Evaluation in field conditions of a three-dimensional architectural model of the maize root system: Comparison of simulated and observed horizontal root maps

Most existing water and nutrient uptake models are based on the assumption that roots are evenly distributed in the soil volume. This assumption is not realistic for field conditions, and significantly alters water or nutrient uptake calculations. Therefore, development of models of root system growth that account for the spatial distribution of roots is necessary.The objective of this work was to test a three dimensional architectural model of the maize root system by comparing simulated horizontal root maps with observed root maps obtained from the field. The model was built using the current knowledge on maize root system morphogenesis and parameters obtained under field conditions. Simulated root maps (0.45 × 0.75 m) of horizontal cross sections at 3 depths and 3 dates were obtained by using the model for a plant population. Actual root maps were obtained in a deep, barrier-free clay-loamy soil by digging pits, preparing selected horizontal planes and recording root contacts on plastic sheets.Results showed that both the number of cross-sections of axile roots, and their spatial distribution characterized with the R-index value of Clark and Evans (1954), were correctly accounted for by the model at all dates and depths. The number of cross-sections of laterals was also correctly predicted. However, laterals were more clustered around axile roots on simulated root maps than on observed root maps. Although slight discrepancies appeared between simulated and observed root maps in this respect, it was concluded that the model correctly accounted for the general colonization pattern of the soil volume by roots under a maize crop.     

Evaluation of parameters describing the root system architecture of field grown maize plants (Zea mays L.)

The objective of this work was to study elongation curves of maize axile roots throughout their elongation period under field conditions. Relationships between their elongation rate and the extension rate of their branched region were also studied. Maize, early-maturing cultivar Dea, was grown on a deep, barrier-free clay loam (depth 1.80m). Trenches were dug during four periods until after silking and axile roots were excavated. Parameters measured were total length and the lengths of basal and apical unbranched zones. The rank of the bearing phytomer and general data about the carrying plant were also recorded. Results showed that axile roots from lower phytomers had similar elongation rates irrespective of the rank of the carrying phytomer. This elongation rate declined with root age. A monomolecular elongation model was fitted to the experimental data. Elongation was much slower in roots from upper phytomers. A rough linear relationship was found between the elongation rate of axile roots and the length of the apical unbranched zone. This result suggests that laterals appeared on a root segment a constant time after it was formed. Possible mechanisms with may account for the declining elongation rate with root age (increasing distance from aerial parts or adverse environmental conditions in deep soil layers) and variability between individual roots are also discussed.     

Volume Contents

Distribution of root systems through soils and recolonization of root channels by successive crops are fundamental, though difficult to study, processes of soil ecology. This article reports a minirhizotron (MR) study of corn and alfalfa root systems throughout the soil profile of Kalamazoo loam (fine-loamy, mixed, mesic Typic Hapludalf) monolith lysimeters for a three-year succession of corn, alfalfa and corn. Multiple-date comparisons within and between years were conducted to estimate total root densities in each soil horizon. Root recolonization was assessed by comparing every video frame of paired minirhizotrons, from recordings conducted one growing season apart. Distributions of corn root systems were modified by tillage practices. In 1994, root populations of corn in the Bt1 horizon peaked 75–90 days after planting (DAP). Numbers of corn roots per m2 in the Bt1 horizon were consistently higher for no-tillage (NT) than for conventional tillage (CT) lysimeters, in 1994 and 1996. Distribution of alfalfa roots within the soil profile was not significantly modified by tillage. However, alfalfa root decomposition rates responded to conventional and no-tillage practices and were specific for each soil horizon. Corn root systems growing in soils previously cropped with alfalfa presented similar patterns of root distribution by horizons as that of the previous alfalfa crop. Successive corn root systems did not display similar distribution patterns throughout the soil profile from one growing season to the next. Proportions of roots of the current crop recolonizing root induced macropores (RIMs) of the previous crop averaged 18% for corn after corn, 22% for alfalfa after corn and 41% for corn after alfalfa, across Bt horizons and tillage treatments. In conclusion, distribution of corn root systems appeared to be modified by tillage practices and root recolonization of RIMs was controlled by the preceding crop.     

