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1.
Recovery of fertilizer nitrogen (N) applied to winter wheat crops at tillering in spring is lower than that of N applied at later growth stages because of higher losses and immobilization of N. Two strategies to reduce early N losses and N immobilization and to increase N availability for winter wheat, which should result in an improved N use efficiency (= higher N uptake and/or increased yield per unit fertilizer N), were evaluated. First, 16 winter wheat trials (eight sites in each of 1996 and 1997) were conducted to investigate the effects of reduced and increased N application rates at tillering and stem elongation, respectively, on yield and N uptake of grain. In treatment 90‐70‐60 (90 kg N ha?1 at tillering, 70 kg N ha?1 at stem elongation and 60 kg N ha?1 at ear emergence), the average values for grain yield and grain N removal were up to 3.1 and 5.0 % higher than in treatment 120‐40‐60, reflecting conventional fertilizer practice. Higher grain N removal for the treatment with reduced N rates at tillering, 90‐70‐60, was attributed to lower N immobilization (and N losses), which increased fertilizer N availability. Secondly, as microorganisms prefer NH4+ to NO3? for N immobilization, higher net N immobilization would be expected after application of the ammonium‐N form. In a pot experiment, net N immobilization was higher and dry matter yields and crop N contents at harvest were lower with ammonium (ammonium sulphate + nitrification inhibitor Dicyandiamide) than with nitrate (calcium nitrate) nutrition. Five field trials were then conducted to compare calcium nitrate (CN) and calcium ammonium nitrate (CAN) nutrition at tillering, followed by two CAN applications for both treatments. At harvest, crop N and grain yield were higher in the CN than in the CAN treatment at each N supply level. In conclusion, fertilizer N use efficiency in winter wheat can be improved if N availability to the crops is increased as a result of reduced N immobilization (and N losses) early in the growth period. N application systems could be modified towards strategies with lower N applications at tillering compensated by higher N dressing applications later. An additional advantage is expected to result from use of nitrate‐N fertilizers at tillering.  相似文献   

2.
Field experiments with silage maize were conducted in 1987 and 1988 on a loess-derived Luvisol in southwest Germany. Four nitrogen fertilizer treatments were compared: application of preplanting NH4 N (plus a nitrification inhibitor, dicyandiamide as Didin) and preplanting NO3-N, split application of NO3-N (preplanting and side dressed 45 days after planting) and a control without nitrogen fertilizer in 1987 and with 64 kg N ha?1 as calcium ammonium nitrate in 1988. The total amounts of soil mineral nitrogen (Nmin+ fertilizer N) were 200 kg N ha?1 in 1987 and 240 kg N ha?1 in 1988. Suction cups and tensiometer were installed at five depths and samples were taken in regular intervals. Nitrate concentrations in the suction solution steeply increased at 15 cm and 45 cm soil depth 3-4 weeks after fertilizer application (1987 up to 160mgNl?1; 1988 up to 170mgN l?1) and steeply decreased up to 75 cm depth with the onset of intensive N uptake at shooting. Ammonium concentrations in the suction solution were very low (0-0.16 mg N l?1). Compared to preplanting NCyN application, preplanting NH4-N and split NO3-N application decreased nitrate concentrations in the suction solution in spring 1987. In 1988, however, nitrate concentrations in the suction solution of preplanting NH4-N and split NO3-N application plots did not fall below 50mgNl?1 at 15 cm depth during the growing season. Nitrate concentrations of split NO3-N application increased again in autumn 1988 and hence doubled the calculated N losses by leaching during the winter months compared to preplanting N applications. At shooting, plants of the preplanting NH4-N treatment had lower nitrate concentrations in leaf sheaths compared to plants of preplanting NO3-N application. Total N uptake of maize between shooting and early grain filling of preplanting NH4-N and split NO3 -N application tended to be higher compared to preplanting NO3-N application, reflecting the higher N availability in the soil later in the season. However, final dry matter yields and N uptake were not significantly affected by N form or time of N application. Since N losses by nitrate leaching between N application and onset of N uptake by plants were negligible on the experimental site, preplanting NH4-N application and split NO3-N application showed no agronomic advantages. High amounts of side dressed NO3-N may increase nitrate leaching during the winter months, especially in years with delayed rainfall after application.  相似文献   

