The effect of low-molecular-weight organic acids and inorganic phosphorus concentration on the determination of soil phosphorus by the molybdenum blue reaction

Low-molecular-weight organic acids play an important role in the mobilization of soil phosphorus (P). The molybdate blue colorimetric method, based on the formation of P molybdenum blue compound, is commonly used for analysis of phosphate in soil and environmental samples. However, some organic acids can act as a ligand to bond with molybdenum acid, which subsequently interfere with the colorimetric reaction. The recoveries of P were inhibited by the addition of oxalic (>2 mM) and citric acids (>3 mM) both in standard P solutions and soil extracts, but formic and maleic acids did not interfere with the P determination. The inhibition of oxalic and citric acids on P recovery remained even at higher level of P (up to 100 μg P 100 ml⁻¹) though such interferences decreased by increasing P concentration. Comparison between oxalic and citric acids revealed the more pronounced interference by the addition of oxalic acid. The results suggested that the interference of organic acids with P determination is related to the types of organic acids and the ratio of organic acid ligands to P anions in the solutions. Thus, analysis of P using the molybdate blue colorimetric method should be undertaken cautiously in the presence of relative strong ligands like oxalic and citric acids.     

基于高速摄像系统的精密排种器性能检测试验

运用高速摄像系统对精密排种器的种子排种过程进行图像采集,将采集的图像进行背景去除、滤波、锐化、二值化等图像处理,提出了根据种子面积和质心位置特征值检测精密排种器性能的方法。在不同的工作参数下对排种精度和播种均匀性进行试验分析。试验结果表明：高速摄像检测和人工检测的排种合格指数相对误差小于1%,变异系数误差小于3%,此方法的检测精度满足精密排种器性能检测要求。     

Energy balance and partition in Inner Mongolia steppe ecosystems with different land use types

Land use change and grassland degradation are two of the most critical problems ubiquitously found in arid and semi-arid areas in Northern China. Energy fluxes, including net radiation (R_n), latent heat flux (LE), sensible heat flux (H) and soil heat flux (G), were examined over an entire year (December 2005 to November 2006) in different steppe ecosystems – the steppe and cropland in Duolun and the fenced and grazed steppe in Xilinhot – in Inner Mongolia based on direct measurements from four eddy-covariance flux towers. The seasonal changes in R_n, LE, H and G of the four sites were similar, with very low values during the period of snow cover from December to February, followed by a gradual increase in the growing season. The opposite seasonal patterns of the LE and H fraction resulted in significant seasonal changes in Bowen ratio (β). Human activity in cropland ecosystems not only resulted in a rapidly shift between LE and H, but also triggered a decrease in latent heat fraction because of a shortened growing season of crop plants. The significantly positive relationships between canopy surface conductance (g_c) and LE/LE_eq of all of the study sites suggested that a lack of precipitation coupled with high VPD conduced remarkable decreases of stomatal conductance. This could impede the latent heat partitioning of available energy (R_n − G) in semi-arid ecosystems, Inner Mongolia. The obvious decrease in the values of g_c and the decoupling factor (Ω) in both the cropland and the degraded steppe suggested that land use change could depress latent flux fraction and increase its sensitivity to air and soil drought.     

农用车辆自动导航定位方法

农用车辆自动导航技术可有效提高作业精度、实现农田规模化生产。该文以电瓶车为试验平台,使用 RTK DGPS、RTD GPS 和电子罗盘分别采集电瓶车的位置信息和航向角度信息,对农用车辆的导航定位方法进行了研究。试验时,以 RTK DGPS 采集的数据作为标准轨迹。在对试验数据进行空间配准后,采用 Kalman 滤波技术对 RTD GPS 和电子罗盘的数据进行了融合;通过计算综合权重值,对单 GPS 系统和融合系统的性能进行测试与评估,其值分别为 0.006、0.002。由此可知,采用 Kalman 滤波的电子罗盘和 RTD GPS 的组合导航系统,定位精度相对较高,稳定性较好,整体性能优于单 GPS 系统。     

农用地等级监测指标体系与方法

通过农用地等级质量监测,实时获取农用地等级质量信息是实现农用地可持续开发利用和耕地占补平衡的基础。在已有农用地分等定级指标体系成果的基础上,通过指标易变性分析选出引起农用地等级质量变化的易变性指标,进一步分析导致易变性指标变化的驱动力,并结合当前相关指标或驱动力因子的监测技术现状,筛选出了能够直接或间接监测并评价农用地等级质量的监测指标,建立了农用地等级质量监测指标体系,并针对各种指标提出了相应的监测方法。分析结果表明,由于充分考虑了驱动力的区域差异性,构建的监测指标体系也具有很强的区域性,相应的监测方法更为实用。     

