Entire Root System Research Articles

Intraspecific variation in root system structure in a Pinus thunbergii stand grown in a gravelly spit coast.

ABSTRACT Root systems of Pinus thunbergii planted in coastal forests exhibit high phenotypic plasticity under edaphic conditions. The objectives of this study were as follows: 1) to determine intraspecific variation in root system traits, maximum root depth and length of horizontal roots of P. thunbergii in a gravelly spit within a stand by excavation of entire root systems, and root system structure modelling from photographs; and 2) to determine whether the root system traits can be inferred from aboveground traits. The P. thunbergii trees grew twisting roots through the hard soil layer of sand and gravel and exhibited variation in root systems; most individuals had inherent tap root systems, but one had a two-tiered thick horizontal root system with a thinner tap root. Although the maximum length of the horizontal root had no relationship with the aboveground traits, the maximum root depth of P. thunbergii was significantly related to tree height. This suggests that tree height can be a predictive indicator of root depth, which is valuable for the rehabilitation of disaster-resistant coastal forests. Both surface and solid models of root system were produced using structure-from-motion with a multi-view stereophotogrammetry method, which enabled continuous estimation of the sum of the root cross-sectional area at any depth in the depth direction. The new method of reconstructing root system models was effective for post-analysis of traits after excavation. We concluded that intraspecific variations in the root system traits of P. thunbergii were observed even at the stand level on a gravelly spit coast.

Long-term warming in a temperate forest accelerates soil organic matter decomposition despite increased plant-derived inputs

Climate change may alter soil microbial communities and soil organic matter (SOM) composition. Soil carbon (C) cycling takes place over multiple time scales; therefore, long-term studies are essential to better understand the factors influencing C storage and help predict responses to climate change. To investigate this further, soils that were heated by 5 °C above ambient soil temperatures for 18 years were collected from the Barre Woods Soil Warming Study at the Harvard Forest Long-term Ecological Research site. This site consists of large 30 × 30 m plots (control or heated) where entire root systems are exposed to sustained warming conditions. Measurements included soil C and nitrogen concentrations, microbial biomass, and SOM chemistry using gas chromatography–mass spectrometry and solid-state 13C nuclear magnetic resonance spectroscopy. These complementary techniques provide a holistic overview of all SOM components and a comprehensive understanding of SOM composition at the molecular-level. Our results showed that soil C concentrations were not significantly altered with warming; however, various molecular-level alterations to SOM chemistry were observed. We found evidence for both enhanced SOM decomposition and increased above-ground plant inputs with long-term warming. We also noted shifts in microbial community composition while microbial biomass remained largely unchanged. These findings suggest that prolonged warming induced increased availability of preferred substrates, leading to shifts in the microbial community and SOM biogeochemistry. The observed increase in gram-positive bacteria indicated changes in substrate availability as gram-positive bacteria are often associated with the decomposition of complex organic matter, while gram-negative bacteria preferentially break down simpler organic compounds altering SOM composition over time. Our results also highlight that additional plant inputs do not effectively offset chronic warming-induced SOM decomposition in temperate forests.

An efficient subsampling method for estimating corn root characteristics with scanner‐based image analysis

AbstractQuantifying root length, surface area, average diameter, and volume of fully‐matured corn (Zea mays L.) is labor intensive, time consuming, and costly. Accurate and efficient subsampling techniques are needed to overcome these limitations. In this study, eight corn root systems were grown to maturity in a sand‐culture hydroponics system to develop and test root system subsampling techniques for accuracy (uncertainty assessment) and efficiency (time). Each entire root system was separated into coarse and fine roots, which were then composited into 65 subsamples, either visually or by mass, followed by subsample scanning to quantify root characteristics. A bootstrap non‐parametric procedure was used to determine the sample size needed to represent the total root system and quantify uncertainty based on the number of subsamples analyzed. When subsamples were composited visually, as many as 60 subsamples (92% of the total root system) were necessary to represent the characteristics of the root system within ±5% of the true mean at a 95% confidence level. In contrast, when subsamples were composited by equal mass, a maximum of 15 subsamples (23% of the total root system) were needed to be representative, requiring 2 h and 15 min per root system. The findings show that separating the entire root system by coarse and fine roots and then weighing into equal mass subsamples before scanning decreased the number of subsamples and time required to accurately estimate corn root characteristics. Thus, this subsampling approach considerably reduced the effort and cost of processing corn root systems.

