Characterization of soil surface properties following disturbance of a clay soil in southern Manitoba

This research demonstrated the use of a laser profiling system (LPS) and digital imagery as useful tools in measuring soil micro-topography and crop residue cover following a soil disturbance event. The soil micro-topography was characterized in terms of surface roughness using two geostatistical approaches; semivariance analysis and the mean absolute-elevation-difference method. Univariate statistical analysis was also used. All three procedures used to describe surface roughness were successful in detecting changes in surface roughness due to soil disturbance and the addition of corn residue. There was a definite advantage in using the geostatistical approaches to characterize surface roughness as the indices they provide give insight into the characteristics of the surface roughness. Crop residue cover was measured using digital images and image analysis software to contrast the soil and the crop residues.The series of field experiments examined the roles of both soil disturbance and corn residue and their interactions on surface roughness, crop residue cover, exposed surface area, and near-surface porosity. Soil disturbance and the addition of corn residue were both found to be significant factors affecting the surface roughness, crop residue cover, exposed surface area, and near-surface porosity. Due to the interaction and added effects of crop residue, it was also demonstrated that the calculated surface area may not be a measure of exposed soil area, but rather it is a combination of soil and residue surface areas. Similarly, the roughness of a surface does not only reflect the soil clods produced during tillage but that of the residue itself. Furthermore, it was demonstrated that the information gathered by the LPS and digital imagery can be used to evaluate surface characteristics arising from different tillage practices.     

Faster residue decomposition of brittle stem rice mutant due to finer breakage during threshing

In intensive tropical rice (Oryza sativa L.) cropping systems with short fallows, it would be advantageous that rice straw decompose fast enough to facilitate land preparation and planting of the subsequent crop. The straw of a brittle stem rice mutant of IR68 was tested for more rapid decomposition compared with non-brittle IR68 straw. The hypothesis was that the brittle mutant straw would break into smaller pieces during threshing, and that both the smaller piece size and the differences in biochemical straw composition would enable more rapid decomposition. Brittle straw broke into smaller pieces than non-brittle straw during a replicated trial of three threshing methods: hand threshing, pedal threshing, and axial-flow machine threshing. In a litter bag study to determine the effect of straw piece size on decomposition rate of each straw type over 10 weeks, smaller straw pieces decomposed faster than larger pieces as indicated by changes in amount of straw and its C/N ratio over time (P < 0.05), but there was no significant difference between straw types at the same size. It was concluded that the finer breakage of brittle straw during field operations is likely to be more important than the biochemical differences in overall residue decomposition rate.     

川芎浸膏萃取溶剂研究及其有机溶剂残留量的测定

本论文基于某已上市复方川芎制剂制备工艺,通过对其制备过程中的萃取溶剂替代研究以及有机溶剂残留测定方法研究,建立了以乙酸乙酯替代原生产工艺中三氯甲烷的川芎浸膏制备方法,同时建立了气相色谱法测定浸膏中有机溶剂的残留。结果表明,以乙酸乙酯作为川芎浸膏的萃取溶剂,与原浸膏HPLC法检测结果一致,并更安全绿色环保。应用所建立的GC法测定浸膏中乙酸乙酯残留,加样回收率98.44%,该方法稳定可靠,可用于测定浸膏中的乙酸乙酯残留。     

苄嘧磺隆·苯噻酰草胺0.42％颗粒剂在稻田中的残留及消解动态

为明确苄嘧磺隆和苯噻酰草胺在稻田系统中的使用安全性,于2010、2011年在杭州、长沙和南宁进行田间试验,研究苄嘧磺隆·苯噻酰草胺0.42％颗粒剂在水稻中的消解动态和最终残留.结果表明,在稻田土壤、水、糙米、谷壳和水稻植株中添加的苄嘧磺隆和苯噻酰草胺的平均回收率为70.78％～ 116.06％,相对标准偏差(RSD)为0.91％～10.24％;苄嘧磺隆和苯噻酰草胺的检出限(LOD)均为0.02 mg/L,最小检出量均为4.0×10-9 g.在水稻移栽后5～7 d,采用直接撒施法在高剂量(270 kg/hm2,其中苄嘧磺隆有效成分为64.8 g/hm2,苯噻酰草胺有效成分为1 069.2 g/hm2)下施药1次的消解动态试验结果表明:苄嘧磺隆和苯噻酰草胺在稻田水、稻田土壤和水稻植株中的消解动态曲线均符合一级动力学方程,苄嘧磺隆在稻田水、稻田土壤和水稻植株中的平均消解半衰期分别为5.35,3.05和3.71 d,苯噻酰草胺在稻田水、稻田土壤和水稻植株中的平均消解半衰期分别为3.61,3.29和3.88 d.分别按低剂量(180 kg/hm2,其中苄嘧磺隆有效成分为43.2 g/hm2,苯噻酰草胺有效成分为712.8 g/hm2)和高剂量(270 kg/hm2)施药1次,在正常收获期采集的稻田土壤、稻杆、谷壳和糙米中均未检测出苄嘧磺隆和苯噻酰草胺.     

