Novel field sampling procedure for the determination of methiocarb residues in surface waters from rice fields.     

T M Primus  D J Kohler  M Avery  P Bolich  M O Way  J J Johnston 《Journal of agricultural and food chemistry》2001,49(12):5706-5709

Methiocarb was extracted from surface water samples collected at experimental rice field sites in Louisiana and Texas. The sampling system consisted of a single-stage 90-mm Empore extraction disk unit equipped with a battery-powered vacuum pump. After extraction, the C-18 extraction disks were stored in an inert atmosphere at -10 degrees C and shipped overnight to the laboratory. The disks were extracted with methanol and the extracts analyzed by reversed-phase high-performance liquid chromatography with a methanol/water mobile phase. Methiocarb was detected by ultraviolet absorption at 223 nm and quantified with the use of calibration standards. Recoveries from control surface water samples fortified at 5.0, 10, 50, and 100 ng/mL methiocarb averaged 92 +/- 7%. A method limit of detection for methiocarb in rice field surface water was estimated to be 0.23 ng/mL at 223 nm.  相似文献   

气候变暖对天水市国有林区林业产值的影响   总被引：3，自引：1，他引：3  

姚晓红  秘晓东  许彦平  王润元 《中国农业气象》2006,27(2):118-121

通过对1971-2000年天水气候及林业产值变化分析,得出影响天水市国有林区林业产值的主要气象条件是4-8月降水量和≥0℃积温;建立了天水林业气候产值的数学模型,得出了适宜天水林业生长的水热匹配规律,水热匹配指标为R年≥0.12∑T年≥0℃.  相似文献   

银川市城市生态旅游研究     

白慧姝  米文宝 《水土保持研究》2007,14(5):192-196

在论述城市生态旅游研究进展的基础上,总结了城市生态旅游的概念,从不同方面阐述了城市生态旅游的特征,运用SWOT模型分析银川发展城市生态旅游的优势、劣势、机遇和挑战,并提出银川城市生态旅游的产品开发类型和发展策略。  相似文献   

不同氮效率玉米杂交种的根系生长、氮素吸收与产量形成   总被引：28，自引：15，他引：28  

春亮  陈范骏  张福锁  米国华 《植物营养与肥料学报》2005,11(5):615-619

以氮效率不同的4个玉米杂交种(组合)为材料,在两个氮水平下分析了根系大小与氮素累积及产量形成方面的相互关系。结果表明,氮高效杂交种(NE1和ND108)吸氮量显著高于氮低效品种,但这种差异主要来自于吐丝后氮累积量,而在前期不同基因型间氮素累积差异不显著。两个氮水平下,氮高效品种NE1和ND108都具有较大的根系;在不施氮条件下,氮低效品种209115的根系干重与ND108相近,而其氮累积量及产量均最低。说明根系大小是决定氮累积量的主导因素,但氮吸收速率的作用也不可忽视。  相似文献   

Nitrogen fertilization management for no-till cereal production in the Canadian Great Plains: a review     

S. S. Malhi  C. A. Grant  A. M. Johnston  K. S. Gill   《Soil & Tillage Research》2001,60(3-4):101-122

Nitrogen (N) is the nutrient most limiting crop production in all areas of the world and is generally applied to soil in the largest quantity. A review of the research on N fertilization management for no-till cereal production in the Canadian Great Plains, on mainly Chernozem and Gray soils, was done to illustrate the management practices which can be used to optimize the N use efficiency so as to minimize the N loss from root zone and environmental damage. Applied N is subject to loss by volatilization, immobilization, denitrification and leaching in soil and its efficiency of use by plants is governed by soil and climatic factors, fertilizer material, and soil, crop and fertilizer management practices. Overall efficiency of applied N has been <70%. Reducing tillage intensity modifies both the demand of crops for N due to changes in yield potential, and the supply of N due to changes in N cycling and losses. Consequently, it may be necessary to compensate for this by adjusting the fertilizer rate. Fertilizer use efficiency may also change with changes in tillage management, microclimate, microbial activity and distribution of fertilizer relative to crop residue. Placing the fertilizer in a band reduces contact with soil microorganisms, reducing immobilization of both ammonium (NH₄) and nitrate (NO₃). Banding also slows the conversion of urea to NH₃ and NH₄ to NO₃, which can reduce losses by denitrification and leaching. The use of the urease inhibitor n-(n-butyl) thiophosphoric triamide (NBPT) shows promise in improving the efficiency of surface-applied urea-containing fertilizers in no-till systems and reducing seedling damage from seed-placed fertilizers. Ultimately, any N fertilization package has advantages and disadvantages. In selecting the optimum fertilizer management system for a farming operation, the balance between rate of application, cost and availability of equipment, soil disturbance, seedbed quality, moisture conservation, time and labor constraints and fertilizer use efficiency must be considered. The “best” management system is not fixed, but depends on the major limiting factors on each individual farm.  相似文献   

