土壤酶活性的总体在评价土壤肥力水平中的作用

土壤酶学的研究,从一开始便与土壤肥力的研究紧密地结合在一起.本世纪五十年代初,Hofmann^[5]提出了用土壤的酶活性作为衡量土壤的生物学活性和生产力的指标.其后,Lajudie与Pochon^[8]指出,根据土壤蛋白酶活性进行的分类,能较好地反映土壤的表观肥力.Moureaux^[9]在研究了许多土壤的转化酶活性后,也提出了类似的见解.     

上海郊区土壤的排水问题

上海郊区水田土壤,可以古岗为界分成东西两部分:浦东的沙泥、夹沙泥、黄泥头以及岗身的沟干泥是由长江沉积物发育起来的草甸土,地势较高(吴淞0.4米以上),地下水位较低(地面1米以下),质地偏中(轻壤-重壤),土壤通气孔隙较多,渗透性较好,因此土壤比较爽水,生产性能好,产量较高;浦西的青紫泥是由古太湖和其他许多湖荡港叉葑淤成陆的沼泽土,地势低洼(地面高程在吴淞零上2.2-3.5米),地下水位高(地面以下0.3-0.8米),质地偏粘(中壤-重壤),土壤通气孔隙少,毛管孔隙多,吸持力强,土壤透水性差,易于囊水,根系环境不良.     

汕优广12亲本开花习性观察初报

杂交水稻新组合汕优广12的父本广12,花时在9～13时,盛花在10～12时,峰值出现在11时,单株花期长达13天。母本珍汕97A花时分散。制种花时相遇在每天9～13时,集中在11～12时。花时全遇时,结实率早造达45.88％,晚造达43.75％。花时相隔48小时授粉,结实率仍可达20％。这一特征,为制种夺高产提供了生物学依据。     

THE EFFECT OF PROLONGED CROPPING ON THE EXCHANGE SURFACES OF THE CLAYS OF BROADBALK FIELD

Earlier studies have shown that the K-(Ca+Mg) exchange isotherms of field soils are not greatly changed by cropping, by additions of K-fertilizer, nor by moderate release of K from fixed forms. The present work shows that very prolonged K-enrichment or depletion in the Broadbalk trials has led to substantial differences between the exchange isotherms of soils from adjacent plots in proportion to the severity of their K-depletion. It is suggested that the changes result from the removal of inter-lamellar K and the consequent increases in the inter-lamellar spacings of parts of the clay crystals, which have increased the extent of the surface areas accessible to K-(Ca+Mg) exchange. It is possible that increases sufficient to cause substantial changes in the exchange isotherms may not be apparent in X-ray diffraction diagrams. Treatment of the K-depleted clays with m CaCl₂ appears to contract the newly expanded parts of the clay crystals, so that exchange on the occluded surfaces is once again too slow to be observed by the procedures used.     

模拟水生生态系中久效磷分配动力学

运用动态试验方法研究了久效磷在水及水生动植物内的吸收、转移、富集和排除的规律。水中久效磷随时间按Cow e~(-λwt)规律消失,面归方程为 _w=1.0000e~(-0.0749t).金鱼藻、螺蛳肉、鱼肉及底泥中久效磷及其代谢物按规律变化,各回归方程为:及水生动植物的生态富集系数按规律变化,各回归方程分别是:和。     

缺锰和多锰对番茄产量及风味品质的影响

通过设置不同的硫酸锰浓度并测定不同供锰水平下番茄的产量及与果实风味品质相关的指标,研究了缺锰和多锰对番茄产量和品质的影响。结果表明,无论缺锰还是多锰处理,番茄叶片叶绿素含量和产量都显著下降,叶绿素含量分别为正常处理的57.31%和61.50%,产量为58.25%和68.35%;叶片POD和SOD活性降低,以缺锰处理较为显著;缺锰和多锰处理的MDA含量分别高于对照71.07%和40.71%。缺锰和多锰处理导致果实的酸度分别增加37.4%和40.1%,可溶性固型物含量降低17.51%和13.19%,两者较正常锰处理均差异达到显著水平,Vc含量降低31.94%和9.45%;此外,2种处理果实中的活性物质番茄红素含量均下降34%左右,总酚和总黄酮含量下降30%~35%,总抗氧化力也明显降低,而且果实的芳香物质种类也少于正常处理。说明适宜的锰浓度是保证番茄高产、优质的重要因素。     

重力式清选机运动状态分析及工作参数的选择

本文在重力式清选机研制课题组理论分析和试验的基础上,建立了筛上物料在气力作用下的运动方程。并验证了工作筛面的运动参数和结构参数对清选质量的影响。     

风化煤对土壤胶体特性的影响

低产土壤是阻碍新疆地区农业生产发展的重要因素之一。这些土壤大部分有机质含$低,并有不同程度地盐碱化,亚待改良。新弧地区拥有较多的风化煤、揭煤、泥炭等资源,其中一些煤呈酸性或强酸性,可溶性有机物含量也较高。近年来,该地区各地群众用这些煤制成的腐铁或将煤粉直接施用于一些低产土壤上,在水稻、玉米、小麦等各种作物上均获得了不同程度的增产效果,其中在板结土、沙性土、粘质土和盐碱土上效果比较显著。连续大t施用煤粉的土壤,群众反映,土壤的肥力也有所提高。     