Orchid Mycorrhizal Association of Cultivated Dendrobium Hybrid and Their Role in Seed Germination and Seedling Growth.

Orchids are crucial for the horticulture industry. Mycorrhizal fungi benefit crops by improving nutrition, plant growth, and disease resistance. However, the mycorrhizal association of horticultural hybrid orchids is poorly understood. To address this, we investigated mycorrhizal colonization in the entire root system and assessed the mycorrhizal community using a Dendrobium cultivar, D. Stardust 'Firebird', obtained from three nurseries. Additionally, we isolated and tested mycorrhizal fungi in symbiotic culture to assess their role in the seed germination and growth of Dendrobium species. All plants were colonized by mycorrhizal fungi, with a higher colonization rate in mature than in juvenile plants. Molecular identification of mycorrhizal fungi by Sanger and high-throughput sequencing revealed that the cultivar was associated with a phylogenetically diverse group of fungi, including mycorrhizal fungi from Tulasnellaceae, and several wood-decaying fungi. The Tulasnellaceae isolates significantly enhanced the seed germination of three Dendrobium species and increased the survival rate and growth of asymbiotic seedlings of D. moniliforme. This study is the first comprehensive examination of mycorrhizal associations in horticultural orchid hybrids, providing valuable insights for commercial production.

Mechanistically derived macroscopic root water uptake functions: The α and ω of root water uptake functions

AbstractWater uptake by plant roots is an important component of the soil water balance. Predicting to what extent potential transpiration from the canopy, that is, transpiration demand, can be met by supply of water from the soil through the root system is crucial to simulate the actual transpiration and assess vegetation water stress. In models that simulate the dynamics of vertical soil water content profiles as a function of water fluxes and soil water potential gradients, the root water uptake (RWU) distribution is represented by macroscopic sink terms. We present RWU functions that calculate sink terms based on a mechanistic model of water flow in the soil–root system. Based on soil–root hydraulics, we define α‐supply functions representing the maximal uptake by the root system from a certain soil depth when the root collar water potential equals the wilting point, ω‐supply factors representing the maximal supply from the entire root system, and a critical ωc factor representing the potential transpiration demand. These functions and factors are subsequently used to calculate RWU distributions directly from potential transpiration or demand and the soil water potentials. Unlike currently used approaches, which define α‐stress functions and ω factors representing ratios of actual uptake to uptake demand, the supply‐based formulations can be derived directly from soil and root hydraulic properties and can represent processes like root hydraulic redistribution and hydraulic lift.

Variation in Root System Architecture Response to Arsenic during Establishment and Onset of Storage Root Formation in Two Sweetpotato (Ipomoea batatas L.) Cultivars

The primary objective of this work was to generate species-specific information about root architectural adaptations to simulated natural levels of arsenic (As) during the establishment phase and onset of storage root formation in sweetpotato. Cultivars Bayou Belle and Beauregard were grown on sand substrate and provided with 0.5X Hoagland’s nutrient solution with varying levels of As (0, 5, 10, or 15 mg⋅L−1). During the first experiment, entire root systems were sampled at 5, 10, and 15 days, corresponding to key adventitious root developmental stages. Compared with the untreated controls at 15 days, ‘Bayou Belle’ and ‘Beauregard’ provided with 15 mg⋅L−1 As showed respective increases in the following root architectural attributes: 168% and 130% in main root length; 168% and 98% in lateral root length; and 140% and 50% in lateral root density. A second experiment was performed to produce storage root samples at 50 days. Storage root length, width, and length/width ratio did not vary with As levels. The accumulation of As in storage roots increased with increasing As levels. The results support the hypothesis that natural As levels stimulate adventitious root development in sweetpotato in a cultivar-dependent manner. The observations are consistent with findings of other species that show similar growth stimulation at low As levels. This is the first report of sweetpotato root system architecture responses to experimental levels of As that are known to be present in agricultural soils. Standardization of experimental procedures and understanding of root system adaptations to natural levels of As could lead to a more systematic exploitation of genome-wide techniques and characterization of the molecular basis of reduced As uptake in plants.