3.
A substantial proportion of ammonical fertilizers applied to lowland rice is lost as gaseous N from the soil–plant system. Besides various environmental factors, the low N use efficiency of flooded rice is also attributed to this factor. As atmospheric ammonia found in the leaf environment of the plants could also be responsible for differences in N use efficiency and fertilizer N losses from lowland rice, a greenhouse study was conducted on three rice cultivars varying in physio-morphological characteristics for their dry matter and nitrogen distribution to grains at maturity in response to ammonia (NH3) exposure at tillering and anthesis growth stages. The results revealed that ammonia exposure of plants at two growth stages did not affect the total dry matter and total N yield of the rice cultivars at maturity; however, the grain yield and grain N yield were negatively effected by NH3 exposure of the plants at anthesis. The variation observed in dry matter and N partitioning at maturity to grains/roots of the plants exposed to NH3 at anthesis indicated that the growth stage of the plants at which they are exposed to NH3 has an influence on N use efficiency of crop plants and subsequent vegetative as well as total N losses from the soil–plant system.  相似文献   

4.
Field experiments were conducted at the Directorate of Rice Research experimental farm, ICRISAT campus, Patancheru, Hyderabad, during 1998–2000 for five consecutive seasons (three wet and two dry seasons) with five treatments [T1 – 100 % straw incorporation; T2 – 50 % straw incorporation; T3 – 100 % straw + green manure (GM) incorporation; T4 – 100 % straw burning and T5 – 100 % straw removal (control)] along with the recommended dose of fertilizers to evaluate the effect of different crop residue management (CRM) practices on yield components and yield of rice in rice–rice cropping sequence. The ammonium N measured at active tillering was higher in 100 % straw‐added plots over 50 % straw addition and straw removal with maximum values in the straw + GM‐incorporated plots. Among the yield components, tillers, panicles and spikelets were influenced from the second season of residue incorporation with significant increase in 100 % straw‐added treatments. The increase in tiller and panicle number could be attributed to the increased NH4‐N in these treatments, which is evident from the significant correlation between tiller number and NH4‐N (r = 0.82**) and panicle number and NH4‐N (r = 0.87**). The influence of residue treatments on rice grain yield was observed from the third season onwards where incorporation of straw alone or in combination with GM and burning of straw significantly increased grain and straw yields. Grain yield showed significant positive correlation with the number of tillers (r = 0.74*–0.81**) and panicles (r = 0.74*–0.84**) in three treatments (T1, T3 andT4) where grain yields were significantly higher. The regression analysis showed that 57–66 % and 64–75 % of the variation in yield could be explained by tillers and panicles together in these three treatments during wet and dry seasons respectively. Thus, CRM practices such as addition of 100 % straw either alone or with GM and straw burning influenced the yield components (tillers, panicles and spikelets) positively and thereby increased rice grain yields.  相似文献   

5.
氮素形态及供应时期对马铃薯生长发育与产量的影响   总被引：3，自引：0，他引：3  
选用马铃薯克新1号和费乌瑞它2个品种,于2013-2014年在沙培条件下,研究了氮素形态及供应时间对马铃薯植株生长、块茎形成及发育的影响。结果表明,在块茎形成前供应NO3-N与NH4-N两种条件下,马铃薯植株高度、叶面积、叶片SPAD值、整株干物质积累量以及块茎重量无显著差异,而块茎形成后供应NH4-N的马铃薯叶片SPAD值、植株生长速度及块茎产量均显著高于NO3-N处理;块茎形成前供应NO3-N的植株结薯数显著高于NH4-N处理,但是氮素形态对干物质在马铃薯块茎中的分配比例无显著影响。因此,马铃薯的氮素养分管理应根据商品薯和种薯生产的不同目标,在块茎形成前后分别供应适宜形态的氮素。  相似文献   

