北京典型边缘区25年来土壤有机质的时空变异特征   总被引：7，自引：1，他引：7  

秦静  孔祥斌  姜广辉  刘怡  李翠珍 《农业工程学报》2008,24(3):124-130

采用地统计学和GIS相结合的方法,研究了北京典型边缘区25 a来两个阶段(1981～2000年,2000～2006年)土壤有机质含量(SOM)的时空变异特征.研究结果表明:土地利用类型及土地利用方式的转换对土壤有机质含量产生重要影响.1981～2000年,荒草地向耕地的转换以及因灌溉设施的完善而引起水浇地面积的增加使得整个研究区域土壤有机质含量普遍增加,有机质含量平均值从9.64 g/kg增加到12.35 g/kg,增加了28%;在利益的驱使下,农户改变了土地利用方式,不再向种植粮食作物的土地追加投入,研究区域土壤有机质含量平均值由12.35 g/kg降低到11.46 g/kg(2000～2006年).空间上,1981年土壤有机质含量自北向南逐渐降低;与1981年相比,2000年的土壤有机质含量普遍增加一个级别,增加最多的区域分布在研究区域的中部,这些区域也是土地利用类型变化明显的地方,主要是荒草地向其他农用地的转换;与2000年相比,2006年研究区域内土壤有机质含量增加的只有3个地区,并且大部分增加不显著,增幅不到1g/kg.  相似文献   

Transitioning from standard to minimum tillage: Trade-offs between soil organic matter stabilization, nitrous oxide emissions, and N availability in irrigated cropping systems     

Angela Y.Y. Kong  Steven J. Fonte  Chris van Kessel  Johan Six 《Soil & Tillage Research》2009,104(2):256-262

Few studies address nutrient cycling during the transition period (e.g., 1–4 years following conversion) from standard to some form of conservation tillage. This study compares the influence of minimum versus standard tillage on changes in soil nitrogen (N) stabilization, nitrous oxide (N₂O) emissions, short-term N cycling, and crop N use efficiency 1 year after tillage conversion in conventional (i.e., synthetic fertilizer-N only), low-input (i.e., alternating annual synthetic fertilizer- and cover crop-N), and organic (i.e., manure- and cover crop-N) irrigated, maize–tomato systems in California. To understand the mechanisms governing N cycling in these systems, we traced ¹⁵N-labeled fertilizer/cover crop into the maize grain, whole soil, and three soil fractions: macroaggregates (>250 μm), microaggregates (53–250 μm) and silt-and-clay (<53 μm). We found a cropping system effect on soil N_new (i.e., N derived from ¹⁵N-fertilizer or -¹⁵N-cover crop), with 173 kg N_new ha⁻¹ in the conventional system compared to 71.6 and 69.2 kg N_new ha⁻¹ in the low-input and organic systems, respectively. In the conventional system, more N_new was found in the microaggregate and silt-and-clay fractions, whereas, the N_new of the organic and low-input systems resided mainly in the macroaggregates. Even though no effect of tillage was found on soil aggregation, the minimum tillage systems showed greater soil fraction-N_new than the standard tillage systems, suggesting greater potential for N stabilization under minimum tillage. Grain-N_new was also higher in the minimum versus standard tillage systems. Nevertheless, minimum tillage led to the greatest N₂O emissions (39.5 g N₂O–N ha⁻¹ day⁻¹) from the conventional cropping system, where N turnover was already the fastest among the cropping systems. In contrast, minimum tillage combined with the low-input system (which received the least N ha⁻¹) produced intermediate N₂O emissions, soil N stabilization, and crop N use efficiency. Although total soil N did not change after 1 year of conversion from standard to minimum tillage, our use of stable isotopes permitted the early detection of interactive effects between tillage regimes and cropping systems that determine the trade-offs among N stabilization, N₂O emissions, and N availability.  相似文献   