A comprehensive analysis of root morphological changes and nitrogen allocation in maize in response to low nitrogen stress

The plasticity of root architecture is crucial for plants to acclimate to unfavourable environments including low nitrogen (LN) stress. How maize roots coordinate the growth of axile roots and lateral roots (LRs), as well as longitudinal and radial cell behaviours in response to LN stress, remains unclear. Maize plants were cultivated hydroponically under control (4 mm nitrate) and LN (40 μm ) conditions. Temporal and spatial samples were taken to analyse changes in the morphology, anatomical structure and carbon/nitrogen (C/N) ratio in the axile root and LRs. LN stress increased axile root elongation, reduced the number of crown roots and decreased LR density and length. LN stress extended cell elongation zones and increased the mature cell length in the roots. LN stress reduced the cell diameter and total area of vessels and increased the amount of aerenchyma, but the number of cell layers in the crown root cortex was unchanged. The C/N ratio was higher in the axile roots than in the LRs. Maize roots acclimate to LN stress by optimizing the anatomical structure and N allocation. As a result, axile root elongation is favoured to efficiently find available N in the soil.     

Field evaluation of laboratory techniques for predicting the ability of roots to penetrate strong soil and of the influence of roots on water sorptivity

The ability of two laboratory screening techniques to predict the abilities of roots of eight crop species to penetrate a compacted soil were evaluated and compared in a field experiment. A soil tilled to remove the effects of mechanical resistance was planted with the same species to serve as a control. Depth of root penetration, root density and the influence of the roots on the sorptivity of water were measured.Roots of all species penetrated deeper in the deep tilled than compacted soils. There were differences in the ability of roots of the species to penetrate the compacted soil. Generally dicotyledonous species had more roots penetrating to depth in both the compact and deep tilled soils. Within the main species classifications, lupin and safflower (dicotyledons) and oats and barley (monocotyledons) had the highest penetration into the compacted soil.Water sorptivities in the deep tilled soils were higher than those of the compact soil. Soil from planted treatments had higher sorptivities than soil which had not been planted. This is attributed to biopores left by the roots. Sorptivities of soils which had dicotyledonous species were generally higher than those of monocotyledons. The soil planted with safflower produced the highest sorptivity in the compacted layer (0.1–0.3 m).A comparison of the accuracy of the two laboratory screening methods in predicting the field penetration of roots suggest that the method involving mechanical stress was better than that involving osmotic stress. Relative root diameter was found to be a better indicator of the penetration ability of roots than relative root elongation.     

Spatio-temporal Variations in Axial Conductance of Primary and First-order Lateral Roots of a Maize Crop as Predicted by a Model of the Hydraulic Architecture of Root Systems

Rates at which water can be transported along plant roots (axial pathway) vary through time, in part depending on xylem maturation. Because of experimental constraints, the dynamics of root functional heterogeneity under field conditions remains mostly uncharted territory. Recent advances in mechanistic modelling offer opportunities to bypass such experimental limitations. This paper examines the dynamics of local variations in axial conductance of primary and first-order lateral roots of a maize crop using the architecture-based modelling approach developed by Doussan et al. (Annals of Botany: 81, 213–223, 1998). Specifically, we hypothesised that points of major resistance to long distance water transfers could arise from discrepancies between the hydraulic maturity (or water carrying capacity) of main axes and branch roots. To test this assumption, spatial distributions of root axial conductance were tested after 30, 60 and 100 days at soil depths of 10, 50 and 100 cm under a maize (Zea mays L.) crop sown at a density of 8 plants m⁻². As the crop developed, the corresponding root populations encompassed ever increasing amounts of hydraulically mature first-order laterals (branch roots): after a 100-day growth period, the vast majority of laterals had reached their maximum axial conductance at all soil depths down to 100 cm. In contrast, the axial conductance of a large proportion of main axes (primary roots) remained low, even at shallow soil depths and after 100 days of growth. The imbalance between the hydraulic maturity of primary and lateral roots was most conspicuous at soil depths of 100 cm, where ~10% only of the former compared to ~80% of the latter, had reached their maximum axial conductance after a 100-day growth period.     

The water status of the roots of soil-grown maize in relation to the maturity of their xylem

The long delayed maturation of the late metaxylem of maize ( Zea mays ) roots imposes a high-resistance barrier between the immature apices and the negative water potential of the leaves. These apices (20+ cm) bear strongly adhering soil sheaths to within 0.5 to 2 cm of the distal end. It was hypothesized that the sheathed immature apices should show less response to transpiration stress than bare regions. Measurements were made of the relative water content (RWC) of the sheathed and bare zones of the axile roots, both at different ages of the plant, and early and late in the day's transpiration. Sheathed roots maintained a steady RWC of about 83% irrespective of age or transpiration. Bare roots had RWCs of about 63% in the morning, but this fell to 55% in the afternoon. The first-order branches on the bare roots in the morning had still lower values of RWC, near 50%. Plots of RWC against water potential were indistinguishable for the three root types. It is concluded that the immature apices are indeed relatively isolated from the fluctuating tensions in the stem xylem, and that these tensions reduce the water content of bare roots and their branches to low values.     

