Investigations on Nitrate Pollution of Soil, Groundwater and Vegetable from Three Typical Farmlands in Beijing Region, China

The aim of this study was to determine the nitrate pollution status of soil, groundwater, and vegetable from three typical farmlands （croplands, vegetable fields, and orchards） in Beijing region. During the investigation, hundreds of the soil, groundwater, and vegetable samples from three typical farmlands were collected and analyzed. In addition, attributes of all samples were recorded for data analysis. The results showed that nitrate was substantially accumulated in soil profiles, while the soil nitrate concentrations of vegetable fields and orchards were higher than those of croplands. Nitrate concentration in 0-30 cm soil of vegetable field and orchard were 3.8 and 1.2 times of that of cropland, respectively. Nitrate content of groundwater in vegetable field was 13.8 mg L-1 （with the over-standard ratio 44.8%）, which was 2.8 folds of that in cropland. Nitrate concentration of groundwater under orchard was 9.3 mg L-1 （with the over-standard ratio 23.5%）, which was 1.9 folds of that in cropland. High concentrations of the nitrate in vegetables were detected, particularly green leafy vegetables ranked first with 2 685.5 mg kg-1, followed by rhizome vegetables, cabbages, and fruit vegetables. The nitrate over-standard ratios of rhizome vegetables, green leafy vegetables, fruit vegetables, and cabbages were 80.9, 37.9, 29.7, and 2.2%, respectively. The results revealed that the high nitrate concentrations of soil, vegetable, and groundwater might result from the high fertilization dose.

Accumulation of Nitrate in Vegetables and Its Possible Implications to Human Health

In recent times, there are two kinds of completely opposite viewpoints about the impacts of nitrate on human health. To further objectively understand the effects of nitrate on human health, both of harmfulness and possible benefits of nitrate to human body., it is discussed in this review from the aspects of nitrate accumulation in vegetables, the source of nitrate ingested into human body, and the transformation of nitrate in human body, as well as the pathogenesis and physiological functions of nitrate metabolism.

Effects of N Forms and Rates on Vegetable Growth and Nitrate Accumulation

Experiments were carried out on a vegetable field with Peking cabbage(Brassica pekinensis (Lour.) Rupr.), cabbage (Brassica, chinensis var. oleifcra Makino and nemoto),green cabbage (Brassica chinensis L.), spinach (Spinacia oleracea L.) and rape(Brassica campestrisL.) to study the effects of N forms and N rates on their growth and nitrate accumulation. Theresults indicated that application of ammonium chloride, ammonium nitrate, sodium nitrate and ureasignificantly increased the yields and nitrate concentrations of Peking cabbage and spinach.Although no significant difference was found in the yields after application of the 4 N forms,nitrate N increased nitrate accumulation in vegetables much more than ammonium N. The vegetableyields were not increased continuously with N rate increase, and oversupply of N reduced the plantgrowth, leading to a yield decline. This trend was also true for nitrate concentrations in somevegetables and at some sampling times. However, as a whole, the nitrate concentrations in vegetableswere positively correlated with N rates. Thus, addition of N fertilizer to soil was the major causefor increases in nitrate concentrations in vegetables. Nitrate concentrations were much higher inroots, stems and petioles than in blades at any N rate.

Effects of Different Preservation Methods on Vitamin C and Nitrate Content in Vegetables

This paper studied and compared the effects of three preservation methods( normal temperature 20℃,fresh-keeping box cold storage 4℃,and fresh-keeping box + fresh-keeping film cold storage 4℃) on six kinds of vegetables. The results showed that the content of vitamin C in the six vegetables was higher in cold storage than in normal temperature storage; the nitrate content was lower in cold storage than in normal temperature storage. In both the normal temperature storage and cold storage,the vitamin C in vegetables declined with the increase of the storage time,while the nitrate content increased with the increase of the storage time. Thus,cold storage has better fresh-keeping effect for vegetables. In cold storage conditions,the vitamin C content was higher in vegetables packaged by fresh-keeping box,and the nitrate content was lower,followed by the fresh-keeping film + fresh-keeping box cold storage. In conclusion,the best preservation method for vegetable is fresh-keeping box cold storage.

