Effects of input management and crop diversity on non-renewable energy use efficiency of cropping systems in the Canadian Prairie     

R.P. Zentner  P. Basnyat  S.A. Brandt  A.G. Thomas  D. Ulrich  C.A. Campbell  C.N. Nagy  B. Frick  R. Lemke  S.S. Malhi  M.R. Fernandez 《European Journal of Agronomy》2011,34(2):113-123

Although producers’ prime objective may be to increase net returns, many are also interested in conserving and enhancing the quality the soil, water and air resources through adopting more environmentally friendly production practices. This study compared non-renewable energy inputs, energy output, and energy use efficiency of nine dryland cropping systems comprised of a factorial combination of three methods of input management [high (HIGH), i.e., conventional tillage plus full recommended rates of fertilizer and pesticides; reduced (RED), i.e., conservation tillage plus reduced rates of fertilizer and pesticides; and organic (ORG), i.e., conventional tillage plus N-fixing legumes and non-chemical means of weed and pest control]; and three crop rotation systems with varying levels of cropping diversity [a fallow-based rotation with low crop diversity (LOW); a diversified rotation using annual cereal, oilseed and pulse grains (DAG); and a diversified rotation using annual grains and perennial forages (DAP)]. The study was conducted over the 1996–2007 period on a Dark Brown Chernozemic soil (Typic Boroll) in the Canadian Prairies. As expected, total direct plus indirect energy input was the highest for the HIGH and RED input treatments (3773 MJ ha^?1 year^?1), and 50% less for ORG management. Most of the energy savings came from the non-use of inorganic fertilizers and pesticides in the ORG management treatments. Further, total energy use was the highest for the DAG treatments (3572 MJ ha^?1 year^?1), and similar but about 18% lower for the DAP and LOW crop diversity treatments compared to DAG. Thus, overall, the HIGH/DAG and RED/DAG systems had the highest energy requirements (4409 MJ ha^?1 year^?1) and ORG/DAP had the lowest (1806 MJ ha^?1 year^?1). Energy output (calorimetric energy content) was typically the highest for the HIGH input treatments (26,541 MJ ha^?1 year^?1), was about 4% less with RED, and 37% less with ORG management. The latter reflected the lower crop yields obtained with organic management. Similarly, energy output was the highest for the DAP treatments (25,008 MJ ha^?1 year^?1), about 5% less for DAG, and 20% less for the LOW crop diversity treatments. The higher energy output with the DAP treatments largely reflected that the entire harvested biomass of the forage crops was included in energy output, while for grain crops only the seed was included. The straw and crop residues from annual crops were returned to the land to protect the soil from erosion and to maintain soil organic matter as this is the recommended practice in this semi-arid region. In contrast to energy output and to net energy produced, energy use efficiency (measured as yield of grain plus forage produced per unit of energy input or as energy output/energy input ratio) was the highest for the ORG input treatments (497 kg of harvested production GJ^?1 of energy input, and an energy output/energy input ratio of 8.8). We obtained lower, but generally similar energy use efficiency for the HIGH and RED input treatments (392 kg GJ^?1 and ratio of 7.1). Thus, overall, ORG/DAP was the most energy efficient cropping system, while RED/LOW and RED/DAG generally ranked the lowest in energy use efficiency. Our findings support the current movement of producers toward ORG management as a means of reducing the reliance on non-renewable energy inputs and improving overall energy use efficiency of their cropping systems. Our results also suggest that moving away from traditional monoculture cereal rotations that employ frequent summer fallowing, toward extended and diversified crop rotations that use reduced tillage methods, although resulting in an increase in energy output, will not significantly reduce the overall reliance on non-renewable energy inputs, nor enhance energy use efficiency, unless perennial legume forages and/or legume grain crops are included in the cropping mix.  相似文献   

Microspectrophotometry of photoreceptor organelles from eyes of the prawn Palaemonetes   总被引：3，自引：0，他引：3  

T H Goldsmith  A E Dizon  H R Fernandez 《Science (New York, N.Y.)》1968,161(840):468-470

Microspectrophotometric measurements of individual dark-adapted rhabdoms of the prawn Palaemonetes vulgaris reveal the presence of two light-sensitive pigments. A pigment with maximum absorbancy at 555 nanometers is converted by light to a long-lived intermediate with wavelength of maximum absorbancy at 496 nanometers. A second pigment with wavelength of maximum absorbancy at 496 nanometers bleaches in the light, seemingly without forming detectable products at wavelengths longer than 375 nanometers. Both pigments occur in each layer of microvilli.  相似文献   

Role of nonimmune IgG bound to PfEMP1 in placental malaria     

Flick K  Scholander C  Chen Q  Fernandez V  Pouvelle B  Gysin J  Wahlgren M 《Science (New York, N.Y.)》2001,293(5537):2098-2100

Infections with Plasmodium falciparum during pregnancy lead to the accumulation of parasitized red blood cells (infected erythrocytes, IEs) in the placenta. IEs of P. falciparum isolates that infect the human placenta were found to bind immunoglobulin G (IgG). A strain of P. falciparum cloned for IgG binding adhered massively to placental syncytiotrophoblasts in a pattern similar to that of natural infections. Adherence was inhibited by IgG-binding proteins, but not by glycosaminoglycans or enzymatic digestion of chondroitin sulfate A or hyaluronic acid. Normal, nonimmune IgG that is bound to a duffy binding-like domain beta of the P. falciparum erythrocyte membrane protein 1 (PfEMP1) might at the IE surface act as a bridge to neonatal Fc receptors of the placenta.  相似文献   