Evolution of bacterial communities in the wheat crop rhizosphere

The gap between current average global wheat yields and that achievable through best agronomic management and crop genetics is large. This is notable in intensive wheat rotations which are widely used. Expectations are that this gap can be reduced by manipulating soil processes, especially those that involve microbial ecology. Cross‐year analysis of the soil microbiome in an intensive wheat cropping system revealed that rhizosphere bacteria changed much more than the bulk soil community. Dominant factors influencing populations included binding to roots, plant age, site and planting sequence. We demonstrated evolution of bacterial communities within the field rhizosphere. Early in the season, communities tightly bound to the root were simplest. These increased in diversity with plant age and senescence. Loosely bound communities also increased in diversity from vegetative to reproductive plant stages but were more stable than those tightly bound to roots. Planting sequence and, to a lesser extent, wheat genotype also significantly affected rhizosphere bacteria. Plasticity in the rhizosphere generated from crop root system management and genetics offers promise for manipulating the soil ecology of intense cereal systems. Analyses of soil microbiomes for the purpose of developing agronomic benefit should include roots as well as soil loosely adhered to the roots, and the bulk soil.     

根区交替控制灌溉条件下玉米根系吸水规律

为了阐明根区交替控制灌溉(CRDAI)条件下玉米根系吸水规律,通过田间试验,在沟灌垄植模式下采用根区交替控制灌溉研究玉米根区不同点位(沟位、坡位和垄位)的根长密度(RLD)及根系吸水动态。研究表明,根区土壤水分的干湿交替引起玉米RLD的空间动态变化,在垄位两侧不对称分布,并存在层间差异;土壤水分和RLD是根区交替控制灌溉下根系吸水速率的主要限制因素。在同一土层,根系吸水贡献率以垄位最大,沟位最低;玉米营养生长阶段,10—30 cm土层的根系吸水速率最大;玉米生殖生长阶段,20—70 cm为根系吸水速率最大的土层,根系吸水贡献率为43.21%—55.48%。研究阐明了交替控制灌溉下根系吸水与土壤水分、RLD间相互作用的动态规律,对控制灌溉下水分调控机理研究具有理论意义。     

黄土高原半干旱区作物水分利用研究新途径

以黄土高原半干旱区农业生产条件 ,特别是土壤水分特性为背景 ,结合植物根冠通讯方面的有关研究进展 ,讨论了根化学信号在本地区的研究与开发潜力 .本地区节水农业的核心是提高作物的水分利用效率 ,其途径包括 :1 )减少土壤表面的无效蒸发量 ;2 )增加深层根量 ,减少表土中的根量 ,优化资源分配模式 ,提高繁殖分配比例 .根化学信号对这两方面都有重要影响 .基于目前的知识积累 ,应在根化学信号对作物生产力的影响方面作深入研究 ,可揭示节水农业中某些重要的理论问题     

Traits and selection strategies to improve root systems and water uptake in water-limited wheat crops

Wheat yields globally will depend increasingly on good management to conserve rainfall and new varieties that use water efficiently for grain production. Here we propose an approach for developing new varieties to make better use of deep stored water. We focus on water-limited wheat production in the summer-dominant rainfall regions of India and Australia, but the approach is generally applicable to other environments and root-based constraints. Use of stored deep water is valuable because it is more predictable than variable in-season rainfall and can be measured prior to sowing. Further, this moisture is converted into grain with twice the efficiently of in-season rainfall since it is taken up later in crop growth during the grain-filling period when the roots reach deeper layers. We propose that wheat varieties with a deeper root system, a redistribution of branch root density from the surface to depth, and with greater radial hydraulic conductivity at depth would have higher yields in rainfed systems where crops rely on deep water for grain fill. Developing selection systems for mature root system traits is challenging as there are limited high-throughput phenotyping methods for roots in the field, and there is a risk that traits selected in the lab on young plants will not translate into mature root system traits in the field. We give an example of a breeding programme that combines laboratory and field phenotyping with proof of concept evaluation of the trait at the beginning of the selection programme. This would greatly enhance confidence in a high-throughput laboratory or field screen, and avoid investment in screens without yield value. This approach requires careful selection of field sites and years that allow expression of deep roots and increased yield. It also requires careful selection and crossing of germplasm to allow comparison of root expression among genotypes that are similar for other traits, especially flowering time and disease and toxicity resistances. Such a programme with field and laboratory evaluation at the outset will speed up delivery of varieties with improved root systems for higher yield.     

