Effect of Deep Placement of N Fertilizers and Different Inoculation Methods of Bradyrhizobia on Growth,N2 Fixation Activity and N Absorption Rate of Field‐grown Soybean Plants

The effects of deep placement (supplied at 20 cm depth from soil surface below plants) of 100 kg N ha^?1 of N fertilizers, urea, coated urea or calcium cyanamide (lime nitrogen) on the growth, nitrogen fixation activity, nitrogen absorption rate and seed yield of soybean (Glycine max L. Merr.) plants were examined by comparing them with control plots without deep placement of N fertilizer in sandy dune field. In addition, three different inoculation methods of bradyrhizobia were used for each N treatment: (1) transplantation of 10‐day‐old seedling in a paper pot with vermiculite inoculated with Bradyrhizobium japonicum USDA110, (2) direct transplantation of inoculated 10‐day‐old seedlings, and (3) transplantation of 10‐day‐old seedlings in a non‐inoculated paper pot. The deep placement of N fertilizers, especially calcium cyanamide and coated urea, markedly increased the growth and total N accumulation in shoot, roots and nodules, which resulted in an increase in seed yield. Daily N₂ fixation activity and N absorption rate were estimated by relative abundance of ureide‐N analysed from the concentration of N constituents (ureide‐N, amide‐N and nitrate‐N) in root bleeding xylem sap and increase in total N accumulation in whole plants at R1, R3, R5 and R7 stages. The total amount of N₂ fixation was about 50 % higher in the plants with calcium cyanamide and coated urea deep placements compared with control plants. Deep placement of slow release fertilizers kept nodule dry weight higher in the maturing stage of seed, possibly through abundant supply of photoassimilate to the nodules by supporting leaf area and activity until late reproductive stages. The results indicate that deep placement of calcium cyanamide or coated urea enhances N₂ fixation activity, which ultimately increases the seed yield. The promotive effect was observed with the seedlings transplanted in paper pot with inoculum of bradyrhizobia within any treatments, although nodulation by indigenous rhizobia was observed in the plants transplanted with non‐inoculated paper pot.     

Differences in nitrogen fixation among field-grown red clover strains at different levels of 15N fertilization

Summary Genetic variation in fixed nitrogen (N) yield of red clover (Trifolium pratense L.) strains and cultivars was investigated using the ¹⁵N isotope dilution method under three regimes of N fertilization: 0.5, 30, and 60 N (kg N ha^–1 per cut). The yield of fixed N per cut (the mean of eight cuts over 2 production years) varied among the strains (progenies of crosses between inbred parents) from 148 to 443 mg per plant at 0.5 N, from 76 to 324 mg at 30 N, and from 69 to 300 mg at 60 N. There were significant and consistent strain differences in the percentage of clover N derived from the atmosphere (% N_dfa). However, %N_dfa was positively correlated with dry mass yield. Consequently, ranking of the strains according to fixed N yield reflected that of dry mass yield. There were only minor strain × N fertilizer interactions, suggesting that selection for enhanced N fixation can be carried out at a single rate of fertilizer N. For a selected pair of strains, the difference in yield of fixed N was confirmed in an Italian ryegrass-red clover mixture, both without and with the addition of N fertilizer (50 kg N ha^–1 per cut). Results with 7-week-old seedling plants in a growth chamber, although obtained in the presence of mineral N and with the isotope dilution method, did not adequately predict field performance. It is concluded that selection for dry matter or total N yield is likely to result in an enhanced yield of fixed N at any level of mineral N availability.Abbreviations % N_dfa percentage of clover nitrogen derived from the atmosphere by symbiotic nitrogen fixation - S₂-F₁-n progeny of pair cross between inbred parents obtained after two generations of selfing     

Effects of reduced nitrogen input on productivity and N2O emissions in a sugarcane/soybean intercropping system