不同预处理方式对柳枝稷厌氧发酵性能的影响   总被引：1，自引：0，他引：1  

杨富裕  丁翠花  李连华  张蕴薇  臧艳运  孙永明  孔晓英  李东 《农业工程学报》2011,27(12):264-268

以柳枝稷为原料,研究微波,蒸汽加热和NaOH预处理方法对柳枝稷的结晶度和纤维结构的影响,同时考察了预处理后的柳枝稷在中温时的厌氧发酵性能.结果显示:3种处理都可以降低原料的结晶度;微波和NaOH处理可以显著降低柳枝稷的中性洗涤纤维、酸性洗涤纤维、木质素等含量;NaOH处理会降低粗脂肪的含量;蒸汽加热处理和原料的累积产气量(28 486和28 686 mL)及产气率(453.60和456.79mL/g)接近,而NaOH预处理由于C/N较高、阳离子毒害作用和抑制物的作用使得厌氧发酵性能降低.可见预处理可以降低柳枝稷纤维含量,但是对厌氧发酵性能并无明显改善作用.  相似文献   

不同硬化地面类型对城市悬铃木物质循环的影响   总被引：7，自引：0，他引：7  

孔正红  李树人  李有福  马建平  张惠琴 《河南农业大学学报》1998,(4)

研究了城市不同硬化地面类型（水泥地面、水泥砖面和踏实土地面）对悬铃木物质循环、水分循环及营养元素（Ｎ,Ｐ,Ｋ）循环的影响。结果表明：自然降水在城市水泥地面,水泥砖面或坚实的地表上很容易形成较大的地表径流,其中以水泥地面最甚,达４８％;各类型地面对雨水的渗透能力有明显差异,对照（花坛土）最强,为８７６％,踏实土（７２８％）次之,水泥砖面较差（３３％）,水泥地面渗透量接近于零。城市土壤营养元素除Ｋ外,Ｎ,Ｐ含量以踏实土最高,分别为００７７７和００８６６,其次为水泥砖面（００６９９和００５８７）及水泥地面（００５６２和００６３１）;生产力排序为：踏实土＞水泥砖面＞水泥地面。树木对土壤养分的吸收量也呈现相似的趋势,表现为：吸收量越大,理论归还量越大,但由于实际归还量较小,则土壤亏损就较多。  相似文献   

PCR技术在住肉孢子虫虫种鉴定上的应用     

汪明  孔繁瑶  肖兵南  董海涛  张长弓 《中国农业大学学报》1998,(Z2)

采用 RAPD 方法对水牛梭形住内孢子虫、待定种及黄牛枯氏住内孢子虫缓殖子基因组 DNA 进行了分析,待定种 PCR 产物的电泳带型与枯氏住肉孢子虫的差异较梭形住内孢子虫大,这与二者表型性状一致的研究结果不吻合.对3种包囊种特异性的 PCR 指纹进行了筛选,回收和纯化了3种包囊种特异性的 DNA 片段,待定种0.7kb 片段经α-~(32)PdATP 标记后用作探针,只与同源 DNA 杂交,不与其它包囊、宿主细胞和艾美耳球虫杂交,用 pGEM-T Easy Vector 对该片段克隆成功,并测出其全长序列,为进一步设计特异引物建立标准 PCR 诊断方法和用作核酸探针奠定了基础。  相似文献   

粗山羊草(Aegilops tauschii)遗传多样性的研究进展     

孔令让  董玉琛 《山东农业大学学报(自然科学版)》1999,30(4):464-470

概述了粗山羊草（Ａｅ．ｔａｕｓｃｈｉｉ（Ｃｏｓｓ．）Ｓｃｈｍａｌ．）的类别和地理分布以及其在山羊草属（Ａｅｇｉｌｏｐｓ）分类中的地位。并从个体、细胞、生化和分子水平上对粗山羊草遗传多样性的研究进展作了系统的综述。这 结果对进一步研究和利用业山羊草以及其它小麦近缘植物具有重要意义。  相似文献   