Development of a Hydroponic Growing Protocol for Vegetative Strawberry Production

Hydroponic growing systems are advantageous for nutrient studies in which root data are important because they alleviate the laborious and time-consuming task of washing roots to remove soilless substrate particulates from them. However, the growing system should be optimized for the crop of interest. Our overall objective was to develop a protocol for hydroponic strawberry (Fragaria ×ananassa) production that provided growth equal to or better than soilless substrate. Plants were initially grown in perlite, sand, deep water culture (DWC), or a peat-based soilless substrate. Aboveground plant growth in DWC was similar to that of plants grown in the peat-based substrate and required minimal effort to harvest the entire root system. However, the pH of the DWC nutrient solution decreased to 4.0 ± 0.1 (mean ± SE) when plants were provided a modified strawberry (Yamazaki) nutrient solution with a ratio of nitrate (NO3−) to ammonium (NH4+) of 80:20. As a result, a subsequent trial was conducted to evaluate the buffering capacity of nutrient solutions with NO3− to NH4+ ratios of 0:100, 20:80, 50:50, 60:40, 80:20, or 100:0, with the addition of potassium bicarbonate (KHCO3). Up to 2.6 mM KHCO3 did not provide adequate buffering in nutrient solutions containing NH4+ (0:100 to 80:20 treatments), and nutrient solution pH decreased by ∼1.5 units every 2 to 3 days. The 100% NO3− nutrient solution, however, maintained a stable pH of 5.9 ± 0.1 when buffered with 0.8 mM KHCO3. Finally, 2(N-Morpholino)ethanesulfonic acid (MES) was evaluated as a potential buffering agent for DWC strawberry production. Plants were grown in a nutrient solution with a 60:40 ratio of NO3−:NH4+. The buffering capacity of the nutrient solution increased as the MES concentration supplied increased from 1 to 5 mM, and the 5 mM MES treatment maintained a pH of 5.6 ± 0.2. In summary, strawberry plants can successfully be grown hydroponically in DWC, provided that nutrient solution pH is adequately managed. The addition of MES buffer provided better pH stability than KHCO3.

Topological data analysis expands the genotype to phenotype map for 3D maize root system architecture.

A central goal of biology is to understand how genetic variation produces phenotypic variation, which has been described as a genotype to phenotype (G to P) map. The plant form is continuously shaped by intrinsic developmental and extrinsic environmental inputs, and therefore plant phenomes are highly multivariate and require comprehensive approaches to fully quantify. Yet a common assumption in plant phenotyping efforts is that a few pre-selected measurements can adequately describe the relevant phenome space. Our poor understanding of the genetic basis of root system architecture is at least partially a result of this incongruence. Root systems are complex 3D structures that are most often studied as 2D representations measured with relatively simple univariate traits. In prior work, we showed that persistent homology, a topological data analysis method that does not pre-suppose the salient features of the data, could expand the phenotypic trait space and identify new G to P relations from a commonly used 2D root phenotyping platform. Here we extend the work to entire 3D root system architectures of maize seedlings from a mapping population that was designed to understand the genetic basis of maize-nitrogen relations. Using a panel of 84 univariate traits, persistent homology methods developed for 3D branching, and multivariate vectors of the collective trait space, we found that each method captures distinct information about root system variation as evidenced by the majority of non-overlapping QTL, and hence that root phenotypic trait space is not easily exhausted. The work offers a data-driven method for assessing 3D root structure and highlights the importance of non-canonical phenotypes for more accurate representations of the G to P map.