Effects of Cooking and Processing Methods on Nitrate Content in Leafy Vegetables

[Objectives]The aim is to provide a theoretical basis for people to store and process vegetables more scientifically.[Methods]Changes in the nitrate content of three kinds of leafy vegetables (cabbage,lettuce and celery) cooked and processed by different methods were studied.[Results]After the three kinds of leafy vegetables were processed by different methods,the nitrate and vitamin C content of the leafy vegetables reduced,and their reduction was above 50% after they were boiled.After they were salted for 5 min,nitrate content decreased by 20%-40%,and changed slightly with time.Salting had a small effect on Vc content.After lettuce and celery were soaked in 0.05% NaCl solution for 30 min,the effect was the best.CaCl2 had an obvious effect on the reduction of nitrate content in lettuce.[Conclusions]The study is of great significance to safety production and evaluation of edible value of agricultural products.

Impact of petroleum refining activities on nitrate and nitrite content of edible vegetables and on their <i>in vivo</i>kinetics in albino rats

The influence of pollution from petroleum refining activities on the levels of nitrates and nitrites in five edible vegetable species was investigated. Besides, the kinetics of nitrite and nitrate was studied in vivo using albino rats with focus on the possible influence of concentration difference on kinetics and implications to toxicity. Leaf samples of the five vegetable species were collected randomly from various locations within Eleme, a host community of Port Harcourt Refinery Company and the Indorama Petrochemical Company. Also, samples were collected from Umuahia, which served as pollution-free control. The leaf samples were analyzed for their nitrite and nitrate contents. Nitrite was determined spectrophotometrically while nitrate was determined after cadmium column reduction. Results showed that samples from Eleme had higher mean nitrate (349.20 mg/100g dry leaf mass;P 0.05) as compared to the same samples from Umuahia. Solutions of nitrate and nitrite, equivalent in concentration to mean nitrate and nitrite content of the vegetable samples from the two locations were administered enterally to four groups of albino rats. Analysis of their blood levels were monitored five times at 30 minutes intervals following administration. Rates of change of blood nitrites and nitrates were found to be fairly constant in absorption as well as in the elimination phase. Their peak blood concentrations varied proportionately with their concentrations in administered solutions. However, peak blood nitrate was attained later in group of animals receiving higher amount of nitrate solution. Refining activities may pre-dispose people living within Eleme community to health hazards through contamination of edible vegetables.

Effect of Intercropping and Nitrogen Regulation on Nitrate and Apparent Loss of Nitrogen in Soil

[Objective] The aim was to investigate effect of intercropping and nitrogen regulation on nitrate and apparent loss of nitrogen, providing theoretical references for reasonable fertilization and pollution reduction. [Method] In the research, deeprooted eggplants and shallow-rooted scallions were intercropped with nitrogen regulat- ed to study on effect of the cropping system on temporal and spatial changes of ni- trate nitrogen and apparent loss of nitrogen. [Result] When the fertilizers were re- duced, contents of nitrate were less in intercropped field than that in mono-cropped one, indicating that eluviation of nitrate would be blocked and nitrate accumulation would be lowered effectively by intercropped eggplants and scallions. With intercrop- ping adopted, the reduced fertilizers would lower nitrate content in soil, deep soil in particular, and nitrate was significantly lower than that fertilized with conventional quantity during vegetable growth period. In addition, nitrate accumulation in soil profiles was also significantly shorter in field applied with reduced fertilizers than that with conventional one. It was shown that intercropping and fertilizer reduction would both cut apparent loss of nitrate down in varying degrees. [Conclusion] The research lays basis for high production of vegetables, reasonable fertilization and pollution reduction.

