Effect of Nitrogen Status on Salinity Tolerance of Tall Fescue Turf

ABSTRACT

Turfgrass salinity tolerance is usually studied under conditions of non-limiting nutrition, even though most turfgrasses are managed with growth-limiting levels of nitrogen (N). This study examined the effect of N status (replete versus deficient) on salinity tolerance in tall fescue (Festuca arundinacea Schreb.). Additionally, the interactive effects of N status and salinity on tissue ion concentrations were determined. Two cultivars (‘Monarch’ and ‘Finelawn I’) were grown in nutrient solution culture. Treatments included N level (100% or 25% of maximum N demand) and salinity (0, 40, 80, 120 meq L^?1). Salinity reduced leaf growth under high-N conditions, but much less so under low-N conditions. Concentrations of potassium (K), sodium (Na), and chloride (Cl) in the leaf sap were significantly higher in low-N than in high-N plants, indicating that increased salinity tolerance in low-N turf was not due to ion exclusion. These results suggest that efforts to screen turfgrasses for salt tolerance should be conducted using realistic N-fertility levels.     

Plant species richness and composition in managed grasslands: The relative importance of field management and environmental factors

Decline of grassland diversity throughout Europe within the last decades is threatening biological diversity and is a major conservation problem. There is an urgent need to determine the underlying factors that control vascular plant species richness and composition in managed grasslands. In this study, 117 grasslands were sampled using standardised methods. Explanatory variables were recorded for each grassland site, reflecting the local field management, site-specific environmental conditions and large-scale spatial trends. Using variation partitioning methods, we determined the pure and shared effects of these three sets of explanatory variables on the plant species richness and composition in grasslands. Most of the explained variation in plant species richness was related to the joint effect of local field management and environmental variables. However, the applied variation partitioning approach revealed that the pure effect of spatial variables contributed relatively little to explaining variation in both the plant species richness and species composition. The largest fractions of explained variation in plant species composition were accounted for by the pure effects of environmental and local field management variables. Moreover, the results revealed that the main mechanisms by which these sets of explanatory variables affect plant species vary according to the type of management regime under study. From our findings we could conclude that particularly a reduction of nitrogen fertilisation on meadows and grazing at a low stocking rate on pastures can help to conserve biodiversity.     

缺氮胁迫对小麦根际土壤微生物群落结构特征的影响

根际微生物在作物养分吸收的过程中发挥着重要作用.为提高小麦的氮肥利用率,有必要深入探究缺氮胁迫对小麦根际微生物群落结构的影响.利用氮素耗竭的陕西关中地区典型的塿土,设置了正常供氮(150 mg·kg-1)和缺氮(不施氮肥)的小麦根箱实验,采用16S rRNA基因扩增子高通量测序技术分析了小麦根际、近根际和非根际土壤微生...     

Influence of staggered sown Spring sunflower (Helianthus Annuus L.) at varying intra–row spacing and applied–N on pre– and post–anthesis N dynamics and dry matter partitioning in Indo–Gangetic Plains Region

In current study, dry–matter accumulation (DMA), pre– and post–anthesis nitrogen (N) accumulation, N translocation (NT) and dry–matter partitioning by sunflower seeds was investigated under three sowing dates (January 20, February 10 & March 2), two intra–row spacings (30 & 24 cm) and four nitrogen doses (0, 45, 60 & 75 kg ha^–1) in two alluvial soils. Early sowing resulted in higher DMA and NT; leading to higher nitrogen use efficiency (NUE) that could be associated with higher pre–anthesis N accumulation. The closer intra–row spacing resulted in higher DMA by all plant parts except seed. Each graded N dose improved DMA, but improvement in dry–matter partitioning to seed was significant up to 60 and 75 kg N ha^–1 during 2014 and 2015, respectively owing to higher NT under respective treatments. NUE was highest at 60 kg N ha^–1 during both years.     

小麦——土壤系统氮肥转化利用的研究进展

施用氮肥是提高小麦籽粒产量、改善品质的重要措施,但是不合理施氮会导致氮肥利用率的降低,氮肥损失的增加。本文综述了小麦-土壤系统中氮肥对土壤氮素转化和小麦氮素吸收利用的影响及氮素损失等方面的研究进展。     

基于土壤氮素平衡的氮肥推荐方法——以水稻为例

基于土壤氮素平衡提出了一种新的氮肥推荐方法——氮素归还指数法,并以水稻为例介绍了其实施过程。经江苏省太湖地区和里下河地区45个水稻田块的举例推荐,用肥料效应函数法推荐的最佳经济施氮量(OENR)、氮素归还指数法推荐的氮素归还施氮量(RNR)和理论施氮量法推荐的理论施氮量(TNR)分别平均为N 246.8±42.5、216.9±27.3和176.9±22.3 kg hm-2。氮素归还指数法可不经过田间试验实现以目标产量为唯一变量的氮肥推荐,但在区域氮素净损失率能否保持相对稳定、长期实施氮素归还施氮量能否使土壤不致产生氮素盈余等方面仍需进一步研究。     

