Determination of critical nitrogen dilution curve based on leaf area index for winter wheat in the Guanzhong Plain,Northwest China

Excessive use of nitrogen(N) fertilizers in agricultural systems increases the cost of production and risk of environmental pollution. Therefore, determination of optimum N requirements for plant growth is necessary. Previous studies mostly established critical N dilution curves based on aboveground dry matter(DM) or leaf dry matter(LDM) and stem dry matter(SDM), to diagnose the N nutrition status of the whole plant. As these methods are time consuming, we investigated the more rapidly determined leaf area index(LAI) method to establish the critical nitrogen(N_c) dilution curve, and the curve was used to diagnose plant N status for winter wheat in Guanzhong Plain in Northwest China. Field experiments were conducted using four N fertilization levels(0, 105, 210 and 315 kg ha-1) applied to six wheat cultivars in the 2013–2014 and 2014–2015 growing seasons. LAI, DM, plant N concentration(PNC) and grain yield were determined. Data points from four cultivars were used for establishing the N_c curve and data points from the remaining two cultivars were used for validating the curve. The N_c dilution curve was validated for N-limiting and non-N-limiting growth conditions and there was good agreement between estimated and observed values. The N nutrition index(NNI) ranged from 0.41 to 1.25 and the accumulated plant N deficit(N_(and)) ranged from 60.38 to –17.92 kg ha~(-1) during the growing season. The relative grain yield was significantly affected by NNI and was adequately described with a parabolic function. The N_c curve based on LAI can be adopted as an alternative and more rapid approach to diagnose plant N status to support N fertilization decisions during the vegetative growth of winter wheat in Guanzhong Plain in Northwest China.     

亏缺灌溉对南疆棉花生长和水分利用的影响

针对南疆地区水资源短缺、作物水分利用效率低等问题,以棉花为试验材料进行田间小区试验,在棉花现蕾期、开花期以及结铃期分别设置3个亏缺灌溉水平(W₁:50%ET_c,W₂:65%ET_c,W₃:80%ET_c,ET_c为作物蒸发蒸腾量),以全生育期100%ET_c灌溉处理为对照(CK),研究膜下滴灌条件下,不同生育期亏缺灌溉对棉花生长、产量、氮素吸收和水分利用效率的影响.结果表明:现蕾期亏水对棉花株高、叶面积指数、地上干物质生长、氮素吸收和产量有不同程度的抑制效应,但复水后补偿效应显著,其中轻度亏水(W₃)在籽棉产量减少3.48%的条件下,WUE高达1.57 kg/m³,显著高于CK的1.48 kg/m³;开花期亏水,棉花的各项生长指标均有显著降低,复水后补偿效应不显著,不利于棉花生长发育;结铃期亏水对棉花地上干物质累积、氮素吸收和产量均有显著的抑制效应,但在W₂和W₃水平下,WUE均达1.51 kg/m³.综合考虑在保证棉花产量的同时达到节水增产的目的,可在棉花蕾期进行80%ET_c灌水,其他生育阶段实施充分灌溉,来控制营养生长,促进生殖生长,获得更高的水分利用效率.     

黑龙江省国有林区脆弱异质性家庭对停伐政策的态度及影响因素研究

基于2016年黑龙江省重点国有林区348户家庭的微观调查数据,实证分析黑龙江省国有林区脆弱异质性家庭对停伐政策的态度及影响因素。采用因子分析与综合评价法将348户职工家庭分为脆弱性家庭和非脆弱性家庭,描述性分析2组样本家庭对停伐政策的态度及认知情况,利用多元有序logit模型分析脆弱性与非脆弱性家庭对停伐政策态度的影响因素。结果表明:非脆弱性家庭对停伐政策的了解程度及执行情况的评价均高于脆弱性家庭,脆弱性家庭相对非脆弱性家庭对停伐政策的认可度较高,但是应对风险冲击的能力相对较低。脆弱性家庭和非脆弱性家庭对停伐政策的态度受户主特征、家庭特征以及政策认知特征变量的显著影响,但脆弱性家庭变量参数估计绝对值相对更大,因而停伐政策对脆弱性家庭有着更为敏感和强烈的冲击。     

氮吸附法分析生物质焦孔隙结构

采用氮吸附法对4种生物质焦(稻壳、树叶、玉米秆、棉花秆)的孔隙结构进行测量,结果表明,不同种类焦样的比表面积和孔径分布有明显差别,树叶的比表面积最大,为242.21 m2·g-1,玉米秆的比表面积最小,为0.81 m2·g-1.850℃时,稻壳、树叶、玉米秆焦样的孔径分布曲线在微孔和中孔范围各有一个分布峰,而棉花秆焦样的孔径分布曲线只在中孔范围内出现一个分布峰.热解温度是影响孔隙结构的一个重要因素,在高温条件下,同步热解得到的焦样的比表面积较大,微孔较多.在本研究中,600℃、850℃的稻壳焦样和850℃的树叶焦样具有较大的比表面积,比较适合做吸附剂.     

