Impacts of conservation agriculture on total soil organic carbon retention potential under an irrigated agro-ecosystem of the western Indo-Gangetic Plains

Sequestration of C in arable soils has been considered as a potential mechanism to mitigate the elevated levels of atmospheric greenhouse gases. We evaluated impacts of conservation agriculture on change in total soil organic C (SOC) and relationship between C addition and storage in a sandy loam soil of the Indo-Gangetic Plains. Cotton (Gossypium hirsutum L.) and wheat (Triticum aestivum L.) crops were grown during the first three years (2008–2011) and in the last year, maize (Zea mays L.), wheat and green gram (Vigna radiate L.) were cultivated. Results indicate the plots under zero tillage with bed planting (ZT-B) and zero tillage with flat planting (ZT-F) had nearly 28 and 26% higher total SOC stock compared with conventional tillage and bed planting (CT-B) (∼5.5 Mg ha⁻¹) in the 0–5 cm soil layer. Plots under ZT-B and ZT-F contained higher total SOC stocks in the 0–5 and 5–15 cm soil layers than CT-B plots. Although there were significant variations in total SOC stocks in the surface layers, SOC stocks were similar under all treatments in the 0–30 cm soil layer. Residue management had no impact on SOC stocks in all layers, despite plots under cotton/maize + wheat residue (C/M+ W RES) contained ∼13% higher total SOC concentration than no residue treated plots (N RES; ∼7.6 g kg⁻¹) in the 0–5 cm layer. Hence, tillage and residue management interaction effects were not significant. Although CT-B and ZT-F had similar maize aboveground biomass yields, CT-F treated plots yielded 16% less maize biomass than CT-B plots. However, both wheat and green gram (2012) yields were not affected by tillage. Plots under C/M + W RES had ∼17, 13, 13 and 32% higher mean cotton, maize, wheat and green gram aboveground biomass yields than N RES plots, yielding ∼16% higher estimated root (and rhizodeposition) C input in the 0–30 cm soil layer than N RES plots. About 9.3% of the gross C input contributed towards the increase in SOC content under the residue treated plots. However, ∼7.6 and 10.2% of the gross C input contributed towards the increase in SOC content under CT and ZT, respectively. Thus, both ZT and partial or full residue retention is recommended for higher soil C retention and sustained crop productivity.     

2016—2018年烟台苹果中杀菌剂残留及其膳食暴露风险分析

为了解烟台主产区苹果中杀菌剂残留状况,评估居民苹果来源杀菌剂膳食暴露风险,采用随机采样方法,2016—2018年每年10月于种植、贮存和流通环节共采集718份样本,进行18种杀菌剂检测。基于蒙特卡罗拟合计算危害指数,评估杀菌剂膳食暴露风险。结果表明,苹果中存在6种杀菌剂残留,检出率53.26%,3年检出率分别为38.43%、67.93%、38.43%,年度间差异显著(α=0.01);多菌灵最高40.39%,戊唑醇最低0.14%。6种杀菌剂残留量均值范围1.03~15.4 μg/kg,组间差异显著(α=0.05),戊唑醇、异菌脲、甲基硫菌灵、多菌灵各自最大残留量远小于最大残留限量(maximum residue limit,MRL),存在咪鲜胺和苯醚甲环唑超过MRL情况,超标率0.28%。6种杀菌剂共检出385频次,多菌灵最高290频次;同一样本存在多种杀菌剂残留,最多同一样本5种杀菌剂残留。各人群分组中,6种杀菌剂的日均膳食暴露量(estimated daily intake,EDI)各异,女性大于男性;未成年人组中,6种杀菌剂的EDI均值与年龄呈现负相关。除2~6岁组外,5种杀菌剂的膳食暴露风险商(hazard quotient,HQ)值远小于1;咪鲜胺HQ>1概率值各异,2~6岁风险概率值最大;多菌灵、苯醚甲环唑HQ>1仅存在全人群2~6岁组,其概率值分别为0.01%、0.02%。苹果来源杀菌剂的慢性膳食暴露风险危害概率值为0.30%~66%,女性大于男性,摄食者大于全人群,2~6岁、7~10岁组是高风险膳食暴露组。苹果中杀菌剂残留的总体质量状况处在可接受安全水平,咪鲜胺是苹果来源杀菌剂膳食暴露风险主要危害因子,尤其对于儿童、少年等低龄人群。     

