喷灌灌水量对冬小麦生长、耗水与水分利用效率的影响

于2006-2008年在中国科学院通州农田水循环与节水灌溉试验基地进行田间试验,研究灌水量对冬小麦生长、耗水、产量和水分利用效率的影响.试验设置了不同的灌水量处理,灌水量以布置在冬小麦冠层顶部20 cm标准蒸发皿蒸发量(E)的倍数表示.试验结果表明:2006-2007生长季节中0.75 E处理和2007-2008生长季节中0.625 E处理所对应的冬小麦产量最高.当灌水量小于0.25 E时,冬小麦生长受到水分胁迫,其产量下降25%以上.两个生长季节中冬小麦耗水量为219～486 mm,耗水量随灌水量的增加而增大.冬小麦产量和水分利用效率与耗水量之间呈二次函数关系.北京地区冬小麦返青后的生长季节内,其适宜喷灌水量为0.50～0.75 E.     

基于SVAT模型的冬小麦光合作用和蒸散过程研究

在已建立的土壤－植被－大气传输（SVAT）模型中,冠层光合作用／气孔导度耦合子模型可区分遮荫叶和受光叶光合作用强度的差异;作物生长模型考虑了生长呼吸和维持呼吸,模拟与实测结果对比发现,日总蒸散量实测和模拟的根均方差（RMSD）为0.65mm,平均绝对差（MAPD）为14％;对冠层上部净光合作用率日变化过程而言,实测和模拟结果具有较好的一致性。利用模型模拟了冬小麦全生育争光合作用率和蒸散的演变过程。最后,分析了冬小麦蒸散和水分利用效率对不同最大叶面积指数,大气CO2浓度和叶片N含量的响应。     

林网保护区冬小麦生长过程的数值模拟

给出了一个模拟冬小麦生长过程的产量生态学模式,并对黄淮海平原林网保护区冬小麦的生长过程进行了数值模拟.模型输出变量包括作物的叶面积指数,根、茎、叶、籽等地上和地下器官生物量,以及与作物生长密切相关的土壤水分变化情况、作物水分利用率、光合/呼吸效率等生理生态因子.结果表明,由于林网地区小气候条件的改善,使得农林复合系统较之单作农田有更强的抗旱能力,在干旱的1994年,林网保护下的农林复合系统生产力较单作农田提高11.6%左右.模式输出的小麦地上部分生物量与生长监测资料十分一致.     

土壤水分和磷营养对小麦根系生长生理特性的影响

采用小偃６号小麦品种,在模拟田间原状土容重的条件下土培,研究了土壤水分和磷营养对小麦根系生长生理特性的效应。结果表明：在土壤相对含水量为４０％─７０％范围内,土壤水分亏缺,小麦根系生长受到限制,根系比表面积（ＲＡ）、根呼吸速率（Ｒｐ）、根水势（Ｒψｗ）和叶片蒸腾强度（ＥＩ）明显降低,根系干物重（ＲＤＷ）减少;轻度干旱有利于根系的延伸生长;在土壤干旱条件下,磷营养可以提高根系ＲＡ,降低根系Ｒｐ,提高Ｒψｗ、增加叶面ＥＩ,促进根系延伸生长,扩大小麦根系对土壤深层水分的吸收和利用,进而促进地下部生长,提高ＲＤＷ。磷除作为一种营养物质促进作物根系生长发育外,在水分胁迫条件下,磷营养可明显改善植株体内的水分关系,增强对干旱缺水环境的适应能力,提高作物抗旱性。促进根系生长,提高水分利用的有效方法是根据土壤水分状况调节磷的用量。     

旱地冬小麦灌浆期冠层温度与产量和水分利用效率的关系

利用红外测温仪,于2005～2006年在甘肃陇东旱原研究了我国北方冬麦区域的23个小麦品种(系)灌浆不同时期冠层温度的差异及其与产量和水分利用效率的关系。结果表明,不同基因型小麦在籽粒灌浆结实期存在着冠层温度高度分异的现象,其分异程度随灌浆过程的进行明显加大,到灌浆中后期达到最大。无论灌浆初期还是中期或中后期,旱地冬小麦产量、水分利用效率与冠层温度均呈极显著的负相关(R2=0.445-0.812),并且随着灌浆期推移,相关性增大,灌浆中后期冠层温度每升高1℃,旱地冬小麦产量减少近280 kg hm-2,水分利用效率下降约0.6 kg hm-2mm-1。灌浆中期以后不同基因型小麦冠层温度保持较高的一致性,冠层温度偏低的品种具有较高的产量和水分利用效率。灌浆中后期的冠层温度在评价小麦产量和水分利用效率上具有较高的可靠性,可作为一个田间选择指标应用。     

