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Adjustments in root biomass allocation, root morphology, carboxylate exudation and mycorrhizal symbiosis are well‐known strategies for plants to cope with phosphorus (P) deficiency. Large genotypic variation in these functional traits has been demonstrated within numerous species. Yet, whether these functional traits are coordinated differently among genotypes of a species to enhance P acquisition remains unknown. We characterized 11 root functional traits associated with P acquisition in 20 chickpea genotypes with contrasting amounts of rhizosheath carboxylates, grown in a glasshouse with severely limiting insoluble (10 mg/kg FePO4), moderately limiting soluble (10 mg/kg KH2PO4) and adequate (50 mg/kg KH2PO4) P supply. Substantial variation was found among genotypes in root functional traits associated with P acquisition. Genotypes with a large amount of carboxylates (HRC) had thinner roots, and a lower root mass fraction and root mass density (RMD), but higher specific root length (SRL) and colonization by arbuscular mycorrhizal fungi (AMF) than genotypes with a small amount of rhizosheath carboxylates. In response to soil P availability, chickpea genotypes showed large plasticity in root biomass allocation, rhizosheath pH, carboxylate amount and colonization by AMF, but a limited response in most root morphological traits (i.e. mean root diameter, RMD and SRL). Shoot P content was strongly correlated with different root functional traits in the three P treatments. Our findings suggest a range of predictable relationships between root functional traits among chickpea genotypes; those with HRC tended to have relatively thinner roots with lower cost of root construction, while allocating more resources to carboxylate exudation and colonization by AMF. The shift in the relationships between shoot P content and root functional traits indicates that root traits and/or trait combinations in chickpea vary in a manner that enhances P acquisition under specific soil P conditions (i.e. P sources/levels). Such knowledge provides valuable information for chickpea genotype breeding and our understanding of evolution of traits with improved root/rhizosphere functioning. A free Plain Language Summary can be found within the Supporting Information of this article. A free Plain Language Summary can be found within the Supporting Information of this article

Purpose The current knowledge of belowground interactions in intercropping systems is limited due to methodological constraints. The current study aimed to investigate cereal-brassica and cereal-legume-brassica cover crop mixtures regarding mixture effects on root and shoot biomass as well as root traits, vertical root niche differentiation, and complementarity. Methods Sole crops and two- and three-species-mixtures of winter rye ( Secale cereale L.), crimson clover ( Trifolium incarnatum L.), and oil radish ( Raphanus sativus L. var. oleiformis Pers.) were grown in Germany in a two-year organic field experiment. Root traits were analysed using the monolith method. For discrimination of species root mass Fourier transform infrared (FTIR) spectroscopy was used. Results Oil radish dominated mixtures above- and belowground. Oil radish and its mixtures had highest root length density (RLD) and root mass density (RMD) in subsoil. Rye had highest root biomass and RLD in topsoil. Clover was uncompetitive and had low RLD and RMD. Large but non-significant mixture effects occurred in the shoot, especially for shoot nutrient uptake. Mixture effects were positive for RLD and RMD in subsoil and positive for specific root length (SRL) throughout the whole profile. There was no clear evidence for vertical root niche differentiation and root mass complementarity. Conclusion Oil radish as a mixing partner increased rooting in subsoil. When comparing mixtures and sole crops, morphological changes, i.e. higher SRL in mixtures, were found. Contrary to expectations, changes in root allocation patterns, such as vertical niche differentiation or complementarity of root mass, were not observed.

Soil water uptake is a function of root growth and distribution. Therefore, restrictions on root system growth may reduce water and nutrient uptake, which results in slower plant growth. The objective of this study was to determine the effects of different irrigation strategies, nitrogen application rates, and planting methods on the winter wheat root growth. The experimental factors included two irrigation strategies (variable alternate furrow irrigation defined as partial root-zone irrigation and ordinary furrow irrigation), two planting methods (in-furrow planting and on-ridge planting), and three nitrogen (N) application rates (0, 150, and 300 kg N ha −1 ) in 2015–2016 and 2016–2017 growing seasons. Results indicated that the in-furrow planting decreased mean root length density and root mass density (8% and 10%, respectively, in the fertilized treatments) compared to that obtained in the on-ridge planting. The partial root-zone irrigation reduced root length density by about 5% and 7% in the fertilized treatments compared to that obtained in full irrigation in the first and second year, respectively; however, these reductions were not statistically significant. Furthermore, the results implied that nitrogen fertilizer application increased root length density by 48% and 24% in the first and second year, respectively. Likely, root mass density increased by 32% and 5% in the first and second year, respectively. The exponential decaying relationship between root length density and soil depth indicated that the in-furrow planting with 300 kg N ha −1 produced the highest root density at the soil surface layer and reduced deep root penetration compared to the on-ridge planting and the other N treatments. Further analysis revealed that grain yield linearly correlated with root length density and root mass density in the first year. However, a polynomial (quadratic) relationship was obtained in the second year. Consequently, increasing the main root traits, including root length and root mass, enhanced winter wheat grain yield until it reached a threshold value. Higher values negatively affected grain yield, which might be due to allocating carbon to roots instead of grains.