First Report of the Root-Lesion Nematode (Pratylenchus thornei Sher and Allen, 1953) Parasitizing Oats in Gansu Province, China.

First Report of the Root-Lesion Nematode (Pratylenchus thornei Sher and Allen, 1953) Parasitizing Oats in Gansu Province, China.

The root of the problem: diverse vulnerability to xylem cavitation found within the root system of wheat plants.

The propagation of xylem embolism throughout the root systems of drought-affected plants remains largely unknown, despite this process being comparatively well characterized in aboveground tissues. We used optical and X-ray imaging to capture xylem embolism propagation across the intact root systems of bread wheat (Triticum aestivum L. 'Krichauff') plants subjected to drying. Patterns in vulnerability to xylem cavitation were examined to investigate whether vulnerability may vary based on root size and placement across the entire root system. Individual plants exhibited similar mean whole root system vulnerabilities to xylem cavitation but showed enormous 6 MPa variation within their component roots (c. 50 roots per plant). Xylem cavitation typically initiated in the smallest, peripheral parts of the root system and moved inwards and upwards towards the root collar last, although this trend was highly variable. This pattern of xylem embolism spread likely results in the sacrifice of replaceable small roots while preserving function in larger, more costly central roots. A distinct pattern of embolism-spread belowground has implications for how we understand the impact of drought in the root system as a critical interface between plant and soil.

Variation in the Root System Architecture of Peach × (Peach × Almond) Backcrosses.

The spatial arrangement and growth pattern of root systems, defined by the root system architecture (RSA), influences plant productivity and adaptation to soil environments, playing an important role in sustainable horticulture. Florida's peach production area covers contrasting soil types, making it necessary to identify rootstocks that exhibit soil-type-specific advantageous root traits. In this sense, the wide genetic diversity of the Prunus genus allows the breeding of rootstock genotypes with contrasting root traits. The evaluation of root traits expressed in young seedlings and plantlets facilitates the early selection of desirable phenotypes in rootstock breeding. Plantlets from three peach × (peach × almond) backcross populations were vegetatively propagated and grown in rhizoboxes. These backcross populations were identified as BC1251, BC1256, and BC1260 and studied in a completely randomized design. Scanned images of the entire root systems of the plantlets were analyzed for total root length distribution by diameter classes, root dry weight by depth horizons, root morphological components, structural root parameters, and root spreading angles. The BC1260 progeny presented a shallower root system and lower root growth. Backcross BC1251 progeny exhibited a more vigorous and deeper root system at narrower root angles, potentially allowing it to explore and exploit water and nutrients in deep sandy entisols from the Florida central ridge.

Plasticity of wheat seedling responses to K+ deficiency highlighted by integrated phenotyping of roots and root hairs over the whole root system

The availability in the soil of potassium (K+), a poorly mobile macronutrient required in large quantities for plant growth, is generally suboptimal for crop production in the absence of fertilization, making improvement of the ability of crops to adapt to K+ deficiency stress a major issue. Increasing the uptake capacity of the root system is among the main strategies to achieve this goal. Here, we report an integrative approach to examine the effect of K+ deficiency on the development of young plant entire root system, including root hairs which are known to provide a significant contribution to the uptake of poorly mobile nutrients such as K+, in two genetically distant wheat varieties. A rhizobox-type methodology was developed to obtain highly-resolved images of root and root hairs, allowing to describe global root and root hair traits over the whole root system via image analysis procedures. The two wheat varieties responded differently to the K+ shortage: Escandia, a wheat ancestor, reduced shoot biomass in condition of K+ shortage and substantially increased the surface area of its root system, specifically by increasing the total root hair area. Oued Zenati, a landrace, conversely appeared unresponsive to the K+ shortage but was shown to constitutively express, independently of the external K+ availability, favorable traits to cope with reduced K+ availability, among which a high total root hair area. Thus, valuable information on root system adaptation to K+ deficiency was provided by global analyses including root hairs, which should also be relevant for other nutrient stresses.

