土壤-蔬菜系统中Cd与硝酸盐复合污染研究现状

阐述了土壤-蔬菜系统中Cd与硝酸盐的主要来源、污染现状,介绍了当前土壤-蔬菜系统中氮污染、Cd污染、Cd与硝酸盐复合污染及不同污染因子的复合污染研究现状,并在此基础上提出了对今后研究发展方向的看法。     

马齿苋营养成分及硝酸盐含量的测定

[目的]分析马齿苋的营养成分和食用安全性。[方法]通过国标法对野生马齿苋可食嫩茎叶的主要营养成分、氨基酸、维生素、硝酸盐和亚硝酸盐含量进行测定并将其与常见栽培蔬菜进行比较。[结果]马齿苋的水分、粗蛋白、粗脂肪、总糖、膳食纤维和灰分含量分别为88．9％、2．8、0．6、3．2、5．6和1．4g／100g。除总糖含量外,马齿苋中其余主要营养成分的含量均高于对比蔬菜。马齿苋的氨基酸总量为22．23mg／g,必需氨基酸总量为8．99mg／g,天冬氨酸含量高达3．24mg／g。马齿苋的β-胡萝卜素和抗坏血酸含量高于对比蔬菜,分别为1996μg／100g和24．2mg／100g。马齿苋的矿质元素含量普遍高于对比蔬菜,其钾和铁的含量分别为340．0和2．1mg／100g．铅和镉的含量仅分别为0．08和0．12mg／kg。马齿苋的硝酸盐和亚硝酸盐含量分别为891．80和0．11mg／kg。[结论]马齿苋是一种安全可食、具有绿色营养和医疗保健功能的野生蔬菜。     

蔬菜硝酸盐累积的影响因子及其防治措施

介绍了蔬菜硝酸盐累积现状,概述了蔬菜种类、品种、不同部位的累积特征的内因,以及施肥、光照、水分、收获时期等外因影响蔬菜对硝酸盐吸收及其硝酸盐的变化动态,进而提出了农艺措施的改进、环境因子的调节和蔬菜新品种的培育等降低蔬菜硝酸盐累积的对策,为降低蔬菜硝酸盐含量的研究提供参考。     

棉花合理施用氮肥及其生理指标的研究初报

 硝酸还原酶（Nitrate reductase，简称NR，下同）是氮素同化的关键酶，与植物对无机氮的利用有着密切的关系。我们在棉株不同生育期分析了棉株顶端下第四片主茎叶的NR活力。结果表明，在蕾期NR活力最高，花铃期急剧下降。NR活力与棉株生长呈正相关。增施氮肥可以提高NR活力。在合理施用氮肥下，蕾期棉株叶片的NR活力在0.2-0.4μmol NO#-2/30分·克鲜重范围，棉株生长正常，而氮肥施用不当，叶片酶活力过高或过低，则导致棉株徒长或早衰。NR活力可作为棉花氮素营养诊断的生理指标。     

Nitrate reduces the detrimental effect of potassium chlorate on longan (Dimocarpus Longan Lour.) trees

A recent finding that potassium chlorate induces longan (Dimocarpus Longan Lour.) flowering at any seasons has led to wide use of this chemical in longan industry for off-season harvest, despite the risk of injury to the tree. In this paper, we examined the influences of pretreatment of nitrate by foliar spray with 3% potassium nitrate on the responses of potted longan (Dimocarpus longan Lour.) cv. Shixia (a subtropical ecotype) trees to soil applications of potassium chlorate at 10 and 20 g plant⁻¹. Chlorate treatments caused severe leaf drop and chlorophyll breakdown and suppressed budbreak, flowering and shoot growth. Pretreatment of potassium nitrate reduced the severity of leaf drop and chlorophyll breakdown caused by chlorate but the extend was less significant in high dosage chlorate (20 g plant⁻¹) treatment than low dosage (10 g plant⁻¹) chlorate treatment. Potassium nitrate did not alleviate the suppression effect of chlorate on budbreak, flowering and shoot growth, although it promoted these processes per se. Chlorate treatment resulted in only a transient accumulation of chlorate in the leaves, which peaked around 14 days after chlorate treatment (DACT), while chloride accumulated constantly within 28 DACT. Pretreatment of potassium nitrate tended to promote chlorate accumulation but did not cause a significant change in chloride accumulation. Severity of leaf drop was not significantly correlated to chlorate accumulation but significantly to chloride accumulation, suggesting that toxicity of chlorate to longan tree was realized during the chloride-producing process of chlorate reduction. Nitrate influenced the correlations between severity of leaf drop and chloride accumulation by reducing the slopes of the regressed lines of leaf drop versus chloride, indicating that nitrate reduced the sensitivity of longan trees to the toxic intermediates produced during chlorate reduction. The results indicate that the application rates were excessive for potted trees. The potential benefit of potassium nitrate in a longan production system based on application of chlorate needs to be evaluated in field trees.     

An automated method for the measurement of methaemoglobin in avian blood

An automated method has been developed for the measurement of methaemoglobin (metHb) in blood using a biochemistry analyser. The method was validated using blood collected from red-legged partridges exposed in vitro to increasing concentrations of nitrite in order to obtain different percentages of metHb. Results obtained using the original manual method and those using the new automated technique were compared and no significant differences were found. Intra-day and inter-day variabilities (8.8% and 2.6%, respectively) were acceptable for samples containing high levels (63-81%) of metHb. Methaemoglobin measured in blood samples stored in liquid nitrogen was stable for 10 days, but increased significantly by day 20 in nitrite-treated samples.     