淮河流域农业生态系统中地下水体氮源追溯

淮河流域地下水体中的氮污染问题一直以来备受关注。为了从源头追溯氮污染物的来源,本文通过清单法收集淮河流域2002—2017年期间35个地级市的农业统计资料,首先构建基于化肥施用氮、人畜粪便返田氮、生物固氮、大气沉降氮、种子带入氮、秸秆带入氮为输入项和作物收获氮、反硝化脱氮、氨挥发脱氮为输出项的氮平衡模型,估算进入淮河流域农业生态系统内的氮盈余量和强度;然后利用氮盈余量与淋滤系数构建氮淋滤模型定量估算氮淋滤到地下水体中的量。研究发现：2002—2017年间淮河流域农业生态系统中氮年均输入量为1 005.01万t·a^-1,化肥施用氮是最大的氮输入源,占总输入量的52.76%;淮河流域农业生态系统中氮年均输出量为706.43万t·a^-1,作物收获氮在氮输出中所占的比例最大,达87.29%。随着时间的增加,氮盈余量和强度逐步降低。本次从地级市角度计算的氮源强度和其时间变化规律与以往从流域角度计算的氮源强度和其时间变化规律相差不大,保证了结果的准确性。从地区上分析,河南省各地级市的氮源强度最高,山东省和安徽省各地级市的最低。2002—2017年间,淮河流域农业区氮盈余量淋滤进入地下水中的氮污染物总量为26.22万~41.71万t·a^-1,淋滤进入到地下水体中的氮污染物平均量为31.41万t·a^-1,其中2006年最高。较大的氮淋滤值对水体环境造成了较大的污染负荷。采用SPSS 21.0中用F统计量和皮尔森相关系数（ρ）对地下水中的实际氮污染物浓度与估算值间的氮污染物量进行相关性检验,最终通过显著性检验且相关系数达到0.517,证实了本次模型选择的准确性。本文研究表示,2002—2017年淮河流域农业生态系统中地下水体中氮的来源主要为化肥输入,最主要的输出途径为作物收获,污染最严重年份为2006年,为解决农业面源污染问题提供了重要的前期资料,对地下水中氮污染的防控具有重要的现实意义。     

施氮量对氮高效水稻种质4007的氮素吸收、转运和利用的影响

田间条件下,以当地水稻品种武运粳15(WJ15)为对照,对氮高效水稻种质4007在不同施氮水平(0、100、150、200和250 kg hm-2)下的氮素吸收、累积、转运、产量及氮肥利用率进行了研究。结果表明施氮量显著促进水稻各生育期地上部氮素的累积,水稻从分蘖盛期到拔节期植株氮素累积量最大,占总生育期的32.7%～41.6%。当施氮量从0增加至250 kg hm-2,水稻种质4007的氮素转运量的从72.0上升至104kg hm-2,氮素转运率从66.2%下降至51.3%;而WJ15的氮素转运量从57.0上升至96.5 kg hm-2,氮素转运率也从57.1%下降至46.8%。籽粒中的氮素65.3%～87.6%来自营养器官的转运,仅12.4%～34.7%是后期从土壤吸收所得。由于较高的收获指数(HI)和氮收获指数(NHI),水稻种质4007的平均氮肥表观回收率(REN)和氮肥农学利用率(AEN)分别较品种WJ15高出24.5%和95.6%。本试验结果还显示4007和WJ15的适宜施氮量分别是150 kg hm-2和200 kg hm-2,此时,水稻可维持较高的产量和保持较高的氮肥利用率。     

温室黄瓜干物质分配与产量预测模拟模型初步研究

依据温室黄瓜(Cucumis sativus)器官生长与温度和辐射的关系,建立了基于分配指数和采收指数的温室黄瓜干物质分配与产量预测模拟模型,并利用不同品种和基质的试验资料对模型进行了检验。结果表明,模型对黄瓜地上部分干重、根干重、茎干重、叶干重、果实干重的预测结果与1∶1直线之间的R²分别为0.98,0.73,0.83,0.92,0.94;RMSE分别为232,6.8,157.6,173.9,196.8 kg/hm²。模型对黄瓜产量的预测结果与1∶1直线之间的R²为0.80,RMSE为7526.4 kg/hm²。本模型对不同基质、品种的黄瓜干物质分配和产量的预测值与实测值符合度均较高,说明本模型的普适性较好。模型不仅能较好地预测中国现有生产水平下温室黄瓜的干物质分配及产量,而且可以为实现中国温室黄瓜生产环境优化调控和模式化栽培管理提供决策支持。     