A seven-year (2009–2015) continuous field experiment was established at the South China Agricultural University in order to identify the effects of sugarcane/soybean intercropping and reduced N rate on ecosystem productivity, yield stability, soil fertility, and N₂O emissions. The randomized block experiment was designed with four cropping patterns (sugarcane monocropping (MS), soybean monocropping (MB), sugarcane/soybean (1:1) intercropping (SB1), and sugarcane/soybean (1:2) intercropping (SB2)) and two rates of N fertilization (300 kg hm⁻² (N1, reduced rate) and 525 kg hm⁻² (N2, conventional rate)). The results showed that the land equivalent ratio (LER) of all intercropping systems was greater than 1 (between 1.10 and 1.84), and the SB2-N1 optimally improved the land utilization rate among all treatments. The cropping patterns and N applied rates had no significant effect on sugarcane yield. The soybean yield was influenced by different cropping patterns because of different planting densities (4, 8 and 16 rows of soybean were plant under SB1, SB2, and MB, respectively) and was adopted in this experiment. In addition, under the SB2 cropping pattern, the soybean yield at the reduced N application rate was higher than that at the conventional N application rate. Wricke’s ecovalence (W_i²), the sustainable yield index (SYI) and the coefficient of variation (CV) were used to evaluate yield stability. Different treatments had no significant effects on sugarcane yield stability, as demonstrated by three indicators (W_i², SYI and CV), which indicated that intercropping with soybean and reduced N rate had no effect on sugarcane yield. For soybeans, the value of W_i² demonstrated that the stability of the intercropping system was higher than its counterpart monocropping system, as SYI and CV values indicated that SB2 had higher stability than SB1. During seven years of experiments, there was no significant difference in the soil fertility between MS and SB patterns. The soybean monocropping had a higher available K, pH and lower available P content than sugarcane inter- and mono-cropping. Different cropping patterns had a slight impact on N₂O emissions and the greenhouse gas intensity (GHGI) value. Higher N input promoted N₂O emissions and increased GHGI values. In conclusion, the present study observed that a 40% reduced nitrogen input combined with intercropping soybeans could maintain sugarcane yield and soil sustainable utilization, and that higher N fertilizer additions induced negative impacts on greenhouse gases emissions. Sugarcane intercropping with soybeans can reduce chemical fertilizer input and simultaneously maintain crop productivity; thus, it can be considered to be a reasonable practice for field management.     

湖南双季稻氮磷钾配方优化及追肥运筹增产效果分析

为了筛选出适合湖南双季稻生产的配方复合肥及追肥模式,采用田间试验的方法,在湖南长沙县开慧镇、干杉镇,岳阳县麻塘镇（晚稻在新墙镇）典型双季稻区开展了水稻氮磷钾肥料配方及2次追肥的增产效果研究。结果表明：与主推的配方肥（早、晚稻N-P₂O₅-K₂O分别为20-10-10和26-10-13）相比,优化配方肥（分别增加磷钾比例）适当减氮,早稻保持平产,晚稻增产187.5~378.0 kg/hm²,增产幅度为2.6%~5.9%。其中,N-P₂O₅-K₂O为18-14-16配方适合早稻的生产,N-P₂O₅-K₂O为18-9-16配方适合晚稻的生产。在追肥量一定的条件下,分蘖期、孕穗期分次追肥较分蘖期一次追肥早稻增产187.5~382.5 kg/hm²,氮肥利用率提高10.9~24.2个百分点;晚稻增产258.0~415.5 kg/hm²,氮肥利用率提高8.3~13.4个百分点。     

Effect of Deep Placement of Slow-release Fertilizer (Lime Nitrogen) Applied at Different Rates on Growth, N2 Fixation and Yield of Soya Bean (Glycine max [L.] Merr.)

