氮肥品种及施肥方式对小白菜产量与品质的影响

氮肥在农业生产中起着重要的作用,但是氮肥的大量施用不仅造成养分比例失调及环境污染,而且会限制产量的提高和品质的改善。针对广东蔬菜氮肥施用不合理的现象,在田间试验条件下研究了不同氮肥品种和不同底追比对小白菜产量和营养品质的影响,旨在为华南地区的蔬菜施用氮肥提供参考。试验结果表明,施氮极显著提高了小白菜的生物量和产量,亦增加了硝酸盐的累积量,其中尿素处理增产效果最好,蔬菜专用肥(磷铵 尿素)处理小白菜硝酸盐累积量最低,其次是碳酸氢铵和氯化铵处理。各氮肥处理间Vc和可溶性糖含量差异达到极显著水平,其中蔬菜专用肥处理含量最高;不同底、追肥处理间产量和Vc含量的差异达到显著或极显著水平,而可溶性糖含量差异未达到显著水平。除底肥70%、追肥30%的处理外,其余处理均极显著提高了硝酸盐含量。在本试验条件下,蔬菜专用肥既可以提高小白菜产量,又可以明显改善小白菜营养品质与卫生品质,如果以尿素为氮源,底肥70%、追肥30%是兼顾产量和品质的优化处理。     

施用中量微量元素对小白菜产量和硝酸盐含量的影响

为研究降低蔬菜硝酸含量的施肥技术，在不同质地的土壤上设置田间试验，对小白菜施用不同的中量和微量元素。结果表明，小白菜对施用的各种中量、微量元素在不同质地的土壤上有不同的响应；在合理施氮、磷、钾肥的基础上，有选择性地适量施用中量、微量元素，不仅可提高蔬菜的产量，而且可降低其体内硝酸盐的含量。     

有机无机肥配合施用对菜园土壤及蔬菜硝酸盐类动态的影响

通过田间小区试验和室内测定,研究了有机肥与化肥以不同比例配合施用对小白菜硝酸盐和亚硝酸盐含量以及土壤硝酸盐含量的影响。结果表明:有机肥与化肥配合施用可以明显降低小白菜硝酸盐含量,减少硝酸盐在土壤剖面中向下淋溶,尤以有机肥与化肥施用比例为1∶1(质量比)时小白菜产量较高,体内硝酸盐含量较低,土壤下层的硝酸盐含量也较低,达到蔬菜高产优质,生态环境清洁健康的目标。     

施肥对小白菜产量和品质的影响

为研究安全的蔬菜施肥技术，通过不同质地土壤的田间试验，研究不同氮、钾质量配比对小白菜产量和品质的影响。结果表明，在固定施磷水平的基础上，在不同质地的土壤上，小白菜对氮、钾质量配比有不同的效应，氮、钾合理配施可使蔬菜高产优质；所施氮的形态，对小白菜硝酸盐含量有显著的影响。     

有机无机肥配施比例对蔬菜产量和品质及土壤重金属含量的影响

关于蔬菜施有机肥和它与无机肥的合理配施比例,对蔬菜的产量和品质有重要影响,对土壤有机质和重金属含量也有影响。为控制施禽畜粪类有机肥对蔬菜的负面影响,探讨蔬菜的合理施用量和有机/无机肥配施比例,在不同质地的土壤上进行田间试验。结果表明,(1)施过量禽畜粪类有机肥对试验蔬菜产量和品质都会产生不良影响,小白菜(Brassica chinensis)和茄子(Eggplant)施禽畜粪超过22500kg/hm2、马铃薯(Solanum tuberosum L.)超过24000kg/hm2时,其产量不再增加,成活率下降,维生素C含量下降,多个试验均表现出有机肥用量增加而小白菜硝酸盐随之增加的典型特征;同时不论土壤的质地轻重,蔬菜重金属Pb有随禽畜粪用量增加而提高的趋势;在质地较轻的土壤上,蔬菜重金属Cd、As有随禽畜粪用量增加而提高的趋势;小白菜施禽畜粪肥超过7500kg/hm2、茄子和冬种马铃薯施禽畜粪肥超过75000kg/hm2,收获后土壤重金属含量高于对照和施无机肥的总Cr和As。(2)蔬菜单独施用有机肥的合适施用量,小白菜在较粘重的土壤上可施到22500kg/hm2,但有机肥与无机肥配合施用时有机肥用量可减量;茄子合适施用量应在22500kg/hm2左右;冬种马铃薯合适施用量应在24000kg/hm2左右。(3)蔬菜的有机/无机肥合理配比,小白菜、茄子、和冬种马铃薯施肥的有机氮与无机氮之比均为0.25∶1至0.5∶1时其产量和品质水平较佳。     