Extraction of nitrogen from soils

Summary A roller bed and rotary end-over-end shaker were compared for the extraction of mineral N from a variety of soil types; both were equally efficient with an optimum extraction time of 30 min. However, the roller bed permitted a greater operational capacity, a faster throughput of samples, and easier identification of sample bottles compared with the end-over-end shaker. More NH₄ ⁺-N and NO₃ ^–-N (P<0.001) was recovered from soil by 2 M KCl than by any other extractant, in a soil: extractant ratio of 1 to 5 (w:v), except water, which was equally efficient at removing NO₃ ^–-N from soils.     

施氮对水稻产量、氮素利用及土壤无机氮积累的影响

通过田间试验研究了不同施氮量(0、60、120、180和240 kg hm~(-2))对水稻氮肥利用、产量、土壤氮素供应及氮素平衡的影响,结果表明,水稻产量随施氮量的增加呈先增后降的趋势,当施氮量超过180 kg hm~(-2)后产量下降,根据水稻产量(y)和施氮量(x)拟合,得出最佳施氮量为204 kg hm~(-2)。施用氮肥可显著增加水稻氮吸收总量,并随施氮量的增加显著增加,当施氮量超过180 kg hm~(-2)后,氮吸收总量不再显著增加。氮肥当季回收率、农学利用率、偏生产力和生理利用率均随施氮量的增加而下降,分别由44.0%、25.5 kg kg~(-1)、145.6 kg kg~(-1)和58.1 kg kg~(-1)下降至31.1%、13.6 kg kg~(-1)、43.6 kg kg~(-1)和43.7 kg kg~(-1)。氮收获指数表现为随施氮量的增加先增后降,以施氮量180 kg hm~(-2)处理最高,为68.7%。土壤无机氮(Nmin)含量在水稻整个生育期呈现先快速下降后缓慢升高的趋势,施氮处理各层土壤Nmin积累量与不施氮处理差异均达显著水平(P0.05),且基本随着施氮量的增加而增加。水稻成熟期土壤残留Nmin量和表观损失均随施氮量的增加而增加。氮盈余主要以土壤Nmin残留量为主,表观损失在氮盈余比例较小,但随着施氮量的增加显著增加。水稻氮吸收量、土壤无机氮残留量和氮素表观损失量与施氮量呈显著的正向相关性。在本试验条件下,综合水稻产量、氮肥利用效率和土壤无机氮积累等方面的因素,在吉林省水稻主产区,适宜施氮量应控制在180~204 kg hm~(-2)范围内。     

Potassium and Nitrogen Distribution Pattern and Growth of Flue-Cured Tobacco Seedlings Influenced by Nitrogen Form and Calcium Carbonate in Hydroponic Culture

ABSTRACT

Grape tomatoes (Solanum lycopersicon L. var. cerasiform) have recently gained in popularity among consumers because they can be eaten without being cut, they are deep red in color, and their flavor is intense and pleasant. Current nitrogen (N) fertilization recommendations were developed for determinate tomato varieties that have a 3-month long growing season, whereas that of the indeterminate grape cultivars may be up to six months. ‘Tami G’ grape tomatoes were grown on a Lakeland fine sand at the North Florida Research and Education Center—Suwannee Valley, near Live Oak, FL in Springs 2005 and 2006 using standard plasticulture practices under 0%, 33%, 66%, 100%, 133%, and 166% of the current recommended N rate for round tomato (224 kg/ha). Due to a longer growing season in 2006, plants received an additional three weekly injections of 22 kg/ha of N each in the 100% rate, that were also proportionally applied to the other treatments. Tomatoes were transplanted March 24, 2005 and April 4, 2006 and harvested, weighed and graded five (2005) and seven (2006) times. Season marketable yield (SMY) responses to N rates were quadratic (both years P < 0.01) and highest SMY (40,340 and 36,873 kg/ha) occurred with 314 and 280 kg/ha of N in 2005 and 2006, respectively. Fruit soluble solids concentrations ranged from 6.25 to 7.5, and 7.0 to 8.3° Brix in 2005 and 2006, respectively, and were not significantly affected by N rate. These results suggest that N fertilization for grape tomato grown in Spring with plasticulture could be done by incorporating 56 kg/ha of N in the bed, followed by daily rates ranging from 0.5 to 3.5 kg/ha/day. Because the length of the growing season for grape tomato may vary, emphasis should be placed on daily N rates and irrigation management, rather than on seasonal N rate.     