Root effects on soil water and hydraulic properties

Plants can affect soil moisture and the soil hydraulic properties both directly by root water uptake and indirectly by modifying the soil structure. Furthermore, water in plant roots is mostly neglected when studying soil hydraulic properties. In this contribution, we analyze effects of the moisture content inside roots as compared to bulk soil moisture contents and speculate on implications of non-capillary-bound root water for determination of soil moisture and calibration of soil hydraulic properties. In a field crop of maize (Zea mays) of 75 cm row spacing, we sampled the total soil volumes of 0.7 m × 0.4 m and 0.3 m deep plots at the time of tasseling. For each of the 84 soil cubes of 10 cm edge length, root mass and length as well as moisture content and soil bulk density were determined. Roots were separated in 3 size classes for which a mean root porosity of 0.82 was obtained from the relation between root dry mass density and root bulk density using pycnometers. The spatially distributed fractions of root water contents were compared with those of the water in capillary pores of the soil matrix. Water inside roots was mostly below 2–5% of total soil water content; however, locally near the plant rows it was up to 20%. The results suggest that soil moisture in roots should be separately considered. Upon drying, the relation between the soil and root water may change towards water remaining in roots. Relations depend especially on soil water retention properties, growth stages, and root distributions. Gravimetric soil water content measurement could be misleading and TDR probes providing an integrated signal are difficult to interpret. Root effects should be more intensively studied for improved field soil water balance calculations. Presented at the International Conference on Bioclimatology and Natural Hazards, Pol’ana nad Detvou, Slovakia, 17–20 September 2007.     

Prospects, advantages and limitations of future crop production systems dependent upon the management of soil processes

Current agriculture in Europe is predominantly reliant upon external inputs, such as fertilisers and pesticides, rather than upon soil processes, for the resources it needs for crop growth. Inputs of fertilisers have environmental disbenefits, some of which have been highlighted by the introduction of the Water Framework Directive. Here we review the scope to improve current production systems so as to reduce environmental impact while broadly maintaining productivity. The review focuses upon both the potential impacts of means of increasing soil nutrient supply, in the absence of fertilisers, and the potential impact on nutrient uptake of modifications to the functioning of the root system. Assessments of the functioning of the root system must allow for all root types and for the contribution of arbuscular mycorrhizal fungi (AMF). The development of productive systems based around soil processes will thus depend upon both better management of soil processes, especially when they relate to holding nutrients such as nitrogen within the system, and to developments in understanding roots and their associated microbes.     

液体地膜覆盖对棉花根系生长发育的影响

基于棉田可持续发展的思想,利用茚三酮法、钼蓝法及土壤双向切片法,研究了液体地膜覆盖对棉花根系生长发育的影响。结果表明,覆盖棉花前期根系生长发育加快,表现为根系活力增强,根系干重较大,但覆盖不利于棉花根系下扎,土壤深层根系衰减较快。与塑料地膜覆盖相比,液体地膜覆盖增强根系吸收与合成能力的效应在棉花各生育阶段均较明显,根系在土壤内分布较为合理,土壤深层根系衰减较慢,更有利于棉株均衡生长发育,防止棉花早衰。在棉花生产上,采用液体地膜覆盖栽培是一项可行技术．     

Improved scaling of minirhizotron data using an empirically-derived depth of field and correcting for the underestimation of root diameters

Background and aims

Accurate data on the standing crop, production, and turnover of fine roots is essential to our understanding of major terrestrial ecological processes. Minirhizotrons offer a unique opportunity to study the dynamic processes of root systems, but are susceptible to several measurement biases.

Methods

We use roots extracted from minirhizotron tube surfaces to calculate the depth of field of a minirhizotron image and present a model to correct for the underestimation of root diameters obscured by soil in minirhizotron images.