根修剪对黄土旱塬冬小麦(Triticum aestivum)根系分布、根系效率及产量形成的影响

通过田间试验研究了不同时期根修剪处理对冬小麦（Triticum aestivum）根系大小与分布、根系效率、水分利用效率及产量形成的影响。设置4个根修剪处理：越冬期小剪根（WS）、越冬期大剪根（WB）,返青期小剪根（GS）、返青期大剪根（GB）,未剪根小麦作为对照（CK）。结果表明,到花期时,各根修剪处理小麦的在0～120cm总根量均显著小于对照。与对照相比各根修剪处理主要是显著地减少了上层土壤中的根量。但WS和GS两小剪根处理和对照相比在中层土壤中有较大的根量;花后各处理小麦旗叶的气孔导度和蒸腾速率均显著大于对照。这说明根修剪处理减少了小麦表层的根量,从而削弱了表土干旱信号对作物与外界气体交换的抑制作用。花期时各根修剪小麦的净光合速率均显著高于对照,而单位面积上的根呼吸速率均显著小于对照,根修剪处理提高了小麦的根系效率,使更多的光合产物用于籽粒生产,从而提高了小麦的收获指数。根修剪还提高了小麦的水分利用效率,其中WS、WB、GS处理的水分利用效率显著高于对照。但是GB处理的水分利用效率却没有显著提高。因此,本研究进一步证明了由不同年代品种得到的推测,认为在旱地农业中,通过遗传育种或采用适当农艺措施优化根系分布,既可以减少生长前期作物对水分的过度消耗,又能够削弱花后表土过度干旱对作物生长抑制作用,同时降低根系对同化产物的消耗,对作物产量及水分利用效率的提高具有积极的作用。     

利用亚像元尺度信息改进区域冬小麦生长的模拟

为了探寻遥感观测面尺度与作物模型模拟点尺度不匹配问题的解决方案并改善区域作物生长模拟精度,以河南省鹤壁市为研究区,以冬小麦为研究对象,基于MODIS、Landsat 8遥感数据和Wheat SM作物生长模型,通过MODIS LAI过程线重建、亚像元尺度信息提取、集合卡尔曼滤波同化等方法,进行了冬小麦生长模拟的研究。结果表明:通过MODIS LAI过程线重建并提取亚像元尺度信息,冬小麦纯度在80%以上的遥感反演LAI与冬小麦两个关键生育期实测冠层LAI的均方根误差(RMSE)为0.69,以最近邻域法赋值到整个模拟区域,研究区2013—2017年模拟总产和实际总产相比的RMSE在未同化遥感反演的LAI信息时为6.73×108kg,同化未利用亚像元尺度信息调整的遥感估算LAI时,RMSE上升到8.24×108kg,同化利用亚像元尺度信息分区赋值的遥感LAI时,RMSE下降到3.48×108kg。利用亚像元尺度信息生成与作物模型时空尺度匹配的格点化LAI遥感产品,可提高作物生长模型区域化应用的精度。     

土壤干旱胁迫对作物影响的模拟研究进展

用于模拟土壤干旱胁迫对作物影响的模型分为两类,一是水分管理模型,此类模型并不模拟作物的生长发育,但可以用于灌溉管理;二是作物生长模拟模型,这类模型模拟作物生长的主要过程(如叶片生长、生物量的积累与分配等),通常以实际蒸腾与潜在蒸腾的比值估算土壤干旱胁迫对作物光合的影响,近年来发展的耦合模型将植物的碳同化、蒸腾、能量平衡以及气孔行为相耦合,使得土壤干旱胁迫对作物影响的模拟更具机理性。本文从不同模型模拟土壤干旱对作物影响的原理入手,阐述了水分管理模型(FAO水分生产函数模型)、作物生长模型(Aqua Crop模型、CERES-Maize模型、WOFOST模型、EPICphase模型、耦合模型)等具有代表性模型是如何模拟土壤干旱胁迫对作物生长发育和(或)产量影响的,提出了作物模型模拟土壤干旱胁迫影响时应着力解决的问题:完善干旱对作物物候的影响模拟;考虑花期不遇对作物产量影响的模拟;考虑后续持续影响的模拟机制;发展更加基于物理和生理过程的模型。提出:作物模型的发展还需要多领域如模型程序员、田间试验、植物生理学家的相互协同与发展,田间试验研究是作物模型发展不可或缺的数据来源与坚实基础。     