Dynamics of residues from a novel nano-imidacloprid formulation in soyabean fields

Imidacloprid has been widely used to control vegetable pests in China. This research was conducted to establish a method for preparing a novel imidacloprid nano-formulation and develop a simple and efficient method for determination of residues of the novel imidacloprid formulation in soyabean fields. Imidacloprid micro-crystals were directly encapsulated with chitosan and sodium alginate through layer-by-layer self-assembly. The coated colloids and photocatalysts were characterized using confocal laser scanning microscopy and scanning electron microscopy. Residues of the novel imidacloprid were determined by HPLC equipped with a UV detector. The results showed that imidacloprid micro-crystals were obtained by association and had a mean length of 7 μm and a zeta potential of −37.5 mV. The pesticide loading and encapsulation efficiency were 56.2 ± 0.96% and 81.6 ± 0.96%, respectively. Degradation of the nano-imidacloprid and the suspension concentrate imidacloprid formulations in soil coincided with C = 0.227e^−0.152t and C = 0.544e^−0.177t with half lives of about 2.8 d and 6.2 d, respectively. Degradation of the two imidacloprid formulations in soyabean plants coincided with C = 6.644e^−0.475t and C = 8.585e^−0.573t with half lives of about 1.9 d and 4.5 d, respectively. Thus, in soil, the degradation rate of the nano formulation was faster than that of the suspension concentrate, but the degradation rates were vice versa in the plant. The final residue of the nano imidacloprid formulation after 35 days was below the limit of detection but in the soyabean plant, the final residue was 0.003 mg kg⁻¹, much lower than the USA Environment Protection Agency’s Maximum Residue Level. Therefore, a dosage of 900 ml hm⁻² is suggested for the nano-imidacloprid concentrate, which could be considered as safe to fields.     

基于Sentinel-2影像和机器学习算法的冬小麦秸秆覆盖度遥感估算

为探究大范围小麦秸秆覆盖度(CRC)估测方法，以冬小麦秸秆为研究对象，基于Sentinel-2遥感卫星影像光谱指数、波段和纹理特征及其不同特征组合，利用灰色关联-随机森林(GRA-RF)敏感特征提取方法，结合高斯过程(GPR)、套索(LASSO)、岭回归(RR)和偏最小二乘(PLSR)等多种机器学习算法，开展小麦CRC估算的最优模型研究。结果表明，基于GRA-RF特征优选后的机器学习模型显著改善了小麦CRC的估算精度，LASSO算法总体对小麦CRC的估测效果最佳，并且针对不同的光谱特征组合表现出差异化的结果。其中，以光谱指数、波段和纹理信息构成的组合特征集构建的CRC遥感估算模型精度最优(r²=0.65,RMSE=9.25%),以波段与纹理两者组合特征估算的CRC精度次之(r²=0.63,RMSE=9.31%),仅利用单一的光谱指数、波段或者纹理特征估算冬小麦CRC的精度均劣于组合特征的结果。这说明应用GRA-RF组合筛选方法能够有效优选秸秆覆盖度的光谱特征；相比于单一特征，光谱指数、波段、纹理信息等构成的组合特征更能有效地监测小麦秸秆覆盖度...     

中国豆粕市场的价格博弈分析

分析了豆粕价格波动现状及对饲料行业和畜牧业的不利影响，构造了n个博弈方的伯特兰德（Bertrand）价格博弈模型，通过求解方程组得出以下结论：异质产品的Bertrand博弈只有一个均衡。对2人情形，得出了均衡对称条件下的市场价格。     