施氮和根间互作对密植大麦间作豌豆氮素利用的协同效应

针对禾豆间作密植机理研究薄弱问题,以大麦间作豌豆为研究对象,设施氮[不施氮:0 mg(N)·kg?1(土);施氮:100 mg(N)·kg?1(土)]、隔根(不隔根、隔根)和密度[低密度:15株(大麦)·盆?1;高密度:25株(大麦)·盆?1]3个参试因子,通过盆栽试验探讨了施氮和根系分隔对密植间作群体氮素竞争互补关系和利用效率的影响,以期为禾豆间作密植和氮素高效利用提供调控依据。结果表明:1)施氮、根间互作和增加大麦密度均可提高大麦||豌豆间作群体的吸氮量,其中施氮较不施氮处理提高33.8%,不隔根处理较隔根处理提高81.1%,高密度较低密度处理提高4.2%;根间互作在低氮条件下对间作吸氮量的贡献相对较高,不施氮和施氮条件下,根间互作提高间作吸氮量的比例分别为92.4%和11.0%;根间互作条件下增大大麦种植密度可显著提高间作群体吸氮量。2)大麦为氮素竞争优势种,密植使大麦氮素竞争比率显著提高,施氮能弱化大麦氮素竞争比率,抽穗期大麦相对于豌豆的氮素竞争优势达到最大值。3)根间互作使大麦、豌豆籽粒氮含量在施氮条件下分别提高126.7%、26.9%,不施氮时分别提高188.5%、46.5%,且施氮水平和根间作用方式对间作籽粒氮含量有显著的交互作用。4)高密度大麦和根间互作可显著提高间作群体的氮肥利用率,根间互作条件下增加大麦密度使间作群体氮肥利用率提高59.8%;大麦相对于豌豆的氮素竞争比率与间作群体氮肥利用率呈显著正相关关系。本研究表明,施氮、根间作用与大麦密度对大麦||豌豆间作氮素利用呈显著的交互作用,适宜的施氮量和充分的根间作用是支撑间作密植、优化种间对氮素的竞争关系,最终提高群体吸氮量和氮肥利用率的重要途径。     

中国稻田施氮技术研究进展

提高N肥利用率,加强稻田养分管理已经成为水稻生产中研究的热点。针对我国稻田N肥利用率低和N素损失严重的现状,综述了国内外提高稻田N肥利用率技术途径的研究进展,包括改进施肥方法(确定适宜施N量、N肥深施、前N后移、平衡施肥、有机与无机肥配施、水肥综合管理)、新型肥料的研制(硝化抑制剂、脲酶抑制剂、表面分子膜、缓控释肥)、计算机决策支持系统指导施肥和实时、实地N肥管理等。展望了今后需要加强研究的几方面工作。     

不同氮效率水稻生育后期氮素积累转运特征

以不同氮效率水稻基因型为供试材料,通过15N标记的氮肥盆栽试验精确定量不同氮效率的水稻齐穗后氮素积累和转运量。结果表明,无论在何种施氮水平下,氮高效水稻(南光和武运粳)的籽粒产量均显著高于氮低效水稻Elio;不同氮效率水稻在齐穗期和齐穗后15天时干物质积累量差异不显著,但在成熟期时氮高效水稻的干物质积累量显著高于氮低效水稻,增幅约为16·4%;与干物质积累相对应的是,不同氮效率水稻的氮素积累量在齐穗期和齐穗后15天也没有差异,但在成熟期时氮高效基因型水稻武运粳和南光的氮素积累量较氮低效基因型水稻Elio高约31%和21%,差异显著。15N标记试验结果可以看出,氮低效水稻Elio齐穗时吸收的一部分15N移出了植株体,其占15N转运量的11%。从齐穗至成熟,氮低效水稻Elio从茎叶转移出的15N量(2·75mg穴-1)远远低于氮高效水稻武运粳(3·54mg穴-1)和南光(3·22mg穴-1),差异显著。氮高效水稻武运粳和南光从茎叶转移出的15N量约占籽粒所需N量的91%和85%,而从土壤中吸收的15N量约占9%和15%。综上所述,氮高效、低效水稻氮素积累和转运特征的差异主要表现在齐穗期以后,氮高效水稻具有强的氮素吸收或者转运能力,以满足籽粒形成期植株对氮素的利用。     

农作物N素利用效率基因型差异及其机理

不同农作物N素利用效率基因型差异主要与N素吸收效率和生理利用效率有关。根系N的吸收动力学、根系形态、吸收时间是影响N素吸收效率的重要因素;N素生理利用效率与N的同化、转运及光合作用、C转运效率等生理过程有关。分析农作物N素利用效率基因型差异机理对提高N肥利用效率,降低N肥损失,充分发挥N肥在农业生产中的作用,降低农业生产成本和保护生态环境,促进农业可持续发展具有重要意义。