A new fertilization method with deep placement of slow‐release N fertilizers, such as coated urea and lime nitrogen (LN) (calcium cyanamide) at 20 cm depth was found to promote soy bean seed yield. In the present study, the effect of deep placement of LN was investigated on different parameters such as growth, N accumulation, N₂ fixation activity and yield of soy bean by applying LN at different rates in the rotated paddy field of Niigata, Japan. In addition to the basal fertilizer, ammonium sulphate (16 kg N ha^?1), deep placement of LN was conducted by applying various amounts such as 50 kg N ha^?1 (A50), 100 kg N ha^?1 (A100) and 200 kg N ha^?1 (A200) at 20 cm depth in separate plots. A ¹⁵N‐labelled LN fertilizer was also employed for each of the above treatments to calculate N utilization from LN in separate plots. Soya bean plant growth and N₂ fixation activity were periodically analysed. Both plant growth and N accumulation were found to increase with LN treatment compared with control plants. An increase in N₂ fixation activity was found in the A100 plots. The total seed yield was the highest in the deep placement of LN with A100 (73 g per plant) compared with other treatments. The visual quality of harvested seeds also showed that A100 enhanced the quality of seeds compared with other treatments. Thus, it is suggested that N fertilization management with particular reference to optimum amount of fertilizers is important for maximum growth, N₂ fixation and enhancement of seed yield of soy bean.     

不同氮肥水平下早熟晚粳氮和磷的吸收利用特性及相互关系

采用大田试验,以长江中下游地区具有代表性的50个早熟晚粳品种为材料,研究7个氮肥水平(0、150.0、187.5、225.0、262.5、300.0、337.5 kg hm^-2纯氮)下水稻氮和磷积累量、吸收速率、利用效率的差异及其相互关系。结果表明：(1)在0~337.5 kg hm^-2纯氮范围内,随着氮肥水平的增加,早熟晚粳的植株含氮率和氮积累量在拔节、抽穗和成熟期均显著增加;植株含磷率和磷积累量在拔节和抽穗期显著增加,成熟期呈先增后减变化。(2)播种至拔节阶段氮和磷吸收速率随施氮量的增加而提高,差异极显著;拔节至抽穗阶段氮和磷吸收速率随施氮量的增加呈现先增加后降低的变化趋势;抽穗至成熟阶段的氮和磷吸收速率规律不明显。(3)在0~337.5 kg hm^-2纯氮范围内,随着施氮量的增加氮素籽粒生产效率和磷素籽粒生产效率均显著降低,随着施氮量的增加基因型之间的差异减小;随着施氮量的增加氮和磷收获指数都呈现抛物线关系,在施氮量为262.0 kg hm^-2纯氮时出现最大值。(4)早熟晚粳对氮和磷的吸收利用具有显著的协同效应,但随生育进程的推进这种效应减弱。水稻在播种至拔节、拔节至抽穗和抽穗至成熟3个生育阶段的氮和磷吸收速率都呈二次曲线关系(r=0.892^**,r=0.736^**,r=0.512^**)。(5)相关分析表明,产量与拔节期、抽穗期和成熟期的吸氮量和吸磷量以及播种至拔节期和拔节至成熟期的吸氮速率和吸磷速率呈极显著正相关关系。增施氮肥有利于水稻氮和磷吸收利用的提高,但氮肥过高时氮和磷吸收利用不再增加,甚至有所降低。     

Residual Effects of Rhizobium and Preplant N Fertilizer on Newly Established Alfalfa1

In areas where ineffective nodulation may be a problem, ‘starter’ nitrogen fertilization is often suggested as a useful management tool to sustain ineffectively nodulated seedling alfalfa (Medicago sativa L.) until an effective population of Rhizobium can develop. Although ineffective nodulation has been reported from several locations around the world, there have been no studies examing this possibility. A field experiment was conducted during 1982 and 1983 on a Woodburn silt loam soil (Aquultic Argixeroll) which contained a symbiotically ineffective native population of Rhizobium meliloti Dang. This study examined the residual and interactive effects of preplant N fertilizer (0, 45, 90 kg N ha^?1) and inoculation on the N nutrition and yield of seedling alfalfa during the first year of growth. The sustaining effects of the fertilizer N were transient and resulted in decreased N₂ fixation until 35 days following harvest. It was concluded that during the establishment year, managerial emphasis should be placed on inoculation and not on N fertilization to obtain a consistent, economical source of N for herbage protein and dry matter production.     