土壤水分与冬小麦根、冠功能均衡关系的模拟研究

利用已建立并经充分验证过的根,冠系统模拟模型,研究了不同土壤水分条件下根、冠之间消长关系,给出了不同１ｍ土体贮水量波动情况下根冠比动态变化模拟结果,并提供了有关试验数据作为佐证,其中有些结论为常规试验不易得到的全新认识,有些结果支持并证实了以往有关结论,均为水分对作物生长实施调控提供了重要依据。     

限量灌溉下冬小麦水分利用效率模拟

用参数调试后的DSSAT-CERES Wheat模型,以郑州地区冬小麦全生育期降水偏缺的2003-2004年逐日气象资料为背景数据,在分析作物阶段缺水量的基础上,限定灌溉量100 mm以内,分不灌水、灌一水、二水、三水处理,着重模拟研究限量灌溉对冬小麦水分利用的影响,并引入田间水分管理反映指标(WMRIs)为优化灌溉方案设计提供综合评价参考.结果表明:限量灌溉可在一定程度上缓解水分胁迫,促进增产并提高水分利用效率;各种处理均较不灌水明显增产,增产率为13.1%～73.3%;小麦对水分的吸收利用总体表现为灌二水优于灌三水优于灌一水;水分利用效率越冬水+灌浆水最高,灌溉水利用效率拔节水最高;拔节期是限量灌溉的最佳时期.     

Modelling crop growth and biomass partitioning to shoots and roots in relation to nitrogen and water availability,using a maximization principle

Many crop models relate the allocation of dry matter between shoots and roots exclusively to the crop development stage. Such models may not take into account the effects of changes in environment on allocation, unless the allocation parameters are altered. In this paper a crop model with a dynamic allocation parameter for dry matter between shoots and roots is described. The basis of the model is that a plant allocates dry matter such that its growth is maximized. Consequently, the demand and supply of carbon, nitrogen, and water is maintained in balance. This model supports the hypothesis that a functional equilibrium exists between shoots and roots.This paper explains the mathematical computation procedure of the crop model. Moreover, an analysis was made of the ability of a crop model to simulate plant dry matter production and allocation of dry matter between plant organs. The model was tested using data from a greenhouse experiment in which spring wheat (Triticum aestivum L.) was grown under different soil moisture and nitrogen (N) levels.Generally, the model simulations agreed well with data recorded for total plant dry matter. For validation data the coefficient of determination (r²) between simulated and measured shoot dry weight was 0.96. For the validation treatments r² was slightly lower, 0.94. In addition to dry matter production the model succeeded satisfactorily in simulating the dry weight of different plant organs. The response of simulated root to shoot ratio to the level of soil moisture was mainly in accordance with the measured data. In contrast, the simulated ratio seemed to be insensitive to the changes in the levels soil N concentration used in the experiment.The data used in the present study were not extensive, and more data are needed to validate the model. However, the results showed that the model responses to the changes in soil N and water level were realistic and mostly agreed with the data. Thus, we suggest that the model and the method employed to allocate dry matter between roots and shoots are useful when modelling the growth of crops under N and water limited conditions.     

计算机模拟渍水时期及持续时间对春玉米生产及产量的影响

借助田间、水槽试验的结果结合Penning de Vries的MACROS模型建立玉米生长发育与水分动态耦合的模拟模型,通过验证后用于模拟不同渍水时期及持续时间对春玉米生长及产量影响的动态,模拟结果表明在田间全程控制水分为田间持水量90％以下,春玉米孕穗期为渍水危害的敏感期,其次为4－6叶期,在自然降水及土壤状况影响下,春玉米幼苗期4－6叶时为渍水的敏感期,8叶及孕穗期相对较耐渍,在玉米4、6叶期时,渍害造成产量下降的临界期为5天;而在8叶、孕穗期为10－15天,但持续20天的渍水对任何时期的春玉米生长都造成严重的影响,因此在生产中应注意在苗期及孕穗期及时排除田间多余的水分及降低地下水位。     