泥沙输移比的研究方法及成果分析

泥沙输移比是反映流域侵蚀产沙输移能力的指标,对正确评价水土保持减沙效益及流域治理决策有着重要的科学意义与应用价值。对国内外泥沙输移比的研究方法及成果进行总结与分析,认为泥沙输移比的研究方法可分为直接计算（根据定义）与模型计算（通过建立泥沙输移比模型）2种。直接计算的关键是土壤侵蚀量的获取,而计算模型目前主要有因子经验模型、分布式模型与物理模型。在对泥沙输移比研究中土壤侵蚀量获取方法及建立的泥沙输移比模型进行总结与评述的基础上,按黄河流域、长江流域、国内其他地区及国外一些地区,分析了其泥沙输移比的研究成果,讨论了目前泥沙输移比研究中存在的3个问题及今后的发展方向。     

基于ANN-产量的耕地地力定量评价模型及其应用

管理水平近似条件下的作物实际产量是耕地地力等级的直观反映,在目前传统耕地地力评价AHP-模糊评判方法的基础上,尝试建立耕地地力的ANN-产量定量评价模型,并以山东省鱼台县为研究对象进行了实例研究.采用相对隶属度对各评价指标进行描述,以实际产量为目标输出标准,经神经网络训练得到评价模型.与传统方法相比,模型不仅能反映耕地地力评价的非线性特征,而且评价过程中不需要确定权重,消除了传统方法确定权值时人为因素的影响,增加了评价结果的客观性.通过与传统方法的对比发现,该模型评价结果与现行耕地地力评价方法的结果较为一致,为耕地地力的定量评价探索了一条新路.     

超高压提取丹参素的研究

该文研究常温下超高压提取丹参素的最优工艺.采用超高压常温提取,正交试验对丹参素超高压提取工艺优化,高效液相色谱法测定丹参素的含量,并与传统的热回流提取法进行比较.结果显示优选的最优工艺为:提取压力300 MPa,溶剂乙醇浓度80%,溶液pH 13,浸泡时间16 h,在此条件下丹参素得率为0.465%.超高压提取不仅得率高、时间短、耗能低,而且提取产物易于分离、纯化,同时超高压提取可以维持在低温下进行,特别适宜于受热不稳定化合物的提取,该技术适合中药有效成分的快速提取.     

Soil chemical properties and microbial biomass after 16 years of no-tillage farming on the Loess Plateau, China

Data from a 16-year field experiment conducted in Shanxi, on the Chinese Loess Plateau, were used to compare the long-term effects of no-tillage with straw cover (NTSC) and traditional tillage with straw removal (TTSR) in a winter wheat (Triticum aestivum L.) monoculture. Long-term no-tillage with straw cover increased SOM by 21.7% and TN by 51.0% at 0–10 cm depth and available P by 97.3% at 0–5 cm depth compared to traditional tillage. Soil microbial biomass C and N increased by 135.3% and 104.4% with NTSC compared to TTSR for 0–10 cm depth, respectively. Under NTSC, the metabolic quotient (CO₂ evolved per unit of MBC) decreased by 45.1% on average in the top 10 cm soil layer, which suggests that TTSR produced a microbial pool that was more metabolically active than under NTSC. Consequently, winter wheat yield was about 15.5% higher under NTSC than under TTSR. The data collected from our 16-year experiment show that NTSC is a more sustainable farming system which can improve soil chemical properties, microbial biomass and activity, and thus increase crop yield in the rainfed dryland farming areas of northern China. The soil processes responsible for the improved yields and soil quality, in particular soil organic matter, require further research.     

玉米/大豆不同间作模式下土面蒸发规律试验研究

为了准确估算间作农田土壤水分动态变化过程,制定合理的灌溉制度,该文采用微型蒸渗仪测定了玉米/大豆不同间作模式下不同位置处的土面蒸发量,分析了相对土面蒸发强度与表层土壤含水率的关系以及相对土面蒸发强度与叶面积指数的关系.结果表明:玉米/大豆间作模式下,不同位置处的土面蒸发量存在差异,2:3间作的累积蒸发量大于1:3间作;相对土面蒸发强度与表层土壤含水率呈指数递增关系,与叶面积指数呈指数递减关系.