二氟沙星残留检测用单克隆抗体的制备及其鉴定

用DFX-BSA免疫BALB/c小鼠,采用显微克隆技术成功筛选出5株特异性分泌细胞株1a6、2b4、4a4、X1和X2。将X1株细胞株直接注入小鼠腹腔获取腹水,腹水纯化后效价达1:1638400。蛋白质含量为6.86mg/ml,单抗X1属IgG2a亚型。X1株单克隆抗体的检测标准曲线方程为Y=0.4813-3.1067X(R=0.9510),最低检测限(LOD)为2ng/ml,线性范围为0.002-5μg/ml,DFX对其IC50为0.085μg/ml。单抗对氟喹诺酮类药物有一定的交叉反应,对沙拉沙星最高可达10.9%,对兽医临床常用抗菌药物氨苄西林、卡那霉素、盐酸四环素、磺胺甲噁唑和氯霉素等没有交叉反应。Ci-ELISA反应中McAb对低浓度的乙腈和丙酮具有良好的耐受性,而低浓度的甲醇对McAb的结合力有一定的影响。     

气相色谱-质谱测定蔬菜与水果中代森锰锌残留量

[目的]建立一种气相色谱-质谱快速测定蔬菜和水果中代森锰锌残留量的方法.[方法]代森锰锌在密闭容器中加热条件下被氯化锡-盐酸溶液酸解生成二硫化碳,二硫化碳经异辛烷收集后用气相色谱-电子捕获检测器和气相色谱-质谱联用(GC-MS)检测,并通过测定蔬菜和水果4种不同基质中残留的代森锰锌对该方法进行了验证.[结果]代森锰锌在0.1 ～ 2.5 mg/kg添加水平下呈良好的线性关系;代森锰锌在蔬菜和水果4种不同基质中的回收率为74.80％ ～ 110.90％,相对标准偏差为3.65％ ～ 19.19％.[结论]该方法简单、快速、准确,适用于蔬菜和水果中代森锰锌残留检测分析.     

不同剂型溴虫腈在桑叶中残留对家蚕生长发育及产茧量的影响

为减少使用桑园害虫防治药剂溴虫腈对养蚕生产的风险性,模拟田间施药条件,分别用乳油、水乳剂、微乳剂和悬浮剂4种剂型溴虫腈的100 mg/L药液喷施桑树,7 d后采叶饲喂家蚕普通品种和三眠蚕品种的2龄起蚕,观察不同剂型溴虫腈残留在桑叶中对家蚕生长发育的影响。结果表明,分别用4种剂型溴虫腈100 mg/L药液喷施桑树后,桑叶中残留药剂对家蚕普通品种和三眠蚕品种的发育历期、眠蚕质量、全茧量、茧层量、蛹体质量和化蛹率均无明显不良影响。此结果可作为采用上述剂型溴虫腈防治桑园害虫的安全性评价的部分依据。     

不同季节8％残杀威可湿性粉剂对家蚕的残毒期

在不同季节测定了8％残杀威可湿性粉剂对家蚕的残毒期,表明春蚕期和晚秋蚕期比中秋蚕期残毒期明显延长。使用8％残杀威可湿性粉剂防治桑园害虫时应注意分析各种因素,正确掌握安全间隔时间。     

甲苯咪唑在鳗鲡体内的药物代谢及组织残留

采用反相高效液相色谱法定量检测抗鳗鲡拟指环虫药物甲苯咪唑及其代谢产物羟基甲苯咪唑和氨基甲苯咪唑。研究欧鳗经1mg／L甲苯咪唑药浴处理后,其皮肤、脂肪、肌肉、肝脏和肾脏中甲苯咪唑的代谢和残留情况。实验结果表明：药浴时,欧鳗在24h内快速吸收药物,皮肤上和脂肪中含有高浓度甲苯咪唑,且甲苯咪唑在欧鳗肝脏和肾脏中转化成羟基甲苯咪唑和氨基甲苯咪唑,其中氨基甲苯咪唑是主要代谢产物;三种化合物在皮肤上的残留量明显高于肌肉;鳗鱼可食用部位（肌肉和皮肤）中甲苯咪唑和羟基甲苯咪唑在3d内代谢浓度降至药残最高限量（0．1mg／kg）,5d内可完全降解消除．但氧墓甲苯眯唑在停药12d后的含量仍高于0．1mg／kg。