Influence of Potassium Fertilization on Yield and Quality of Foliar Vegetable Crops

Over a period of two years , field experiments were conducted on four silty loam soils grown with foliar vegetable crops including Chinese cabbage (Brassica pekinensis Rupr., cv. Lu-Bai 3), autumn greens (B. chinensis L., cv. Piao-Geng-Bai), winter greens (B. var. rosularis Tsen et Lee, cv. You-Dong-Er), and summer greens (B. chinensis L., cv. Zao-Shu 5), respectively. Each experiment included one CK treatment without K, N and P fertilizers applied, and four treatments with from low to high doses, 0-300 kg hm-2 for Chinese cabbage, 0-150 kg hm-2 for autumn and winter greens and 0-180 kg hm-2 for summer greens, of K fertilizers in the form of sulfate of potash (SOP) applied together with N and P fertilizers. One treatment of K fertilizer in the form of muriate of potash (MOP) applied at high levels (150 or 180 kg hm-2) together with N and P fertilizers was included in the experiments of autumn, winter and summer greens , respectively, in order to compare the effects of SOP and MOP. The market yields of the tested crops increased significantly with the increasing rate of K application. The crops supplied with K fertilizers yielded more stably as the CV% of their yields decreased with the rate of K application. K fertilization increased not only K contents but also the amounts of N, P and K absorbed in shoots of autumn, winter and summer greens, which were statistically significantly correlated to their yields. It can also be found that potassium improved the quality of the foliar vegetable crops as their dry mater contents were generally increased and Vc contents obviously increased and nitrate contents markedly decreased. As compared to MOP, SOP was more effective on the yields and quality of autumn, winter and summer greens at the high levels of fertilization.

Nitrogen/Ammonium Concentration Response of Vegetable and Flower Crops

Nitrogen （N） is the element with the greatest influence on the growth of vegetables and ornamentals, however, form of delivery, either as nitrate （NO3） or ammonium （NH4＋） has different effects on plant development. The NO3 is the main form of N that plants absorb, but when it is the only source of N that has slight effects on root growth, no effects over enzymatic activities, and stimulates the absorption and translocation of cations within the plant. The NH4＋ is the easiest way of assimilation but is highly toxic when the only source or with respect to the concentration of NO3 is too high. To avoid toxicity, the NH4＋ must not exceed 20% of the total N amount in the formulation, however, it is important to consider the species, variety and environmental conditions. The N as supplied also affects the resistance or susceptibility of plants to diseases, but depends on the species and the type of pathogen.

Quality Analysis of Five Edible Wild Vegetables in Chongqing

[Objectives]This study was conducted to analyze the quality of several kinds of wild vegetables in Yongchuan District,Chongqing City.[Methods]Five common edible wild herbs,Plantago asiatica,Taraxacum mongolicum,Pteridium aquilinum(L.)Kuhn var.latiusculum(Desv.)Underw.ex Heller,Brasenia schreberi and Houttuynia cordata in Yongchuan District,Chongqing,were tested for nitrate,amino acid,reducing sugar,and vitamin C contents.[Results]The vitamin C content was the highest in B.schreberi,reaching 1056 mg/kg,and the lowest in P.aquilinum var.latiusculum,at only 61 mg/kg.T.mongolicum had the highest reducing sugar(E value)and amino acid contents,at 1.01 and 24.3 mg/kg,respectively,and the values were the lowest in P.asiatica,at 0.15 and 9.1 mg/kg,respectively;and the nitrate contents ranked as H.cordata(2529 mg/kg)﹥B.schreberi(2188 mg/kg)﹥P.aquilinum var.latiusculum(1900 mg/kg)﹥P.asiatica(1097 mg/kg)﹥T.mongolicum(1079 mg/kg),which were at the level of medium to high pollution,but within the scope of the national acceptable daily intake(ADI).The nutritional value of wild vegetables is higher than that of vegetables grown in the field,but some wild vegetables are also toxic,which will have adverse effects on human health.[Conclusions]People need to develop and utilize wild vegetable resources scientifically and rationally according to their own needs.

