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1.
为了确定大麦籽粒产量和苗期耐低氮能力与小孢子培养阶段的氮胁迫下愈伤组织产量之间是否存在一致性,以2份大麦基因型为供试材料,进行了以下3项研究：（1）培养基中水解干酪素和谷氨酰胺使用量对小孢子培养愈伤组织产量的影响;（2）营养液中NH4NO3不同添加量对大麦苗期生长量的影响;（3）盆栽时正常施氮与不施氮处理对大麦单株产量的影响。结果表明,培养基中氮含量的下降明显降低小孢子培养愈伤组织产量,2份基因型的降幅存在明显的差异;营养液中氮使用量的下降明显降低植株高度、主根长度和植株及根干重,2份基因型之间的降幅也存在明显的差异;盆栽时不施氮处理的大麦有效穗和单株产量低于正常施氮的对照,2份基因型间有差异。氮素胁迫下,2份基因型小孢子培养愈伤组织产量的相对值与苗期植株高度、茎叶干重、主根长度和根干重的相对值以及单株产量的相对值存在一致性,说明供试基因型小孢子水平与植株水平的耐低氮性存在相关性。 相似文献
2.
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
3.
《Plant Production Science》2013,16(2):138-143
AbstractPotato 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
4.
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
5.
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
6.
试验利用盆栽,选用远征808(收敛型)和四单19(平展型)作试验材料,研究了增铵营养对玉米子粒中蛋白质、淀粉和可溶性糖含量的影响.在氮素水平一致的条件下,设6个处理,NO3--N和NH4+-N比例分别是3:0、2:1、1:1、1:2、0:3及对照(不施氮).试验表明,增铵营养可以提高玉米子粒中蛋白质含量,但不同类型品种表现有差异,远征808在NO3--N和NNH4+-N比例为2:1时蛋白质含量最高,而四单19在1:2时 相似文献
7.
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
8.
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
9.
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
10.
Growth and carbon economy of nodulated white clover in the presence and absence of combined nitrogen
An investigation of the carbon economy of single S184 white clover plants nodulated with an effective strain of Rhizobium trifolii growing on N-free nutrient solution and supplied with 150 parts/106 N as NH4NO3 has shown that 10% more of the C fixed per day is available for growth in the plants supplied with combined N. The difference between the two groups of plants is a result of higher respiratory activity in the roots of plants growing exclusively on N2. In terms of shoot growth, however, the difference in growth rate is likely to be less than 10%, because the rate of root growth is greater in the plants supplied with a moderate level of combined N. There is no evidence that NO-3 and CO2 compete for photosynthetically produced reductant in the leaves of plants grown on N2+NH4NO3, since no reduction in net photosynthesis was observed in plants assimilating combined N. An experiment carried out on detached leaflets of white clover grown on N2 and on N2+ NH4NO3 has shown that NO-3 -reducing activity is present in the leaflets of plants grown on N2+ NH4NO3 but not in plants grown on N2 and that the activity is light-dependent. Measurements of 14CO2 respired in the light and dark by leaflets previously allowed to photosynthesize 14CO2 showed that the ratio of 14CO2 output in the light to 14CO2 output in the dark was no higher in plants grown on N2+ NH4NO3 than in plants grown on N2. This observation is consistent with the finding that N source does not affect net photosynthesis in whole plants. 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.
Defining the critical nitrogen concentration (Nc; g N kg?1) for maximum growth of forage brassicas will aid in the fertilizer management of these crops. Typically, the Nc value decreases with increasing crop biomass. In this paper, we used a nitrogen (N) response experiment with kale (Brassica oleracea) to define a critical N dilution (Nc = 55·3 × biomass?0·47). However, at biomass <3·4 t ha?1, a constant NC of 31·2 g N kg?1 was found. This N dilution curve compared favourably with published data sets for a range of forage brassicas but was substantially different from the established N dilution curve for oilseed rape (Brassica napus). This study also found a strong relationship (R2 = 0·81) between the nitrogen nutrition index (NNI) and the NO3 content of forage brassicas from a range of data sets. The NNI is the actual N concentration of the shoot as a ratio of the Nc from the established curve. The relationship between NNI and NO3 contents was significantly different between leafy forage brassica crops and root forage brassicas. For each 0·1 increase in NNI, the proportion of total N that was in the form of NO3 increased by 2·7% for leaf/stem brassicas and 0·60% for root crop brassicas. The critical dilution curve defined in this study can be used to manage fertilizer N in forage brassica crops, so that growth can be maximized but the risk of high NO3 concentrations in the forage can be minimized. 相似文献
13.