有机肥施用量与蔬菜硝酸盐和重金属关系初探

为控制施肥对蔬菜和土壤的负面影响,探讨蔬菜合理的有机肥施用量,在不同质地土壤上,田间试验小白菜、苦瓜、豇豆三种蔬菜施不同量有机肥,收获时测定其产量、品质、硝酸盐、重金属及试验前后土壤有机质含量。结果表明,(1)在施适量无机NPK的条件下,每造蔬菜的有机肥施用量(禽畜粪便,下同),砂土上小白菜为4500kg/hm2、苦瓜和豇豆为3000kg/hm2;壤土上,小白菜和苦瓜均宜施3000kg/hm2,豇豆则宜施4500kg/hm2;粘土上,小白菜每造只宜施1500~3000kg/hm2的有机肥。(2)有机肥必须与无机肥合理配合施用,才能获得最佳的产量和品质效果,在砂土上有机肥施得越多,蔬菜的硝酸盐含量越高,其它土壤也有类似趋势。(3)施高量(7500kg/hm2)有机肥的小白菜重金属含量最高,其次是施中量(3000kg/hm2)有机肥的,尤其是Cd。(4)施有机肥3000~4500kg/hm2 适量无机肥可使土壤有机质水平保持在种植蔬菜前的含量水平,该施肥量和方式不仅可使蔬菜高产、优质,还有利于保护土壤肥力。     

有机无机肥配合施用对菜园土壤及蔬菜硝酸盐类动态的影响

通过田间小区试验和室内测定，研究了有机肥与化肥以不同比例配合施用对小白菜硝酸盐和亚硝酸盐含量以及土壤硝酸盐含量的影响。结果表明：有机肥与化肥配合施用可以明显降低小白菜硝酸盐含量，减少硝酸盐在土壤剖面中向下淋溶，尤以有机肥与化肥施用比例为1：1(质量比)时小白菜产量较高，体内硝酸盐含量较低，土壤下层的硝酸盐含量也较低，达到蔬菜高产优质，生态环境清洁健康的目标。     

啤酒废水灌溉对6种蔬菜硝酸盐亚硝酸盐含量的影响

通过啤酒废水灌溉对６种蔬菜硝酸盐等的影响研究认为：啤酒废水灌溉对６种蔬菜灰分含量无明显影响;明显提高莴苣、马铃薯和甘蓝中维生素Ｃ的含量;提高韭菜、莴苣和甘蓝硝酸盐的含量;降低大葱硝酸盐的含量;可提高韭菜和马铃薯中亚硝酸盐的含量,而对于大葱、莴苣、小白菜和甘蓝中亚硝酸盐含量无明显影响     

栽培水分对采摘后油菜硝酸盐与亚硝酸盐含量的影响

采用盆栽方法栽培油菜(Brassicaca mpestrisL.),研究了灌水水平对采摘后油菜植株体硝酸盐与亚硝酸盐含量随时间变化的影响。共设高(灌水控制上限为田间持水量)、中(灌水控制上限为田间持水量的75%)和低(灌水控制上限为田间持水量的50%)3个灌水水平。油菜采摘后恒温贮存,定期测定油菜植株体内硝酸盐、亚硝酸盐含量。研究结果表明:不同灌水水平和贮存时间以及两者的交互作用都能显著地影响油菜植株体硝酸盐和亚硝酸盐含量;在采摘后的8d时间里,低灌水水平处理(0.50θf处理)的油菜植株体硝酸盐含量一直高于其它两处理;采摘后当天测定高灌水水平处理(1.00θf处理)的油菜植株体硝酸盐含量最低,以后则以中等灌水水平处理(0.75θf处理)的油菜植株体硝酸盐含量为最低。采摘后当天测定油菜植株体亚硝酸盐含量,亦以高灌水水平处理(1.00θf处理)为最低。采摘后油菜植株体硝酸盐和亚硝酸盐含量都经历一个先降低、后升高、再降低的变化过程。因此,从对人体健康及卫生的角度出发,以较高灌水水平栽培油菜,采摘后在一两天内食用,有利于将其硝酸盐和亚硝酸含量控制在较低水平。     

