膜下滴灌对水稻根系形态及生理性状的影响

为探明水稻在膜下滴灌灌溉方式下根系生长发生的变化,设置小区试验与传统淹灌进行对比,以粳稻品种“T-04”和“T-43”为材料,研究了膜下滴灌灌溉方式对水稻根系形态、根系氧化力和硝酸还原酶的影响.结果表明:土表下20 cm深度,膜下滴灌水稻的根系长度、表面积、体积和平均直径都高于传统淹灌,并且差异具有统计学意义.土表下40 cm,膜下滴灌对水稻根系形态影响不具有统计学意义;水稻根系氧化力都是呈先增大,后减小的趋势,水稻根系氧化力最大期因品种而异.分蘖期膜下滴灌对水稻根系氧化力的影响因品种而异,但在拔节孕穗期、齐穗期和乳熟期,膜下滴灌水稻根系氧化力高于传统淹灌,并且差异具有统计学意义,膜下滴灌水稻后期根系具有较强的抗衰老能力;膜下滴灌水稻根系硝酸还原酶活性高于传统淹灌,但在分蘖期和乳熟期的差异不具有统计学意义,在拔节孕穗期和齐穗期差异具有统计学意义.     

基于AHP法的4U-1400马铃薯收获机机械结构的设计

通过对机械设计方法学知识的理解与运用,给出了4U-1400马铃薯联合收获机的黑箱模型和形态学矩阵及功能原理的设计方法,提出其潜在可能的设计方案;利用层次分析法(AHP法),建立了马铃薯收获机的评价指标体系,对不同方案进行定性和定量的综合性评价和优劣排序;最后得出4U-1400马铃薯收获机机械结构的最优设计方案。     

我国农业机械化与城镇化关系的协整分析

在讨论我国农业机械化发展的内在机制以及与城镇化关系的基础上,运用协整分析方法建立时间序列数据模型,经过格兰杰因果关系检验,验证农业机械化与城镇化之间的长期稳定关系,进一步建立误差修正模型探讨这种稳定关系在长期内与短期内的动态变化特征,并预测我国2020年农业机械化发展水平。结果表明,在长期内,城镇化率增加一个单位农业机械化水平将提高1.09个单位。但是,农业机械化对当期城镇化的推进反应是滞后的,而是反映在长期趋势上。预测显示,2020年我国农业机械化水平将达到67.45%。     

Initial and residual efficacy of insecticides on different surfaces against rice weevil Sitophilus oryzae (L.)

The aim of the study was to investigate how various types of storage facilities with, e.g., concrete, metal, and plywood surfaces interfere with the activity of different insecticide formulations used for rice weevil Sitophilus oryzae (L.) control: malathion (EC), pirimiphos-methyl (EC), and lambda-cyhalothrin (CS and WP). Initial and residual efficacy were determined in the laboratory. Knockdown data for the initial effects were processed by probit analysis and presented as knockdown time (KDT) parameters with kdt-p lines. Delayed effects were shown as knockdown efficacy (%) determined after 24 h of weevils’ contact with 7-, 14-, 30-, 60-, 90-, 120-, 150-, and 180-day-old deposits on each surface. Malathion (EC) and pirimiphos-methyl (EC) showed the highest initial knockdown efficacy on metal, while it was 3.6 (3.4)- and 4.4 (3.3)-fold lower on concrete and plywood, respectively. Lambda-cyhalothrin (CS and WP) showed the highest initial efficacy on concrete, and slightly lower (1.3 and 2.4) fold on metal and plywood, respectively. Both formulations of lambda-cyhalothrin and malathion on metal, as well as pirimiphos-methyl on plywood were 100 % efficient against S. oryzae 180 days after the treatment. Delayed efficacy of both formulations of lambda-cyhalothrin decreased on plywood after 120 days, and after 180 days the efficacy was 55 %. All insecticides, except lambda-cyhalothrin (CS), expressed low knockdown efficacy on concrete, while the deposit of lambda-cyhalothrin (CS) on concrete was 100 % efficient during 90 days, and after 120, 150, and 180 days the efficacy was 83, 65, and 17 %, respectively.     

覆盖对红叶石楠和红豆杉生长的影响

在相同地域条件下,采用传统养护方式与覆盖养护方式的对比试验,研究覆盖对红叶石楠和红豆杉生长的影响。结果表明:合理有效的覆盖养护方式,可以明显的改良土壤肥力,促进植株生长。     

石竹各器官生物量回归模型研究

利用石竹地上部分生物量调查资料 ,探讨各器官平均生物量与胸径、地径、竹高、枝下高的相关关系 ;应用回归分析方法 ,选择不同的回归方程来拟合生物量估测数学模型。结果表明 :以幂函数W =cDaHb 所拟合的生物量估测模型最佳 ,经实用性检验 ,可靠性较高 ,具有很好的实用价值。     

