各部位的激素以玉米素及玉米素核苷(Z ZR)的含量最高,生长素(IAA)其次,赤霉素(GA3)和脱落酸(ABA)含量很低;在各部位间总体以茎尖最高,叶鞘其次,叶片最低。其中Z ZR含量在肉质茎膨大前即已明显上升,膨大开始后显著下降;IAA含量在肉质茎膨大后期至末期才出现下降;叶片内ABA含量在肉质茎膨大前即开始上升,叶鞘内ABA．含量在肉质茎膨大后期上升,茎尖内则无明显变化;各部位GA2含量在整个生育期内无明显变化。肉质茎的干重增加也与其Z ZR含量下降密切相关。认为Z ZR是刺激肉质茎膨大的关键激素。品种间差异表现为各部位激素含量及其变化有一定差异,尤其是肉质茎膨大阶段差异比较明显。     

供氮水平对爬山虎幼苗生长形态和氮分配的影响

通过水培试验,研究了不同氮素水平(0、0.15、0.3、0.45、0.6和0.75g.L-1)条件下爬山虎幼苗的生长形态和体内氮分配状况.结果表明:低氮处理的爬山虎侧枝发育较小,而较高氮处理的侧枝着生位置低,且长度显著高于低氮处理;供氮水平的提高能促进植株的生物量及茎、叶、根氮含量和氮累积量的增加,其中叶生物量占全株生物量的比例最高,在50%以上;叶的氮累积量占整个植株总氮量的60%～70%.     

矮化苹果氮肥施用技术

以8年生烟富3/M26/平邑甜茶为试材,采用¹⁵N同位素示踪技术,研究不同施氮方式(Ⅰ:春季1次性施氮,Ⅱ:分2次施氮,Ⅲ:集约技术施氮,即氮肥减量和分次施氮)对烟富3/M26/平邑甜茶¹⁵N-尿素吸收、利用、损失和果实品质的影响.结果表明:处理Ⅲ植株叶片的叶面积、叶绿素含量(SPAD)、光合速率(P_n)、叶片全氮含量和生物量(果实除外)显著高于处理Ⅰ和处理Ⅱ,植株根冠比也显著增加.处理Ⅲ显著提高了叶片的保护酶活性(超氧化物歧化酶、过氧化物酶和过氧化氢酶),降低了叶片丙二醛(MDA)含量.3个处理各器官从肥料中吸收分配到的¹⁵N量对该器官全氮量的贡献率(Ndff)表现一致,果实的Ndff值最大,其次是一年生枝、叶片和根,且各器官的Ndff值均以处理Ⅲ最大.在果实成熟期,处理Ⅲ的单株总氮含量为93.0 mg·kg^-1,显著高于处理Ⅰ(70.2 mg·kg^-1)和处理Ⅱ(81.9 mg·kg^-1);处理Ⅲ的¹⁵N肥料利用率为33.6%,显著高于处理Ⅰ(20.4%)和处理Ⅱ(26.0%);而¹⁵N损失率为46.9%,显著低于处理Ⅰ(56.5%)和处理Ⅱ(52.9%).不同施氮方式下植株的平均单果质量、可溶性固形物、硬度、可溶性糖、可滴定酸、糖酸比均存在显著差异,且均以处理Ⅲ最高,其次是处理Ⅱ,处理Ⅰ最低.     

Methane and nitrous oxide fluxes in annual and perennial land-use systems of the irrigated areas in the Aral Sea Basin

Land use and agricultural practices can result in important contributions to the global source strength of atmospheric nitrous oxide (N₂O) and methane (CH₄). However, knowledge of gas flux from irrigated agriculture is very limited. From April 2005 to October 2006, a study was conducted in the Aral Sea Basin, Uzbekistan, to quantify and compare emissions of N₂O and CH₄ in various annual and perennial land-use systems: irrigated cotton, winter wheat and rice crops, a poplar plantation and a natural Tugai (floodplain) forest. In the annual systems, average N₂O emissions ranged from 10 to 150 μg N₂O-N m⁻² h⁻¹ with highest N₂O emissions in the cotton fields, covering a similar range of previous studies from irrigated cropping systems. Emission factors (uncorrected for background emission), used to determine the fertilizer-induced N₂O emission as a percentage of N fertilizer applied, ranged from 0.2% to 2.6%. Seasonal variations in N₂O emissions were principally controlled by fertilization and irrigation management. Pulses of N₂O emissions occurred after concomitant N-fertilizer application and irrigation. The unfertilized poplar plantation showed high N₂O emissions over the entire study period (30 μg N₂O-N m⁻² h⁻¹), whereas only negligible fluxes of N₂O (<2 μg N₂O-N m⁻² h⁻¹) occurred in the Tugai. Significant CH₄ fluxes only were determined from the flooded rice field: Fluxes were low with mean flux rates of 32 mg CH₄ m⁻² day⁻¹ and a low seasonal total of 35.2 kg CH₄ ha⁻¹. The global warming potential (GWP) of the N₂O and CH₄ fluxes was highest under rice and cotton, with seasonal changes between 500 and 3000 kg CO₂ eq. ha⁻¹. The biennial cotton–wheat–rice crop rotation commonly practiced in the region would average a GWP of 2500 kg CO₂ eq. ha⁻¹ yr⁻¹. The analyses point out opportunities for reducing the GWP of these irrigated agricultural systems by (i) optimization of fertilization and irrigation practices and (ii) conversion of annual cropping systems into perennial forest plantations, especially on less profitable, marginal lands.     

