The purpose of this study is to obtain the biocontrol bacteria to control the soft rot disease of Chinese cabbage.An antagonistic strain 26B was screened from 38 actinomycete strains isolated from the rhizosphere of Chinese cabbage by Oxford cup method.Strain 26B was identified as Streptomyces based on its morphological characteristics and its 16S rRNA gene sequence analyses.The cell free fermentation filtrate of strain 26B showed high antibacterial activity against Pectobacterium carotovorum subsp.brasiliensis BC1 and three casual bacteria of potato blackleg disease,and the antibacterial diameter against BC1 reached 23.97 mm.The germination assay by seed-soaking showed that the cell free fermentation filtrate of strain 26B significantly promoted the germination potential,germination index,root length and fresh weight of Chinese cabbage seeds.Effects of cell free fermentation filtrate of strain 26B on the inhibition of BC1-gfp colonized on the Chinese cabbage roots was examined by root-dipping method.The results showed that the number of BCl-gfp on cabbage roots reached 2.3×109 CFU/g after 48 hours’ incubation in the treatment with BCl-gfp suspension,while no BCl-gfp was detected on the cabbage roots treated with the premixed mixture of BCl-gfp suspension and sterilized fermentation filtrate of strain 26B at a volume ratio of 10%.The bioassay test in potting soil showed that the efficacy of cell free fermentation filtrate of strain 26B on the control of soft rot disease reached 96.0% and 89.8%,respectively,in soil with water content of 14% and 20%.The above results indicated that Streptomyces 26B has great potential to be applied as a biocontrol strain,and its biocontrol efficacy can be improved through coordinately management of soil water content.

通过对北京市2011—2021年微量元素水溶肥料的监测,分析北京市微量元素水溶肥料重金属含量和污染情况.结果表明,北京市微量元素水溶肥产品仍存在重金属含量超标问题.5个重金属元素的合格率均在90％以上,As和Cd的合格率最低,超标量最高;2015年和2017年的As和Cd元素Pi值超过1,达到了重污染程度.2011—2021年内梅罗综合污染指数P综分别是0.527、0.37、0.57、0.278、38.514、0.337、18.553、0.264、0.432、0.338、0.533,这说明自2017年之后重金属污染情况逐年趋于良好.

随着畜牧业集约化和规模化的发展,畜禽粪便产生量不断增加,畜禽粪肥还田利用率不断提高,但畜禽粪肥重金属污染问题日益突出.为防控畜禽粪肥的环境污染、促进养殖业废弃物安全利用和有机农产品的生产,以2012—2019年抽检的畜禽粪肥样品为主要研究对象,通过了解北京市畜禽粪肥中的Hg、As、Pb、Cr和Cd重金属含量情况,采用内梅罗综合污染指数评价法和Hakanson生态风险指数法评价其污染程度和潜在生态风险程度.结果表明,各类畜禽粪肥重金属的平均含量均在《畜禽粪便堆肥技术规范》的限量范围内,整体超标率较低;重金属综合污染指数均在安全范围内,农用还田利用不会引起严重重金属污染,但仍存在一定的潜在生态危害,尤其以羊粪中的Cd和农家堆肥中的Hg、Cd最为严重,达到强或很强生态风险污染程度.在今后畜禽粪肥的堆肥和无害化处理中,应加强管理,严防生态污染.

研究分析北京地区水溶肥料中的重金属元素,为农产品质量安全生产提供基础依据.对2012—2019年水溶肥料样品中Hg、As、Pb、Cr和Cd等有害元素进行调查统计,参照中国农业行业标准和内梅罗综合污染指数法进行分析与污染评价.结果表明,水溶肥料中Hg、As、Pb、Cr和Cd平均质量分数分别为0.04、3.8、3.9、4.3和1.2 mg·kg?1,均符合农业行业标准NY/T 1110—2010限量要求.水溶肥料样品中的Hg、As、Cr和Cd存在超标现象,As超标率为2.5％,Cd超标率为0.5％,超标情况为:As>Cd>Cr=Hg>Pb=0,超标现象主要分布在大量元素水溶肥料、微量元素水溶肥料和含腐殖酸水溶肥料中.5种重金属单因子污染指数均小于0.7,全部为清洁等级,其中As污染程度最高,其次是Cd;综合污染指数在0.11—0.51之间,全部为安全等级,微量元素水溶肥料综合污染程度最大,含氨基酸水溶肥料综合污染程度最小.总体而言,北京市水溶肥料重金属状况整体良好,环境污染风险较小,但同时应加强关注As和Cd在水溶肥料长期应用中的安全性问题.