粳稻品种(系)抗稻瘟病特性分类的研究   总被引：2，自引：0，他引：2  

孔秀英  崔成焕 《东北农业大学学报》1999,30(2):116-121

用日本７个粳型单基因鉴别菌系将黑龙江省的一些粳稻品种（系）初步划分为８个抗性基因型：砦１号型、ＰｉＮｏ．４、Ｚｅｎｉｔｈ型、福锦型、杜稻型、下北型、关东５１号型、爱知旭型;根据供试品种（系）对黑龙江省四个优势小种的反应,将其划分为８个抗性类群,用日本鉴别菌系鉴定属于同一类群的品种,而用黑龙江省优势小种鉴定又被划分为不同类群,这说明同一抗性类型的品种可能含有相同的抗性基因,也可能含有不同的抗性基因。此外,在供试的粳稻品种（系）中没有发现对黑龙江省优势小种呈全抗反应类型的品种（系）。  相似文献   

Vertical and leaf-age-related variations of nonstructural carbohydrates in two alpine timberline species, southeastern Tibetan Plateau     

Ming-cai Li  Gao-qiang Kong  Jiao-jun Zhu 《Journal of Forest Research》2009,14(4):229-235

Spatial pattern of nonstructural carbohydrates (NSC) was analyzed in two alpine timberline species (Abies georgei and Juniperus saltuaria) growing at the timberline in Sergyemla Mountain, southeastern Tibetan Plateau. We aimed to examine the effect of canopy height and leaf age on balance between carbon uptake and consumption of timberline tree species in extremely environmental condition. The results showed that no significantly vertical variation in sugars, starch or NSC (soluble sugars plus starch) in A. georgei was found for any aged needles. Also, there were no significant differences among vertical gradients in both current and last-year leaves for J. saltuaria. However, different-aged needles/leaves showed significant differences in NSC concentrations in both A. georgei and J. saltuaria. For A. georgei, needle mean NSC across vertical canopies showed a significant increase from current-year to 2-year needles (P < 0.05), followed by a gradual decrease from 2- to 5-year needles (P < 0.05), whereas for J. saltuaria, last-year leaves had significant higher NSC except sugars compared with current-year leaves across canopies (P < 0.01). The observed trends of NSC along vertical canopy heights and leaf ages suggested that, in extreme environmental condition, not only light-induced carbon acquisition in photosynthesis but also carbohydrate export from leaves should be taken into account to explain the spatial pattern of NSC.  相似文献   

丘陵地区光伏智能施肥灌溉系统设计     

沈林晨  刘霓红  孔政 《现代农业装备》2017,(4)

生态农业的发展离不开施肥灌溉等设施的支持。本文介绍了光伏智能施肥灌溉系统的相关配置方案、设计方法、设备选型及计算方式;设计了一套以独立光伏提供能源动力、以GRPS提供无线远程控制,并结合现有智能化施肥灌溉技术的智能施肥灌溉系统,为丘陵山区农作物远程智能化施肥灌溉提供了新的解决方案。  相似文献   

比格犬胫神经皮层体感诱发电位正常值研究     

李拓  丛心宇  孔学礼  朱玉欣  张银  姜代勋  陈武 《中国农学通报》2017,33(5):112-115

为了测定比格犬胫神经皮层体感诱发电位(somatosensory evoked potential,SEP)的波形及其潜伏期和波幅的正常值。选用15只健康比格犬,在异氟烷吸入麻醉状态下,使用肌电诱发电位仪电刺激其胫神经,将自制参考电极和记录电极分别放置于头部Fz处和Cz处记录SEP波形。结果表明:15只比格犬刺激左右侧胫神经均可记录到清晰的双向SEP波。刺激左侧胫神经引发的波形潜伏期为P(21.71±1.978)ms、N(32.61±2.568)ms、P-N(10.90±1.338)ms,其变异系数分别为9.11%、7.87%、12.88%;波幅为(2.762±1.230)μV,变异系数为41.47%;刺激右侧胫神经引发的波形潜伏期为P(21.49±1.985)ms、N(32.55±2.359)ms、P-N(11.06±1.153)ms,其变异系数分别为9.24%、7.25%、10.24%;波幅为(2.634±1.092)μV,变异系数为44.55%。潜伏期和波幅左右侧差异均不显著(P0.05)。对正常比格犬胫神经皮层SEP的测定,获得了清晰的SEP波形及各波潜伏期和波幅的正常值,印证了潜伏期的稳定性优于波幅的稳定性,可以为实验室研究犬病理状态下的SEP和宠物临床应用SEP诊断疾病提供参考依据。  相似文献