膜下滴灌技术生态-经济与可持续性分析——以新疆玛纳斯河流域棉花为例

利用2000、2004、2006和2009年玛纳斯河流域的调查数据,以棉花为例,从生态、经济和社会可持续发展三个角度对比分析了膜下滴灌技术的应用效果.生态效益主要表现为,采用膜下滴灌比沟灌平均节水41.92％,流域内农业节约水量约为多年河道来水的9.34％,基本满足河道最小生态需水;采用膜下滴灌比沟灌节约化肥用量18.38％,节约农药用量17.00％.经济效益主要表现为,采用膜下滴灌棉花(籽棉)单产提高23.15％,水分利用效率(WUE)提高70.70％.社会效益主要表现为,采用膜下滴灌农业管理效率提高3-4倍,节约了农业劳动力.采用Bossel理论综合评价膜下滴灌技术的社会可持续性性,结果为良好.总体分析结果表明,采用膜下滴灌技术有利于区域社会经济的发展和生态环境的保护.本文的研究结果可为今后膜下滴灌技术的推广应用提供参考.     

Impacts of Intensive Management and Landscape Structure on Timber and Energy Wood Production and net CO2 Emissions from Energy Wood Use of Norway Spruce

The aim of this study was to analyze the effects of intensive management and forest landscape structure (in terms of age class distribution) on timber and energy wood production (m³?ha^?1), net present value (NPV, ? ha^?1) with implications on net CO₂ emissions (kg CO₂ MWh^?1 per energy unit) from energy wood use of Norway spruce grown on medium to fertile sites. This study employed simulations using a forest ecosystem model and the Emission Calculation Tool, considering in its analyses: timber (saw logs, pulp) and energy wood (small-sized stem wood and/or logging residuals for top part of stem, branches, and needles) from the first thinning and harvesting residuals and stumps from the final felling. At the stand level, both fertilization and high pre-commercial stand density clearly increased timber production and the amount of energy wood. Short rotation length (40 and 60?years) outputted, on average, the highest annual stem wood production (most fertile and medium fertile sites), the 60?year rotation also outputted the highest average annual net present value (NPV with interest rates of 1?C4%). On the other hand, even longer rotation lengths, up to 80 and 100?years, were needed to output the lowest net CO₂ emissions per year in energy wood use. At the landscape level, the largest productivity (both for timber and energy wood) was obtained using rotation lengths of 60 and 80?years with an initial forest landscape structure dominated by older mature stands (a right-skewed age-class distribution). If the rotation length was 120?years, the initial forest landscape dominated by young stands (a left-skewed age-class distribution) provided the highest productivity. However, the NPV with interest rate of 2% was, on average, the highest with a right-skewed distribution regardless of the rotation length. If the rotation length was 120?years, normal age class distribution provided, on average, the highest NPV. On the other hand, the lowest emissions (kg CO₂ MWh^?1a^?1) were obtained with the left-skewed age-class distribution using the rotation lengths of 60 and 80?years, and with the normal age-class distribution using the rotation length of 120?years. Altogether, the management regimes integrating both timber and energy wood production and using fertilization provided, on average, the lowest emissions over all management alternatives considered.     