本研究从实验室前期构建的粉红螺旋聚孢霉67-1寄生核盘菌转录组中获得1个差异表达的短链脱氢酶编码基因CrSdr.实时荧光PCR定量监测显示,菌核诱导下24 h时CrSdr基因的表达水平提高4倍.通过基因敲除与回补研究其功能结果表明,CrSdr敲除后对菌株的生长没有影响,但产孢量比野生菌株提高了43.2％,并且对NaCl、KCl和山梨醇引起的渗透压胁迫更为敏感.敲除突变株对番茄灰霉病菌、大豆菌核病菌和黄瓜枯萎病菌的拮抗作用明显减弱(P<0.05),对核盘菌菌核的寄生能力由野生型菌株的4级降为2级,温室对菌核病的防效降低了50.5％,基因回补后生防作用恢复,表明短链脱氢酶基因在粉红螺旋聚孢霉寄生及生防过程中起着重要的作用.本研究将为揭示粉红螺旋聚孢霉菌寄生机制奠定基础,并对高效植病生防真菌菌剂的研发具有一定的指导意义.

通过北京市2012—2019年的788个商品有机肥料样品检测,分析北京市商品有机肥料重金属含量状况和污染程度情况.结果表明,重金属Hg、As、Pb、Cr和Cd的含量差异和变异系数值均较大,平均值分别为0.3、8.0、11.5、53.9和0.3 mg/kg,均符合农业行业标准NY 525—2012有机肥料中重金属限量标准.近8年来重金属Hg、As、Pb、Cr和Cd含量整体呈下降趋势,分别下降了50.0％、21.2％、26.1％、48.1％和50.0％.5种重金属元素总体超标状况为As>Cr>Pb>Hg>Cd,超标率较低,合格率以2.4％/a的趋势增长.Cr每年都有超标,As仅有2017年未超标,As和Cr含量成为限制商品有机肥品质提高的关键因素.5种重金属单因子污染指数均小于1.0,全部为清洁等级范围.内梅罗综合污染指数P综除2016年在警戒线边缘(P综=0.75),其他全部为安全级别(P综≤0.7).因此,北京市商品有机肥重金属整体质量状况和污染程度发展趋势良好,但在施用过程中应注重控制使用量,防止环境污染的风险,尤其加强As和Cr元素防控.

京津冀协同发展是重大国家战略, 推动京津冀农业协同发展既是落实国家战略的必要举措, 也是增强区域发展活力的必然选择. 京津冀人口超过1亿,土地面积21.6万km2,三地农业发展各具特色,各有优势. 随着京津冀现代农业协同发展的不断加快,农业的规模化、集约化、现代化种植将越来越普遍, 肥料施用对三地现代农业产业化发展必将产生重要影响. 化肥施用不合理会引发日益严重的环境问题,对大气环境、土壤、水环境及农产品质量和人体健康等均产生严重影响[1],因此要高度重视化肥的施用,以促进农业增效、保障我国农产品质量安全和经济稳定发展.

随着我国农业进入高产、优质、高效、生态与安全阶段,促进农民增收、农业增效成为农业发展的主旋律,随之新型肥料应用越来越广泛,产品进入快速发展的重要时期.在新环境下,制约新型肥料产业发展的重要问题就是如何做好新型肥料的推广应用工作.基于此,从新型肥料应用现状出发,分析新型肥料推广应用过程中存在的问题,并提出新型肥料的推广策略.

