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1.
We test the hypothesis that reduction in grain N concentration under elevated CO2 concentration (e[CO2]) is associated with N types (NH4+ and NO3−) and their ratios. Wheat (Triticum aestivum L. cv. H45) was grown in a glasshouse under two CO2 concentrations (389 μmol mol−1 and 700 μmol mol−1), supplied with equal amount of N with different ratios of NH4+ and NO3−: (i) 100% NO3−–N; (ii) 50% NO3−–N and 50% NH4+–N; and (iii) 25% NO3−–N and 75% NH4+–N. Plant growth, N uptake and partitioning were measured during plant development. Plant biomass and grain yield was increased at e[CO2] when N was supplied as an equal proportion of NO3− and NH4+. Despite the yield increment, grain N concentration was not affected by e[CO2], in 50% NO3−–N treatment. In contrast, grain N concentration decreased in 100% NO3−–N and 25% NO3−–N treatments. In 50% NO3−–N treatment, N uptake during post-anthesis stage (from 69 to 141 days after planting) was significantly stimulated under e[CO2] compared to 100% NO3−–N and 25% NO3−–N treatments. We concluded that supplement of N in an equal proportion of NO3− and NH4+ which increases post-anthesis N uptake, avoid the reduction of grain N concentration under e[CO2].  相似文献   

2.
《Plant Production Science》2013,16(2):138-143
Abstract

Potato tuber initiation and its growth are key processes determining tuber yield, which are closely related to stolon growth, and are influenced by many factors including N nutrition. We investigated the influences of different forms of nitrogen (N) on stolon and tuber growth in sand culture with a nitrification inhibitor during 2010 – 2011, and using two potato cultivars. Plants supplied with NO3-N (N as nitrate, NO3-) produced more and thicker stolons than those supplied with NH4-N (N as ammonium, NH4+) at tuber initiation stage. In the plants fed NO3-N, the stolon tips swelled or formed tubers earlier and produced more tubers than in those fed with NH4-N. However, no significant difference was observed among N forms in terms of tuber yield at harvest, this may have been because of the shoot growth rate at tuber initiation stage was lower in the plants fed NO3-N. During the tuber bulking stage, the difference in shoot DWs among N forms began to decrease, and the shoot DW of plants fed NO3-N was even heavier than those fed NH4-N in some cases. The influence of N form on potato plant growth may therefore vary with the potato growth stage.  相似文献   

3.
Nitrogen fertilization is one of the factors that influences Bemisia tabaci (Gennadius) population density. The aim of this study was to determine the effects of three N application rates (75, 205 and 335 mg/l) and three ratios of NO3−:NH4+ ions (92:8, 75:25 and 55:45) in standard nutrient solution (205 mg/l N) on the population density of B. tabaci. The experiments were conducted on spring-summer hydroponic crops of tomato. The effect of plant stratum on the whitefly population was also determined. The aggregation of B. tabaci adults as well as their oviposition rate was higher at 205 and 335 mg/l N than on plants grown at 75 mg/l N. By the end of the experiment (60 d after infestation), the number of nymphs on plants at 205 mg/l N was higher than on plants at 75 mg/l N. The number of pupae was lowest on plants supplied with 75 mg/l N. An increase in NH4+ percentage in standard nutrient solution (from 25% to 45% of the total N) reduced adult population density and oviposition rate. The density of nymphs and pupae, at 60 d after infestation, was lower on the tomato plants grown at 75:25 and 55:45 NO3−:NH4+ ratios compared to the 92:8 ratio. The 75:25 and 55:45 NO3−:NH4+ ratios resulted in a higher incidence of blossom-end rot of tomato fruit, with a lower incidence of disorder at 75:25 than at the 55:45 ratio. Plant stratum influenced adult whitefly distribution in two years of the study. Middle stratum leaves were more attractive to adults in both years. The results demonstrate the effects of N fertilization (N rate and the ratio of NO3−:NH4+) and plant stratum on B. tabaci population density.  相似文献   

