蚯蚓体表液的组成及其减粘脱土机理分析

蚯蚓的体表液利于减粘脱土。本文利用现代测试仪器,结合生物化学分析技术,研究了蚯蚓体表液和泥鳅分泌液的组成;并应用土壤力学和生物化学等方面的理论,初步探讨了蚯蚓体表液减粘脱土的机理。     

甘薯天蛾虫蛹蛋白水解特性及其氨基酸营养液的制作工艺研究

甘薯天蛾虫蛹用远天２３和远天１２蛋白酶水解，当底物鲜虫蛹液１２ｍＬ（浓度为２０％，Ｗ／Ｖ），添加１％酶液１ｍＬ，其适宜的水解条件：ｐＨ６～７，５０℃水解１２０ｍｉｎ并加热至７０℃继续水解３０ｍｉｎ；远天２３的酶解效果优于远天１２，添加磷酸（钠）盐和ＥＤＴＡ２Ｎａ可增加可溶性含氮物总量，添加ＶＣ则无效；底物粗蛋白的提取率为８１．２％。文章对虫蛹氨基酸营养液的制作工艺、配方及产品质量要求等亦做了介绍。     

基质浓度对淡紫拟青霉“NH-PL-03”菌株生长的影响

通过测定不同基质浓度(C N=0.001g/mL、0.005g/mL、0.015g/mL、0.045g/mL、0.135g/mL)对淡紫拟青霉“NH-PL-03”菌株生长的影响结果表明,基质浓度对菌体生长有明显影响,基质浓度为0.045g/mL时菌丝生长旺盛,培养10d每瓶干物质量达到0.82g,对茎线虫校正致死率在8d达到峰值52.30%。基质浓度为0.015g/mL的实验组合产孢量最大,培养8d产孢量达峰值69.20百万个/mL。0.135g/mL的基质浓度对菌生长表现出明显抑制作用,培养10d其干物质量和产孢量仅分别为0.23g和15.10百万个/mL。     

Irrigation with plant extracts in ecofarming increases biomass production and mineral and organic nitrogen content of plants

Seedlings of alfalfa, rape, spinach, and wheat, potted on sandy soil, were irrigated with an aqueous extract of pea shoot (PE, 9.84 g dry weight l^–1) or a solution of Ca, K, Mg, P, and NO₃‐N salts (SS) in a concentration similar to that in PE, for 31–48 days. In comparison to water‐irrigated controls, both SS and PE treated plants showed nearly equal increases in shoot dry weight (29–40 %), whereas PE‐treated plants had higher fresh weights (38–84 %) due to increased succulence. Treatment with SS did not enhance, but sometimes even reduce, the concentrations of Ca, K, Mg, and several trace elements in shoot tissues. In contrast, PE‐treated plants had higher Ca, K, Mg, and organic N, but lower As and Ni contents and were thus of higher nutritive value. Reduced contents of metals in plant tissue correlated with their reduced solubility in the soil solution, which was not due to changes in pH. Fertilizer components such as K and Mg (metals of lower exchange intensity) were incorporated into the soil to release Ca, Sr, and Ba (metals of higher exchange intensity) and reduce the solubility of most trace elements and metal‐complexing humic substances. In addition, application of Ca precipitated heavy metals and humic complexes directly from the soil solution. This effect was partially overcome by PE. Its carboxylic acids could act as phytochelators of metal ions and as mobilizers of the highly diffusible humic substances which carry metals to roots. It is concluded that continuous PE application replaces the quantities of Ca, K, Mg, P, and organic N, but not of NO₃‐N consumed during plant growth. Using PE does not add any relevant quantities of toxic metals to the plant‐soil system.     

Free and HF-HO-extractable amino acids determined by high performance liquid chromatography in a loamy sand soil

Summary Amino acids were extracted from fertility plots of a loamy sand soil with 0.05 M HF-HCl and with a 10% ethanol solution (free amino acids) and analysed by reverse-phase high performance liquid chromatography (HPLC). The total quantities of amino-N compounds analysed were 4.4 g/g soil for the acid treatment and 22.6 g/g soil for the 10% ethanol extract. Glycine and glutamic acid were the most abundant of 15 amino-N compounds in the HF-HCl extracts, whereas glutamic acid and ornithine + NH⁺ ₄ were found in the highest concentration in the 10% ethanol extracts. The HF-HCI pretreatment is used to increase the efficiency of the extraction of soil organic matter. Although this pretreatment removed some amino acids, the acids extract less than 1% of the total amino-N content of the crude soil extracts. The pretreatment, therefore, was not overly destructive. Comparisons between the amino acids extracted from the fertility plots were not conclusive, except for glycine, which was greater in concentration in the higher fertilizer N plots of the same crop rotation.     