6.
为确定黄瓜幼苗对氮素用量及氮素形态的响应特性以指导育苗期间合理施肥,以硝酸铵磷（NO3--N:NH4+-N为0.9:1.0）为供试肥料,研究同时提供NO3--N和NH4+-N的情况下,不同氮素用量对黄瓜幼苗生长及养分吸收的影响。结果表明：与不施氮对照相比,氮素施用可显著增加植株叶面积和株高,但各施氮处理之间差异不明显（50~200 mg N/株）;植株幼苗茎粗和地上部干物质累积量不同处理间差异不显著;施用氮素黄瓜幼苗根系的根长、根表面积和干物质累积量降低（尤其氮用量100 mg/株）,根系直径在0.5~1.3 mm和1.8~2.6 mm范围内的根长下降明显。氮素用量显著影响了地上部氮、磷、钾的浓度及吸收量,对根系的磷、钾浓度和氮、磷、钾的吸收量影响较小;综合地上部和根系的生长状况,氮素用量在50 mg/株及150 mg/株时,黄瓜幼苗的生长健壮。  相似文献   

7.
The field experiments conducted on the grey‐brown podzolic soil in the four growing seasons (1998–2001) at Krzeslice Farm, central‐western Poland comprised seven fertilization variants: 80NF + 80CAN; 80CAN + 80CAN; 80AN + 80AN; 80NF + 50CAN + 30CN; 80CAN + 50CAN +30CN; 80AN + 50AN + 30CN (where NF – nitrofos NPK; CAN – calcium‐ammonium nitrate; AN – ammonium nitrate; CN – calcium nitrate) and control (without N) applied in split rates at the beginning of spring regrowth (80 kg N ha?1), stem elongation (80 or 50) and flower buds visible stages (30). The yielding effect of tested fertilization variants was significant in comparison with the control (2.24 t ha?1). The highest mean seed yield (3.64 t ha?1) was collected from 80AN + 80AN and 80CAN + 80CAN variants. Mean values of 4 years indicate that the second N rate division (80 + 50 + 30) decreased yield, although not significantly in comparison with these two N treatments. Plants grown on these treatments have developed different patterns of growth to yield the seeds. These patterns were characterized by very high crop growth rate during flowering (above 21 g m?2 day?1) and negative at maturation (down to ?2.5 g m?2 day?1). Plants fertilized with ammonium nitrate (80AN + 80AN) reached maximum growth rate earlier (65 days), which lasted longer (20 days) than plants fertilized with calcium‐ammonium nitrate (71 days lasting 17.5 days). Plants grown on the control treatment reached the highest crop growth rate within 79 days (14.8 g m?2 day?1), which lasted 15 days.  相似文献   

8.
Forage chicory cultivars vary in origin and morphology and may respond differently to nutrient inputs because of photosynthate allocation and resource acquisition. Understanding nitrogen (N) influences on chicory seedling development and allocation of photosynthates among plant parts is important in terms of stand establishment, plant persistence, herbage production and nutritive value. We conducted experiments in the glasshouse to determine if amount (0, 50 and 100 mg N kg?1 soil) and source (ammonium nitrate or urea) of exogenous N influenced leaf dry‐matter (DM) production, N nitrate (NO3) and total non‐structural carbohydrate (TNC) allocation among roots and shoots in the chicory cultivars Forage Feast, Lacerta or Grasslands Puna. Herbage DM productivity and the ratio of energy (TNC) : protein varied among cultivars because of differential photosynthate allocation between shoots and roots, and occurred later in the growth interval when N was applied. Forage Feast, compared with the other cultivars, produced the largest roots and greatest herbage DM without added N. Leaf appearance rate in Lacerta and Grasslands Puna increased with increasing N. Instantaneous growth rates of Grasslands Puna and Lacerta at 100 N were three times that of 0 N plants. Nitrate concentrations were very high in young seedlings of all three cultivars before applying N. The findings help define application practices for these cultivars and N management practices for optimal leaf production in establishing forage chicory plants.  相似文献   