Use of the Nitrogen Index to assess nitrate leaching and water drainage from plastic-mulched horticultural cropping systems of Florida

Water quality in Florida is significantly impacted by nitrate(NO_(3)-N)leaching losses from agriculture in a large part of the state.Horticultural crops are planted across large areas of Florida on coarse sandy soils with low soil water retention and soil organic matter,increasing the potential for NO_(3)-N leaching.Nitrate leaching losses from the root zone of vegetable cropping systems can negatively impact groundwater.New tools such as the Nitrogen Index(N-Index)are able to quickly assess N use efficiency and losses via NO_(3)-N leaching from agricultural systems.Furthermore,the N-Index provides technical information about N losses pathways tied to agricultural management practices with a great level of confidence;this information has been used by researchers,growers and policymakers as a decision support system.However,the current version of the NIndex that has been used for different field crops has not been calibrated to be used in plastic-mulched horticultural cropping systems.The aim of this work was to calibrate and validate the N-Index for plasticmulched horticultural cropping systems of Florida.This study found that the N-Index tool accurately identified and ranked the risk of N losses in the evaluated horticultural systems.The N-Index was calibrated for Florida's plastic-mulched horticultural cropping systems using a sensitivity analysis.The adjusted N-Index was validated using compiled data of vegetables grown under plastic mulching systems during three consecutive seasons.Results from these studies suggest that the N-Index can be an easy-to-use tool capable of assessing nitrogen management practices for vegetable systems.The tool can be used to guide nutrient managers in the implementation of best nitrogen management practices that could contribute to reduced NO_(3)-N leaching losses from vegetable systems in Florida,contributing to a smaller environmental footprint and conservation of water quality.

蔬菜中硝酸盐、亚硝酸盐残留状况及调控对策

硝酸盐和亚硝酸盐残留量是评价蔬菜等农产品安全的一个重要指标。在查阅国内外文献资料基础上,结合上海市蔬菜产品中硝酸盐、亚硝酸盐含量的检测结果,对蔬菜中硝酸盐和亚硝酸盐的危害、残留状况进行了梳理分析。对有机蔬菜和常规种植蔬菜、不同种类蔬菜、同一种类蔬菜不同品种、不同收获时间之间硝酸盐(亚硝酸盐)的残留差异与可能的原因进行了探讨,提出了科学施用氮肥等调控对策,并呼吁科研工作者加快开展蔬菜中硝酸盐(亚硝酸盐)生态减控综合技术集成研究及田间生产应用。

浓度直读法快速测定市售腌菜中的硝酸盐和亚硝酸盐含量

该研究探讨建立一种快速检测硝酸盐和亚硝酸盐含量的方法。结果表明,pH为2~6时,加入1 mL氨基磺酸溶液消除NO 2-的干扰,在此基础上,用浓度直读法测定5种市售腌菜中硝酸盐和亚硝酸盐含量,其亚硝酸盐含量在2.76~67.5 mg/kg之间,硝酸盐含量在37.58~149.7 mg/kg之间,回收率在91.0%~110.0%之间。与GB 5009.33-2016第二法相比,经F检验和t检验,二者结果之间无显著性差异。与国标法相比,该方法具有操作简单、无需进行复杂计算、测定速度快、仪器便于携带等优点,适用于腌菜中亚硝酸盐及硝酸盐含量的测定。