Soil desiccation for Loess soils on natural and regrown areas

In the Loess Plateau, soil desiccation has become a serious problem for forest and grass vegetation. Soil desiccation leads to the formation of a dried soil layer (DSL). This paper presents the results of research carried out in the central part of the Loess Plateau. The objective of the research was to produce a statistically supported set of indicators for evaluating soil desiccation of forestlands, to present a heuristic idea for soil desiccation and to supply scientific support for replacing farmland with forest or grass in the Loess Plateau and other regions of China. Here, we suggest that more attention should be paid to soil desiccation and its effects on the ecosystem of the region in the future. The results showed that natural Quercus liaotungensis forestlands (NQF) retained more water content than regrown Robinnia pseudoscacia forestlands (RRF). Significant DSLs were formed in the RRF but not in the NQF. A possible reason for no formation of DSL in NQF could be due to the presence of an arbor–shrub–herb stand structure and large humus and litter accumulation, which increased the natural forest's (NF) adaptability to the environmental conditions. Soil water content in the north-facing slope was significantly larger than in the south-facing slope. DSLs formed in the 0–500 cm layer of the south-facing slope. When slope gradient was greater than 25°, soil water content deceased sharply and showed significant difference compared with 9°, 15° and 20° (P < 0.05). So, we conclude that plant species, aspect and slope angle could be the predicators for the formation of DSLs. The analysis on soil physical properties of 0–60 cm layer indicated that plant species, aspect and slope angle also have significant effects on bulk density, porosity, plant-available capacity, and hydraulic conductivity, especially in the 0–20 and 20–40 cm layers. In the NQF and RRF with north-facing slope, soil physical properties were improved.     

Degradation Kinetics of an Aged Hydrocarbon-Contaminated Soil

PM2.5 and PM10 samples were collected in the urban atmosphere of Elche (southeastern Spain) between December 2004 and November 2005. The samples were analyzed for mass and water-soluble inorganic ions (Na⁺, ${\text{NH}}^{{\text{ + }}}_{{\text{4}}}$ , K⁺, Ca²⁺, Mg²⁺, Cl^?, ${\text{NO}}^{{\text{ - }}}_{{\text{3}}}$ and ${\text{SO}}^{{{\text{2 - }}}}_{{\text{4}}}$ ) with the aim of investigating the influence of the climatic and geographic features of a coastal semiarid area on the contribution of these species to PM levels. Secondary inorganic ions ( ${\text{SO}}^{{{\text{2 - }}}}_{{\text{4}}}$ , ${\text{NO}}^{{\text{ - }}}_{{\text{3}}}$ , ${\text{NH}}^{{\text{ + }}}_{{\text{4}}}$ ) were the major components in the fine fraction (PM2.5), accounting for 40% of the total mass. The relationship between non-marine ${\text{SO}}^{{{\text{2 - }}}}_{{\text{4}}}$ and ${\text{NH}}^{{\text{ + }}}_{{\text{4}}}$ indicated that fine sulfate particles were completely neutralized by ammonium. In the coarse fraction (PM10–2.5), nitrate (as NaNO₃ and Ca(NO₃)₂), together with crustal (CaCO₃) and marine species (NaCl) accounted for almost 50% of the total mass. Fine sulfate and coarse nitrate showed summer maximums. In contrast, the concentrations of fine ${\text{NO}}^{{\text{ - }}}_{{\text{3}}}$ were lowest in the warm period. Ammonium presented both winter and summer maximums. The levels of marine ions, except for coarse Cl^?, were highest in summer when the dominant wind flow is from the sea. No significant seasonal variations were observed for coarse Ca²⁺ and ${\text{SO}}^{{{\text{2 - }}}}_{{\text{4}}}$ . The concentrations of all inorganic ions increased during Saharan dust events, in particular, fine ${\text{NH}}^{{\text{ + }}}_{{\text{4}}}$ and ${\text{SO}}^{{{\text{2 - }}}}_{{\text{4}}}$ and coarse $NO_3^ - $ . Coarse calcium was proved not to be a good tracer for this type of episode in our region since the average levels of this cation are elevated and the relative increase in its concentrations during African events was not as high as expected.     

模拟降雨条件下成垄压实对硝态氮迁移的影响

利用人工模拟降雨研究了成垄压实施肥条件下不同的垄坡度及不同压实的障碍层对硝态氮迁移的影响。结果表明,对一次60mm的降雨,无障碍层存在时,平地施肥条件下NO3--N淋溶剧烈,土壤表层施肥部位的NO3--N仅余总施入量的0.1%左右。垄沟施肥因其将入渗水分与施肥区分开,从而可以降低NO3--N的淋溶。不同的垄坡度对NO3--N的淋溶略有影响,30垄坡条件下上层土壤NO-残留量略大于20、40。相对于不同坡度垄沟,在施肥带部位通过压实形成水分运动的障碍层对防止NO3--N淋溶的效果较为显著,当压实层的土壤容重为1.36g/cm3时,施肥部位残余NO3--N就可达727.40mg,占原施入量的17.2%;对容重1.42g/cm3的压实层,其施肥部位残余NO3--N已占到原施入量的23.6%。以上结果表明通过压实在施肥部位形成障碍层的成垄压实施肥法,减小通过施肥区的入渗水量,从而可减少施肥部位的NO3--N随入渗水分向深层土壤的迁移和累积,这对提高氮肥利用率,保护地下水资源具有重要意义。     

不同比例尺DEM提取地面坡度的精度研究——以在黄土丘陵沟壑区的试验为例

以陕北绥德县韭园沟流域为试验样区 ,采用高精度 1∶ 1万 DEM所提取的坡度为准值 ,应用多层面复合分析和比较分析的方法 ,研究该地区 1∶ 5万 DEM提取地面坡度的误差特征与纠正方法。试验结果显示 ,所获得的不同空间尺度下 DEM所提取坡度值的转换图谱 ,可对 1∶ 5万 DEM计算的地面坡度统计值进行有效修正。该成果对于 DEM数据在水土保持领域若干应用标准的制定 ,提供了重要的理论依据与技术路线