This paper provides an overview of the existing literature on the subject of the assessment and monitoring of tree roots and their interactions with the soil. An overview of tree root system architectures is given, and the main issues in terms of tree health and stability, as well as the impact of trees on the built environment, are discussed. An overview of the main destructive and non-destructive testing methods is presented, and a lack of available research-based outputs in the fields of tree root interconnectivity and soil interaction is highlighted. The effectiveness of non-destructive methods in these areas is demonstrated, in particular that of ground-penetrating radar. The paper references recent developments in estimating tree root mass density and health.

The preservation of natural assets is nowadays an essential commitment. In this regard, root systems are endangered by fungal diseases which can undermine the health and stability of trees. Within this framework, ground penetrating radar (GPR) is emerging as a reliable non-destructive method for root investigation. A coherent GPR-based root-detection framework is presented in this paper. The proposed methodology is a multi-stage data analysis system that is applied to semi-circular measurements collected around the investigated tree. In the first step, the raw data are processed by applying several standard and advanced signal processing techniques in order to reduce noise-related information. In the second stage, the presence of any discontinuity element within the survey area is investigated by analysing the signal reflectivity. Then, a tracking algorithm aimed at identifying patterns compatible with tree roots is implemented. Finally, the mass density of roots is estimated by means of continuous functions in order to achieve a more realistic representation of the root paths and to identify their length in a continuous and more realistic domain. The method was validated in a case study in London (UK), where the root system of a real tree was surveyed using GPR and a soil test pit was excavated for validation purposes. Results support the feasibility of the data processing framework implemented in this study.

BACKGROUND AND AIMS: Growth and distribution of fine roots closely depend on soil resource availability and affect soil C distribution in return. Understanding of relationships between fine root distribution and soil C can help to predict the contribution of fine root turnover to soil C accumulation. METHODS: A study was conducted in a subtropical Cunninghamia lanceolata plantation to assess the fine root mass density (FRMD), fine root C density (FRCD) of different fine root groups as well as their relations with soil C. RESULTS: The FRMD and FRCD of short-lived roots, dead roots and herb roots peaked in the 0–10 cm soil layer and decreased with soil depth, while FRMD, FRCD of long-lived roots peaked in the 10–20 cm soil layer. Soil C was positively related to FRMD and FRCD of total fine roots (across all three soil layers), dead roots (0–10 cm) and herb roots (10–20 cm) as well as FRCD of short-lived roots (20–40 cm) (P <0.05). CONCLUSIONS: Soil C was mainly affected by herb roots in upper soil layers and by woody plant roots in deeper soil layers.

Imbalanced nutrient fertilization adversely affects root growth and alters the nutrient use efficiency of a crop. This study aimed to understand the influence of integrated nutrient management on root characteristics and nitrogen use efficiency in the vegetable-based agroecosystem. The field trial was conducted at the Department of Soil Science and Water Management of Dr. Y S Parmar University of Horticulture and Forestry Nauni, Solan (HP) India in 2019 and 2020. There were nine treatments viz. T1- control, T2-100% farmyard manure (FYM; N equivalent basis), T3-100% N, T4-100% NP, T5-100% NK, T6-100% PK, T7-100% NPK, T8-100% NPK + FYM (recommended practice), and T9-150% NPK + FYM on root densities (mass, volume, and length) and N use efficiency of cauliflower and capsicum. The results observed that different treatments exert significant effects on measured as well as derivative parameters. In detail, the application of 150% NPK + FYM recorded significantly higher root-mass density (0.72 and 1.71 g m−3 × 10−3), root-volume density (4.49 and 2.52 m3 m−3 × 10−3), and root-length density (1.21 and 0.81 cm m−3 × 10−4) in cauliflower and capsicum, respectively, which was statistically at par with treatment T9 (100% NPK + FYM). Similarly, this treatment (150% NPK + FYM) resulted in a maximum positive N (774.6 kg ha−1), P (650.4 kg ha−1), and K (334.9 kg ha−1) balance of soil after the complete harvest of two cropping-sequence cycles. However, maximum agronomic N use efficiency (59.9 and 67.9 kg kg−1) and apparent recovery of N (39.3 and 59.7%) were recorded under 100% FYM (N equivalence) in cauliflower and capsicum, respectively, but this treatment produced the negative N balance (−91.7 kg ha−1) and K (−340.3 kg ha−1) in soil, whereas significant improvement in agronomic use efficiency, apparent recovery of applied N, as well as in soil, and the NPK balance was recorded under 100% NPK + FYM over the other treatment. This study recommended an integrated nutrient module that is the application of 100% NPK + FYM to ensure better root growth and positive nutrient balance in the soil.