果菜秸秆生物炭吸附设施土壤硝态氮性能与机制研究

在农业生产中,过量偏施氮肥导致的硝酸盐富集是次生盐渍化、酸化等土壤障碍的重要诱因。生物炭因良好的吸附特性逐渐成为缓解盐渍化的土壤调理剂,但果菜秸秆生物炭对硝酸盐等离子的吸附研究鲜见报道。以甜椒、番茄和茄子3种果菜秸秆为原料热解制备生物炭,进行硝态氮吸附试验。通过扫描电镜(SEM)和傅里叶近红外光谱(FTIR)等技术对生物炭吸附前、后表面形貌、官能团等进行表征分析,利用吸附动力学模型和等温吸附模型等进行拟合分析,综合模型参数和形貌表征解析果菜秸秆生物炭的吸附性能和机制。研究结果表明,3种果菜秸秆生物炭对硝态氮均具有一定吸附能力,茄子秸秆生物炭吸附能力最强,最大理论平衡吸附量为114.788 mg/g,其次为番茄(29.736 mg/g)和甜椒(9.759 mg/g);茄子和甜椒秸秆生物炭吸附性能优于玉米、稻壳等大田作物秸秆生物炭,吸附过程符合准二级动力学模型,受化学键吸附、表面吸附和内扩散吸附过程的控制,番茄秸秆生物炭吸附过程符合准一级动力学模型,主要为物理吸附;FTIR分析显示,3种生物炭均含有羟基、甲基、亚甲基、羧基和羰基官能团,除此之外,甜椒和茄子秸秆生物炭还含有醚键,番茄秸秆生物炭含有醇羟基。因此,3种果菜秸秆生物炭对硝态氮均具有吸附能力,茄子秸秆生物炭吸附能力最强,受孔隙填充、官能团和络合作用等多种理化机制的影响,具有消减土壤次生盐渍化的潜力。本研究对盐渍化土壤修复和果菜秸秆资源化利用具有理论意义。

豫北蔬菜种植区浅层地下水硝酸盐来源及对强降雨事件的响应

我国北方蔬菜种植过程中大量施用化学肥料和人畜粪肥,引起区内浅层地下水硝酸盐(NO_(3)^(-))浓度急剧升高,但高浓度NO_(3)^(-)来源及在浅层地下水环境中转化的过程尚缺乏同位素证据,特别是强降雨事件对其影响尚不清楚。化学肥料中铵盐(NH_(4)^(+))转化为NO_(3)^(-)是造成蔬菜种植区浅层地下水中NO_(3)^(-)浓度升高的重要原因,强降雨事件导致浅层地下水水位升高,土壤和包气带中剩余NH 4+氧化为NO_(3)^(-)造成地下水NO_(3)^(-)浓度升高。为验证上述假设,选择豫北某蔬菜种植基地浅层地下水作为研究对象,通过对比分析枯水期(2021年4月)和丰水期(2021年10月)浅层地下水NO_(3)^(-)浓度及同位素组成(δ^(15)N-NO_(3)^(-)和δ^(18)O-NO_(3)^(-)),结合水化学以及水的氢氧同位素组成(δD-H_(2)O和δ^(18)O-H_(2)O),辨识浅层地下水高浓度NO_(3)^(-)来源及其对强降雨事件的响应。结果表明:(1)丰水期浅层地下水中ρ(NO_(3)^(-))范围较枯水期更大,中间值更高,分别为177.47和114.68 mg·L^(-1);(2)丰水期浅层地下水中δ^(15)N-NO_(3)^(-)和δ^(18)O-NO_(3)^(-)范围较枯水期更宽泛,δ^(15)N-NO_(3)^(-)中间值升高,丰水期和枯水期分别为7.8‰和7.3‰,但δ^(18)O-NO_(3)^(-)中间值降低,丰水期和枯水期分别为5.1‰和6.4‰;(3)丰水期浅层地下水δ^(18)O-H_(2)O范围较枯水期变窄,中间值升高,分别为-8.8‰和-9.2‰。氘盈余值(d_(e)=δD-8×δ^(18)O)范围变小,中间值降低,丰水期和枯水期分别为6.9‰和9.5‰;(4)强降雨洗脱包气带中富集15 N的NH_(4)^(+)转化为NO_(3)^(-),导致浅层地下水ρ(NO_(3)^(-))升高,δ^(15)N-NO_(3)^(-)值升高,但δ^(18)O-NO_(3)^(-)值降低;(5)贝叶斯同位素混合模型的解析结果表明,丰水期浅层地下水中NO_(3)^(-)来自于粪肥贡献率较枯水期增加,来自于土壤有机氮贡献率降低,化肥中铵态氮贡献率变化不大,但硝态氮肥贡献率增加,同时大气降水硝酸盐贡献率降低。研究结果证实,持续强降雨导致包气带中剩余的NH_(4)^(+)发生硝化作用,产生更多NO_(3)^(-)进入浅层地下水;同时降雨将地表粪肥NH_(4)^(+)转化来的NO_(3)^(-)携带进入浅层地下水。因此,需要加强蔬菜种植区肥料田间管理,做到有效使用肥料,避免过度施用肥料对浅层地下水水质的危害。