Results

Non-linear regression analysis resulted in an estimated depth of field of 0.78 mm for minirhizotron images. Unadjusted minirhizotron data underestimated root net primary production and fine root standing crop by 61 % when compared to adjusted data using our depth of field and root diameter corrections. Changes in depth of field accounted for >99 % of standing crop adjustments with root diameter corrections accounting for <1 %.

Conclusions

Our results represent the first effort to empirically derive depth of field for minirhizotron images. This work may explain the commonly reported underestimation of fine roots using minirhizotrons, and stands to improve the ability of researchers to accurately scale minirhizotron data to large soil volumes.     

Soil strength and water content influences on corn root distribution in a sandy soil

Initial field observations revealed a shallow corn (Zea mays L.) root system on a Zimmerman fine sand in a corn/soybean (Glycine max L.) rotation. Since root distribution influences crop water and nutrient absorption, it is essential to identify factors limiting root growth. The objective of this study was to determine the factor(s) limiting corn rooting depth on an irrigated fine sand soil. Bulk density, saturated hydraulic conductivity, and soil water retention were measured on undisturbed soil cores. Corn root distribution assessed at tasseling over a 3-yr period showed an average of 94% of total root length within the upper 0.60 m of soil with 85% in the upper 0.30 m of soil. Mechanical impedance was estimated with a cone penetrometer on two dates with differing water contents. Cone penetrometer measurements greater than 3 MPa indicated mechanical impedance in soil layers extending from 0.15 to 0.35 m deep. Penetration resistance decreased as soil water content increased. However, soil water contents greater than field capacity were required to decrease penetration resistance below the 3 MPa threshold. Such water saturated conditions only occurred for short periods immediately after precipitation or irrigation events, thus roots usually encountered restrictive soil strengths. The soil layer from 0.15 to 0.60 m had high bulk density, 1.57 Mg m^-3. This compacted soil layer, with slower saturated hydraulic conductivities (121 to 138 mm hr-1), held more water than the soil above or below it and reduced water movement through the soil profile. Crop water use occurred to a depth of approximately 0.75 m. In conclusion, a compacted soil layer confined roots almost entirely to the top 0.60 m of soil because it had high soil strength and bulk density. The compacted layer, in turn, retained more water for crop use.     

Architectural Tradeoffs between Adventitious and Basal Roots for Phosphorus Acquisition

Adventitious rooting contributes to efficient phosphorus acquisition by enhancing topsoil foraging. However, metabolic investment in adventitious roots may retard the development of other root classes such as basal roots, which are also important for phosphorus acquisition. In this study we quantitatively assessed the potential effects of adventitious rooting on basal root growth and whole plant phosphorus acquisition in young bean plants. The geometric simulation model SimRoot was used to dynamically model root systems with varying architecture and C availability growing for 21 days at 3 planting depths in 3 soil types with contrasting nutrient mobility. Simulated root architectures, tradeoffs between adventitious and basal root growth, and phosphorus acquisition were validated with empirical measurements. Phosphorus acquisition and phosphorus acquisition efficiency (defined as mol phosphorus acquired per mol C allocated to roots) were estimated for plants growing in soil in which phosphorus availability was uniform with depth or was greatest in the topsoil, as occurs in most natural soils. Phosphorus acquisition and acquisition efficiency increased with increasing allocation to adventitious roots in stratified soil, due to increased phosphorus depletion of surface soil. In uniform soil, increased adventitious rooting decreased phosphorus acquisition by reducing the growth of lateral roots arising from the tap root and basal roots. The benefit of adventitious roots for phosphorus acquisition was dependent on the specific respiration rate of adventitious roots as well as on whether overall C allocation to root growth was increased, as occurs in plants under phosphorus stress, or was lower, as observed in unstressed plants. In stratified soil, adventitious rooting reduced the growth of tap and basal lateral roots, yet phosphorus acquisition increased by up to 10% when total C allocation to roots was high and adventitious root respiration was similar to that in basal roots. With C allocation to roots decreased by 38%, adventitious roots still increased phosphorus acquisition by 5%. Allocation to adventitious roots enhanced phosphorus acquisition and efficiency as long as the specific respiration of adventitious roots was similar to that of basal roots and less than twice that of tap roots. When adventitious roots were assigned greater specific respiration rates, increased adventitious rooting reduced phosphorus acquisition and efficiency by diverting carbohydrate from other root types. Varying the phosphorus diffusion coefficient to reflect varying mobilities in different soil types had little effect on the value of adventitious rooting for phosphorus acquisition. Adventitious roots benefited plants regardless of basal root growth angle. Seed planting depth only affected phosphorus uptake and efficiency when seed was planted below the high phosphorus surface stratum. Our results confirm the importance of root respiration in nutrient foraging strategies, and demonstrate functional tradeoffs among distinct components of the root system. These results will be useful in developing ideotypes for more nutrient efficient crops.     