肥料增效剂对夏玉米植物学性状、产量构成及土壤中NH4+-N和NO3--N的动态影响 总被引：1，自引：1，他引：0
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
14.
The nitrogen response of potato (Solanum tuberosum L.) in the field: nitrogen uptake and yield, harvest index and nitrogen concentration 总被引：1，自引：0，他引：1
J. Vos 《Potato Research》1997,40(2):237-248
Summary The response of potato to different rates of nitrogen supply ranging from 0–40 g m−2 N was studied in five field experiments near Wageningen. NL (520 North). In total two late potato cultivars and two sites were used during successive seasons. The results are summarized
in a set of regression equations separately for total crop and tubers. The relation between nitrogen taken up (g m−2) in the total crop and total dry matter production (g m−2) could be described with the exponential equation: 1942–1900 * 0.93X (r2=0.953, n=62). Nitrogen concentrations in the dry matter increased linearly with nitrogen uptake. Harvest indices for dry
matter and nitrogen tended to decline with increase in N uptake. Cultivars differed only in the effect on N on tuber dry matter
concentration. The relation between nitrogen uptake and nitrogen supply could be fitted with quadratic regression models.
but coefficients were influenced by site and season. 相似文献
15.
E. Chakwizira P. Johnstone A. L. Fletcher E. D. Meenken J. M. de Ruiter H. E. Brown 《Grass and Forage Science》2015,70(2):268-282
Nitrogen fertilizer is applied to supplement soil nitrogen supply to maximize forage brassica crop dry-matter production. However, nitrogen fertilizer applications in excess of that required to maximize growth result in potentially toxic nitrate–nitrogen (NO3–N) concentrations in grazeable plant tissues. Three experiments, two for forage kale at Lincoln (Canterbury) and one for forage rape at Hastings (Hawke's Bay) in New Zealand were grown under different rates of nitrogen (0–500 kg N ha−1) to determine the effect of different rates of nitrogen on NO3–N content of different plant parts of the crops. One of the kale experiments was grown with either full irrigation or no rain and no irrigation over summer, hereafter referred to as summer drought. The NO3–N concentration on a whole plant (weighted average) basis increased from 0·1 mg g−1 dry matter for the control plots to 2·30 mg g−1 for the 500 kg N ha−1 plots for forage kale. It increased from 0·99 for the control plots to 3·37 mg g−1 for the 200 kg N ha−1 plots for forage rape crops. However, NO3–N concentration increased with N supply under the summer-drought plots from an average of 0·33 mg g−1 when ≤120 kg N ha−1 was applied to 2·30 mg g−1 for the 240 kg N ha−1 treatments but was unaffected by N supply under irrigation. The NO3–N concentrations were higher in the stems and the petiole (which included the midrib of the leaf) than leaves in all three experiments. The NO3–N concentration was highest at the bottom of the kale stem and decreased towards the top. We recommend N application rates based on soil tests results, and for conditions similar to the current studies up to 300 kg N ha−1 under irrigation and adjusted lower N rates for regions prone to dry summers. 相似文献
16.
The effects of sulphur dioxide (SO2) and nitrogen dioxide (NO2), singly and in combination, on the shoot and root growth of two potato cultivars sensitive to these pollutant gases were determined using rooted cuttings in controlled conditions. Plants were exposed to 0.11 ppm SO2 and/or 0.11 ppm NO2 for 24 hours a day for 7 or 14 days. Kennebec plants had significantly lower root fresh and dry weights after 7 days in the mixture treatments and lower root fresh weight in the NO2 treatment. Russet Burbank plants were more sensitive to SO2 and NO2 than Kennebec. Russet Burbank plants had significantly reduced leaf area, and leaf, stem, and root fresh and dry weights after 7 and 14 days of mixture treatment, and the leaf to root dry weight ratio was higher than in control plants. The combination treatment and SO2 alone resulted in visible injury on leaves of both cultivars. Changes in tissue water concentration, decreased specific leaf area and decreased root growth suggested that SO2 and NO2 altered plant water status and interfered with partitioning of dry matter from the leaves to other plant parts. 相似文献
17.