咀嚼时间对蔬菜中硝酸盐和亚硝酸盐含量变化的影响研究

目的以蔬菜(中青、芽白秧、生菜、油麦菜和包菜)为原料,探讨咀嚼时间对蔬菜所含硝酸盐和亚硝酸盐含量变化的影响。方法采用超声提取技术提取经志愿者咀嚼不同时间后各种蔬菜中的硝酸盐及亚硝酸盐,以盐酸萘乙二胺为显色剂,采用酶标仪测定两者的含量。结果咀嚼后的中青、芽白秧、生菜和油麦菜的硝酸盐含量达到最高值分别是咀嚼20、5、5和10 s,包菜的硝酸盐含量无显著性变化;咀嚼后蔬菜的亚硝酸盐含量均显著升高(P<0.05),不同蔬菜的亚硝酸盐含量达到最高值的咀嚼时间基本不同,其中中青和生菜的亚硝酸盐含量变化均呈先上升后下降的趋势,分别在20 s[(4.67±0.89)μg/kg]和15 s[(3.63±0.44)μg/kg]达到最高;芽白秧的亚硝酸盐含量则是先上升后下降又上升,在10s达到最高(4.09±0.57)μg/kg;油麦菜的亚硝酸盐含量在0~20 s不断升高到(6.42±0.70)μg/kg,在10~25 s过程中无显著性变化;包菜的亚硝酸盐含量则是不断上升,在25s达到最高[(3.48±0.48)μg/kg]。结论蔬菜因品种、种植条件及营养成分不同,其硝酸盐及亚硝酸盐含量皆不同,各自达到最高值的咀嚼时间也不尽相同,为了减少因摄入亚硝酸盐所带来的健康风险,建议对于烹饪手法采用焯水或水煮的蔬菜并不食用蔬菜汤,咀嚼方式上细嚼慢咽,咀嚼时间至少为10 s。

含腐殖酸液体肥(UAN型)在叶菜上的应用

为考察含腐殖酸液体肥(UAN型)在叶菜上的应用效果,以竞品液体肥为对照,以香叶饺子菜、上海青、生菜、菠菜为试验对象,开展了田间小区试验。结果表明:与对照处理相比,冲施含腐殖酸液体肥(UAN型)处理的4种叶菜的株高、地上部和地下部鲜质量均高于对照处理的;上海青和菠菜的叶片叶绿素相对含量(SPAD值)低于对照处理的,香叶饺子菜和生菜的叶片SPAD值高于对照处理的;4种叶菜的维生素C含量低于对照处理的,而硝酸盐含量高于对照处理的。

西安市设施菜地土壤硝态氮现状分析

摸清设施菜地土壤硝态氮现状对区域设施菜地氮素管理和设施蔬菜产业可持续性发展意义重大。采取大样本调研方法对西安市设施菜地土壤硝态氮现状进行全面分析评价。结果表明:(1)全市设施菜地土壤硝态氮含量平均值为55.22 mg/kg,丰缺等级属“中等”水平。(2)设施菜地土壤硝态氮含量区域分异较为明显,其中蓝田县设施菜地土壤硝态氮含量平均值最高(92.40 mg/kg),周至县设施菜地土壤硝态氮含量平均值最低(28.10 mg/kg)。(3)随着种植年限的增加,设施菜地土壤硝态氮含量总体呈现出降低趋势,其中1~5年的设施菜地土壤硝态氮平均值最高(57.67 mg/kg)。(4)设施菜地土壤硝态氮含量随土壤质地变化表现出明显的规律性,土壤质地越粗硝态氮含量越低,土壤质地越细硝态氮含量越高。(5)设施菜地土壤硝态氮仅与有效磷之间存在极显著的正相关性,与有机质、碱解氮、速效钾、pH、电导率等均无极显著相关性。综合来看,西安市设施菜地表层土壤暂不存在硝态氮过量累积问题,但在施肥管理过程中需注意降氮和平衡施肥。