精梳棉卷成卷过程中起泡问题分析

介绍了成卷工艺对棉卷结构的影响以及棉卷成卷过程中起泡现象与准备工艺的关系.分析了棉卷成卷工艺过程中起泡过程和起泡原因,提出了防止起泡的措施.     

棉花不同时期去叶源对库源关系影响的初步研究

通过对棉花不同时期去主茎叶、叶枝叶、果枝叶和全部叶片的研究,初步探讨了棉花叶源对库的影响.结果表明:无论蕾期还是盛铃期,叶片是棉花光合产物的主要来源,没有叶片棉花就不能正常生长,也很难保证其产量;不同部位的叶片中,主茎叶的作用显著,蕾期去主茎叶后株高日增长量减少0.5 cm以上,干物质积累明显下降,盛铃期则导致棉铃大量脱落,成铃平均减少2个以上;去果枝叶的作用相对较小,去叶枝叶几乎无影响.     

Acclimation abilities of three tropical rainforest seedlings to an increase in light intensity

Current practices in many nurseries involve the germination of tropical rainforest seedlings in shaded conditions and transferral, at a later date, to environments with greater light intensities. Determination of the ability of these seedlings to acclimate to increased light intensities will allow seedling stock to be processed with maximum efficiency within the nursery. The acclimation abilities of three species, Agyrodendron actinophyllum, Cardwellia sublimis, and Flindersia brayleyana, commonly found in north Queensland's rainforests were investigated in this study. These particular species are highly valued for their cabinet timber qualities and are being reared in nurseries for use in reforestation trials and programs in north Queensland. Seedlings were initially raised in greenhouse conditions under two layers of shade cloth (16% of full sunlight) and then transferred into full sunlight at three different ages (3 weeks, 10 weeks, 14 weeks). Upon transfer, organ ratios and the direction of dry matter distribution was determined for each species and age group. Approximately 3 months after the seedlings were transferred, the acclimation ability of each species and age group was then determined. Dry matter distribution was found to change with age, irrespective of light environment. Individuals within a species with larger root systems and thicker or more dense leaves had a greater acclimation ability than those with smaller root systems and thinner or less dense leaves. Furthermore, individuals within a species whose dry matter distribution upon transfer was directed towards developing a large root system, and a small photosynthetic area and mass, had a greater acclimation ability than those whose dry matter distribution was directed away from such morphologies. Awareness of these relationships allows a better understanding of seedling response to gap formation in natural forests, and also allows plant nursery operators to make a more informed decision about when to move seedlings to environments with a higher light intensity.     

地膜覆盖对棉枯萎病发生的影响

地膜覆盖显著降低了棉花枯萎病的发病率与病情指数，极显著地提高了棉花的产量。     

几种分析方法对杂种棉后代综合评价的比较研究

为了明确几种分析方法对杂种棉后代综合评价的异同，于2002-2003年通过聚类分析、关联度分析以及多目标综合值评定分析原理对10个杂种棉后代在不同生态点的主要农艺及经济性状进行了分析．结果表明：3种分析方法对杂种棉后代的综合评价趋势基本上一致．从纤维品质来看，以湘Z-010，湘Z-004，湘Z-008，湘Z-007纤维品质较好．从产量性状来考虑，以湘Z-001，湘Z-002，湘Z-004产量较高．从湖南定位50-60支纱区划方针和产量性状来看，以湘Z-004表现最好，属于高产优质品种．     

广东山区开发的理论与实践：—广东山区开发理论与实践研讨会综述

本文述了“广东山区开发理论与实践研讨会”所达成共识的观点：广东山区开发具有重要的战略意义，广东山区开发必须走可持续肆展，农业产业化经营、工业化道路，同时必须搞好基础设施建设，组织好商品流通工作，优化资源配置。