村镇生活垃圾焚烧底渣农用的重金属污染风险评价

随着生活垃圾焚烧处理方式的不断推广,生活垃圾焚烧底渣的处置也成为一个日益严峻的问题。为了明确生活垃圾底渣农用的可行性,于2014年在江苏常熟农业生态实验站进行了小白菜(Brassica rapa L.Chinensis Group.)盆栽试验,各施肥处理土壤中分别添加底渣的比例为0%、5%、10%、20%、50%、100%,以不施肥处理和单施底渣(10%)处理为对照。于小白菜收获时,取样分析小白菜产量、品质,以及小白菜和土壤中Cd、Cr、Cu、Ni、Pb、Zn含量,并采用内梅罗综合污染指数法和目标危害系数法评价了底渣农用的重金属污染风险。结果表明,施用适量的底渣可以有效增加小白菜产量,亦增加了小白菜中可溶性糖、维生素C和硝酸盐含量,并且硝酸盐含量未超过中国无公害蔬菜安全要求;小白菜地上部重金属含量和土壤重金属含量在不同处理中均随底渣施用比例的增加而增加,且底渣施用量超过12.2%时,土壤内梅罗综合污染指数大于1,土壤呈轻度重金属污染,底渣施用量超过15%时,小白菜地上部重金属Cr含量超过中国食物污染物的限量标准;小白菜单一重金属目标风险系数在不同处理中均小于1,而底渣用量大于或等于10.7%时小白菜重金属复合目标风险系数大于1,存在食用健康风险,健康风险以Pb、Cd为主,并且儿童更易遭受小白菜重金属危害。因此,在保证小白菜产量、品质和土壤安全下,底渣一次性安全施用比例不能超过10%。     

水分和氮素供应对菠菜硝酸盐累积和钾素吸收的影响

研究了水分和氮素供应对露地秋菠菜的硝酸盐累积和钾、氮吸收的影响。结果表明：与传统的水氮管理措施相比，采用水分平衡法和氮素专家系统进行的水氮供应并没有造成作物减产，但对钾、氮元素的吸收却有明显的影响，同氮素吸收相比，作物对钾素的吸收数量更高；并且作物对钾、氮的吸收比例随氮素供应水平的增加而降低，试验还动态监测了菠菜最新展开叶的叶柄汁液中的硝酸盐和K^ 浓度在一天内的变化情况。结果表明，不同水氮处理的菠菜叶柄汁液的硝酸盐浓度在白天均没有发生显著变化；叶柄汁液中的K^ 浓度和NO3^-／K^ 的浓度比在白天受氮素供应水平的影响很大，供氮量高，K^ 浓度和NO3^-／K^ 浓度比的变化也大，但受灌水量影响不大。图3表2参17。     

灌淤土施氮后土壤硝态氮的动态变化

通过室内模拟试验,探讨不同水分条件下灌淤土施用不同氮肥后硝态氮随时间的变化规律,并在田间条件下,测定不同氮肥形态和数量对土壤硝态氮含量的影响。灌淤土施氮后土壤硝态氮含量变化与土壤含水量及氮肥种类有关。施肥9d后,土壤中的硝态氮迅速增加;土壤水分低于田间持水量的50%或水分过饱和都明显影响灌淤土的硝化作用;施用大颗粒尿素产生的硝态氮最少,淋失或流失的几率小。灌淤土土体中硝态氮的残留与施氮种类及数量有直接关系。施肥使土壤表层硝态氮显著增加,施用大颗粒尿素尤为突出,但施大颗粒尿素后,60cm土体中残留的硝态氮总量最少。随着施氮量增加,表层土体中硝态氮含量增加。合理的施肥水平一般不会造成硝态氮的大量累积,而过量施氮则导致硝态氮明显积累,对通气透水性好的灌淤土,容易造成硝态氮淋失。     

Effects of nitrate concentration on biological hydrogen production by mixed cultures

The effects of nitrate on fermentative hydrogen production and soluble metabolites from mixed cultures were investigated by varying nitrate concentrations from 0 to 10 g N/L at 35°C with an initial pH of 7.0. The results showed that the substrate degradation rate, hydrogen production potential, hydrogen yield, and average hydrogen production rate initially increased with increasing nitrate concentrations from 0 to 0.1 g N/L, while they decreased with increasing nitrate concentrations from 0.1 to 10 g N/L. The maximum hydrogen production potential of 305.0 mL, maximum hydrogen yield of 313.1 mL/g glucose, and maximum average hydrogen production rate of 13.3 mL/h were obtained at a nitrate concentration of 0.1 g N/L. The soluble metabolites produced by the mixed cultures contained only ethanol and acetic acid (HAc) without propionic acid (HPr) and butyric acid (HBu). This study used the Modified Logistic model to describe the progress of cumulative hydrogen production in batch tests. A concise model was proposed to describe the effects of nitrate concentration on average hydrogen production rate.     