Investigation of the association between gall bladder wall thickness and hypoalbuminaemia in dogs     

J. Sparago  N. Rademacher  S. Dehghanpir  J. Post  C. C. Liu  A. N. Johnston 《The Journal of small animal practice》2021,62(11):973-978

  相似文献   

沙质土壤改良剂对旱作谷子苗期生长及土壤保水性能的影响   总被引：1，自引：0，他引：1  

米俊珍  刘景辉  杨彦明  徐胜涛  任鹏  于彩霞 《灌溉排水学报》2015,34(2)

为明确沙质土壤改良剂的抗旱保苗效果,研究了沙质土壤改良剂不同施用量(0、6 000、12 000、18 000、24 000和30 000kg/hm2)对土壤保水性能和谷子苗期生长状况的影响。结果表明,施用沙质土壤改良剂能促进谷子出苗及苗期生长,谷子出苗率较不施改良剂处理提高了2.20%~19.78%,出苗稳定时间缩短了1~2d;施用沙质土壤改良剂能增加植株地上部分鲜、干质量,且随着施用量的增加呈先增加后略降低的趋势;施用沙质土壤改良剂能抑制土壤水分蒸发,土壤质量含水率较不施改良剂处理提高了2.59%~23.30%,土壤贮水量较不施改良剂增加了3.12%~48.55%,且随着施入年限的增加,提高幅度也呈增加趋势。沙质土壤改良剂具有明显的抗旱保苗效果,且随施用年限增加而增强,施用量以18 000、24 000kg/hm2为宜。  相似文献   

青海省干旱灾害时间序列分形特征研究     

米财兴  张鑫 《灌溉排水学报》2015,34(3)

采用标度变换法,计算了1470—1970年青海省总体干旱灾害、各等级旱灾及旱季序列的时间分维数,并探讨了各等级旱灾及旱季序列时间分维的动态变化特征。结果表明,干旱灾害时间序列存在自相似性,具有分形特征。各等级旱灾以及各旱季时间分维数与其发生频次正相关。不同等级干旱灾害的时间重演规律不同,旱灾程度越重,无标度区越宽、分维值越低;旱灾程度越轻,无标度区越窄、分维值越高。旱灾序列时间分维数与区域气候条件有关。研究时段内,总体旱灾和轻度旱灾的发生趋向混沌无序化,短周期更加明显;中度旱灾变化较无序;春旱趋向混沌无序的平衡态,夏旱则出现短周期与长周期、有序与无序的交替现象。  相似文献   

基于人工神经网络的黑龙江省农机总动力预测   总被引：3，自引：0，他引：3  

赖庆辉  米伯林  杨志坚 《农机化研究》2005,(4):272-274

黑龙江省农机总动力的建模和预测是制定黑龙江省农机发展计划的重要依据。为此,应用BP人工神经网络技术(BP-ANN)处理1980～1998年农机总动力数据,建立正确的预测模型。利用此模型预测出1999～2003年黑龙江省农机总动力数值,预测结果和实际结果有很好的一致性;同时,预测了2004～2006年黑龙江省农机总动力数值,为今后制定农机发展战略提供参考依据。  相似文献   

降低大豆抗原诱导断奶仔猪肠道损伤反应的研究进展     

米萌萌  秦贵信  赵元  赵寒冬 《饲料研究》2021,(2):113-116

大豆中含有的热稳定性抗营养因子——大豆抗原,具有免疫原性,且在仔猪肠道内不易被降解消化,会诱导断奶仔猪肠道损伤。文章总结大豆抗原诱导的断奶仔猪肠道损伤的特点,重点阐述缓解损伤的方法及作用机理,为进一步优化缓解大豆抗原诱导的肠道损伤的方法及保护仔猪肠道健康提供参考,为研究大豆抗原致仔猪肠道损伤的机制提供参考。  相似文献