灰黄霉素在家兔组织中的分布及残留消除规律研究

研究灰黄霉素在家兔组织中的分布及消除规律,为灰黄霉素用于治疗家兔真菌病的安全性评价提供依据。选择42只新西兰白兔,于饲料中添加灰黄霉素（800g／1000kg）混饲,连续饲喂14d,分别于停药后1、3、5、7、9、14、21d,各处死6只,取其肝、肾、肌肉、皮肤及脑组织。以盐酸普萘洛尔为内标,二氯甲烷提取后用高效液相色谱-串联质谱仪（HPLC—MS／MS）进行各种组织中灰黄霉素浓度分析。结果显示,连续用药14d后,灰黄霉素在家兔组织中的分布情况为：肝组织浓度最高（134．61μg／kg）,肾组织次之（54．09μg／kg）,脑组织浓度最低（未检出）;停药后,随着时间的延长,灰黄霉素在肌肉、肝、肾和皮肤组织中的浓度逐渐下降,且在肝脏中的消除速度最快,停药21d后,灰黄霉素在肾组织中浓度为3．39μg／kg,在肝组织中浓度为12．36μg／kg,其他组织低于定量限或未检出。建议家兔生产中慎用灰黄霉素。     

液相色谱-串联质谱法检测猪肉中20种违禁药物残留的研究

建立了猪肉中违禁药物（糖皮质激素、性激素、β2-肾上腺素受体激动剂、玉米赤霉烯酮4类）同时测定的高效液相色谱-串联质谱方法。试样经盐酸水解,乙酸乙酯提取,低温冷冻去除脂类,亲水亲脂平衡固相萃取柱净化。采用C18反相色谱柱分离,以乙腈+水为流动相梯度洗脱,分别在电喷雾离子源正、负离子模式下以多反应监测模式（MRM）分段扫描同时检测,基质匹配内标法定量。结果表明,20种违禁药物在相应的浓度范围内线性良好,相关系数均大于0.99;该方法在猪肉中的检测限（LOD,S/N=3）和定量限（LOQ,S/N=10）分别为0.5、1.0 μg/kg。在0.5~10 μg/kg添加浓度水平下,平均回收率为63.9%~117%,批内变异系数1.9%~9.1%,批间变异系数4.9%~13.1%。该方法简单、快速、准确,适用于猪肉中多类违禁药物的残留检测。     

Residue chemistry and microbial community structure during decomposition of eucalypt, wheat and vetch residues

Previous studies have shown that residue chemistry and microbial community structure change during decomposition, however little is known about the relationship between C-chemistry and microbial community structure. To address this knowledge gap, we studied C-chemistry and microbial community structure during the decomposition of eucalypt, wheat and vetch residues with and without additional inorganic N. Bags containing ground residues of eucalypt, wheat, and vetch were buried in sand microcosms after inoculation with a diverse microbial community. Respiration was measured over an incubation period of 150 days. At different times during incubation, total C and N of the residues were analysed and residue carbon chemistry was determined by ¹³C-NMR (nuclear magnetic resonance) spectroscopy. Microbial communities were assessed by phospholipid fatty acid (PLFA) analyses.Results indicated that during decomposition, residue C-chemistry and microbial community composition changed over time and differed between residue types. Changes in microbial community structure were associated with changes in residue C-chemistry, mainly the relative content of aryl-C and O-alkyl-C. Addition of N increased cumulative respiration, altered C-chemistry during decomposition, particularly in high C/N residues (wheat and eucalypt), and changed microbial succession leading to an earlier establishment of a stable microbial community structure. N addition to eucalypt and wheat reduced the decomposition of aryl-C compounds.     

Tillage and cropping sequence impacts on nitrogen cycling in dryland farming in eastern Montana, USA

Information on N cycling in dryland crops and soils as influenced by long-term tillage and cropping sequence is needed to quantify soil N sequestration, mineralization, and N balance to reduce N fertilization rate and N losses through soil processes. The 21-yr effects of the combinations of tillage and cropping sequences was evaluated on dryland crop grain and biomass (stems + leaves) N, soil surface residue N, soil N fractions, and N balance at the 0–20 cm depth in Dooley sandy loam (fine-loamy, mixed, frigid, Typic Argiboroll) in eastern Montana, USA. Treatments were no-tilled continuous spring wheat (Triticum aestivum L.) (NTCW), spring-tilled continuous spring wheat (STCW), fall- and spring-tilled continuous spring wheat (FSTCW), fall- and spring-tilled spring wheat–barley (Hordeum vulgare L.) (1984–1999) followed by spring wheat–pea (Pisum sativum L.) (2000–2004) (FSTW-B/P), and spring-tilled spring wheat–fallow (STW-F). Nitrogen fractions were soil total N (STN), particulate organic N (PON), microbial biomass N (MBN), potential N mineralization (PNM), NH₄-N, and NO₃-N. Annualized crop grain and biomass N varied with treatments and years and mean grain and biomass N from 1984 to 2004 were 14.3–21.2 kg N ha⁻¹ greater in NTCW, STCW, FSTCW, and FSTW-B/P than in STW-F. Soil surface residue N was 9.1–15.2 kg N ha⁻¹ greater in other treatments than in STW-F in 2004. The STN at 0–20 cm was 0.39–0.96 Mg N ha⁻¹, PON 0.10–0.30 Mg N ha⁻¹, and PNM 4.6–9.4 kg N ha⁻¹ greater in other treatments than in STW-F. At 0–5 cm, STN, PON, and MBN were greater in STCW than in FSTW-B/P and STW-F. At 5–20 cm, STN and PON were greater in NTCW and STCW than in STW-F, PNM and MBN were greater in STCW than in NTCW and STW-F, and NO₃-N was greater in FSTW-B/P than in NTCW and FSTCW. Estimated N loss through leaching, volatilization, or denitrification at 0–20 cm depth increased with increasing tillage frequency or greater with fallow than with continuous cropping and ranged from 9 kg N ha⁻¹ yr⁻¹ in NTCW to 46 kg N ha⁻¹ yr⁻¹ in STW-F. Long-term no-till or spring till with continuous cropping increased dryland crop grain and biomass N, soil surface residue N, N storage, and potential N mineralization, and reduced N loss compared with the conventional system, such as STW-F, at the surface 20 cm layer. Greater tillage frequency, followed by pea inclusion in the last 5 out of 21 yr in FSTW-B/P, however, increased N availability at the subsurface layer in 2004.     