氮肥后移对玉米间作豌豆耗水特性的调控效应

针对水资源不足严重制约干旱灌区间作发展,间作中以氮调水理论研究的薄弱,生产实践中缺乏氮肥运筹同步提高间作产量和水分利用效率的措施等问题。2012-2013年,以河西走廊规模化应用的玉米间作豌豆为研究对象,在总施氮量相同且基肥和孕穗肥分别占10%和50%条件下,设氮肥后移30% (N₁,拔节肥0+花粒肥40%)、氮肥后移15% (N₂,拔节肥15%+花粒肥25%)、传统制度(N₃,拔节肥30%+花粒肥10%) 3个施氮处理,探讨氮肥后移对间作产量和水分利用效率(WUE)的影响,以期为禾豆间作优化施氮制度、提高产量和水分利用效率提供理论依据。结果表明,氮肥后移对玉米间作豌豆总耗水量(ET)影响不显著,但降低了棵间蒸发量(E)和棵间蒸发量占总耗水量的比例(E/ET);与传统施氮处理相比,氮肥后移15%使玉米间作豌豆的E和E/ET降低6%和4%,氮肥后移30%使玉米间作豌豆的E和E/ET均降低2%。在间作系统中,豌豆带、玉米带的棵间蒸发量分别为329 mm、232 mm,表明豌豆带的无效耗水显著高于玉米带。氮肥后移15%间作的混合籽粒产量、WUE较传统施氮间作分别高出6%、5%,氮肥后移30%间作混合籽粒产量、WUE较传统施氮间作分别提高3%、2%。因此,玉米间作豌豆结合氮肥后移15%,即豌豆开花结荚期(玉米拔节期)追施氮肥67.5 kg hm^-2、玉米大喇叭口期追施氮肥225 kg hm^-2、玉米花后15 d追施氮肥112.5 kg hm^-2,可作为绿洲灌区玉米间作豌豆增产和提高WUE的农艺措施之一。     

不同施肥量对稻田一年生黑麦草产量及氮磷钾吸收的影响

通过大田试验,研究不同施肥量对黑麦草产量及养分吸收的影响,找到南方稻田种植黑麦草的最佳基肥肥料配比。氮、磷、钾肥施用量分别设4个水平,试验设11个处理。测定每次刈割黑麦草的干草产量和氮、磷、钾养分含量,计算氮磷钾的养分吸收量。结果表明：花岗岩发育的水稻土上种植黑麦草,施肥尤其是氮肥能增加黑麦草的株高和产量;基施磷肥和追施氮肥能促进黑麦草的再生。增加氮、磷肥施用量,黑麦草氮、磷含量也增加,钾肥施用达到一定量后,再增加施用量,黑麦草钾含量变化不大。增加氮、磷、钾肥的施用能提高黑麦草氮、磷、钾的吸收量。南方花岗岩发育的水稻土上种植黑麦草的N、P、K肥基肥最佳施用量（折纯）分别为：210.0 kg/hm² N、108.0 kg/hm² P₂O₅、117.5 kg/hm² K₂O。     

机插条件下低氮密植栽培对“早晚兼用”双季稻产量和氮素吸收利用的影响

为了缓解长江中下游双季稻区机插双季稻生育期不配套的矛盾,2014—2015年早晚两季均以常规早稻品种中嘉早17为材料,在大田栽培条件下研究机插密度(36.4、28.6、19.0穴m–2)与施氮量(0、110~140、176~189 kg N hm–2)对机插双季稻产量及氮肥利用率的影响。结果表明:采用"早晚兼用"机插双季稻栽培模式有利于早、晚2季周年高产,以"高密+高氮"处理产量最高,2年分别达到16.94 t hm–2和16.99 t hm–2,但与"高密+低氮"处理的产量差异不显著;氮肥利用率随氮肥用量增加而下降,随栽插密度增加而提高,以"高密+低氮"处理最高,2年4季分别为62.77%、55.75%、65.82%、64.37%,比"高密+高氮"处理分别提高12.11%、9.01%、8.49%、2.14%;"高密+低氮"处理与"低密+高氮"处理相比,群体干物质积累量及辐射利用率均有一定的优势。由此可见,在此模式下适当增加机插密度,减少氮肥用量,既可实现高产,又能显著提高氮素利用率。采用"早晚兼用"品种搭配模式,低氮、密植栽培可作为长江中下游双季稻区机插双季稻生产的关键技术。     

