玉米田杂草马唐的生长特性研究

在田间和室内条件下研究了马唐的生长特性。结果表明 ,马唐种子具有短期休眠 ,其出苗的适宜土壤深度为 0 .5～ 4 .0cm ;随着密度的增加和出苗时间的推迟 ,马唐的单株生长量逐渐下降。     

缺铁黄瓜地上部对根系适应性反应的调节

用营养液培养方法研究了黄瓜地上部对根系缺铁适应性反应的调节。缺铁导致植株根系Fe     

不同生境柚园果熟期橘小实蝇诱捕效果及种群密度比较

【目的】掌握不同生境柚园果熟期橘小实蝇种群密度和活动规律，探索不同色板、不同方位和不同气温环境对橘小实蝇的诱捕效果。【方法】于 2019 年 9—11 月在两类不同生境柚园开展橘小实蝇监测诱捕试验。【结果】经单因素方差分析表明，自然生境柚园中亮黄板每板诱捕数量为 24.84（±1.90）头，示范标准柚园中为 4.29（±0.44）头，诱捕效果显著高于土黄板和蓝板，自然生境柚园诱捕数量显著高于示范标准柚园。自然生境柚园中南面色板诱捕数量为 12.01（±2.02）头，示范标准柚园为 2.52（±0.44）头，均较其他方位多。气温与规范管理柚园橘小实蝇种群密度呈一定程度的负相关。两类柚园 11 月诱捕数量显著高于 9 月和 10 月。【结论】亮黄色粘虫板对柚园橘小实蝇有明显的防治效果。在示范标准柚园果实成熟期应结合自然条件下橘小实蝇的种群变化规律提前做好预防工作，根据柚园生境因地制宜，综合治理。     

不同白肋烟品种叶面腺毛密度的动态变化

以6个白肋烟品种为材料,对烟叶成熟过程中叶面腺毛形态和密度的变化规律进行了跟踪研究.结果表明,叶面总腺毛密度随着烟叶的成熟呈下降趋势.移栽后56～86天,长柄腺毛密度逐渐减少,短柄腺毛密度明显下降.不同品种间腺毛密度差异明显,不同部位腺毛密度表现为上部叶＞中部叶.长柄腺毛是白肋烟叶片上腺毛的主要类型.随着烟叶成熟,长柄腺毛所占比例逐渐增加,腺毛头部的分泌物增多充盈,到过熟期,腺毛萎缩、衰老和脱落的速度加快.     

和胃保肝对建鲤肠绒毛高度和肝细胞的影响

挑选个体大小、体重相近(15g左右)的建鲤50尾,随机分为5组(G1、G2、G3、G4和G5),即基础料组(对照组)、0.1%和胃保肝添加组、0.2%和胃保肝添加组、0.4%和胃保肝添加组和0.8%和胃保肝添加组,每组2个重复,每个重复10尾建鲤。饲喂3周后取建鲤肠道和肝脏制成组织切片,测定肠绒毛高度。结果表明:0.1%、0.2%、0.4%、0.8%和胃保肝不同添加量试验组建鲤的肠绒毛高度都极显著高于对照组(P0.01),各试验组建鲤肝脏细胞的胞浆密度比对照组的大。在建鲤饲料中添加0.4%和胃保肝,促进建鲤肠绒毛增长和提高肝脏细胞胞浆密度效果最好。     

Effects of Clear‐Cutting Alder Coppice on Surface Soil Properties and Aboveground Herbaceous Plant Biomass

The purpose of this investigation was to evaluate the effects of clear‐cutting and skidding impacts on surface soils in an alder coppice and aboveground herbaceous biomass. For this purpose, experimental sites used in the study were a randomized complete block with four replications. Some soil properties were measured at 60 pits at 0 to 5 cm and 5 to 10 cm deep in control, normal harvest, and main skid trail sites. In the main skid trail site, as compared to the control and normal harvest site, the bulk density increased from 0.90 to 1.52g cm^?3, the soil organic‐matter content decreased from 4.77% to 1.65%, and saturated hydraulic conductivity decreased from 86.34 to 9.6 cm h^?1 at 0 to 5 cm deep. Optimization of harvesting time and rehabilitation of skid roads needed to be done to prevent and minimize negative impacts of the skid roads on soils.     