滴灌水氮耦合对欧美108杨林木生长和土壤氮素的影响

采用地表滴灌技术,田间设计9个水氮耦合处理,以不灌溉不施肥为对照(CK),9个耦合处理由3个灌溉水平(灌溉土壤水势起始阈值为-75、-50、-25 kPa)和3个施N水平(150、300、450 g·tree^-1·a^-1)组合,于2012和2013年2个生长季的滴灌水氮耦合措施后,研究耦合措施对欧美108杨林木胸径、树高和蓄积量的年增量及0～60 cm土层全氮含量的影响.结果表明: 水氮耦合措施可显著促进108杨林木生长并有效提高林地生产力,耦合措施第一年,9个耦合处理中高水高肥处理(土壤水势-25 kPa+施N量450 g·tree^-1·a^-1)使108杨蓄积年增量达到11.54 m³·hm^-2·a^-1,相比CK的8.01 m³·hm^-2·a^-1提高了44.1%,耦合措施第二年,中水高肥处理(土壤水势-50 kPa+施N量450 g·tree^-1·a^-1)使108杨蓄积年增量达到27.85 m³·hm^-2·a^-1,较CK的20.48 m³·hm^-2·a^-1提高36.0%.连续的水氮耦合措施显著提高了林地0～20 cm土层全N含量,耦合措施第一和第二年高水高肥处理各土层全N含量分别比CK高出12.3%～59.4%和71.1%～81.1%.108杨胸径和树高增量与土壤全N含量呈显著正相关,施N水平和水氮交互作用对林木生长和土壤全N含量具有显著的影响,而灌溉水平的影响不显著.综合表明,滴灌水氮耦合措施可通过改善林地土壤肥力,尤其是浅土层全氮含量来有效促进林木生长并提高林地生产力.     

Contribution of root respiration to soil respiration in a C3/C4 mixed grassland

The spatial and temporal variations of soil respiration were studied from May 2004 to June 2005 in a C₃/C₄ mixed grassland of Japan. The linear regression relationship between soil respiration and root biomass was used to determine the contribution of root respiration to soil respiration. The highest soil respiration rate of 11-54 Μmol m^-2 s^-1 was found in August 2004 and the lowest soil respiration rate of 4.99 Μmol m^-2 s^-1 was found in April 2005. Within-site variation was smaller than seasonal change in soil respiration. Root biomass varied from 0.71 kg m^-2 in August 2004 to 102 in May 2005. Within-site variation in root biomass was larger than seasonal variation. Root respiration rate was highest in August 2004 (5.7 Μmol m^-2 s^-1) and lowest in October 2004 (1.7 Μmol m^-2 s^-1). Microbial respiration rate was highest in August 2004 (5.8 Μmol m^-2 s^-1) and lowest in April 2005 (2.59 Μmol m^-2 s^-1). We estimated that the contribution of root respiration to soil respiration ranged from 31% in October to 51% in August of 2004, and from 45% to 49% from April to June 2005.     

Whole-system estimation of denitrification in a plains river: a comparison of two methods

Whole-system denitrification in the South Platte River was measured over a 13-month period using an open-channel N₂ method and mass-balance measurements. Concentrations of dissolved N₂ were measured with high precision by membrane-inlet mass spectrometry and estimates of denitrification were based on the mass flux of N₂, after correction for reaeration and groundwater flux. Open-channel estimates of denitrification ranged from 0 to 3.08 g N m^–2 d^–1 and the mean annual rate was 1.62 g N m^–2 d^–1, which corresponds to removal of approximately 34% of the nitrate transported by the river over a distance of 18.5 km. Over the same period of time, estimates of denitrification based on mass-balance measurements ranged from 0.29 to 5.25 g N m^–2 d^–1 and the mean annual rate was 2.11 g N m^–2 d^–1. The two methods revealed similar seasonal patterns of denitrification the highest rates were measured from late April to August and the lowest rates were in winter. Both methods provide whole-system estimates of denitrification in running waters; where reaeration rate coefficients are low and flux of groundwater is well quantified, the open-channel method has fewer sources of uncertainty and is easier to implement.     

温室滴灌条件下土壤水分亏缺对番茄产量及其形成过程的影响

采用小区试验,在温室滴灌条件下研究了不同生育阶段土壤水分状况对番茄果实大小、坐果数、畸形果及产量形成过程的影响,分析了温室滴灌条件下番茄总产量与灌水量的关系.结果表明：番茄苗期适度水分亏缺（田间持水量的50%～55%）可提高坐果率,畸形果形成减少,但果实总体偏小,果实成熟主要集中在采摘后期;开花坐果期过度水分亏缺（田间持水量的65%以下）虽可促进果实成熟,但降低了坐果数,易形成小果和畸形果;采摘期水分过高（田间持水量的80%以上）或过低（田间持水量的65%以下）均可降低番茄产量,水分亏缺（田间持水量的65%以下）则使坐果数降低、畸形果增加.各水分处理对果实成熟时间无明显影响;温室番茄总产量、灌溉水利用效率与全生育期灌水总量之间均呈二次抛物线关系;当番茄土壤水分（占田间持水量的百分比）下限控制在苗期60%～65%、开花坐果期70%～75%、成熟采摘期70%～75%时,番茄畸形果形成量减少,产量及坐果率较高,可作为滴灌条件下温室番茄适宜的土壤水分控制指标.     