海南典型稻菜轮作区和香蕉园氮磷盈余及土壤硝态氮累积

【目的】海南省是我国稻菜轮作和香蕉种植面积较大的省份,农户投入的氮(N)和磷(P)肥远超过了作物的养分需求,对海南生态环境可能造成不利影响。研究海南典型作物体系氮磷输入、输出、盈余及土壤硝态氮累积,为评价其养分损失及环境影响、提高养分管理水平提供科学依据。【方法】2021—2022年选取海南稻菜轮作和香蕉种植典型区域澄迈县为研究区,确定20个稻菜轮作田块和15个香蕉园。采用跟踪记录的方法获取所有地块的化肥施用量、有机肥施用量和秸秆还田方式及还田量等信息。采用跟踪采样的方法测定作物生物量及其养分含量。采用文献调研的方法获取研究区域土壤-作物体系养分沉降和生物固氮等其他来源数据。选取5个旱地香蕉园,采用土钻法采集土壤并测定0—400 cm土壤剖面硝态氮累积量。【结果】海南典型稻菜轮作区氮肥和磷肥投入量分别为1308 kg N·hm^(-2)(化肥和有机肥分别为975和333 kg N·hm^(-2))和515 kg P·hm^(-2)(化肥和有机肥分别为385和130 kg P·hm^(-2)),作物地上部吸氮量和吸磷量分别为248 kg N·hm^(-2)和48 kg P·hm^(-2),稻菜轮作区氮素和磷素盈余分别为1196 kg N·hm^(-2)和484 kg P·hm^(-2)。香蕉园氮肥和磷肥投入量分别为1340 kg N·hm^(-2)(化肥和有机肥分别为1293和47 kg N·hm^(-2))和447 kg P·hm^(-2)(化肥和有机肥分别为442和5 kg P·hm^(-2)),香蕉地上部吸氮量和吸磷量分别为242 kg N·hm^(-2)和23 kg P·hm^(-2),氮素和磷素盈余分别为1271 kg N·hm^(-2)和435 kg P·hm^(-2)。香蕉园0—400 cm土壤剖面硝态氮累积量为1131 kg N·hm^(-2)。【结论】过量施用氮肥和磷肥,导致海南典型区土壤-作物体系存在大量的养分盈余,旱地土壤也累积了大量的硝态氮。海南以较大的养分损失和环境代价生产热带高值水果和蔬菜,未来必须优化农田养分管理措施以保障其生态环境安全。

集约化养猪场粪污堆肥对菜地土壤污染的影响

[目的]评估集约化养猪场粪污堆制的有机肥在蔬菜种植应用中的土壤污染风险,进而为提高蔬菜产量和改善蔬菜品质,减少土壤污染提供科学依据。[方法]设计了4个等氮用量处理:CK:纯无机肥;M 1:有机肥(1/3)+无机肥(2/3);M 2:有机肥(2/3)+无机肥(1/3);M 3:纯有机肥,进行田间小区试验,研究了猪粪有机肥对蔬菜(茼蒿)地土壤理化性质和重金属含量的影响。[结果]各处理硝态氮(NO-3-N)含量从土壤表层到深层均表现为递减趋势,其主要分布在0—40 cm土层,高量有机肥的投入会引起土壤上层轻微的NO-3-N淋溶,但不会对地下水造成污染;施用有机肥可不同程度地增加土壤表层速效磷和水溶性磷的含量,存在一定的磷污染风险,对深层土壤无显著影响;施用有机肥后土壤和蔬菜中的重金属元素Cd,Pb,As,Hg,Cr及微量元素Cu的含量均在安全标准以内,未导致土壤重金属污染和蔬菜品质下降;随着有机肥施用量的增加,产量反而呈下降趋势,低量有机肥配施减量化肥(M 1),即可显著增加蔬菜产量。[结论]在菜地生产中建议采用化肥与适量有机肥配施,可促使蔬菜产量、品质提升和土壤污染防治等多目标协同实现。