АСПИРАЦИОННЫЙ МЕТОД САНАЦИИ КОРНЕВОГО КАНАЛА

To achieve high efficiency of endodontic treatment, it is necessary to ensure high-quality cleaning of the root canal. Using only mechanical processing, it is impossible to completely clean the entire root system. For drug treatment of root canals, a wide range of antiseptic agents is used, the most popular of which is a remedy based on sodium hypochlorite solution. For maximum therapeutic effect, the irrigation solution must be in direct contact with the entire surface of the root canal dentin, penetrating into all its branches. Therefore, the creation of an adequate taper, the choice of the optimal method of supplying the agent based on sodium hypochlorite solution affects the quality of drug treatment of the root canal and subsequent obturation. Target. To evaluate the penetration efficiency of the agent based on 3% sodium hypochlorite solution into the macrocanal of the tooth and its branches, depending on the choice of the method of mechanical and medical treatment of root canals in vitro. Materials and research methods. The data obtained as a result of a survey of practicing dentists were statistically processed in Microsoft Excel 6. In the course of the work, root canals were treated with manual and machine tools, followed by washing with a drug based on sodium hypochlorite solution using various methods Results. The highest degree of diffusion of the agent based on sodium hypochlorite solution was established in root canals treated with machine tools using the aspiration method of sanitation. Manual preparation of root canals showed the lowest degree of penetration of the irrigant into the root canal compared to machine processing. Regardless of the method of root canal preparation, it was found that the best degree of penetration of the agent based on sodium hypochlorite solution was observed with the aspiration method of debridement than with the traditional method of antiseptic treatment using an endodontic needle.

Acquisition of 3D Root System Simulation Parameters Using 2D Extracted Image Data and Genetic Programming

Root studies like propagation and morphological traits unlock a higher-level understanding of plants to better the growth of agricultural crops and maximize farm yields. As they are located underground, there is an additional challenge in elucidating their structure and behavior. Root imaging allows for real-time observations and there are several known methods. One imaging dataset simulated entire 3D root systems to create 2D images for data analysis and measurements. In this study, the dataset’s extracted measurements will be used to reconstruct the true parameters of the simulated 3D root system through the use of multigene symbolic regression genetic programming (MSRGP). Eleven (11) parameters were selected as the output variables, each for monocot and dicot data for a total of 22 MSRGP models. Among these, thirteen of them showed high R2 values greater than 80%, proving the high accuracy of the MSRGP method. Input variables that were frequently used across multiple models were also noted, such as tip count, exploration ratio, and area. In addition to the accuracy that MSRGP provides in predicting variables, the computation time of these models is found to be as low as a few milliseconds. Once trained, this speed allows the models to be integrated into relevant applications without significant increases in computation cost.

Effects of variable temperature and moisture conditions on respiration and nonstructural carbohydrate dynamics of tree roots