Different populations of bacteria associated with sheathed and bare regions of roots of field-grown maize

It has been previously shown that soil sheaths cling tightly to some portions of all axile roots and cover all but the growing tips of the young roots of field-grown maize. These sheaths overlie immature regions of the roots which have intact epidermal cells with root hairs, and living, thus non-conducting, late metaxylem elements. Loss of the soil sheath in the proximal region coincides with the opening of these large metaxylem vessels. Now, total, and viable counts have been recorded of bacteria associated with the root surface and adhering soil of sheathed and bare regions. These showed some common features, in that populations of similar size were associated with the two root regions in plants beginning to flower. Each population included about the same numbers of bacteria that were viable on each of three selective media (nitrogen-free, Pseudomonas F or MacConkey). However, more spore-formers capable of growth on nitrogen-free media and more fluorescent bacteria were isolated from the sheathed regions. Actinomycetes were absent from sheathed but plentiful on bare regions.The high numbers of diverse types of bacteria associated with both root surfaces can be related to the previously demonstrated similarity in amounts of organic carbon released from each region. The proliferation of actionomycetes on the bare roots and their exclusion from sheathed roots may in part be due to the lower water status of the bare region, which is related to its greater axial conducting capacity. Thus the distribution of the two types of root surface within an individual root system has important implications for the choice of root and rhizosphere sampling techniques and for root bacterization work.     

A screening method to identify genetic variation in root growth response to a salinity gradient

Salinity as well as drought are increasing problems in agriculture. Durum wheat (Triticum turgidum L. ssp. durum Desf.) is relatively salt sensitive compared with bread wheat (Triticum aestivum L.), and yields poorly on saline soil. Field studies indicate that roots of durum wheat do not proliferate as extensively as bread wheat in saline soil. In order to look for genetic diversity in root growth within durum wheat, a screening method was developed to identify genetic variation in rates of root growth in a saline solution gradient similar to that found in many saline fields. Seedlings were grown in rolls of germination paper in plastic tubes 37 cm tall, with a gradient of salt concentration increasing towards the bottom of the tubes which contained from 50-200 mM NaCl with complete nutrients. Seedlings were grown in the light to the two leaf stage, and transpiration and evaporation were minimized so that the salinity gradient was maintained. An NaCl concentration of 150 mM at the bottom was found suitable to identify genetic variation. This corresponds to a level of salinity in the field that reduces shoot growth by 50% or more. The screen inhibited seminal axile root length more than branch root length in three out of four genotypes, highlighting changes in root system architecture caused by a saline gradient that is genotype dependent. This method can be extended to other species to identify variation in root elongation in response to gradients in salt, nutrients, or toxic elements.     

不同水分条件对冬小麦根系时空分布、土壤水利用和产量的影响

为了明确华北严重缺水区晚播冬小麦灌水对根系时空分布和土壤水分利用规律的影响,以冬小麦石麦15为材料,利用田间定位试验研究了不同灌水处理(春季不灌水W0;春季灌拔节水75mm,W1;春季灌起身水、孕穗水和灌浆水共225mm,W3)对根系干重密度(DRWD)、根长密度(RLD)、体积密度、分枝数等在0—200cm土层的垂直分布、动态变化及其对耗水和产量的影响,结果表明:随着春季灌水量的减少,开花后0—80cm土层的根干重密度、根长度密度、体积密度和分枝数密度均显著减少,80cm—200m土层的根干重密度、根长度密度、体积密度和分枝数密度却显著增加,并且显著增加冬小麦在灌浆期间对100cm以下深层土层水分的利用,总耗水量W1和W0分别比W3减少70.9mm、115.1mm,土壤耗水量分别比W3增加79.1mm、108.9mm,子粒产量W1和W0分别比W3减少653.3kg/hm2、1470kg/hm2,水分利用效率(WUE)则分别比W3提高0.09kg/m3、0.06kg/m3。晚播冬小麦春季灌1水(拔节水)可以促进根系深扎,增加深土层的根系分布量,提高对深层土壤贮水的吸收利用量,有利于实现节水与高产的统一。