基于HYDRUS-2D的地下滴灌下水分运移数值模拟研究

利用HYDRUS-2D软件模拟了地下滴灌条件下滴头周围黏壤土的土壤水分动态,并与田间观测进行对比;通过分析不同滴头流量对试验地土壤湿润模式的影响,明确了最佳灌水技术参数。结果表明,HYDRUS-2D软件模拟结果与观测值一致,体积含水率均方根误差为1.2%~4.5%,湿润范围均方根误差变化范围为2.1~3.87cm。     

玉米秸秆残茬覆盖对大豆田土壤水温效应的影响

研究了传统耕作、玉米原垄留茬耕作、玉米原垄留茬全覆盖、玉米留茬条带覆盖、浅松覆盖和深松覆盖6种耕作方式下土壤含水率、棵间蒸发量和地温的变化。结果表明,条带覆盖对大豆不同生育期土壤剖面含水率影响最大;其他耕作方式对棵间蒸发的抑制作用均小于传统耕作;日平均地温在苗期变化明显;保护性耕作对日平均地温影响较大,传统耕作最高,留茬全覆盖最低。     

温度对绿豆芽苗菜产量和营养成分的影响

研究了不同温度对绿豆芽苗菜产量和营养成分的影响.结果表明:处理④绿豆芽苗菜生长速度最快且产量最高.其次是处理③,处理④与处理③的产量达显著差异,处理③、④与处理①、②的产量达极显著差异;营养成分中,Ve与胡萝卜素含量的大小是处理④＞处理③＞处理②、处理①;K+含量的大小是处理③＞处理④＞处理②=处理①.     

Evaluation of finger weeder safety and efficacy for intra-row weed removal in irrigated field crops

Increased demand for pesticide-free food and the development of herbicide-resistant weed populations have created a need for non-chemical weed-control tools. A candidate mechanical tool for controlling weeds in the seeding line (intra-row zone) is the finger weeder. This study thus aimed to evaluate the safety and weed-control efficacy of the finger weeder in various irrigated field crops. Eight field trials were conducted in processing tomato, sweet corn, sunflower, cotton, and beetroot over 2 years. The finger weeder treatments were applied as the sole weed-control method (single or double treatments) and in combination with herbicides. A mini meta-analysis was used to evaluate the overall effect of the finger weeder treatments on crop stand and yield and on weed control efficacy. Weed density in the control not treated with herbicides nor a finger weeder ranged between 2 and 62 weeds m⁻². The finger weeder treatments resulted in a significant reduction in weed density, which ranged between 40% and 90%. The weed density following the double finger weeder treatment was not significantly different from that for the conventional herbicide-based treatment (p = 0.32) and could therefore be considered as an effective environmentally friendly alternative. Furthermore, a single FW treatment integrated with herbicide application gave better weed control than the conventional herbicide treatment (p = 0.04). This treatment was safe for the crops with no significant stand (p = 0.19) or yield (p = 0.29) reductions compared to commercial treatment. The results of this study demonstrate the promise of the finger weeder as an effective tool within integrated weed management systems for conventional agro-systems. The tool offers a rational weed-control solution for sustainable systems under irrigation.     

2022年上海市稻田杂草大发生原因剖析及对策建议

在对稻田杂草发生危害长期跟踪监测和调查走访的基础上, 从主观?客观和管理层面的10个方面, 对2022年上海市稻田杂草大发生原因进行了剖析, 并针对当前稻田杂草防除中存在的问题, 从政策引导?技术支撑?组织管理等方面提出了对策建议?     

蒜和葱上二斑叶螨的发生为害及其抗药性监测

二斑叶螨寄主植物范围极广, 但其对百合科蔬菜造成危害的研究报道极少?本研究采集了来自北京海淀百合科蔬菜蒜和葱上的2个二斑叶螨种群, 生物测定结果显示, 2个种群对阿维菌素呈现出极高水平抗性, 对哒螨灵为中等以上抗性(LC50>5 000 mg/L), 对新型药剂联苯肼酯?虫螨腈和腈吡螨酯也表现出中等到高水平抗性?抗性基因突变频率检测发现, 与阿维菌素抗性相关基因G314D和G326E位点以及和哒螨灵抗性相关基因H92R位点的突变频率均高达100%, 为纯合抗性种群?因此, 本研究所测试的2个二斑叶螨种群对阿维菌素和哒螨灵单剂的敏感性极低, 需慎重选用这2种药剂, 而3种新型杀螨剂联苯肼酯?虫螨腈和腈吡螨酯在田间需轮换使用?     

果蔬产品变色原因分析及其控制

分析了果蔬产品在加工贮存中变色的原因,综述了目前生产中常用的行之有效的护色措施,包括生物、化学和物理等方面的处理方法。     

Physical simulation of fluid field and structure optimization in two-strand tundish

The influence of the structure and location of dam and weir on fluid flow state in a two-strand tundish is studied, and a set of optimal structure, combining with the average residence time calculated from RTD curve, is obtained. The result indicates that the fluid flow state can be changed and the path of the fluid flow can be prolonged as well as the average residence time is improved after using dam and weir. But there are some dead zones after fluid passed through the dam and weir. Combination scheme of No. one dam and weir is better than the others. Its average residence time is 299 s and the volume fraction of dead zone is 31.0%. After the optimization of flowing control parameters in tundish, the best case is that the distance between dam and weir is 290 mm and the distance between weir and the long nozzle is 383 mm. The longest average residence time is 351 s and the minimum volume fraction of dead zone is 19.0% under the above situation. Compared with that of no dam and weir, the average residence time increases by 65 s and the dead zone volume fraction decreases by 15.0%. Based on Newton formula, the calculated results show that the inclusions with diameter larger than 17.5 μm can float up within 351 s under this optimization situation.     

Solution the Polarization Field Strength inside Ellipsoid in a Homogeneous Dielectric

The solution of polarization field strength in ellipsoid and a homogeneous dielectric in condition of a constant external field is obtained with strict derivation and ellipsoidal coordinate. The conclusion that some textbooks given: the direction of polarization field strength with the direction of external field holds strict anti-parallel must be supplemented with additive certain conditions, otherwise it will not be correct. By means of the latticework and the step change calculation, the angle value of polarization vector with the external field is calculated and the changing situation about the angle value with the change of three half axes of ellipsoid is analysied.