Effect of nitrogen supply on nitrogen uptake,accumulation and assimilation in Porphyra perforata (Rhodophyta)

Porphyra perforata J. Ag. was collected from a rocky land-fill site near Kitsilano Beach, Vancouver, British Columbia, Canada and was grown for 4 d in media with one of the following forms of inorganic nitrogen: NO ₃ ^- , NH ₄ ⁺ and NO ₃ ^- plus NH ₄ ⁺ and for 10 d in nitrogen-free media. Internal nitrogen accumulation (nitrate, ammonium, amino acids and soluble protein), nitrate and ammonium uptake rates, and nitrate reductase activity were measured daily. Short initial periods (10 to 20 min) of rapid ammonium uptake were common in nitrogen-deficient plants. In the case of nitrate uptake, initial uptake rates were low, increasing after 10 to 20 min. Ammonium inhibited nitrate uptake for only the first 10 to 20 min and then nitrate uptake rates were independent of ammonium concentration. Nitrogen starvation for 8 d overcame this initial suppression of nitrate uptake by ammonium. Nitrogen starvation also resulted in a decrease in soluble internal nitrate content and a transient increase in nitrate reductase activity. Little or no decrease was observed in internal ammonium, total amino acids and soluble protein. The cultures grown on nitrate only, maintained high ammonium uptake rates also. The rate of nitrate reduction may have limited the supply of nitrogen available for further assimilation. Internal nitrate concentrations were inversely correlated with nitrate uptake rates. Except for ammonium-grown cultures, internal total amino acids and soluble protein showed no correlation with uptake rates. Both internal pool concentrations and enzyme activities are required to interpret changes in uptake rate during growth.     

Nitrate reductase and glutamine synthetase activity,internal N pools,and growth of<Emphasis Type="Italic"> Ulva lactuca</Emphasis>: responses to long and short-term N supply

Fast-growing macroalgae, including Ulva lactuca Linnaeus, respond rapidly to changes in nutrient conditions, particularly to short-term N supply. This ability to rapidly take up and assimilate N contributes to the increasing occurrence of macroalgal blooms in heavily N loaded coastal ecosystems. To determine whether long-term nutrient histories affect short-term responses in activity of N-assimilating enzymes, including nitrate reductase (NRA) and glutamine synthetase activity (GSA), internal N storage, and macroalgal growth, we conducted an in situ nitrate fertilization experiment between 7 and 22 July 2004, with fronds of U. lactuca collected from estuaries with high and low N loads in Waquoit Bay, Cape Cod, Massachusetts, USA (N 41° and W 70°). Initial NRA, GSA, % N, δ¹⁵N, and growth of U. lactuca fronds were higher in the site where nitrate was in high supply. Differences in NRA persisted even after short-term experimental enrichment. Differences in internal N pools, δ¹⁵N, and growth, in contrast, mirrored the changes of nutrient supply. The rate of turnover of the internal N content of U. lactuca was quite short (<2 d), and turnover of enzyme activity may have been even shorter. N isotopic fractionation by U. lactuca appeared to be of small magnitude, unlike the case of phytoplankton, and similar to that of vascular plants. δ¹⁵N was a better indicator of short-term response to external and internal nutrient supplies in U. lactuca than enzyme activity or N content, and may reliably detect rapid changes in N availability, source, and uptake and assimilation processes.     

Combined effects of enhanced ultraviolet-B radiation and mineral nutrients on growth, biomass accumulation and yield characteristics of two cultivars of Vigna radiata L

In a field experiment, the effect of enhanced UV-B radiation (simulating 20% ozone depletion at Allahabad, 20 degrees 47' N latitude) was studied on two cultivars of Vigna radiata L. with various levels of mineral nutrients (N and P). Study showed decrease in total biomass accumulation, harvest index, RSR and yield after exposure with enhanced level of UV-B. RGR and CGR also showed decline after exposure with UV-B. Application of recommended dose of mineral nutrients alleviated the deleterious effect of UV-B and increased plant dry matter vis a vis yield. Both cultivars showed sensitivity to UV-B but cultivar Malviya Janpriya was more responsive to UV-B than Malviya Jyoti.     