4.
The pool of nitrate-N (NO3–-N) in the soil is more prone to losses than that of ammonium-N (NH4+-N) so any shift towards NO3–-N dominance in the soil pools, caused by management intensity, could have environmental implications. The change in the balance of soil NH4+-N and NO3–-N content with time was studied using grazed grass swards receiving different fertilizer N inputs. In addition, the effect of past management on net nitrification of 400 μg NH4+-N g–1 was investigated in a soil incubation study. Mineral N was determined at frequent intervals (at least every 2 weeks) throughout the year in the top 5 or 7·5 cm of a sandy clay-loam soil at the Agricultural Research Institute of Northern Ireland at Hillsborough, County Down, for a 7-year period (1989–90 to 1995–96). The treatments were a perennial ryegrass–white clover sward receiving no fertilizer N, together with perennial ryegrass swards receiving 100, 200, 300, 400 or 500 kg N ha–1 year–1 as calcium ammonium nitrate. The plots were continuously grazed by beef steers from April to October to maintain a constant sward height of 7 cm. There was little or no change in average soil NO3–-N and NH4+-N content from 1989–90 to 1995–96 on the grass–clover sward and plots receiving 100 and 200 kg N ha–1 year–1. However, with the plots receiving 300, 400 and 500 kg N ha–1 year–1 NO3–-N became progressively more dominant with time. The incubation study confirmed that this was due to an increase in net nitrification rate. There was evidence that rapid microbial assimilation of NO3–-N occurred during the soil incubations. Past management history can play an important role in determining soil NO3–-N content and hence potential losses of N to the environment.  相似文献   

5.
This study aims to assess the nitrogen contamination of groundwater in paddy and upland fields. A reactive chemical transport model PHREEQC and a variable saturated groundwater flow and transport model FEMWATER were used to evaluate the vertical transport of nitrogen compound in various soil types of paddy and upland. The shallow groundwater quality monitoring data of 2003, 2006, 2009 in the Choushui river alluvial fan, the major agriculture production area in Taiwan, were applied to support the validity of the numerical simulation findings. Results from PHREEQC and FEMWATER simulations showed that the organic-rich impermeable plow sole layer underneath the muddy layer of rice paddy can effectively reduce NO3 − and N2 to NH4 + and retard the movement of NH4 +. However, in the upland field which has no plow sole layer, the NH4 + can move easily to the shallow aquifer and contaminate the groundwater. The spatiotemporal distribution of NO3 −–N and NH4 +–N in the Choushui river alluvial fan revealed that high nitrate–N contamination areas were located mainly in the upland field of the proximal fan, where the granular unconfined aquifer was vulnerable to surface contaminants. Moreover, the unconfined nature of the aquifer allows the oxidization of NH4 + to NO3 − and accelerates the plume movement. High ammonium–N concentration areas were mostly dispersed in the distal-fan area where upland planting and aquacultural farming were prevailed. The high NH4 +–N found in the northern Choushui river alluvial fan was attributed to the alternative planting of rice and upland crops, and the plow sole layer was broken to maintain the quick drainage upland crop needs.  相似文献   

6.
Summary Different nitrogen sources (NO3 −, NH4 +, glutamic acid and their combinations) influenced the growth and morphogenic responses (node number, shoot length, and stem, leaf and root dry weight) of three micropropagated potato cultivars (Spunta, Kennebec, Huinkul). Addition of reduced nitrogen (NH4 + or glutamic acid) in a nitrate medium increased shoot length and leaf number. The large increase in growth in plants fed with NO3 −, NH4 + could be explained by higher organic nitrogen content and enhanced dry matter partition to the shoot. This suggests that reduced nitrogen source is required, at least as a supplement to NO3 −, to enhance N assimilation and growth.  相似文献   

7.
通过田间试验,研究6种(N_1~N_6)硝态氮与铵态氮配比处理对旱地全膜双垄沟播玉米植株氮素积累、转运、氮素利用及子粒产量的影响。结果表明,单施硝态氮时玉米的养分吸收、氮素利用及产量均最低。N6(硝态氮与铵态氮3∶1配比)处理下玉米全生育期氮素积累量最高,氮素吸收强度较单施硝态氮处理高55.19%~73.28%(P0.05),该处理下叶片和茎中氮素转移量较单施硝态氮处理高78.99%和93.52%(P0.05);叶片和茎中分别有66.50%~71.89%和43.44%~55.59%的氮素转移到子粒中;叶片和茎对子粒的氮素贡献率分别较单施硝态氮处理高43.80%和56.00%(P0.05);玉米子粒产量、氮素吸收效率及氮肥偏生产力较其他处理显著增加3.31%~9.94%、4.62%~33.89%和3.31%~9.93%。硝态氮和铵态氮配施对玉米的养分吸收有明显的促进作用,提高硝态氮的施用比例有利于提高玉米叶片和茎对子粒氮素的贡献率,硝态氮与铵态氮按3∶1比例配施有利于提高当地玉米子粒产量。  相似文献   