土壤缓慢脱水对开花期小麦根系及叶片渗透调节及渗透调节物质的影响

以抗旱性不同的小麦品种为材料,在小麦的水分临界期开花期进行缓慢脱水处理,分别在脱水的不同阶段取样测定叶片及根系的渗透调节能力及渗透调节物质。结果表明：随着土壤含水量的降低,叶片与根系的饱和渗透势同步下降,表现出叶片与根系对水分胁迫反应的一致性,但根系的渗透调节能力低于叶片。根系与叶片的渗透调节物质,一方面在物质总含量方面,表现出与渗透调节能力的一致性,另一方面各种物质的相对含量又有一定差异,叶片中可溶性糖与K+的含量及增加量都高于根系,而根系中的游离氨基酸与Ca2+的相对增加量则大于叶片。     

土壤缓慢脱水对开花期小麦根系及叶片渗透调节及渗透调节物质的影响

以抗旱性不同的小麦品种为材料,在小麦的水分临界期开花期进行缓慢脱水处理,分别在脱水的不同阶段取样测定叶片及根系的渗透调节能力及渗透调节物质。结果表明：随着土壤含水量的降低,叶片与根系的饱和渗透势同步下降,表现出叶片与根系对水分胁迫反应的一到场生,但根系的渗透调节能力低于叶片。根系与叶片的渗透调节物质,一方面在物质总含量方面,表现出与渗透调节能力的一致性,另一方面各种物质的相对含量又有一定差异,叶片中可溶性糖与K＋含量及增加量都高于根系,而根系中的游离氨基酸与Ca^2 的相对增加量则大于叶片。     

Is low rooting density of faba beans a cause of high residual nitrate content of soil at harvest ?

It was the aim of this study was to evaluate the hypothesis that low rooting density of faba beans is the major reason for the comparable low depletion of N_min-nitrogen from the rooted soil volume during the vegetation period. Therefore a simulation study was carried out using data from a two-year field experiment with faba beans and the reference crop oats. Since the nitrate dynamics in the soil is closely coupled with the water budget, the model simulated also the water uptake by plants, movement and content in the soil applying a numerical solution of the Richard's equation. The nitrogen budget part of the model includes calculation of vertical nitrate movement in the soil, mineralisation of nitrate from organic matter and nitrate uptake by the crop. Vertical nitrate movement was simulated with the convection-dispersion equation. Mineralisation was computed from a simple first order kinetic approach using only one fraction of mineralisable organic matter. Nitrate uptake was assumed to be determined either by the nitrogen demand of the crop, which was estimated from a logistic growth equation that was fitted to measured data of N-accumulation, or by the maximum nitrate transport rate towards the root surface. The latter was computed from a steady state solution of the diffusion - mass flow equation for cylindrical co-ordinates.For oats the model calculated a maximum nitrate transport rate towards roots that was quite close to the measured N-uptake of that crop. For faba beans, however, the calculated maximum nitrate transport towards roots was much lower than total N-uptake and lower than for oats. Consequently, simulated N_min-contents below faba beans were during the growing season about 20-30 kg N ha^–1 higher than below oats. This difference matches quite close with the observed differences between the two crops. Therefore it was concluded that low nitrate uptake resulting from low rooting density is the main reason for higher residual nitrate contents below faba beans at harvest time.     

Die Reaktion anfälliger und resistenter Gerstensorten auf pilzliche Krankheitserreger

Response to fungus pathogen in susceptible and resistant barley cultivars IV. Water- and dry matter content
The changes in dry matter- and water content dynamics in the root and shoots of barley infected with the fungus Erysiphe graminis f. sp. hordei Marchal were studied in variously receptive cultivars. Cultivation of plants in solid (perlite) or liquid medium was compared.
The response of susceptible barley to mildew infection is characterized at First by an increase in water content and slightly in dry matter of shoots accompanied with an unsignificant decrease in root growth. However, as the fructification progressed, barley growth is reduced in all investigated parameters. The infected resistant barley indicates unsignificantly increased values in water content of shoots, only.
In the susceptible host the growth of roots in relation to shoots is markedly reduced after infection.
The percentage of water content of shoots is slightly increased in both cultivars during the first phases of infection. Then, in susceptible barley it declines, compared with the control, from the stage of full developed fructification. In the resistant barley it doesn't change more expressively. In roots of infected plants the increased hydratation is found during the whole observation period (in the resistant barley only with plants growing in liquid medium).     