9.
Implementation of water-saving irrigation practices in lowland rice results in increased availability of nitrate (NO3−) in the soil and favours germination of upland weeds. Since plant species show a specific preference for either ammonium (NH4+) or NO3− as nitrogen (N) source, changes in both soil NO3− concentration and weed flora may affect the competition between rice and weeds. Further, the transpirational demand of the atmosphere might affect growth and competitiveness of lowland (wetland) and upland (dryland) weeds differently due to their adaptation to different ecological environments. Therefore, the study aimed to evaluate the effects of N source on growth, N uptake and competition between rice and common upland and lowland weeds under high and low vapour pressure deficit (VPD). Two rice (Oryza sativa) varieties (NU838 and KD18) differing in growth characteristics and two weed species (Echinochloa crus-galli and Solanum nigrum) differing in their natural habitat were selected and grown hydroponically as monoculture or mixed culture at low or high VPD. N was supplied as 75%/25% or 25%/75% NH4+/NO3−. N uptake rates were measured in the first week, whereas dry matter (DM), N concentration in the plant, total N uptake and the activities of nitrate reductase and glutamine synthetase in the fresh leaves were determined two weeks after the onset of treatments. Independent of N source, both rice varieties and E. crus-galli took up a larger share of NH4+, whereas S. nigrum took up a larger share of NO3−. N uptake of rice and E. crus-galli was hardly affected by N source, whereas high NO3− led to significantly higher N uptake rates and total N uptake of S. nigrum. NU838 showed a higher competitiveness against weeds than KD18. In competition, high NO3− decreased the competitiveness of E. crus-galli against NU838 but increased the competitiveness of S. nigrum against NU838. High VPD did not affect DM but increased N uptake of S. nigrum, leading to increased competitiveness of the weed at high transpirational demand. Competitiveness for N uptake appears to be an important trait as the relative N concentration in mixed plant communities was correlated with the activity of N-assimilating enzymes and leaf growth, with a stronger response in rice than in weeds. Our results support the hypothesis that increased availability of NO3− in aerobic rice soils may be advantageous for the competitiveness of upland weeds, especially at high VPD, whereas it may be disadvantageous for common lowland weeds.  相似文献   

10.
浮床栽培鱼腥草对吉富罗非鱼养殖池塘水质的影响   总被引：8，自引：5，他引：3  
为研究浮床栽培鱼腥草(0、5%、10%和15%种植面积)对吉富罗非鱼养殖池塘的水质净化作用,测定了NH_4+~-N、NO_3~--N、NO_2~--N、TN、TP、CODMn等主要水质指标。结果表明,在同样的试验条件下,7—8月份鱼腥草处理组NO_3~--N下降,与此同时带来了NH_4~+-N(除5%处理组)和NO_2~--N的上升。9月份浮床栽培鱼腥草对5种水质指标的平均去除率在3%~38%之间。5%鱼腥草种植面积适合进行中试。通过鱼腥草的采收,5%鱼腥草处理组叶、根茎的产量分别可达112.4、1619.2 kg/hm~2,且可从养殖水体带走0.38 g/m~2的总氮,0.06 g/m~2的磷元素;同时收获鱼总重和所测生物学指标(除体重)显著高于对照和其他处理组,且对成活率和饵料系数无多大影响。  相似文献   

11.
Genotypic variations in leaf gas exchange and grain yield were analysed in 10 highland‐adapted quinoa cultivars grown in the field under drought conditions. Trials took place in an arid mountain region of the Northwest of Argentina (Encalilla, Amaicha del Valle, 22°31′S, 65°59′W). Significant changes in leaf gas exchange and grain yield among cultivars were observed. Our data demonstrate that leaf stomatal conductance to water vapour (gs) is a major determinant of net CO2 assimilation (An) because quinoa cultivars with inherently higher gs were capable of keeping higher photosynthesis rate. Aboveground dry mass and grain yield significantly varied among cultivars. Significant variations also occurred in chlorophyll, N and P content, photosynthetic nitrogen‐use efficiency (PNUE), specific leaf area (SLA), intrinsic water‐use efficiency (iWUE) and carboxylation capacity (An/Ci). Many cultivars gave promissory grain yields with values higher than 2000 kg ha?1, reaching for Sayaña cultivar 3855 kg ha?1. Overall, these data indicate that cultivars, which showed higher photosynthesis and conductances, were also generally more productive. Carbon isotope discrimination (Δ) was positively correlated with the grain yield and negatively with iWUE, but δ15N did not show significant correlations. This study provides a reliable measure of specific responses of quinoa cultivars to drought and it may be valuable in breeding programmes.  相似文献   