红桦幼苗根系对水-氮耦合效应的生理响应

采用两因素随机区组设计,设置了5个水分梯度,即40%(W_1)、50%(W_2)、60%(W_3)、80%(W_4)、100%(W_5)的土壤田间持水量(FC)和3个施氮梯度,即模拟氮沉降施加0(对照,N_0)、20(N_1)、40(N_2)g N m~(-2)a~(-1)的硝酸铵,研究了水-氮耦合效应对川西亚高山主要阔叶树种红桦(Betula albosinensis)幼苗根系生理活性的影响及根系在土壤水、氮胁迫下的生理调控机制。结果表明:1)随土壤含水量降低,根系活力和根系呼吸速率显著降低,膜脂过氧化产物(丙二醛)、渗透调节物质(脯氨酸、可溶性蛋白质和可溶性糖)含量及抗氧化物酶(超氧化物歧化酶、过氧化物酶和过氧化氢酶)活性显著升高。2)水-氮耦合效应对红桦幼苗根系生理特征影响显著:施氮(N_1和N_2)在土壤水分良好(W_4和W_5)时使根系活力和根系呼吸速率显著升高,而在土壤水分不足(W_1和W_2)时显著降低了根系活力和根系呼吸速率;且在水分不足时,施氮浓度越大根系活力、MDA含量、脯氨酸及可溶性蛋白质含量变化越显著;在W_3条件下,只有N_1对根系生理功能促进作用显著。3)根系活力和根系呼吸速率与丙二醛含量呈显著负相关性。因此,一定范围内的氮沉降在土壤水分状况良好时对植物根系生理特征具有显著正效应,而在土壤水分不足时则使根系细胞膜系统受损,抑制根系生理活性,但根系可通过增加渗透调节物质含量和增强抗氧化物酶活性来抵御一定范围的环境胁迫。     

Nitrous oxide and nitric oxide emissions from an irrigated cotton field in Northern China

Cotton is one of the major crops worldwide and delivers fibers to textile industries across the globe. Its cultivation requires high nitrogen (N) input and additionally irrigation, and the combination of both has the potential to trigger high emissions of nitrous oxide (N₂O) and nitric oxide (NO), thereby contributing to rising levels of greenhouse gases in the atmosphere. Using an automated static chamber measuring system, we monitored in high temporal resolution N₂O and NO fluxes in an irrigated cotton field in Northern China, between January 1st and December 31st 2008. Mean daily fluxes varied between 5.8 to 373.0 µg N₂O-N m^?2?h^?1 and ?3.7 to 135.7 µg NO-N m^?2?h^?1, corresponding to an annual emission of 2.6 and 0.8 kg N ha^?1?yr^?1 for N₂O and NO, respectively. The highest emissions of both gases were observed directly after the N fertilization and lasted approximately 1 month. During this time period, the emission was 0.85 and 0.22 kg N ha^?1 for N₂O and NO, respectively, and was responsible for 32.3% and 29.0% of the annual total N₂O and NO loss. Soil temperature, moisture and mineral N content significantly affected the emissions of both gases (p?<?0.01). Direct emission factors were estimated to be 0.95% (N₂O) and 0.24% (NO). We also analyzed the effects of sampling time and frequency on the estimations of annual cumulative N₂O and NO emissions and found that low frequency measurements produced annual estimates which differed widely from those that were based on continuous measurements.     

秸秆还田配施不同比例化肥对晚稻产量及土壤养分的影响

在不同秸秆还田方式对早稻的效应研究确定的最佳还田方式和还田量(粉碎还田3000 kg/hm2)基础上,以单施秸秆为对照,研究了秸秆还田配施不同比例化肥对晚稻产量、干物质积累与分配及土壤养分的影响。结果表明:(1)与对照相比,秸秆3000 kg/hm2+N 150 kg/hm2+P2O575 kg/hm2+K2O 37.5 kg/hm2增产效果最为显著,在水稻的每穗粒数、千粒重、结实率、充实度和产量等方面增加幅度最大,分别为9.32%、4.28%、13.70%、2.74%和26.38%。(2)各处理的干物质茎鞘比例随着生育进程不断降低,从孕穗期的66.68%—77.00%降低至成熟期的25.97%—34.79%,除SNPK1外,叶片比例从孕穗期的23.00%—33.32%降低至成熟期的7.41%—21.03%;秸秆还田配施不同比例化肥处理的茎鞘比例在孕穗期、抽穗期和成熟期高于对照,而叶片比例与茎鞘比例呈相反趋势。(3)与对照相比,秸秆还田配施不同比例化肥处理提高了土壤pH值、有机碳、全氮、碱解氮、全磷、有效磷、全钾、速效钾,降低了土壤C/N比。研究结果说明,秸秆还田配施不同比例化肥可以提高植株干物质积累速率、群体生物量,合理改善土壤养分,保证较高的水稻增产潜力,其中秸秆3000 kg/hm2+N 150 kg/hm2+P2O575 kg/hm2+K2O 37.5 kg/hm2效果最为显著。