施肥对蕹菜生长及品质的影响

在褐土上采用盆栽试验研究了鸡粪、包衣尿素、素、硝铵4种肥料对蕹菜硝酸盐累积以及其他品质指标的影响，结果表明，在低量施氮下，鸡粪处理表现缺氮症状，长势不及等氮量的尿素处理，在中量施氮情况下，蕹菜长势为：鸡粪，包衣尿素＞硝铵＞尿素。在硝酸盐指标上，施用等量鸡粪可以明显降低其含量；在中量施氮情况下，植株的硝酸盐含量为：尿素＞硝铵、包衣尿素＞鸡粪；随着施氮量的增加，植株硝酸盐呈增加趋势，以尿素处理增加更为明显。鸡粪的施用量增加有利于提高蕹菜的Vc有可溶糖含量，但尿素素处理没有表现出类似的结果：在中量氮素投入情况下，硝铵及包衣尿素处理的Vc含量相对较高、中、高量化学氮肥施用显著地促进了土壤无机氮累积，其中又以尿不处理累积为甚，包衣尿素累积量较少，因此在生产中鸡粪或化学氮施肥用量的合理控制是蔬菜施肥中一项非常重要的工作。     

秸秆还田条件下适量施氮对冬小麦氮素利用及产量的影响

2011—2012和2012—2013年生长季,通过田间定位试验,研究了秸秆还田配施氮肥对冬小麦干物质积累、氮效率、土壤硝态氮积累及产量的影响。与单施氮肥(对照)相比,秸秆还田显著提高冬小麦全生育期干物质积累总量,降低开花前干物质积累量及其占全生育期比例;秸秆还田配施纯氮225 kg hm–2处理的氮肥偏生产力、氮素利用效率、氮素收获指数分别提高7.5%、6.4%和5.2%。秸秆还田显著降低了不同土层硝态氮积累量,尤其是0~30 cm和30~60 cm土层。秸秆还田配施纯氮225 kg hm–2的产量最高,且显著高于其他处理,增产幅度最大,因此可作为当地秸秆还田模式下适宜推荐的施氮量。     

水氮耦合对甜瓜氮素吸收与土壤硝态氮累积的影响

在西北干旱半干旱地区,设置3个水分水平和3个氮素水平,共9个处理,应用完全随机区组试验设计,研究不同水氮处理组合对温室甜瓜氮素吸收分配、产量及土壤硝态氮分布和累积的影响。试验结果表明:甜瓜成熟期地上部干物质量以及氮素累积量以中水中氮(W2N2)处理为最大,甜瓜采收后各处理硝态氮含量在0~15 cm土层内最高,随土层的加深硝态氮含量逐渐减小。0~60 cm土层内硝态氮累积量随施氮量的增加而增大,随灌水量的增加而减小。甜瓜产量随灌水量和施氮量的增加而提高,但是在高水和高氮条件下略有下降。滴灌施肥的施氮量和灌水量控制在N2(130 kg/hm2)和W2(1.0ETc)时,有利于提高甜瓜产量,是试验地区膜下滴灌条件下温室甜瓜生产中适宜的水氮组合。     

Identification of irrigation and N management practices that contribute to nitrate leaching loss from an intensive vegetable production system by use of a comprehensive survey

Considerable NO₃⁻ contamination of underlying aquifers is associated with greenhouse-based vegetable production in south-eastern Spain, where 80% of cropping occurs in soil. To identify management factors likely to contribute to NO₃⁻ leaching from soil-based cropping, a survey of irrigation and N management practices was conducted in 53 commercial greenhouses. For each greenhouse: (i) a questionnaire of general irrigation and N management practices was completed, (ii) amounts of N applied in manure were estimated; and for one crop in each greenhouse: (a) irrigation volume was compared with ETc calculated using a mathematical model and (b) total amount of applied fertiliser N was compared with crop N uptake. Total irrigation during the first 6 weeks after transplanting/sowing was generally excessive, being >150 and >200% of modelled ETc in, respectively, 68 and 60% of greenhouses. During the subsequent period, applied irrigation was generally similar to modelled ETc, with only 12% of greenhouses applying >150% of modelled ETc. Large irrigations prior to transplanting/sowing were applied in 92% of greenhouses to leach salts and moisten soil. Volumes applied were >20 and >40 mm in, respectively, 69 and 42% of greenhouses. Chemical soil disinfectants had been recently applied in 43% of greenhouses; associated irrigation volumes were >20 and >40 mm in, respectively, 78 and 48% of greenhouses conducting disinfection. Nitrogen and irrigation management were generally based on experience, with very little use of soil or plant analysis. Large manure applications were made at greenhouse construction in 98% of greenhouse, average manure and N application rates were, respectively, 432 m³ ha⁻¹ and 3046 kg N ha⁻¹. Periodic manure applications were made in 68% of greenhouses, average application rates for farmyard and pelleted manures were, respectively, 157 and 13 m³ ha⁻¹ (in 55 and 13% of greenhouses); the average N rate was 947 kg N ha⁻¹. Manure N was not considered in N fertiliser programs in 74% of greenhouses. On average, 75% of fertiliser N was applied as NO₃⁻. Applied fertiliser N was >1.5 and >2 times crop N uptake in, respectively, 42 and 21% of crops surveyed. The survey identified various management practices likely to contribute to NO₃⁻ leaching loss. Large manure applications and experiential mineral N management practices, based on NO₃⁻ application, are likely to cause accumulation of soil NO₃⁻. Drainage associated with: (i) the combined effect of large irrigations immediately prior to and excessive irrigations for several weeks following transplanting/sowing and (ii) large irrigations for salt leaching and soil disinfection, is likely to leach accumulated NO₃⁻ from the root zone. This study demonstrated that surveys can be very useful diagnostic tools for identifying crop management practices, on commercial farms, that are likely to contribute to appreciable NO₃⁻ leaching.