Modelling the effect of varying soil water on root growth dynamics of annual crops

We present a simple framework for modelling root growth and distribution with depth under varying soil water conditions. The framework considers the lateral growth of roots (proliferation) and the vertical extension of roots (root front velocity). The root front velocity is assumed to be constant when the roots descend into an initially wet soil profile. The lateral growth of roots is governed by two factors: (1) the current root mass or root length density at a given depth, and (2) soil water availability at that depth.Under non-limiting soil water conditions, the increase in root mass at any depth is governed by a logistic equation so that the root length density (R _v) cannot exceed the maximum value. The maximumR _v, is assumed to be the same for all depths. Additional dry matter partitioned to roots is initially distributed according to the current root mass at each depth. As the root mass approaches the maximum value, less dry matter is partitioned to that depth.When soil water is limiting, a water deficit factor is introduced to further modify the distribution of root dry matter. It is assumed that the plant is an energy minimiser so that more root mass is partitioned to the wetter regions of the soil where least energy will be expended for root growth. Hence, the model allows for enhanced root growth in areas where soil water is more easily available.Simulation results show that a variety of root distribution patterns can be reproduced due to varying soil water conditions. It has been demonstrated that broad patterns of root distribution reported in the literature can also be simulated by the model.     

Simulated nitrogen dynamics and nitrate leaching in a perennial grass ley

A soil nitrogen model was used for a 4-year simulation of nitrogen dynamics and nitrate leaching, both during grass ley growth and after ploughing a grass ley. Model results were compared with field measurements of soil mineral-N status and leaching. A soil water and heat model provided daily values for abiotic conditions, which were used as driving variables in the nitrogen simulation. Simulated values for mineral-N levels in the soil agreed well with field data for the first 3 years of the simulation. During the final year the model predicted considerably higher levels of soil mineral-N content compared with measurements. To reach the mineral-N level measured at the time of ploughing the ley, the simulated N-uptake by plants had to be increased by 8 g N m⁻². Simulations of nitrate leaching suggested that estimates of leaching based on measurements in tile-drained plots can be considerably underestimated. Accurate quantification of leaching in tile-drained plots often requires additional information on water-flow paths. A substantial increase in simulated and measured values for the mineral-N content of the soil occurred after ploughing the ley. In the simulation, most of the increase was due to a high crop residue input and the absence of a growing crop after ploughing. Litter accumulations in the soil during the 4-year period contributed little to the increase in soil mineral-N.     

A Coordination Model of Whole-plant Carbon Allocation in Relation to Water Stress

Although water is an important determinant of the allocationof material between roots and shoots during growth, and oftenparallels the effects of nitrogen, few models have explicitlyconsidered allocation in relation to water supply. We use coordinationtheory to develop a simple exponential model that considersallocation of dry matter between shoots and roots during growthin relation to carbon and watersupplies, and accounts for theeffects of water stress on growth. We compare coordinationvs.optimization(global and local) versions of the exponential model by examiningsimilarities and differences in model behaviour obtained underconstant and variable environmental conditions, and with drasticallychanging conditions (mild, moderate and severe water stress).The greatest differences between coordination and optimizationexist in the drastically changing conditions. In a second versionof the model, we remove the restriction of exponential growthand show how coordination principles can be extended to a morecomplicated structure. The non-exponential model is used toanalyse experimental data on the effects of different pot sizes(and hence water availability) on root restriction and plantgrowth as reported by Thomas and Strain (Plant Physiology96:627–634, 1991). With further refinements, the coordinationmodel has potential as a tool to model plant growth in relationto water supply under various environmental conditions. Optimization; functional balance; root: shoot ratio; root restriction     

Effects of flooding on carbohydrate and ABA levels in roots and shoots of alfalfa

Alfalfa is sensitive to waterlogging, and its yields are significantly reduced under this condition. We investigated the effects of soil flooding on free abscisic acid (ABA) accumulation in shoots and roots of alfalfa in relation to plant growth and stomatal conductance responses. The production of dry matter in alfalfa was significantly affected by flooding mainly as a result of a rapid reduction in root growth. Shoot dry matter accumulation was maintained during the first 10 d of treatment and started to decline thereafter. Foliar concentration of the major mineral elements (N, P, K) was reduced by flooding, whereas only K concentration decreased in roots of flooded plants. Regrowth declined with duration of flooding and was less than 50% of controls after 2 weeks. While no changes in ABA concentration could be detected in flooded roots, an increase was noted within a few days in leaves when compared to unflooded controls. This increase in free ABA coincided with the accumulation of large quantities of starch in leaves and a rapid decline in leaf stomatal conductance. Our results support the suggestion that leaf ABA originates from the leaf itself and may be accumulating along with starch as a result of reduced translocation to the roots. Our observation of large accumulations of sucrose in flooded roots agrees with previous reports that supply of carbohydrates is not a limiting factor to root anaerobic metabolism in flooded alfalfa.