Effects of nitrate on the diurnal vertical migration,carbon to nitrogen ratio,and the photosynthetic capacity of the dinoflagellate Gymnodinium splendens

A non-thecate dinoflagellate, Gymnodinium splendens, was studied in a 12 d laboratory experiment in 2.0x0.25 m containers in which light, temperature, and nutrients could be manipulated. Under a 12 h light: 12 h dark cycle, the dinoflagellates exhibited diurnal vertical migrations, swimming downward before the dark period began and upward before the end of the dark period. This vertical migration probably involved geotaxis and a diel rhythm, as well as light-mediated behavior. The vertical distribution of nitrate affected the behavior and physiology of the dinoflagellate. When nitrate was present throughout the container, the organisms resembled those in exponential batch culture both in C:N ratios and photosynthetic capacity (P_max); moreover, they migrated to the surface during the day. In contrast, when nitrate was depleted, C:N ratios increased, P_max decreased, and the organisms formed a subsurface layer at a depth corresponding to the light level at which photosynthesis saturated. When nitrate was present only at the bottom of the tank, C:N ratios of the population decreased until similar to those of nutrient-saturated cells and P_max increased; however, the dinoflagellates behaved the same as nutrient-depleted cells, forming a subsurface layer during the light period. Field measurements revealed a migratory subsurface chlorophyll maximum layer dominated by G. splendens. It was just above the nitracline during the day, and in the nitracline during the night, which concurs with our laboratory observations.     

两种菠菜累积硝酸盐特性差异的研究

水培试验结果表明,日本超能菠菜生长后期的生长量较大,硝酸盐累积量较低,氮素吸收量较少,可以肯定其优良性;在生长后期供给等量硝、铵态氮的条件下,日本超能菠菜吸收硝态氮较少,还原硝酸盐的相对能力又较高,因而累积硝酸盐较宁夏圆叶菠菜低;在仅供给铵态氮源的条件下,日本超能菠菜还原硝酸盐能力较小,可能与其易于吸收和利用铵态氮源有关。     

Seasonal variation in total and soluble tissue nitrogen of Pleurophycus gardneri (Phaeophyceae: Laminariales) in relation to environmental nitrate

Seasonal variations in tissue nitrogen (ethanol soluble nitrate and ninhydrin positive substances, as well as total nitrogen) of different thallus parts of Pleurophycus gardneri Setchell and Saunders were monitored simultaneously with ambient seawater nitrate from 1982 until 1984 in Bamfield, Vancouver Island, British Columbia, Canada. A trend of low, nearly zero levels in ambient nitrate typical for the area in late spring and early summer normally contrasts with average nitrate concentrations of 10 mol NO₃ ^- l^-1 in late fall and winter. Total nitrogen content was greater in the perennial thallus parts, stipe and holdfast than in the annual blade and peaked in fall and early winter. The longitudinal thallus distribution of nitrate revealed a distinct and significant concentration of nitrate in the haptera reaching at maximum 8% nitrate-N of the internal total nitrogen. Internal nitrate concentration ranged from 20 to 5 000 times the ambient nitrate concentration in the midrib, and from 40 to 3 100 times in the wing, while the range was greatest with 400 to 14 000 times in the haptera. P. gardneri contained at most about 7 mol NO₃ ^- g fresh wt^-1 in the blade, which corresponds to about 6% of total tissue nitrogen. Ninhydrin positive substances comprised the major portion of the soluble N pool in P. gardneri and showed a pronounced seasonality. Concentrations of ninhydrin positive substances ranged from 20 to 800 g N g fresh wt^-1 in the midrib and in the wing. In the stipe, ninhydrin positive substances varied from 180 to 2 200 g N g fresh wt^-1, and from 250 to 1 200 g N g fresh wt^-1 in the haptera. Evidence is given that (1) the perennial parts, stipe and haptera of P. gardneri contain the majority of nitrogen products independent of season and ontogenetic stage; (2) ninhydrin positive substances are the most abundant internal nitrogen constituents; (3) the low N values in the blade in summer suggest a nitrogen limited growth; and (4) nitrate may not be the predominant external nitrogen source.