8.
2014、2015年夏季,试验采用单因素随机区组设计,以先玉335为材料,设置两种肥料增效剂、7种施肥方式,研究大喇叭口期和抽雄期植物学性状、施肥后0、14、28、42 d时0~30 cm和31~60 cm土壤中NH_4~+-N和NO_3~--N含量以及收获时玉米穗部性状和产量差异。结果表明,分期施肥比全部氮肥作底肥更能促进夏玉米茎粗、叶面积、气生根数量、穗长、穗行数和行粒数等增加。与对照和不施用肥料增效剂相比,0~30 cm和31~60 cm土层中施用两种肥料增效剂的NH_4~+-N含量较高,NO_3~--N含量较低,控制了NH_4~+/NO_3~-比例。两种肥料增效剂相比,Entrench效果明显优于NMAX。  相似文献   

9.
The effects on clover and grass growth of five levels of ammonium nitrogen (NH4-N) applied before sowing, at sowing and after nodule initiation have been investigated. A pot experiment in which S184 white clover was grown in a peat soil showed that NH4-N up to 688 mg N per pot (approx. equivalent to a field rate of 120 kg ha-1 N) applied before sowing and at sowing did not affect clover growth. N-fixing activity (C2H2-reduction), on the other hand, was reduced progressively up to the highest level (688 mg N per pot). Application after nodule initiation increased growth relative to the zero-N treatment at all levels of application. Maximum growth and N fixation occurred at 516 mg N per pot where the DM yield was 70% higher than in the absence of added N. A field trial in which S184 clover and S24 perennial ryegrass were surface sown on to a peat soil showed an increase in grass and clover growth in the first year in response to 120 kg ha-1 N applied at sowing. Grass growth alone was increased at 120 kg ha -1 N applied 40 d before sowing. Lower rates of application before sowing and at sowing did not affect clover or grass growth. The effect of the delayed application of NH4-N on legume growth was less marked than that in the pot experiment, 90 kg ha-1 N stimulating clover growth by 40% in the first year. The effect was however different from that in the pot experiment, in that, whilst 30kg ha-1 N increased N fixation relative to the zero-N treatment, plants exposed to higher levels showed a depression in N-fixing capacity. N-fixation was correlated with nodule numbers in the delayed NH4-N application, the closest correlation being with the number of multilobed nodules which was highest at 30 kg ha-1 N and lowest at 120 kg ha-1 N. It is suggested that circumstances exist when the use of a relatively low starter N dressing (20–60 kg ha-1 N) at sowing would not increase clover or grass growth in the early stages of the establishment of a hill reseed. Under such circumstances higher rates of application (100 kg ha -1 N), preferably delayed until the seedlings are in a position to take up the nitrogen rapidly, would have the greatest effect.  相似文献   

10.
为明确外源硝态氮对高铵胁迫下小麦幼苗生长的影响及其生化机理,采用温室水培的方式,以豫麦49(耐高铵品种)和鲁麦15(高铵敏感型品种)为材料,研究了外源硝态氮对高铵胁迫下小麦幼苗形态、激素含量和抗氧化系统的影响。结果表明,高铵胁迫条件下,外源硝态氮显著增加两个小麦品种株高、根长、干重,其中鲁麦15的地上部干重增加量高于豫麦49,而根系干重增加量则表现为豫麦49高于鲁麦15。高铵胁迫下,两个小麦品种植株的IAA、CTK含量、IAA/CTK显著低于对照;外源硝态氮处理5 d后,豫麦49地上部和根系IAA含量、根系CTK含量显著增加,恢复至对照水平;鲁麦15植株虽亦表现显著增加,但仍低于对照。另外,外源硝态氮对高铵胁迫下两个小麦品种地上部和根系的O■释放速率、SOD和POD活性及MDA含量没有显著影响。综上,外源硝态氮缓解小麦幼苗生长高铵胁迫的原因可能是通过增加IAA和CTK合成和转运,影响IAA和CTK之间的平衡,进而达到缓解效果。品种间比较,耐铵型品种豫麦49缓解作用可能源于对地上部和根系IAA含量以及根系CTK含量的协同调控;而高铵敏感型品种鲁麦15的缓解作用可能主要源于对地上部IAA含量的调控。  相似文献   