自动双环入渗仪设计与试验

为克服传统双环入渗仪的供水不稳定、读取和记录数据工作量大的问题,该文基于定水头法测量导水率的原理,设计了一种高效的自动双环入渗仪。该入渗仪采用非接触式电容感应液位传感器来监测内环和外环内的水位(精度1.5mm);将激光测距传感器(精度1mm)安装在圆柱形蓄水器的顶部,以连续自动监测供水量;高精度液位控制系统与电磁阀组合以保持恒定水头。通过理论分析,增大蓄水器中的液面与双环中的液面之间的压力差,可使自动双环入渗仪的初始供水速率远高于马氏瓶的初始供水速率。自动双环入渗仪的精度和可靠性试验于2019年7月至2019年10月在中国农业大学绿苑试验场进行,并进行了该自动双环入渗仪和传统双环入渗仪之间的比较。试验结果显示,在选定土壤的稳定入渗阶段,用马氏瓶测量的稳定入渗速率为0.068 5 cm/min,该自动双环入渗仪的稳定入渗速率为0.068 7 cm/min,自动双环入渗仪实测数据与Philip的理论入渗模型计算结果吻合(R20.99)。结果表明,该自动双环入渗仪的自动化测量结果可靠,对今后土壤水分入渗过程研究提供了更加高效的手段。     

Evidence of peptides in low-molecular-weight fractions of soil organic matter

Summary Organic matter was extracted from three soils, a Berwick sandy loam, a Franklin loamy sand, and a Cumberland silty loam. The extracts were separated into high (>8000 daltons) and low-molecular-weight (<8000 daltons) fractions using gel filtration. Reverse-phase high performance liquid chromatography at 214 nm was used to separate the peptides into low-molecular-weight fractions. Peptide samples were collected with an integrated fraction collector and hydolyzed with an immobilized protease column reactor. High performance liquid chromatography with fluorescence detection was used to determine the amino-acid contents of the collected samples. The results indicated that peptide intermediates are present in soil size fractions. Greater quantities of several amino acids were released from the peptide hydrolyzates of the Berwick sandy loam and Franklin loamy sand, compared with the Cumberland silty loam, an uncultivated soil. These findings indicate that organic intermediates (e.g., peptides) are more prevalent in biologically active soils than in relatively inert soils.     

生鲜乳中兽药残留的快速筛查与风险预警体系构建

该研究探索并构建一种基于历史数据分析的安全预警方法,对生鲜乳中兽药残留情况进行识别、控制与评价,以便在风险发生之前做出准确判断。首先利用高效液相色谱-高分辨飞行时间串联质谱(High Performance Liquid Chromatography-high Resolution Time-of-flight Tandem Mass Spectrometry,HPLC-TOF-MS/MS)方法对上海市各牧场的生鲜乳进行兽药残留筛查,然后以生鲜乳中泼尼松(Prednisone,Pre)残留检出数为例,利用休哈特控制图(Shewhart control charts)构建风险预警体系。结果表明:在300个生鲜乳样品中共筛查出42种兽药残留,涉及类固醇类(12种)、糖皮质类(6种)和镇静剂(5种)等12大类;在筛查的6个星期中,泼尼松检出数(Number of Prednisone Detected,Pn)控制图呈现稳定的状态;当假设第7周泼尼松检出数为6时,Pn控制图呈现稳态,未触发预警;当假设第7周泼尼松检出数为10时,Pn控制图出现异常,稳态遭到破坏,此时该批样品触发风险预警。综上,利用HPLC-TOF-MS/MS能对生鲜乳样品进行高通量的兽药残留筛查,再利用休哈特控制图结合历史数据可以对生鲜乳样品的兽药残留进行有效的风险监测和预警。     

液氮冷媒介质对速冻饺子冻裂率的影响

研究饺子新型冻结技术,探索液氮速冻工艺对调理食品品质的作用规律。该文以饺子为研究对象,和面水面质量比、皮馅质量比、面粉品质、馅料配比、产品规格、冻结时间、冻结方式、冻结介质等诸多因素对饺子冻裂率都有重要影响。该试验以猪肉、香菇、大豆组织蛋白为饺子馅主要原料,研究了和面时的水面质量比、面团的静置时间、皮馅比、饺子在液氮池中的沉浸时间对饺子冻裂率的影响。结果表明:以上四因素对饺子的冻裂率都有不同程度的影响。和面水面质量比为56∶100、面团静置时间在10 min、皮馅质量比在1∶1.3、液氮池沉浸时间为40 s,制作好的饺子在立即速冻后的冻裂率为37%,感官评定得分为77.6。该研究为液氮沉浸速冻工艺在调理食品的应用提供了一定的理论参考。