12.
The fate of 15NH4-N labelled cattle slurry applied before sowing in September of a winter wheat crop was studied on a loamy sand soil. The aim was to quantify immobilization of slurry NH4-N into microbial biomass, the speed at which nitrate derived from the slurry NH4-N was transported down the soil profile, and the utilization of slurry NH4-N by the winter wheat crop. Cattle slurry was applied at a rate corresponding to 75 kg NH4-N ha−1 , with very little loss by volatilization (<4%) due to rapid incorporation by ploughing. The slurry amendment resulted in a doubling of soil surface CO2 flux, an index of microbial activity, over non-amended soil within the first c. 2 weeks, but ceased again after c. 4 weeks, due to depletion of the easily degradable substances, e.g. volatile fatty acids, in the slurry. Nitrification of the applied NH4-N was fast and complete by 3 weeks from application, and at this time, the maximum immobilization of slurry NH4-N into the microbial biomass (23% of applied 15NH4-N) was also observed, although no significant increase in total microbial biomass was observed. Rapid turnover of the microbial biomass quickly diluted the assimilated 15N, with only 6% of applied 15NH4-N remaining in the microbial biomass by next spring. Downwards transport of nitrate was rapid in spite of lower than normal precipitation, and slurry-derived 15NO3-N appeared in ceramic suction cups installed at 60 cm depth already 2 months after slurry application. Due to the unusually low winter precipitation in the experimental year, wheat yields were high, and the recovery of N in above-ground plant biomass derived from slurry NH4-N at harvest reached 32%. An additional 45% of the applied slurry NH4-N could be found in the soil to a depth of 100 cm (mostly in organic form in the plough layer), indicating that 23% had been lost by leaching or in gaseous form. It was concluded that although significant immobilization of slurry NH4-N did occur, this was not sufficient to prevent leaching of slurry-derived N over the winter and that the relatively high recovery of slurry-derived N in the wheat crop was due partly to lower than normal winter percolation and partly to a relatively high rooting depth on this particular site.  相似文献   

13.
Field experiments were carried out on grey‐brown podzolic soil in the four consecutive growing seasons (1998–2001) at Krzeslice Farm, central‐western Poland. The effect of seven N fertilization treatments (in kg N ha?1): 80NF + 80CAN; 80NF + 50CAN + 30CN; 80CAN + 80CAN; 80CAN + 80CAN + 30CN; 80AN + 80AN; 80AN + 50AN + 30CN, where, NF – nitrofos NPK, CAN – calcium‐ammonium nitrate, AN – ammonium nitrate, CN – calcium nitrate and control (without N) on N uptake dynamics and N efficiency was studied. Mineral fertilizers were applied at the start of spring regrowth, beginning of stem elongation and at the flower‐bud‐visibility stage. The study revealed two distinct strategies of oilseed rape plants’ adaptation to timing and N fertilizer application sequences. Both strategies based on nitrogen uptake rate (NUR), were analysed at different plant growth stages. Ammonium nitrate (AN) applied in the two‐split system gave the highest NUR (387 mg m?2 day?1) during stem elongation (for comparison, a value of 166 mg m?2 day?1 was obtained in the control). In the case of calcium‐ammonium nitrate (CAN), a moderate level of NUR was obtained (304 mg m?2 day?1) but N uptake lasted 12 days longer compared with the AN treatment. Hence, N accumulation in leaves at the end of flowering explained about 81 % of yield variability. The second adaptation strategy was attributed to the three‐split N treatment. Plants fertilized with AN and CAN fertilizers showed an inconsistent pattern of NUR with time. Nitrogen accumulation in stems at the beginning of maturity, explained 69 % of yield variability. Nitrogen‐use efficiency did not show any response to N treatments.  相似文献   