11.
为了解不同氮效率小麦品种根系氮代谢特征及其吸收能力的差异,明确小麦氮高效利用的生理机制,在水培条件下,研究了氮高效小麦品种漯麦18和氮低效小麦品种西农509的根系氮代谢特征和对NO-3、NH+4吸收的动力学特征。结果表明,漯麦18的根系GS活性、硝酸还原酶活性、游离氨基酸含量、可溶性蛋白质含量均高于西农509;而西农509的根系硝态氮和铵态氮含量高于漯麦18;漯麦18根系对NO-3、NH+4吸收的最大吸收速率(Vmax)显著高于西农509;漯麦18根系对NO-3、NH+4的亲和力(以Km的倒数衡量)低于西农509。结果说明,氮高效型小麦品种根系对NO-3、NH+4的吸收能力和同化能力均显著高于氮低效型小麦品种;小麦根系对NO-3、NH+4的吸收和同化是相互促进的关系。  相似文献   

12.
Nitrogen contamination in ground water of potato (Solanum tuberosum L.) producing areas has indicated a need for improved management of N and water, particularly on sandy soil. Therefore, a field experiment was conducted with the objective of following the recovery and partitioning of starter15NH4 and15NO3 into potato plant tops and tubers in conjunction with additional supplementarily applied NH4NO4. Potato plants treated with starter15NH4 or15NO3 tended to increase the percent recovery of starter15N in tubers sampled from one growth time to the next to reach nearly 40% recovery toward the end of the season. Whole plants reached peak recovery of around 50% of the starter15N near mid-season. From then on, there was a trend for loss of starter15N by senescence, defoliation or translocation to the roots. The percent recovery of starter15N was significantly higher at final tuber harvest (not whole plants) for the treatment with starter15NH4 at 112 kg ha?1 combined with 112 kg ha?1 of supplemental N as compared to the treatment with 112 kg ha?1 of starter15NH4 plus 224 kg ha?1 of supplemental N. This difference may have been a result of isotope dilution. Early in June the accumulation of starter15NO3 in whole plants was about five times as high as that from starter15NH4. Later there was no difference in percent recovery of these two forms of N. The temporary delay in starter15NH4 uptake was probably related to slow nitrification early in the season instead of preferential uptake of starter15NO3.  相似文献   

13.
A field experiment was carried out to research the changes and spatial distributions of soil nutrients in saline–sodic soil for different number of cultivated years under drip irrigation. The distributions of available potassium (AK), available phosphorus (AP), nitrate nitrogen (NO3 ?–N), ammonium nitrogen (NH4 +–N), as well as the amount of total nitrogen (TN), total phosphorus (TP) and organic carbon (OC) in the 0–40 cm soil layers in saline–sodic soils planted with Leymus chinensis for 1, 2, and 3 years were studied. The results showed that the distance from the emitter had an obvious effect on soil nutrients. Drip irrigation had substantial effects on levels of AK, AP, and NO3 ?–N. The contents of AK, AP, and NO3 ?–N were very high in the area near the emitter in the horizontal direction. In the vertical direction, levels of all of the available and total soil nutrients decreased with increased soil depth. Levels of AK, AP, NO3 ?–N, NH4 +–N, TN, TP, and OC all increased with continued cultivation of crops on saline–sodic soil using drip irrigation. Compared to the nutrients found in soils from the natural L. chinensis grasslands, the contents of AK and TP were higher in the drip-irrigated soils, although the contents of AP, NO3 ?–N, and NH4 +–N were broadly comparable. Given the rate of improvements in nutrient levels, we forecast that the nutrients in drip-irrigated saline–sodic soils should match those of the natural L. chinensis grasslands after 3–6 years of cultivation.  相似文献   

14.
The effect of controlled irrigation and drainage on N leaching losses from paddy fields was investigated by controlling root zone soil water content and water table depth using a lysimeter equipped with an automatic water table control system. Three treatments that combined irrigation and drainage managements were implemented: controlled irrigation (CI) + controlled water table depth 1 (CWT1), CI + controlled water table depth 2 (CWT2), and flooding irrigation (FI) + actual field water table depth (FWT). Controlled irrigation and drainage had significant environmental effects on the reduction of NH4 +–N and NO3 ?–N leaching losses from paddy fields by decreasing water leakage. The NH4 +–N leaching losses from CI + CWT1 and CI + CWT2 were 3.68 and 4.45 kg ha?1, respectively, which significantly reduced by 59.2 and 50.7 % compared with FI + FWT (9.02 kg ha?1). The NO3 ?–N leaching losses from CI + CWT1 and CI + CWT2 were 0.88 and 0.43 kg ha?1 with a significant reduction of 45.2 and 73.2 %, respectively, compared with FI + FWT (1.61 kg ha?1). The application of CI + CWT1 can be a pollution-controlled water management method of reducing N leaching losses from paddy fields.  相似文献   