• Low soil moisture lowered the root respiration rate of boreal Scots pines. Root respiration was clearly higher in warm and dry than cool and moist year. • Root respiration peaked after the aboveground growth began to decrease. • The root fructose and glucose contents correlated negatively with soil moisture. The method used to determine root respiration should be selected carefully. In warming climates, soil water content (SWC) may act as an important factor in determining belowground carbon dynamics in boreal forests. Here, we estimated the respiration and nonstructural carbohydrate (NSC) concentrations of tree roots in a mature Scots pine ( Pinus sylvestris L.) stand in southern Finland during two growing seasons with contrasting weather conditions. Root respiration was estimated with four different methods: 1) incubating excised roots, 2) partitioning forest floor respirations with root exclusion, or 3) based on temperature response functions and 4) modelling with the whole-tree carbon model ‘CASSIA’. In addition, we conducted a drought experiment in a greenhouse to determine the effect of reduced soil-water availability on respiration by incubating soil and roots of Scots pine saplings. We observed that the respiration of incubated roots of Scots pine saplings and soil decreased with drying after excluding the effect of temperature on respiration (R RES ), soil being more sensitive to drought than roots. Similarly, R RES of incubated roots in the field was significantly decreased by lowered SWC, whereas respiration of the entire root system estimated with other methods was clearly higher in dryer and warmer than moister and cooler year. Nevertheless, incubated roots excavated from the topsoil are most affected by drying soil, which might not reflect the response of the entire root system. R RES of incubated roots was negatively associated with root fructose and glucose concentrations. At the same time, root fructose, glucose and sucrose concentrations were negatively associated with SWC due to their role in osmoregulation. Thereby it seems that R RES does not directly follow the changes in NSCs despite the apparent correlation. Our study highlights the responsive nature of root carbon dynamics in varying weather events that should be taken into account in estimating and modelling the impacts of warming climate.

Volatile Organic Compounds and Physiological Parameters as Markers of Potato (Solanum tuberosum L.) Infection with Phytopathogens.

The feasibility of early disease detection in potato seeds storage monitoring of volatile organic compounds (VOCs) and plant physiological markers was evaluated using 10 fungal and bacterial pathogens of potato in laboratory-scale experiments. Data analysis of HS-SPME-GC-MS revealed 130 compounds released from infected potatoes, including sesquiterpenes, dimethyl disulfide, 1,2,4-trimethylbenzene, 2,6,11-trimethyldodecane, benzothiazole, 3-octanol, and 2-butanol, which may have been associated with the activity of Fusarium sambucinum, Alternaria tenuissima and Pectobacterium carotovorum. In turn, acetic acid was detected in all infected samples. The criteria of selection for volatiles for possible use as incipient disease indicators were discussed in terms of potato physiology. The established physiological markers proved to demonstrate a negative effect of phytopathogens infecting seed potatoes not only on the kinetics of stem and root growth and the development of the entire root system, but also on gas exchange, chlorophyll content in leaves, and yield. The negative effect of phytopathogens on plant growth was dependent on the time of planting after infection. The research also showed different usefulness of VOCs and physiological markers as the indicators of the toxic effect of inoculated phytopathogens at different stages of plant development and their individual organs.

Carbon allocation to root exudates is maintained in mature temperate tree species under drought.

Carbon (C) exuded via roots is proposed to increase under drought and facilitate important ecosystem functions. However, it is unknown how exudate quantities relate to the total C budget of a drought-stressed tree, that is, how much of net-C assimilation is allocated to exudation at the tree level. We calculated the proportion of daily C assimilation allocated to root exudation during early summer by collecting root exudates from mature Fagus sylvatica and Picea abies exposed to experimental drought, and combining above- and belowground C fluxes with leaf, stem and fine-root surface area. Exudation from individual roots increased exponentially with decreasing soil moisture, with the highest increase at the wilting point. Despite c. 50% reduced C assimilation under drought, exudation from fine-root systems was maintained and trees exuded 1.0% (F. sylvatica) to 2.5% (P. abies) of net C into the rhizosphere, increasing the proportion of C allocation to exudates two- to three-fold. Water-limited P. abies released two-thirds of its exudate C into the surface soil, whereas in droughted F. sylvatica it was only one-third. Across the entire root system, droughted trees maintained exudation similar to controls, suggesting drought-imposed belowground C investment, which could be beneficial for ecosystem resilience.