Field-specific variable rate fertilizer application based on rice growth diagnosis and soil testing for high quality rice production

This study was carried out to verify the applicability of variable rate fertilization (VRF) based on soil testing and diagnosis of rice plant growth for high quality rice production of var. Chucheongbyeo at the farm level. The field trials were conducted at Icheon in Gyeonggi province on a 10 ha farm consisting of 45 experimental fields. For comparative study, 15 field trials were carried out adopting fertilizer management (FPM) practices currently used by farmers. FPM fields were managed by each rice grower using current cultivation methods, but in each VRF field fertilizer application was prescribed using soil test results and the amount of N fertilizer for top-dressing at panicle initiation stage was calculated using rice growth value at that stage. In VRF fields, the total amount of N fertilizer application was less (72 kg ha⁻¹) than that in FPM fields (103 kg ha⁻¹). However, the amount of K₂O fertilizer application was more in VRF fields (60 kg ha⁻¹) than that in FPM fields (52 kg ha⁻¹). The amount of P₂O₅ fertilizer application was similar between the VRF and FPM fields. Plant height was significantly shorter and the number of tillers was significantly more at VRF fields than at the FPM fields. Coefficient of variation (CV) of each growth characteristic measured in VRF was lower than that of FPM fields at panicle initiation stage. There was no difference in culm and panicle length and panicle number between them at the grain filling stage, but CV of panicle numbers per m² decreased in VRF compared with that of the FPM fields. Rice yield was not different between VRF and FPM fields despite higher brown rice recovery and 1,000-grain weight in VRF fields. Under VRF management, head rice yield increased due to an increase in head rice ratio accompanied by a reduction in brown rice protein content and variation of quality characteristics. These results suggest that VRF application based on soil tests and measurement of rice growth value at panicle initiation stage has the potential for quality control and production of high quality rice through increasing uniformity of growth and reducing the variability in quality among individual fields.     

Heterosis of interspecific soybean hybrids for traits related to N2 fixation

Summary Three greenhouse experiments were conducted to compare the performance of soybean (Glycine max (L.) Merr.), wild soybean (G. soja Sieb. et Zucc.), and soybean x wild soybean hybrids for traits relating to N₂ fixation including nodulation, acetylene reduction, nodule leghemoglobin concentration, and nitrogen (N) accumulation and dry matter (DM) accumulation. In all three experiments G. max generally exceeded G. soja in nodulation, acetylene reduction, and N and DM accumulation while the soybean possessed higher nodule leghemoglobin concentration. In Experiment I, the mean of the hybrids did not differ significantly from the G. max parent in nodule mass, acetylene reduction activity, nodule leghemoglobin concentration, or DM accumulation. The hybrids did exceed the soybean parent in N accumulation, thus demonstrating high parent heterosis. In Experiments IIA and IIB with a more carefully chosen set of G. soja parents, high parent heterosis of individual crosses was common. Across the three experiments average high parent heterosis was 34, 28, and 28%, respectively, for nodule mass, N accumulation, and DM accumulation. If one accepts the assumption that hybrid vigor results from the accumulation of dominant alleles, then these alleles could theoretically be accumulated via selection in a homozygous genotype. If this is true than the results of the experiments reported here suggest that interspecific soybean x wild soybean crosses could serve as sources of homozygous lines which would exceed currently available soybean cultivars in nodule mass, and N and DM accumulation.This work was supported in part by the USDA Competitive Grants Program, Grant 82-CRCR-1-1039 and Cooperative Agreement 58-32U4-2-370 between the U.S. Department of Agriculture and the Agronomy Department, University of Maryland, Scientific Article No. A-4648, Contribution No. 7644 of the Maryland Agricultural Experiment Station.     