14.
 通过在棉田中施用硝化抑制剂双氰胺（DCD）实现棉花增铵营养的途径,来改变传统棉田氮肥运筹途径和营养状况,同时考察了由此导致的棉田土壤和棉株功能叶片中氮素变化动态。结果表明：2％DCD的施用促进了棉株对氨基态氮的吸收而抑制棉株对硝态氮的吸收;同时也减少了棉田土壤中残留全氮含量、维持了土壤较高的氨基态氮含量,提高了氮肥吸收利用效率、节约了氮肥资源。进一步表明棉田中施用增铵营养在生理和生态上具有重要的意义。  相似文献   

15.
Drought stress and zinc (Zn) deficiency are serious abiotic stress factors limiting crop production in Turkey, especially in Central Anatolia. In this study, the effects of Zn deficiency and drought stress on grain yield of 20 wheat cultivars (16 bread wheat, Triticum aestivum; four durum wheat, Triticum durum cultivars) were investigated over 2 years under rainfed and irrigated conditions in Central Anatolia where drought and Zn deficiency cause substantial yield reductions. Plants were treated with (+Zn: 23 kg Zn ha−1, as ZnSO4·7H2O) and without (−Zn) Zn under rainfed and irrigated conditions. Both Zn deficiency and rainfed treatments resulted in substantial decreases in grain yield. Significant differences were determined between both bread wheat and durum wheat cultivars in terms of drought stress tolerance. Considering drought sensitivity indices over 2 years, the bread wheat cultivars Yayla‐305, Gerek‐79, Dagdas‐94 and Bolal‐2973 were found to be more drought‐tolerant than the other cultivars under both −Zn and +Zn treatments. Especially the durum wheat cultivars Cakmak 79 and Selcuklu 97 showed much greater drought susceptibility under Zn deficiency, and irrigation alone was not sufficient to obtain satisfying grain yield without Zn application. The results indicate that sensitivity to Zn deficiency stress became more pronounced when plants were drought‐stressed. The effect of irrigation on grain yield was maximized when Zn was adequately supplied, leading to the suggestion that efficient water use in Central Anatolia seems to be highly dependent on the Zn nutritional status of plants.  相似文献   

16.
We tested the hypothesis that by reducing the application of N, based on the decrease in evapotranspiration (ET) expected due to increase in soil salinity, it is possible to reduce N loss without causing N deficiency or further yield loss in salt‐stressed maize plants. We tested four levels of salinity of irrigation water (S1 = 0.5; S2 = 2.5; S3 = 5.0; and S4 = 7.5 dS m?1) and four N rates using outdoor soil columns with five replicates. The N rates were as follows: N1: N recommendation for maize (2.6 g per column); N2: 0.3 times the N recommendation (0.78 g per column); N3: reduction in N1 based on the decrease in ET caused by salinity; and N4: reduction in N2 based on the decrease in ET caused by salinity. The amounts of N for N3 and N4 were reduced (in relation to N1 and N2) by 7 %, 15 % and 30 % for 2.5, 5.0 and 7.5 dS m?1, respectively. Salinity caused NO3? accumulation in the soil, plant growth inhibition and stomatal closure. The low rates of N (N2 and N4) did not meet the N demand of maize plants, especially for low levels of salinity (control and 2.5 dS m?1). On the other hand, based on the available growth data, physiological responses and nutritional status, one can conclude that plants under N1 and N3 had the same potential for final yield. For these N rates, reduction in N application according to ET (N3 rate) not only allowed plant growth and maize physiological responses, but also increased N‐use efficiency and greatly reduced soil nitrate accumulation compared to N1 rate, at the same levels of salinity. We conclude that reduction in N application, based on reductions in ET, is a good strategy to reduce both the risk of ground water contamination by NO3? leaching and fertilization costs, without causing additional damage to plant development under salt stress.  相似文献   