Variations in Soil Physical Properties in a Cleared Forestland Continuously Cultivated for Seven Years in Eastern Nsukka,Nigeria

In this study, soil physical properties were evaluated in the top 40 cm of cleared forestland that had been subjected to continuous cultivation for 7 years to ascertain selected crop or crop combinations that influenced the soil physical properties the most. There was no significant effect of crop treatment on particle‐size distributions over 6 years of cultivation. In year 7, clay values were significantly (p = 0.05) greater in plots grown with solely cassava (SC) and solely maize (SM) than in the plots grown with solely pigeon pea (SP). The soil depth effects over the 7 years were significant on the clay content. The mean values of bulk density, pore‐size distribution, and hydraulic conductivity obtained from each plot fluctuated over the years. The bulk density values in 1998 ranged from 1.29 to 1.43 g cm³, but from 1999 to 2004, the range was from 1.12 to 1.40 g cm³. Thus, bulk density generally decreased when compared with their respective values in 1998. The greatest decrease of ≈ 22% was in 2000. More than 70% of the macroporosity values were significantly less than their respective values in 1998. The greatest decease of 72% was obtained from SM plots in 2001. All the microporosity were significantly more than the 1998 values. All the increases were >100% of the original values. These increases were reflected in the variations of total and saturated hydraulic conductivity (Ks) values. However, in 2004, Ks values decreased in the plots grown to C + P, SP, and SM. Generally, the C + M + P mixture appeared to be the most consistent in improving micro‐ and total porosities and Ks among the crop treatments.     

关于水力报警阀的几点看法

本文主要论述了水力报警阀的工作原理及其应用。     

Experimental Results on the Effects of Nonregular Spatial Patterns of Plants on Yield per Area

Based on several simplifying assumptions, a stochastic approach was developed which allows an estimation of the effects of nonregular spatial patterns of the distribution of individual plants on yield per area (F). In this approach, two random variables were attached to each plant: single plant yield (E) and individual space per plant (A). The latter was estimated by the area of Thiessen polygons. Yield per area was calculated theoretically by the expectation of the ratio E / A. Appropriate approximations of this expectation depend on the means (ē and ā), coefficients of variation (vE and vA) of E and A and their correlation (rEA). Yield per area can be decomposed into two additive terms: the first term gives the commonly used estimate ē/ā— or h(ā)/ā if a functional relationship between E and A is assumed: E = h(A). In this study, the two relationships E = k1 + k2 · ln A and E = A/(k3 + k4A) were used (with appropriately chosen constants k1, k2, k3, and k4). The second term in the decomposition of F can be interpreted as the effect of variable individual plant spaces on yield per area. In this paper, all theoretical concepts and results were applied to 17 experimental data sets of three cultivars of winter oilseed rape (Brassica napus L.). Single plant yields (E) and individual plant areas (A) were positively correlated with correlation coefficients from 0.64 up to 0.91. The ranges for both coefficients of variation were similar: 0.27 ≤ vE ≤ 0.65 and 0.28 ≤ vA ≤ 0.59. One obtains no significant differences in the goodness-of-fit for both tested relationships between E and A although the logarithmic relationship seems to be slightly superior. For only three data sets one obtains negative values for the percentage of the second term in the decomposition of F. This indicates an overestimation of yield per area by the commonly used estimates h(ā)/ā and ē/ā, respectively. These overestimations, however, are less than 5 %. In all other cases with positive values for the second term the yield per area is underestimated by the common estimates. For almost all data sets, however, the percentages of F which are explained by the common estimates are much larger than 90 %.     

Effect of Tillage and Plant Residue Management Practices on Shrinkage of a Vertisol

A study was carried out to determine the effects of different tillage and plant residue management practices on different soil moisture and shrink-swell properties of a Vertisol (very fine, semctitic, thermic, chromic Haploxerert (with less than 1 % slope). The core samples were collected in July (after harvesting of lentil) and in November (after planting of wheat) 1993. The two tillage methods were moldboard (T1) and chisel (T2). The two plant residue incorporation dates were in August (R1) and in October (R2). Results indicated that T2 tends to give higher water holding capacity and available moisture than T1. Immediate incorporation of plant residue (R1) tends to increase the bulk density and to decrease soil specific volume and void ratio when compared to late incorporation treatment (R2). In general, the two tillage treatments tend to decrease moisture availability, shrinkage characteristics, soil specific volume, and void ratio. They also tend to increase the soil shrinkage (subsidence and cracks volume) and bulk density. Chisel plough is recommended in Vertisols, if it is to be used before the rainfall.