敌百虫在乌鳢体内和水环境中的代谢动力学及残留研究

[目的]明确敌百虫在水产养殖中的安全性。[方法]全池泼洒0.5 mg/L敌百虫,采用气相色谱法测定敌百虫在乌鳢体内的代谢动力学和残留消除规律。[结果]乌鳢组织和水样中敌百虫的最低检测限为0.02μg/m L。随着时间的延长,敌百虫在乌鳢血液中的浓度逐渐升高,120 h达最高,为0.072 mg/kg,至360 h时未检出。肌肉中12 h内未检出,24 h浓度为0.023 mg/kg,120 h检出最大浓度0.051 mg/kg,至288 h未检出。肝脏8 h未检出,12 h检出浓度为0.026 mg/kg。使用敌百虫后,乌鳢体内的药物残留量均低于我国的兽药最高残留限量要求,但在养殖水体中的残留时间较长,降解半衰期为35.19 h。[结论]为确保敌百虫使用后对水生态环境及食品安全,建议敌百虫使用后的休药期为150℃·d。     

吡喹酮及其主要代谢产物在草鱼体内代谢动力学研究

[目的]研究吡喹酮及其主要代谢产物在草鱼体内的代谢动力学规律。[方法]运用高效液相色谱法(HPLC),研究淡水草鱼在单次口灌给药10 mg/kg剂量条件下,鱼体各组织中吡喹酮(PZQ)及吡喹酮一羟基代谢物(M1)的药动学差异。[结果]草鱼血浆、肠道、肝脏和肾脏内PZQ在各个时间点的药物浓度存在极显著差异(P0.01);PZQ在血浆、肠道、肝脏和肾脏的达峰时间分别为1.0、0.5、1.0和1.0 h,而药物峰浓度为0.41、0.45、0.72和0.44 mg/L,M1在血浆、肠道、肝脏和肾脏的达峰时间分别为48.0、0.5、6.0和48.0 h,而药物峰浓度为0.72、0.45、0.42和0.42 mg/g。这表明PZQ在草鱼体内吸收分布快,M1的达峰时间滞后于PZQ。二者达峰浓度相似表明M1是PZQ在草鱼体内主要代谢物。PZQ在血浆、肠道、肝脏和肾脏的消除半衰期(t_(1/2))分别为16.41、4.77、37.16和8.74 h,M1在血浆、肠道、肝脏和肾脏的消除半衰期(t_(1/2))分别为124、71、246和162 h,其消除半衰期明显比PZQ长,说明在鱼体中M1的残留时间比PZQ更长。[结论]在实际生产中,应注意对M1的检测。     

植物饼渣液体有机肥生产关键技术研究进展

以植物饼渣为主要原料,运用生物技术和物理化学方法相应设计了生产液体有机肥完整的工艺流程。文章主要介绍了目标营养元素的确定、水解条件的优化、蛋白酶产生菌种的培育以及大量营养元素强化等技术,针对各种控制方法,阐述了其原理、应用条件及研究进展情况,提出了低成本规模化制作植物液体有机肥的新思路,为有机肥料的资源化利用提供了参考。     

甲基异柳磷在土壤中的残留降解分析

该实验应用气相色谱法测定了土壤中的甲基异柳磷的残留降解情况,以丙酮-正己烷(2∶1,V/V)为提取剂,氮吹仪浓缩定容,经气相色谱外标法定量测定。结果表明,当添加水平为0.05mg/kg时,甲基异柳磷在土壤中的回收率为91.33%,添加水平为0.1mg/kg时回收率为100.5%;添加浓度0.1mg/kg的甲基异柳磷在土壤中半衰期为9.58~11.27d。     

河三角洲地区棉田地膜残留特征研究

为准确掌握黄河三角洲地区棉田土壤残膜的分布特征、科学制定棉田地膜污染防治对策,在黄河三角洲棉花主产区东营市开展了棉田地膜调查与残留监测研究,选择5个典型棉田进行取样,测定土壤中的残膜数量、分布密度及残膜面积等.结果表明:20年以上棉田的土壤地膜残留量为18.84～53.53 kg/hm2,地块间差异较大.地膜残留密度22.5万块/hm2～34.0万块/hm2,残膜大小差异较大;25 cm2以上的残膜占残膜总块数的94.1％,100 cm2～500 cm2的残膜占一半以上,500 cm2以上的大片残膜约占21％.黄河三角洲棉区,土壤中地膜残留以”残块大、厚度薄、回收难”为主要特征,并具有向深土层迁移的可能,生态风险较高.     

Intercropping maize and wheat with conservation agriculture principles improves water harvesting and reduces carbon emissions in dry areas

In arid and populated areas or countries, water shortage and heavy carbon emissions are threatening agricultural sustainability with food security severely, and becoming a major issue. It is unclear whether improved farming systems can be developed to tackle those issues through a sustainable agriculture. Here three farming practices that have proven to be essential and successful, which were: (a) crop intensification through strip intercropping, (b) water harvesting through conservation tillage; and (c) carbon sequestration through improved crop residue management options, were integrated in one cropping system. We hypothesize that the integrated system allows the increase of crop yields with improved water use efficiency, while reducing carbon emissions from farming. The hypothesis was tested in field experiments at Hexi Corridor (37°96′N, 102°64′E) in northwest China. We found that the integrated system increased soil moisture (mm) by 7.4% before sowing, 10.3% during the wheat–maize co-growth period, 8.3% after wheat harvest, and 9.2% after maize harvest, compared to the conventional sole cropping systems. The wheat/maize intercrops increased net primary production by 68% and net ecosystem production by 72%; and when combined with straw mulching on the soil surface, it decreased carbon emissions by 16%, compared to the monoculture maize without mulch. The wheat/maize intercrops used more water but increased grain yields by 142% over the monoculture wheat and by 23% over the monoculture maize, thus, enhancing water use efficiency by an average of 26%. We conclude that integrating strip intercropping, conservation tillage as well as straw mulching in one cropping system can significantly boost crop yields, improve the use efficiency of the limited water resources in arid areas, while, lowering the carbon emissions from farming. The integrated system may be considered in the development of strategies for alleviating food security issues currently experienced in the environment-damaged and water-shortage areas.