17.
Water deficit is generally thought to negatively impact crop yields, including grain sorghum (Sorghum bicolor L.), but a small body of literature reports changes in crop physiology and growth in plants with short‐term imposition of water deficit during vegetative development that could lead to increased yield. In a replicated and repeated pot experiment in which water deficit was imposed for 10‐day periods in grain sorghum plants that were otherwise well‐watered, we tested the hypothesis that relatively severe, short‐term water deficit imposed during early vegetative development could enhance grain sorghum yield. The results showed that severe water deficit (~30% of control ET) imposed during two vegetative periods enhanced grain yield compared to continuously well‐watered plants by 21% (p = .0356). Grain yield was correlated with average grain weight, grain number per head and shoot‐to‐root ratio. Yield enhancement was associated with a substantial shift in resource partitioning, as water deficit reduced root mass (p = .0032), stem/leaf mass (p < .0001) and total biomass (p = .0005), resulting in a 60% increase in harvest index. Imposition of water stress during vegetative growth in sorghum can increase grain yield.  相似文献   

18.
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.  相似文献   

19.
To study the effects of early drought priming at 5th‐leaf stage on grain yield and nitrogen‐use efficiency in wheat (Triticum aestivum L.) under post‐anthesis drought and heat stress, wheat plants were first exposed to moderate drought stress (drought priming; that is, the leaf water potential reached ca. ?0.9 MP a) at the 5th‐leaf stage for 11 days, and leaf water relations and gas exchange rates, grain yield and yield components, and agronomic nitrogen‐use efficiency (ANUE ) of the primed and non‐primed plants under post‐anthesis drought and heat stress were investigated. Compared with the non‐primed plants, the drought‐primed plants possessed higher leaf water potential and chlorophyll content, and consequently a higher photosynthetic rate during post‐anthesis drought and heat stress. Drought priming also resulted in higher grain yield and ANUE in wheat under post‐anthesis drought and heat stress. Drought priming at vegetative stage improves carbon assimilation and ANUE under post‐anthesis drought and heat stress and their combination in wheat, which might be used as a field management tool to enhance stress tolerance of wheat crops to multiple abiotic stresses in a future drier and warmer climate.  相似文献   

20.
Possibilities to improve maize harvest index and nutrient utilization efficiency by application of plant growth regulators were investigated. In container experiments, the effects of different growth regulators on the development of the maize (Zea mays L.) cultivars Pioneer 3906 and Fabregas were tested. Paclobutrazol (PAC) and chlorocholine chloride (CCC), two inhibitors of gibberellin biosynthesis, as well as gibberellic acid (GA3) were applied at growth stage V5. Three weeks after application of PAC, shoot growth of both maize cultivars was strongly affected with a significant decrease in plant height in the PAC treatment by 44% and 36% for Pioneer 3906 and Fabregas, respectively. The growth‐retarded plants had higher leaf areas and reduced transpiration rates. The higher shoot growth after GA3 application was accompanied by a reduction in leaf area and an increase in transpiration rate during 1 week before anthesis. CCC treatment showed no significant effects on plant height, leaf area and transpiration rate. The PAC‐treated cultivar Pioneer 3906 produced several cobs per plant, which were mainly barren at maturity. However, PAC application to Fabregas resulted in just one cob per plant with good kernel development and a grain yield, which was not significantly reduced in comparison with the control. With this similar grain yield in combination with a straw yield decrease of 32%, the harvest index was significantly improved by 12%. In addition, with PAC‐treated Fabregas plants, a 19% increased water use efficiency of the grain (WUEgrain) during the critical period of kernel setting was achieved. In this maize cultivar, CCC application also improved harvest index by 5%, but no effect on WUEgrain occurred. GA3 treatment decreased harvest index of both maize cultivars, and it either reduced WUEgrain (Pioneer 3906) or showed no effect (Fabregas). Utilization efficiencies of N, P and K were not increased with growth regulator application, even in the PAC‐treated Fabregas plants with a significantly improved allocation of assimilates to the grain, mirrored by the higher harvest index. The results indicate that fertilizer applications must be adjusted to the reduced demand of growth‐retarded plants, most likely leading to higher nutrient utilization efficiencies.  相似文献   

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