持续、低剂量金霉素对肉仔鸡免疫机能的抑制作用研究   总被引：14，自引：0，他引：14  

佟建明  张日俊等 《中国农业科学》2001,34(2):200-204

270只Abore Acre商品代肉用公鸡随机分成3组，金霉素在饲料中添加水平分别为0、50只和150mg/kg，研究饲用金霉素对肉仔鸡法氏囊、脾脏和胸腺等免疫器官发育、以及免疫反应的影响。结果表明50mg/kg的金霉素对肉仔鸡脾脏和21日龄的胸腺无明显抑制作用，对T、B淋巴细胞转化率也无明显抑制作用（P＜0.05），而且显著促进法氏囊的萎缩（P＜0.05）。金霉素对T淋巴细胞转化率有明显的直接抑制作用；50mg/kg和150mg/kg的金素对BAS特异性抗体的产生均有显著的抑制作用（P＜0.01）。研究结果表明，持续、低剂量和金霉素对肉 鸡免疫器官发育和免疫应答具有显著的抑制作用，抑制作用随剂量增加而加强，150mg/kg的金霉素对肉仔鸡具有显著促生长作用。  相似文献   

Quantum-confined stark effect in single CdSe nanocrystallite quantum dots     

SA Empedocles  MG Bawendi 《Science (New York, N.Y.)》1997,278(5346):2114-2117

The quantum-confined Stark effect in single cadmium selenide (CdSe) nanocrystallite quantum dots was studied. The electric field dependence of the single-dot spectrum is characterized by a highly polarizable excited state ( approximately 10(5) cubic angstroms, compared to typical molecular values of order 10 to 100 cubic angstroms), in the presence of randomly oriented local electric fields that change over time. These local fields result in spontaneous spectral diffusion and contribute to ensemble inhomogeneous broadening. Stark shifts of the lowest excited state more than two orders of magnitude larger than the linewidth were observed, suggesting the potential use of these dots in electro-optic modulation devices.  相似文献   

RNA structure. Pulling on hair(pins)     

Fernandez JM  Chu S  Oberhauser AF 《Science (New York, N.Y.)》2001,292(5517):653-654

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基于EDA技术的自动立木整枝机无线遥控接收系统   总被引：1，自引：0，他引：1  

张俊梅  李文彬  撒潮  王德明 《北京林业大学学报》2007,29(4):19-21

在分析自动立木整枝机工作过程和控制要求的基础上,该文详细阐述了自动立木整枝机无线遥控接收系统的组成及工作原理,进而采用电子设计自动化(EDA)技术设计了自动立木整枝机无线遥控接收系统的数字控制逻辑.通过优化CPLD内部逻辑电路,有效消除了逻辑竞争冒险.仿真结果表明,该系统控制可靠性较高,能有效提高自动立木整枝机的功能安全性.   相似文献   

Human chromosome 7: DNA sequence and biology     

Scherer SW  Cheung J  MacDonald JR  Osborne LR  Nakabayashi K  Herbrick JA  Carson AR  Parker-Katiraee L  Skaug J  Khaja R  Zhang J  Hudek AK  Li M  Haddad M  Duggan GE  Fernandez BA  Kanematsu E  Gentles S  Christopoulos CC  Choufani S  Kwasnicka D  Zheng XH  Lai Z  Nusskern D  Zhang Q  Gu Z  Lu F  Zeesman S  Nowaczyk MJ  Teshima I  Chitayat D  Shuman C  Weksberg R  Zackai EH  Grebe TA  Cox SR  Kirkpatrick SJ  Rahman N  Friedman JM  Heng HH  Pelicci PG  Lo-Coco F  Belloni E  Shaffer LG  Pober B  Morton CC  Gusella JF  Bruns GA  Korf BR 《Science (New York, N.Y.)》2003,300(5620):767-772

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Masson三色染色与HE染色在豚鼠牙齿组织石蜡切片中的比较研究及应用     

韩天龙  王敏  红敏  萨其仍贵  查干其其格  和希格  孙德欣 《中国畜牧兽医》2011,38(3):55-57

针对牙齿组织形态学研究的难点,选择适宜固定液,用EDTA-2Na进行脱钙,完成了牙齿组织石蜡切片的制作。通过确定染色程序及各种染料的最佳作用时间,分别利用Masson三色染色法、传统的苏木精和伊红（HE）染色法对牙齿组织切片进行了染色观察。染色结果表明,与HE染色法相比,Masson三色染色更能使牙齿的各主要成分以不同颜色显现出来,色彩对比鲜明,亮丽润眼,为牙齿组织生理及病理组织形态学研究奠定了基础。针对机体中硬组织的相似特性,该试验方法可以在骨骼、软骨等硬组织的形态学研究中参考、改进并推广使用。  相似文献   

骨质疏松症治疗药物的研究进展     

刘宇桐  赵晓蕾  王小瑜  鲍丽  撒楠  魏长征  金黎明 《畜牧与饲料科学》2011,(4)

骨质疏松症是以骨量减少、骨的微观结构退化为特征,致使骨的脆性增加并易于发生骨折的一种全身性骨骼疾病,是当前严重危害人类特别是绝经妇女和老人的疾病之一.近年来出现了许多预防和治疗骨质疏松症的药物,极大地推动了骨质疏松症理论基础的完善和临床治疗研究.就该领域的研究进展进行了简要综述.  相似文献