THE ORIGIN OF THE PENTOSE FRACTION OF SOIL POLYSACCHARIDE

Incubation of soil with monosaccharide for 224 days resulted in the evolution of about 80 per cent of the substrate carbon as CO₂ and the transformation of 3 per cent to soil sugars whether the substrate was ¹⁴C-glucose or xylose and whether the soil was pH 7.4 or pH 5.0. There was no detectable change in the total amounts of individual sugars in the soil during incubation. ¹⁴C-glucose and xylose gave the same distribution of radioactivity among the soil sugars : hexoses and 6-deoxy-hexoses were initially well labelled, with glucose having twice the specific activity of the other sugars. As the incubation progressed some activity appeared in the pentoses (the activity in xylose became very low within the first 14 days of the ¹⁴C-xylose incubation) and that in the hexoses slowly declined, with glucose no longer predominant. Nevertheless after 448 days the hexoses were still 3–4 times more radioactive than the pentoses. The activity in rhamnose did not decline with time so that eventually it became the most strongly labelled sugar. Incubation of soil with glucose and ¹⁴C-acetate showed very little transformation of the acetate to sugars indicating that glucose is not metabolized to C₂ compounds before it is transformed to other sugars. Ammo-acids in soil incubated for 7 days with ¹⁴C-glucose had much lower levels of radioactivity than hexoses or 6-deoxy-hexoses. It is concluded that if soil pentose originates by microbial synthesis it must accumulate slowly by a long process of selective decomposition of a mixture of polysaccharides.     

物料颗粒在滚筒式干燥机内停留时间的确定

通过对物料颗粒在滚筒内的运动分析,不仅确立了物料在干燥机内停留时间的计算公式,而且提出了滚筒式干燥机设计的两个重要条件,为滚筒干燥机的结构设计奠定了理论基础。     

南疆平原干旱土的微形态特征

通过野外调查 ,应用扫描电镜和偏光显微镜等手段 ,结合理化分析 ,研究了南疆平原干旱土的微形态特征和母质成因。结果表明 :南疆平原干旱土含有大量的由砂质原生矿物组成的骨骼颗粒 ,在这些颗粒之间填充着细粉砂质原生矿物及由隐晶质、微晶质碳酸盐和粘粒所组成的细粒物质。大部分原生矿物外形完好。同一剖面从表层向下骨骼颗粒增多 ,细粒物质减少。南疆平原干旱土的基本垒结类型为斑晶骨骼嵌埋状、聚积状和漂白砂型微垒结。土壤形成物主要是铁质、碳酸盐和石膏浓聚物 ,石灰、石膏的形态和其含量有关。碳酸盐一般以内晶霜形式存在 ,含量高时出现自生方解石颗粒、胶膜、凝团、凝块和凝粒 ;石膏以隐晶质、微晶质及针状、纤维状晶体的方式散布于细粒物质当中 ,石膏含量高时呈纺锤形晶体 ;在铁质粘化层中粘粒和粉砂明显增多 ,铁质浓聚物以铁染基质存在。石英砂表面超微结构特征表明 :南疆平原干旱土的母质搬运距离较短 ,同一剖面有不同的成因或多种成因组合 ,各种成因的母质都受到风成作用的影响 ,具有风蚀、风积的特征。     

黄土高原四种能源灌木林的研究

通过对4种能源灌木林的研究表期:同一树种生长量由于造林密度的增大而减小,而产量则由于造林密度的增大而提高。树种产量高低的顺序是:沙棘、柠条、沙柳、紫穗槐。4种能源灌木树种高密度（1333株/亩）林地的土壤水分高于或相近于中密度（666株/亩）的林地,其中耗水程度高的能源灌木树种为沙棘和紫穗槐,柠条和沙柳较低。从而可为半干旱黄土丘陵区发展和营造能源灌木林选择适宜的造林密度提供科学依据。     

ABA对水稻花后剑叶光合产物输配作用的示踪动力学研究

运用示踪动力学分析方法,分析 ABA 涂稻穗及剑叶后,剑叶中几种光合产物的变化,发现 ABA 涂稻穗后,能抑制剑叶中暂不输配物质的形成,对可输配物质的形成与光合产物的输出速率具促进作用。ABA 涂剑叶后,对暂不输配物质、结构物质与呼吸消耗具抑制作用,对可输配物质的形成具促进作用。     

THE UNIQUENESS OF THE MOISTURE CHARACTERISTICS

Experiments, designed to test the non-uniqueness which has been reported in the relationship between moisture content and suction in porous materials during transient flow conditions, are escribed. When a vertical column of sand was brought to uniform moisture content and uniform suction in a draining condition by percolating a constant flow through it until apparent equilibrium conditions ensued and then placed horizontally at the same time as the flow was stopped, the suction was found to decrease with time over a period of a day, indicating that the sand was now wetting up. This decrease was smaller the drier the sand. However, when the column was left in a vertical position with the water percolating through it for three hours after apparent equilibrium conditions were reached, a small adjustment of moisture content and suction was observed; when it was then placed horizontally as in the previous experiments little decrease of suction was observed. No change in suction was observed in either case if the equilibrium condition was reached in a wetting porous material. These experimental results and those of previous workers are explained by the hypothesis that, during drainage, some water is left in pores from which the air-water interface has already retreated to drain through film flow, more slowly, subsequently to the continuous water body. Additional experiments showed that the release of entrapped air may have a small effect on the uniqueness of the moisture characteristics.