为了明确土壤调理剂在改良设施土壤理化性状及增加作物产量方面的作用,确定土壤调理剂产品的最佳施用量,便于在农业生产中的应用推广,笔者研究了土壤调理剂对设施菜田(以北京市房山区为例)土壤性状及农作物生产的影响.结果表明:施用土壤调理剂对提高设施土壤田间持水量、土壤阳离子交换量及番茄产量作用明显,土壤调理剂施用量与土壤田间持水量、阳离子交换量及番茄产量的关系分别可以用方程y=-8×10-5x2+ 0.0329x+ 27.34(R2=0.958),y=-0.0004x2+0.0639x+ 16.39(R2=0.9344)和y=-0.004 1x++0.5155x+77.725(R2=0.9877)拟合.土壤调理剂施用量60～75 L/hm2对改善土壤理化性状、增加番茄产量最优.

为了探讨氮肥种类和用量对土壤无机氮及土壤有效态镉含量的影响,采用恒温培养的方法,研究不同尿素用量及硫酸铵、硝酸钙、控释尿素和双氰胺(硝化抑制剂,简称DCD)对土壤镉氮含量变化的影响差异.结果表明,高施氮量的尿素处理具有较高的铵态氮和硝态氮含量.DCD能明显抑制硫酸铵的硝化作用.控释尿素通过自身包膜的作用,减缓了尿素向铵态氮和硝态氮转化的趋势.氮素施入土壤后,在微生物的作用下,会发生水解反应和硝化反应,使土壤pH发生变化,从而使土壤中有效态镉含量升高或降低.

Effect of water-soluble chitosan fertilizer application on the growth and yields of watermelon was studied by apply-ing chitosan water-soluble fertilizer in different ways and in different dosage in greenhouse. Two kinds of application methods were set with 4 level for each method. The eight treatments, were sprayed with water, sprayed with chitosan which be dilu-ted 1 000 times, 500 times and 250 times, drip irrigation water, drip irrigation 450 mL/hm2 every time, 900 mL/hm2 ev-ery time and 1 800/hm2 every time. Every treatment was repeated three times. The results showed that after 35 days plant-ing, chlorophyll, stem diameter, number of leaves and stem length of watermelon for the sprayed with chitosan treatments were significantly greater than those for spraying water treatment. The highest chlorophyll content and the maximum length of the main stem occurred in the treatment sprayed with chitosan diluted 250 times, with the value of 65. 90 and 80. 73 cm, re-spectively. After 50 days watermelon planting, there was no significant difference. Application of water-soluble chitosan fertilizer could significantly increase the yield of watermelon, and spraying was better than drip irrigation. The highest yield of watermelon was 49 550 kg per hectare, which was drip irrigated 1 800 mL/hm2 every time water-soluble chitosan. Whether spraying or drip irrigation, water soluble chitosan were able to significantly increase watermelon sugar content. Ac-cording to the test results, the spraying pattern method was better than drip irrigation. In summary, the application of wa-ter-soluble chitosan fertilizers could significantly improve the growing of watermelon, sugar content and yield, and spraying was recommended as the better method.

A reliable high performance liquid chromatography-tandem mass spectrometric(HPLC-MS/MS) method has been developed for determination of eight plant growth regulators [ diethyl aminoethyl hexanoate(DA-6),betaine, chlormequat chloride, avermectin, forchlorfenuron, sodium nitrophenolate, sodium a-naphthyl acetate, and gibberellic acid] in watersoluble fertilizers. In this study, the content of analytes was determined by high performance liquid chromatography-tandem mass spectrometry and calculated by external standard method. Multiple reaction monitoring mode was utilized. Diethyl aminoethy hexanoate,betaine, chlormequat chloride, avermectins and forchlorfenuron were scanned in positive ion mode and sodium nitrophenolate, sodium a-naphthyl acetate, gibberellic acid were scanned in negative ion mode. Average recoveries of the eight analytes ranged from 91. 7% to 102. 2% at three spiking levels. Relative standard deviations were between 1.5% and 7. 5%. The method detection limits of DA-6, betaine, chlormequat chloride, avermectins, forchlorfenuron, sodium 4-nitrophenolate, nitroguaiacolsodiumsalt were 2 mg/kg, and the method detection limits of sodium a-naphthyl acetate were 2. 5 mg/kg, and the method detection limits of sodium 2-nitrophenolate,gibberellic acid were 20 mg/kg. The result showed that the method is convenient, fast, safe, with good reproducibility, and can be used to simultaneously and quickly confirm the content of plant growth regulators in water-soluble fertilizers.