15.
Russet Burbank and Shepody potatoes were grown with at-planting nitrogen fertilizer rates varying from 0 to 270 kg ha?1 following small grains and red clover. Petiole samples were collected from the 4th and 5th leaflets at four to six dates each during the 1986 to 1989 growing seasons. The samples were dried and analyzed for NO 3 ? N content. Petiole NO 3 ? N levels were strongly related to nitrogen rate regardless of cultivar, growing season, and cropping system. Differences among treatments and NO 3 ? N content varied substantially as the growing season progressed with petiole NO 3 ? N levels declining rapidly in underfertilized plots as the plants aged. Petiole NO 3 ? N levels were higher at midseason following red clover than following small grains. Sampling 50 to 60 days after planting (DAP) is most appropriate as a tool for scheduling supplemental nitrogen applications. At 50 DAP, critical petiole NO 3 ? N levels were 1.6 and 1.7% for Russet Burbank and Shepody, respectively. Petiole NO 3 ? N levels above 2.2% at 50 DAP resulted in lower yields of Russet Burbank than when petiole NO 3 ? N levels were in the 1.6 to 2.2% range. Petiole NO 3 ? N testing should be particularly useful as a diagnostic tool in management strategies which make maximum use of previous crop residues, organic amendments, and soil reserves as nitrogen sources.  相似文献   

16.
Gymnema sylvestre is an important medicinal plant which bears bioactive compound namely gymnemic acids. The present work deals with optimization of cell suspension culture system of G. sylvestre for the production of biomass and gymnemic acid and we investigated effects of macro elements (NH4NO3, KNO3, CaCl2, MgSO4 and KH2PO4 - 0.0, 0.5, 1.0, 1.5 and 2.0× strength) and nitrogen source [NH4+/NO3− ratio of: 0.00/18.80, 7.19/18.80, 14.38/18.80, 21.57/18.80, 28.75/18.80, 14.38/0.00, 14.38/9.40, 14.38/18.80, 14.38/28.20 and 14.38/37.60 (mM)] of Murashige and Skoog medium on accumulation of biomass and gymnemic acid content. The highest accumulation of biomass (165.00 g l−1 FW and 15.42 g l−1 DW) was recorded in the medium with 0.5× concentration of NH4NO3 and the highest production of gymnemic acid content was recorded in the medium with 2.0× KH2PO4 (11.32 mg g−1 DW). The NH4+/NO3− ratio also influenced cell growth and gymnemic acid production; both parameters were greater when the NO3− concentration was higher than that of NH4+. Maximum biomass growth (159.72 g l−1 of FW and 14.95 g l−1 of DW) was achieved at an NH4+/NO3− ratio of 7.19/18.80, and gymnemic acid production was also greatest at the same concentration of NH4+/NO3− ratio (11.35 mg g−1 DW).  相似文献   

17.
Increasing global atmospheric CO2 concentrations are expected to influence crop production. To investigate the effect on rice (Oryza sativa L.), plants were grown under ambient CO2 (AMB) or free-air CO2-enrichment (FACE) at CO2 concentrations ranged from 275 to 365 μmol mol−1 above AMB. We supplied 13CO2 to the plants at different growth stages so we could examine the contribution of carbohydrate stored during the vegetative stage or newly fixed carbohydrate produced during the grain-filling stage to ear weight at grain maturity. In plants supplied with 13C at the panicle-initiation or pre-heading stages, plants grown under FACE had more starch in the stems at heading, but there was no difference in stem 13C content. Furthermore, there were no differences between treatments in whole-plant 13C contents at heading and grain maturity. In contrast, plants supplied with 13C at the grain-filling stage had more 13C in the whole plant and the ears at grain maturity under FACE than under AMB, indicating that the increased amount of photosynthate produced at the grain-filling stage under CO2 enrichment might be effectively stored in the grains. Furthermore, regardless of when the 13C was supplied, plants had more 13C in starch in the ears at grain maturity under FACE than under AMB. Therefore, CO2 enrichment appears to promote partitioning of photosynthate produced during both vegetative and grain-filling stages to the grains.  相似文献   