Interactive effects from combining fertilizer and organic residue inputs on nitrogen transformations

Concerns about sustainability of agroecosystems management options in developed and developing countries warrant improved understanding of N cycling. The Integrated Soil Fertility Management paradigm recognizes the possible interactive benefits of combining organic residues with mineral fertilizer inputs on agroecosystem functioning. However, these beneficial effects may be controlled by residue quality. This study examines the controls of inputs on N cycling across a gradient of (1) input, (2) residue quality, and (3) texture. We hypothesized that combining organic residue and mineral fertilizers would enhance potential N availability relative to either input alone. Residue and fertilizer inputs labeled with ¹⁵N (40–60 atom% ¹⁵N) were incubated with 200 g soil for 545 d in a microcosm experiment. Input treatments consisted of a no-input control, organic residues (3.65 g C kg⁻¹ soil, equivalent to 4 Mg C ha⁻¹), mineral N fertilizer (100 mg N kg⁻¹ soil, equivalent to 120 kg N ha⁻¹), and a combination of both with either the residue or fertilizer ¹⁵N-labeled. Zea mays stover inputs were added to four differently textured soils (sand, sandy loam, clay loam, and clay). Additionally, inputs of three residue quality classes (class I: Tithonia diversifolia, class II: Calliandra calothyrsus, class III: Z. mays stover) were applied to the clay soil. Available N and N₂O emissions were measured as indicators for potential plant N uptake and N losses. Combining residue and fertilizer inputs resulted in a significant (P < 0.05) negative interactive effect on total extractable mineral N in all soils. This interactive effect decreased the mineral N pool, due to an immobilization of fertilizer-derived N and was observed up to 181 d, but generally became non-significant after 545 d. The initial reduction in mineral N might lead to less N₂O losses. However, a texture effect on N₂O fluxes was observed, with a significant interactive effect of combining residue and fertilizer inputs decreasing N₂O losses in the coarse textured soils, but increasing N₂O losses in the fine textured soils. The interactive effect on mineral N of combining fertilizer with residue changed from negative to positive with increasing residue quality. Our results indicate that combining fertilizer with medium quality residue has the potential to change N transformations through a negative interactive effect on mineral N. We conclude that capitalizing on interactions between fertilizer and organic residues allows for the development of sustainable nutrient management 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.     

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.     

叶枯唑在桃和土壤中的残留分析

样品经乙酸乙酯-二甲基甲酰胺(20∶1,V/V)混合液提取后,采用高效液相色谱法(配紫外检测器)建立了桃和土壤中叶枯唑残留检测方法。结果表明,叶枯唑添加量为0.1、0.5、1.0 mg/kg时,桃和土壤中的叶枯唑回收率在79.0～97.0,相对标准偏差在1.6%～6.8%;叶枯唑在桃和土壤中的最小检出量均为0.5×10-9g,最低检测浓度均为0.1 mg/kg,满足农药残留分析要求。     

人参和土壤中异菌脲残留分析

[目的]建立异菌脲在人参和土壤中的残留分析方法。[方法]人参和土壤样品分别用丙酮-石油醚和乙腈-水的混合溶剂提取、SPE柱净化,采用高效液相色谱法(HPLC)测定人参和土壤中的异菌脲残留量。[结果]在0.04～5.00 mg/kg浓度范围内,异菌脲浓度(x)与峰面积(y)的线性回归方程为:y=42.495x-0.674,r=0.999 7,线性关系良好。异菌脲在土壤和人参中的添加回收率分别为96.60%～100.80%和92.90%～105.70%,变异系数分别为1.54%～2.78%和7.20%～9.50%。异菌脲在土壤和人参中的最小检出量均为3.0×10-10g,实际土壤、人参添加异菌脲的定量限分别为0.04和0.09 mg/kg。[结论]该方法准确、快速、灵敏度高,能够满足农药残留分析要求。     

铜制剂农药对生态环境影响研究

阐述了因长期施用波尔多液致使铜在果园土壤中的残留积累状况及其对果 园作物生长的影响。对几种新的铜制剂农药在果树和蔬菜上的残留进行了试验，并对其在今 后使用中铜在土壤中的积累规律及允许安全使用年限作了预测。