为揭示大气NH3浓度升高和施氮对冬小麦生物量和氮素利用的影响，通过开顶式气室，以小偃22为试验材料，于2020-2022两年进行田间微区试验，设置3个施氮水平（0、180和240 kg·hm-2）和两种大气NH3浓度（空气背景NH3浓度:0.01~0.03 mg·m-3;高NH3浓度:0.30~0.60 mg·m-3）,对不同处理下小麦地上部和根系干物质、氮素积累量及氮素利用效率进行分析。结果表明，大气NH3浓度升高能显著提升小麦地上部生物量、根系生物量、地上部氮素积累量和根系氮素积累量，2年内平均增幅分别为5.77%、6.74%、8.94%和9.98%。在空气背景NH3浓度下，施氮后小麦显著增产， 180和240 kg·hm-2施氮水平下产量较0 kg·hm-2施氮水平分别提高了45.26%和50.67%。在大气NH3浓度升高环境中，随着施氮量的增加，小麦产量出现先升后降趋势， 180 kg·hm-2施氮水平下产量最高， 240 kg·hm-2施氮水平下小麦产量较0 kg·hm-2施氮水平降低17.97%，小麦氮肥农学效率和氮素利用率也随之降低。这说明，大气NH3浓度升高的环境中适当减少氮肥施用量能有效提升冬小麦的氮素利用率，稳定小麦产量。 相似文献
18.
水分胁迫和供氮形态耦合作用下分蘖期水稻的光合速率、水分与氮素利用 总被引：6，自引：2，他引：6
采用室内营养液培养及PEG模拟水分胁迫的方法,在3种供氮形态\[NH4+、NO3-、NH4+/NO3-(质量比)为50∶50\]下,主要研究分蘖期水稻在非水分胁迫及水分胁迫条件下的氮素利用效率及对不同形态氮素的消耗。在非水分胁迫条件下,分蘖期水稻在NH4+/NO3-为50∶50时生物量增量最大;而在水分胁迫条件下,单一供NH4+ N营养的水稻生物量增量最大。在两种水分条件下,当NH4+/NO3-为50∶50时,分蘖期水稻对营养液中NO3- N的消耗量明显大于NH4+ N;此外,在两种水分条件下,均以单一供NH4+ N营养水稻的光合速率、氮素利用率和水分利用率最高。 相似文献
19.
A highly efficient regeneration protocol for oilseed crop Crambe abyssinica has been developed using hypocotyls as explants in this study. Crambe is a potential engineering oilseed crop for industrial purposes as it contains 55-60% erucic acid in its oil and, more importantly, it does not outcross with any food oil seed crops. However, the low regeneration frequency with the currently available protocols is still a limiting factor for genetic modification of Crambe. In this study, we investigated the effects of N-source, C-source, AgNO3, cultural conditions as well as the concentration and combination of plant growth regulators (PGR) on the regeneration frequency of C. abyssinica. The results showed that all these factors, especially the N-source and PGR concentrations and combinations, played an important role in shoot regeneration. Among all the factors tested, the combination of using hypocotyls from C. abyssinica cv. galactica, the Lepiovre basal medium supplemented with 16 g l−1 glucose, 0.5 g l−1 AgNO3, 2.2 mg l−1 thidiazuron (TDZ), 0.5 mg l−1 α-naphthaleneacetic acid (NAA), 2.5 g l−1 Gelrite, seeds germinated in dark for 3 days and explants cultured in light, gave the best regeneration frequency (over 95%). The results also suggest that reducing the content of NH4+ or keeping a suitable NO3−/NH4+ ratio in the regeneration medium would be crucial to Crambe shoot regeneration. 相似文献
20.
Effects of alternate wetting and drying irrigation on percolation and nitrogen leaching in paddy fields 总被引：4，自引：2，他引：2
Xuezhi Tan Dongguo Shao Huanhuan Liu Fengshun Yang Chun Xiao Haidong Yang 《Paddy and Water Environment》2013,11(1-4):381-395
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