公顷产10000kg小麦氮素和干物质积累与分配特性

以泰山23和济麦22为试验品种,通过连续2年的田间试验,对单产高达10 000 kg hm^-2的小麦进行了施氮量和氮素吸收转运和分配特性的研究。在2006—2007年生长季,随着施氮量的增加,小麦籽粒产量先增加后降低,施纯氮240 kg hm^-2 (N240)和270 kg hm^-2(N270)处理的产量分别达9 954.73 kg hm^-2和10 647.02 kg hm^-2,比不施氮肥处理(N0)分别增加11.20%和18.93%。与N0处理相比,施氮处理显著增加了小麦植株氮素积累量、籽粒氮素积累量和开花后营养器官氮素向籽粒的转运量;随着施氮量的增加,成熟期小麦植株氮素积累量呈先增后降趋势,以N270处理最高;开花后营养器官氮素向小麦籽粒转运量和转运率先升后降,转运量以N270处理最大,为213.78 kg hm^-2;而转运率以N240处理最高,为67.98%。随施氮量的增加,小麦成熟期各器官干物质积累量、花后营养器官干物质再分配量和再分配率先增后降,均以N270处理最高;开花后干物质积累对籽粒的贡献率亦呈先增后降的趋势,以N240处理最高。2005—2006年的试验结果呈相同变化趋势。在本试验条件下,小麦产量水平达10 000 kg hm^-2时的适宜施氮量为240~270 kg hm^-2,可供生产中参考。     

公顷产10000kg小麦氮素和干物质积累与分配特性

以泰山23和济麦22为试验品种,通过连续2年的田间试验,对单产高达10 000 kg hm^-2的小麦进行了施氮量和氮素吸收转运和分配特性的研究。在2006-2007年生长季,随着施氮量的增加,小麦籽粒产量先增加后降低,施纯氮240 kg hm^-2 (N240)和270 kg hm^-2(N270)处理的产量分别达9 954.73 kg hm^-2和10 647.02 kg hm^-2,比不施氮肥处理(N0)分别增加11.20%和18.93%。与N0处理相比,施氮处理显著增加了小麦植株氮素积累量、籽粒氮素积累量和开花后营养器官氮素向籽粒的转运量;随着施氮量的增加,成熟期小麦植株氮素积累量呈先增后降趋势,以N270处理最高;开花后营养器官氮素向小麦籽粒转运量和转运率先升后降,转运量以N270处理最大,为213.78 kg hm^-2;而转运率以N240处理最高,为67.98%。随施氮量的增加,小麦成熟期各器官干物质积累量、花后营养器官干物质再分配量和再分配率先增后降,均以N270处理最高;开花后干物质积累对籽粒的贡献率亦呈先增后降的趋势,以N240处理最高。2005-2006年的试验结果呈相同变化趋势。在本试验条件下,小麦产量水平达10 000 kg hm^-2时的适宜施氮量为240~270 kg hm^-2,可供生产中参考。     

养分管理对直播稻产量和氮肥利用率的影响

为探明不同养分管理模式在实地农户种植条件下对直播水稻产量和氮肥利用率的影响。本试验于2011年6月至2013年11月在江苏省兴化市茅山镇基本农田保护区的田间稻麦轮作条件下,分别选取茅山东村、茅山西村和冯顾村各8个农户,开展3个不同养分管理模式试验,设置了不施肥对照(CK)、农民习惯施肥(FFP)和优化施肥(OPT1和OPT2)4个处理,主要研究了水稻产量及构成因子、氮累积分配和氮肥利用率等对不同养分管理模式的响应。结果表明：(1)施肥较不施肥显著提高水稻产量,优化施肥(226 kg N hm^-2)在较习惯施肥(333 kg N hm^-2)平均减氮32.1%的基础上显著提高水稻产量5.5%,增产原因是提高了穗粒数、结实率和千粒重;OPT2较OPT1平均增产3.1%,其原因是在孕穗期增施了钾肥(18 kg hm^-2 K₂O)。(2)优化施肥水稻植株各部位氮浓度、百千克籽粒需氮量和秸秆氮累积均显著低于习惯施肥,且降低营养器官的氮素分配比例。(3)优化施肥较习惯施肥显著提高水稻氮肥利用率,其氮肥偏生产力(PFP_N)、氮肥农学效率(AE_N)、氮肥回收效率(RE_N)和氮肥生理效率(PE_N)分别平均增加55.5%、79.1%、18.7%和48.7%。(4)水稻植株氮累积与产量呈显著正相关,且优化施肥单位氮累积的增产效果高于习惯施肥。因此,基于氮肥总量控制、分期调控和增施钾肥的养分优化管理措施可在实地农户直播稻种植上协同实现水稻高产和氮肥高效。     