Installation and imaging of thousands of minirhizotrons to phenotype root systems of field-grown plants

BackgroundRoots are vital to plant performance because they acquire resources from the soil and provide anchorage. However, it remains difficult to assess root system size and distribution because roots are inaccessible in the soil. Existing methods to phenotype entire root systems range from slow, often destructive, methods applied to relatively small numbers of plants in the field to rapid methods that can be applied to large numbers of plants in controlled environment conditions. Much has been learned recently by extensive sampling of the root crown portion of field-grown plants. But, information on large-scale genetic and environmental variation in the size and distribution of root systems in the field remains a key knowledge gap. Minirhizotrons are the only established, non-destructive technology that can address this need in a standard field trial. Prior experiments have used only modest numbers of minirhizotrons, which has limited testing to small numbers of genotypes or environmental conditions. This study addressed the need for methods to install and collect images from thousands of minirhizotrons and thereby help break the phenotyping bottleneck in the field.ResultsOver three growing seasons, methods were developed and refined to install and collect images from up to 3038 minirhizotrons per experiment. Modifications were made to four tractors and hydraulic soil corers mounted to them. High quality installation was achieved at an average rate of up to 84.4 minirhizotron tubes per tractor per day. A set of four commercially available minirhizotron camera systems were each transported by wheelbarrow to allow collection of images of mature maize root systems at an average rate of up to 65.3 tubes per day per camera. This resulted in over 300,000 images being collected in as little as 11 days for a single experiment.ConclusionThe scale of minirhizotron installation was increased by two orders of magnitude by simultaneously using four tractor-mounted, hydraulic soil corers with modifications to ensure high quality, rapid operation. Image collection can be achieved at the corresponding scale using commercially available minirhizotron camera systems. Along with recent advances in image analysis, these advances will allow use of minirhizotrons at unprecedented scale to address key knowledge gaps regarding genetic and environmental effects on root system size and distribution in the field.

First Report of Fusarium avenaceum, Fusarium oxysporum, Fusarium redolens, and Fusarium solani Causing Root Rot in Pea in France.

First Report of Fusarium avenaceum, Fusarium oxysporum, Fusarium redolens, and Fusarium solani Causing Root Rot in Pea in France.

Influence of the Irrigation Regime on the Soybeans (Glycine Max) Root System

The efficiency of crop irrigation depends largely on the extent of the root system and the corresponding depth at which the soil is moistened by irrigation. The incorrect determination of irrigation rates can cause water stress or unnecessary irrigation costs, and in both cases the efficiency of irrigation decreases. The aim of this work is to study the root system of soybean plants irrigated with full and reduced irrigation rates. The research work was been carried out on alluvial meadow soil from Bulgaria. The variety “Biser” is used. Treatments of the experiment: 1) without irrigation; 2) full irrigation (100%m), 3) irrigation with 70% of the full irrigation application rate (70%m), 4) 50%m, 5) 30%m. Water applications in treatment 2 were realized at 80% of FC (field capacity) pre-irrigation soil moisture in the 0-60 cm soil layer. Irrigation water was applied in short closed furrows. The weight of the roots and their distribution in soil layers were established. For this purpose, soil monoliths with dimensions of 10x35x10 cm at a depth of up to 100 cm have been cut. The irrigation regime had a significant impact on the soybean root weight. The small irrigation rates can increase their dry weight by almost a quarter. The higher irrigation rates can increase the root weight between 64 and 73%. The main part of the soybean roots (37-44%), regardless of the irrigation regime, is located in the surface soil layer 0-20 cm. Most of it is in the 10-20 cm soil layer. In the critical soil layer (20-40 cm), 23% of the roots of non-irrigated plants and 27% of the roots of those irrigated with low irrigation rates (30%) are formed. When applying irrigation rates in the range of 50-100%, the relative share is the same (30-31%). If irrigation rate is calculated to moisten the layer 0-40 cm, it can provide water to 67-70% of the entire root system. If it is calculated for 0-60 cm, it covers 86-89% of the root system. The conclusion is that the criterion for irrigation should be provides the optimal soil moisture in the layer 0-40 cm, and irrigation rates should be moisten the soil layer up to 0-60 cm.