18.
The widely adopted alternate wetting and drying (AWD) irrigation for rice production is increasingly needed to quantify the different water outflows and nitrogen leaching losses. We investigated the effects of AWD on percolation, water productivity, nitrogen leaching losses, and nitrogen productivity through in situ experiments. Results show that AWD reduced irrigation water without a significant impact on grain yields and increased the mean water productivity by 16.9 % compared with continuously flood irrigation (CFI). The mean nitrogen productivity of 135 kg ha?1 N level was 22.2 % higher than that of 180 kg ha?1 N level, although grain yields substantially increased because of nitrogen fertilization application. The percolation was also reduced by 15.3 % in 2007 and 8.3 % in 2008 compared to CFI. However, the cumulative percolation of the first 5 days after irrigation in AWD plots is significantly larger than that in CFI plots. The NH4 +–N and TN leaching losses of AWD and CFI had no significant variations while the NO3 ?–N leaching losses were increased caused by AWD. The total NH4 +–N, NO3 ?–N, and TN leaching losses of AWD in the first 3 days after irrigation were higher than that of contemporaneous CFI. The results indicate that the bypass or preferential flow and strengthened nitrification–denitrification nitrogen transformation processes because of alternate wetting and drying potentially decrease the water saving effectiveness and increase the NO3 ?–N loading to the groundwater.  相似文献   

19.
In order to study the response of the rice photosynthetic-fluorescence characteristics to the application of different nitrogen forms with water-saving irrigation, by using LI-6400XT-type photosynthetic apparatus and other equipment, the fluorescence parameters, stomatal resistance and photosynthetic-CO2 response curves of rice were measured at the critical stages under water-saving irrigation methods. Results showed that the change trend of ETR and photochemical fluorescence quenching coefficient (Qp) with different nitrogen forms were declining–rising–declining. Compared with CK (control treatment), ETR and Qp with NO3? treatment were better than the others, which indicated that this treatment was most advantageous to increasing ETR. The electron flow from PSII oxidation-lateral to PSII was enhanced. The potential quantum efficiency (Fv/Fm) was the lowest at tillering stage and the highest at heading stage. Compared with CK, at heading stage, Fv/Fm with NO3?, NH4+ NO3? and NH4+ treatments was increased by 1.68, 0.61 and 1.81%, respectively, while NO3? and NH4+ played a more important role in promoting the ability to capture light. The change trend of non-photochemical fluorescence quenching coefficient with different treatments was not obvious. During the growth period, the stomatal resistance (Rs) was changed dynamically, reaching the second peak at the jointing stage and the highest peak at the milk-ripe stage, and both were higher than CK. The Rs of different nitrogen forms was as NH 4 +? >?NH4+NO 3 ?? >?NO3?, which showed that with different nitrogen forms, Rs of NO3? treatment was low, stomatal opening was correspondingly greater than the other nitrogen forms, and under the same moisture conditions, this treatment of stomatal opening was more beneficial for gas exchange and external CO2 flowing into the leaf cells, which could increase photosynthetic physiological response. By fitting the parameters of photosynthetic-CO2 response curve, it was concluded that the photorespiration rate (RP) was greater than CK, but it was different for three nitrogen treatments during different periods. Rice light saturation point and apparent carboxylation efficiency (α) of NO3? treatment during three growth periods were more uniform, indicating that this treatment had a higher utilization rate for low concentration of CO2. Maximum photosynthetic rate (Pmax) with NO3? and NH4+ treatments of the three growth periods was 29.396–31.208 and 28.969–31.371, respectively. The CO2 compensation point and curve angle (θ) had no stable trend during the whole growth period. Therefore, the nitrogen forms could influence the photosynthetic characteristics of the rice leaves, and the result can provide theoretical guidance and scientific basis for increasing the efficiency of nitrogen utilization.  相似文献   

20.
Two field studies were conducted to determine the effects of soil fumigation on the response of Russet Burbank potatoes (Solanum tuberosum L.) to NH4-N or NH4NO3 fertilizers. In one study fumigation increased yields but N source had no effect. In the other study fumigation had no effect but NH4-N provided higher yields than NH4NO3. Microbial studies indicated that although populations of nitrifying bacteria were initially altered by fumigation, nitrification rates were similar to those in non-fumigated soil. In a controlled environment study in which potatoes were grown in fumigated field soil, neither N source nor fumigation had any effect on growth or yield. These studies indicated that fumigation had no effect on the response of potatoes to NH4-N or NH4NO3 fertilizers.  相似文献   

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