减量施氮对玉米-大豆套作系统中作物产量的影响

通过田间试验,研究了种植模式(玉米单作、大豆单作、玉米-大豆套作)和施氮水平(0、180、240 N kg hm^–2)对作物产量和大豆光合特性、干物质积累的影响。结果表明,大豆叶片P_n、G_s、C_i、T_r和植株干物质积累量随生育时期的推移呈先增加后降低的趋势。与单作相比,套作处理大豆的P_n、G_s、T_r在V5期(玉米大豆共生期)显著降低,但在R2、R4、R6期(玉米收获后)无显著差异,地下部、地上部及总干物质积累量在各生育时期呈降低趋势,R4~R6期的作物生长率和经济系数则显著提高。玉米-大豆套作体系下,施氮显著提高了大豆花后叶片P_n、G_s、T_r和植株地下部、地上部及总干物质积累量,增加了大豆单株荚数和产量,与习惯施氮(240 N kg hm^–2)相比,减量施氮处理(180 N kg hm^–2)大豆的P_n在R4、R6期提高了3.57%、11.82%,总干物质积累量在R6、R8期提高了5.06%、10.21%,单株荚数、产量提高了8.30%、10.15%。减量施氮处理下,玉米-大豆套作系统的总产量最高,总经济系数为0.49,LER达2.17。玉米-大豆套作减量一体化施肥有利于提高大豆光合特性和干物质积累,提高大豆产量和玉米-大豆套作系统总产。     

N2O-Freisetzung auf gemähtem Dauergrünland in Abhängigkeit von Standort und N-Düngung

N₂O Emissions from True Meadows Dependent on Location and N Fertilization Agricultural production is thought to be a main anthropogenic emitter of nitrous oxide (N₂O), which contributes to global warming and the destruction of the ozone layer. There is still considerable uncertainty about the amount of N₂O emission, and the site‐specific parameters that affect N₂O emission. From October 1995 until March 1998 experiments were conducted at established field plots (true meadows) at three different sites, i.e. low mountain range (Eifel), lowland (Niederrhein), and moist meadows (Münsterland). Plots were fertilized with calcium ammonium nitrate (CAN) at nitrogen equivalents ranging from 0 to 360 kg N ha^–1. N₂O fluxes were measured throughout the whole year using the closed‐chamber method. In addition, data on temperature, water‐filled pore space and precipitation were collected. N₂O emission rates (mg N₂O‐N ha^–1 h^–1) were highest either after fertilizer application or in winter during frost, depending on the experimental site and N dosage. The annual amount of N losses due to N₂O emission was dependent on the experimental site and the type and dosage of fertilizer. Disregarding the 360 kg N ha^–1 level of the CAN treatments, the N losses in this experiment were less than 1.5 kg N₂O‐N ha^–1 yr^–1. At low fertilizer dosage there was no reliable correlation between the amount of N that was applied and the amount of N₂O that was emitted. However, with high fertilizer levels the N₂O emissions increased gradually. Finally, N₂O emissions were more influenced by the amount of CAN than by the site.     