Background and aims This study investigated whether root traits at the seedling stage are maintained at the flowering stage in two chickpea ( Cicer arietinum ) genotypes with contrasting root morphology and physiology; and whether the genotype with greater rhizosheath carboxylates mobilises more poorly-available phosphorus (P) pools to increase shoot P at flowering/podding and seed yield at maturity. Methods Two chickpea genotypes were grown in a low P soil with or without P addition (0 and 40 µg P g −1 soil as KH 2 PO 4 ) under controlled glasshouse conditions and harvested at seedling, flowering/podding, physiological maturity. Results At the seedling and flowering/podding stages, ICC2884 had thinner roots and greater root mass ratio, specific root length and rhizosheath carboxylates per root dry weight (DW) than ICC456. Both genotypes had smaller root diameter, higher carboxylates and acid phosphatase activity in rhizosheath soil at flowering/podding than at seedling. In the rhizosheath soil of both genotypes, NaHCO 3 -Pi concentration was depleted under P0 only; under both P0 and P40, NaHCO 3 -Po concentration increased while NaOH-Pi and NaOH-Po concentrations decreased at the seedling stage but accumulated at the flowering/podding stage, relative to the bulk soil. ICC2884 did not mobilise more poorly available soil P or acquire more P at the seedling or flowering/podding stages, or produce higher seed yields than ICC456. Conclusion ICC2884 and ICC456 maintained the difference in root morphological and physiological characteristics from the seedling stage to the flowering/podding stage. The genotype with greater rhizosheath carboxylates (root DW basis) did not produce higher yield than genotype with less rhizosheath carboxylates.

Potatoes are a high-value crop with a shallow root system and high fertilizer requirements. The primary emphasis in potato production is minimizing nitrogen-leaching losses from the shallow root zone through fertigation. Therefore, a field experiment was conducted for two consecutive years, 2018–2019 2019–2020 to assess the effect of nitrogen and irrigation amount and frequency on tuber yield, water balance components and water productivity of potatoes under surface and subsurface drip irrigation. The experiment was laid out in a split-plot design with three nitrogen levels (187.5 kg N ha−1 (N1), 150 kg N ha−1 (N2) and 112.5 kg N ha−1 (N3)) in main plots and six irrigation levels in the subsurface (drip lines were laid at 20 cm depth) and one surface drip in subplots. Irrigation scheduling was based on 100% of cumulative pan evaporation at an alternate (I1) and two-day interval (I2), 80% of cumulative pan evaporation at an alternate (I3) and two-day interval (I4), 60% of cumulative pan evaporation at an alternate (I5) and two-day interval (I6) and 80% of cumulative pan evaporation at alternate days with surface drip (I7). Our results showed that potato transpiration was higher in N1 and N2 compared to N3, while soil evaporation was higher in N3 over N1 and N2. Irrigation regimes I5 and I6 had lower transpiration than I1, I2, I3 and I7, while I7 had more soil evaporation than I1, I2 and I3. Leaf area index (LAI), dry matter accumulation (DMA), root mass density (RMD) and tuber yield in N1 and N2 were at par but significantly higher than N3. The LAI and DMA were statistically at par in I1, I2 and I3 but significantly higher than recommended irrigation (I7). Tuber yield was statistically at par in I1, I2, I3 and I7 but I3 and I7 saved 20% irrigation water compared to I1 and I2. On the other hand, real water productivity (WPET) under N1 and N2 were comparable in I3 and I4 but significantly higher than recommended practice (I7) as pooled evapotranspiration (ET) and soil evaporation (E) in I7 were 19.5 and 20.6 mm higher, respectively, than in I3. Among interactive treatment combinations, N1I1, N1I2, N1I3, N1I7, N2I1, N2I2 and N2I3 recorded the highest tuber yields without any significant differences among them. Treatment N2I3 saved 20% nitrogen and irrigation water compared to all other combinations. Water productivity in N1 and N2 was comparable in I3 and I4 but significantly higher than recommended practice (I7).

Conducting research on the dynamic behavior of root–soil systems is crucial for accurately assessing the seismic response of ecological slopes, thereby providing a scientific foundation for the development of appropriate seismic design measures. Documentation of the improvement of soil dynamics through vegetation root systems is insufficient in the current research. This study utilizes resonance column tests to explore how root systems influence the dynamic properties of clayey soil and to uncover the mechanisms behind this enhancement. The results indicate that both root distribution and mass density have a significant impact on the soil’s dynamic shear modulus and damping ratio. When roots are distributed in the upper part of the soil, the dynamic shear modulus and damping ratio of the soil are higher than in cases of even distribution or concentration in the lower part. The dynamic shear modulus initially increases and then decreases with the increase in root mass density, reaching its peak at a root mass density of 1.5% g·cm−3. The damping ratio is influenced by both root mass density and confining pressure, with different critical root mass densities observed under varying confining pressures. The maximum enhancement in dynamic shear modulus is 27.6%, achieved at a 3% root mass density, with a peak damping ratio of 5.39%. Variations in both dynamic shear modulus and damping ratio with shear strain follow the Hardin–Drnevich hyperbolic curve.