减少化肥配施有机肥对滴灌棉花N、P吸收和产量的影响

施用有机肥是作物增产和提升地力的有效途径。本试验在连续定位施肥的第3年,研究了常规单施化肥(CF)和化肥减量20%~40%、配施3000~6000 kg·hm-2不同种类的有机类肥料对棉株干物质质量,产量,氮、磷吸收量,土壤保水性以及养分利用率的影响。结果表明,与单施化肥相比,减化肥配施有机肥各处理的生物量在蕾期、铃期和吐絮期分别增加4.3%~30.0%、16.8%~35.1%和18.5%~38.8%;棉花产量在第3年提高了6.9%~18.5%,其中施用6000 kg·hm-2生物有机肥获得最高产,子棉产量为7578 kg·hm-2。施用有机肥能增加棉株对氮、磷养分的吸收,且显著提高了氮肥利用率(P0.05)以及田间持水量,生物有机肥对磷肥利用率的提高优于普通有机肥。     

Interaction Amongst Soybean [Glycine max (L.) Merrill] Genotype, Soil Type and Inoculant Strain with Regard to N2 Fixation

The nitrogen (N₂)‐fixing bacterial inoculant strain for soybean [Glycine max (L.) Merrill] is not indigenous to South African soils. The interaction between soybean genotype, soil type and inoculant strain, however, has a definite influence on soybean production and compatibility should be optimized. This paper reports a growth chamber study using three different soybean genotypes (Barc‐9, Avuturda and Talana), three Bradyrhizobium japonicum inoculant strains (WB108, WB112 and WB1) and three soil types (Avalon, Arcadia and sand) to evaluate the effectiveness of N₂ fixation by different genotype × soil type × inoculant strain combinations, using different measuring parameters. These parameters included nodule fresh mass (NFM), amount of N₂ fixed (P_fix), as determined by the ureide method, seed protein content (SPC), average seed mass per plant (SMP) and average foliar N content (FNC). The comparison amongst the three‐way interactions, genotype × soil type × inoculant strain, did not differ significantly for the parameters used. Significant two‐way interactions were soil × inoculant for FNC, P_fix and SMP; soil × genotype for FNC and SMP, and inoculant × genotype for FNC (P < 0.05). The soil × inoculant strain interaction was significant for P_fix (P < 0.05). NFM, P_fix, FNC, SMP and SPC correlated positively with soil pH and negatively with soil clay content and soil NO₃^– and NH₄⁺ content (P < 0.05). SPC was significantly different (P < 0.05) for soil type, genotype and inoculant strain. P_fix and NFM did not reflect the protein content of the seeds, indicating that nodule evaluation should be used with caution as a N₂ fixation parameter. Low soil pH and high mineral N content inhibited N₂ fixation. NFM correlated negatively with the clay content of the soil. This finding confirms that soybean production in South Africa can be improved by appropriate selection of genotypes and inoculant strains for their compatibility in different soils.     

断根追钾条件下减量施氮对烟株后期氮、钾吸收及烟叶产量质量的影响

以烤烟K326品种为材料, 通过田间试验比较了正常施氮但打顶时不断根不追钾(CK)、正常施氮但打顶时断根并追钾(CK+C+K)、减量施氮(为正常施氮量的80%)但打顶时断根并追钾(RN+C+K)对烟株后期氮、钾吸收和干物质累积及烟叶产量、质量的影响, 以期阐明在打顶时断根追钾条件下, 烟株整个生育期的施氮量是否应该减少的问题。结果表明: 断根追钾明显促进烟株后期的生长。RN+C+K虽少施20%的氮肥, 但其与CK+C+K两处理烟株田间中、上部烟叶的开片和SPAD值, 采烤结束时的干物质和氮、钾累积量, 烟叶的产量、产值以及烟碱和钾含量等质量指标皆优于CK。同时, RN+C+K烟株的干物质和氮、钾累积量以及烟叶产量达到了CK+C+K的97.2%、97.8%、98.9%和98.6%, 而产值比后者高2.0%; 其烤后上部叶的烟碱含量比CK和CK+C+K两处理分别降低了6.7%和4.5%, 而钾含量则分别增加了18.9%和5.6%, 且其他化学成分也更为协调。这说明在断根追钾条件下应该减少氮肥施用量, 以更有利于增加烟农收入、降低肥料成本、节省氮肥资源和提高烟叶质量。