Intercropping is a farming practice involving two or more crop species, or genotypes, growing together and coexisting for a time. On the fringes of modern intensive agriculture, intercropping is ...important in many subsistence or low‐input/resource‐limited agricultural systems. By allowing genuine yield gains without increased inputs, or greater stability of yield with decreased inputs, intercropping could be one route to delivering ‘sustainable intensification’. We discuss how recent knowledge from agronomy, plant physiology and ecology can be combined with the aim of improving intercropping systems. Recent advances in agronomy and plant physiology include better understanding of the mechanisms of interactions between crop genotypes and species – for example, enhanced resource availability through niche complementarity. Ecological advances include better understanding of the context‐dependency of interactions, the mechanisms behind disease and pest avoidance, the links between above‐ and below‐ground systems, and the role of microtopographic variation in coexistence. This improved understanding can guide approaches for improving intercropping systems, including breeding crops for intercropping. Although such advances can help to improve intercropping systems, we suggest that other topics also need addressing. These include better assessment of the wider benefits of intercropping in terms of multiple ecosystem services, collaboration with agricultural engineering, and more effective interdisciplinary research.
The physical role of root hairs in anchoring the root tip during soil penetration was examined. Experiments using a hairless maize mutant (Zea mays: rth3–3) and its wild-type counterpart measured the ...anchorage force between the primary root of maize and the soil to determine whether root hairs enabled seedling roots in artificial biopores to penetrate sandy loam soil (dry bulk density 1.0–1.5 g cm−3). Time-lapse imaging was used to analyse root and seedling displacements in soil adjacent to a transparent Perspex interface. Peak anchorage forces were up to five times greater (2.5 N cf. 0.5 N) for wild-type roots than for hairless mutants in 1.2 g cm−3 soil. Root hair anchorage enabled better soil penetration for 1.0 or 1.2 g cm−3 soil, but there was no significant advantage of root hairs in the densest soil (1.5 g cm−3). The anchorage force was insufficient to allow root penetration of the denser soil, probably because of less root hair penetration into pore walls and, consequently, poorer adhesion between the root hairs and the pore walls. Hairless seedlings took 33 h to anchor themselves compared with 16 h for wild-type roots in 1.2 g cm−3 soil. Caryopses were often pushed several millimetres out of the soil before the roots became anchored and hairless roots often never became anchored securely. The physical role of root hairs in anchoring the root tip may be important in loose seed beds above more compact soil layers and may also assist root tips to emerge from biopores and penetrate the bulk soil.
Matching roots to their environment White, Philip J; George, Timothy S; Gregory, Peter J ...
Annals of botany,
07/2013, Volume:
112, Issue:
2
Journal Article
Peer reviewed
Open access
BackgroundPlants form the base of the terrestrial food chain and provide medicines, fuel, fibre and industrial materials to humans. Vascular land plants rely on their roots to acquire the water and ...mineral elements necessary for their survival in nature or their yield and nutritional quality in agriculture. Major biogeochemical fluxes of all elements occur through plant roots, and the roots of agricultural crops have a significant role to play in soil sustainability, carbon sequestration, reducing emissions of greenhouse gasses, and in preventing the eutrophication of water bodies associated with the application of mineral fertilizers.ScopeThis article provides the context for a Special Issue of Annals of Botany on ‘Matching Roots to Their Environment’. It first examines how land plants and their roots evolved, describes how the ecology of roots and their rhizospheres contributes to the acquisition of soil resources, and discusses the influence of plant roots on biogeochemical cycles. It then describes the role of roots in overcoming the constraints to crop production imposed by hostile or infertile soils, illustrates root phenotypes that improve the acquisition of mineral elements and water, and discusses high-throughput methods to screen for these traits in the laboratory, glasshouse and field. Finally, it considers whether knowledge of adaptations improving the acquisition of resources in natural environments can be used to develop root systems for sustainable agriculture in the future.
•Recent improvements and integration of VESS for topsoil and subsoil are described.•VESS detects compaction well and discriminated between damage by tractors and livestock.•Visual soil evaluation can ...estimate the risk of loss of N2O, soil carbon and nutrients.•Visual soil evaluation can bring an awareness of soil quality to a range of users.
Visual soil evaluation techniques have gained popularity and are increasingly used in agriculture and soil science for research, consultancy and teaching purposes. We describe recent applications, developments, opportunities and limitations, mainly of the Visual Evaluation of Soil Structure (for topsoil (VESS) and for subsoil (SubVESS)), and of the Visual Soil Assessment (VSA). Data are taken from experiments on compaction and from assessments made in farmer’s fields in the UK, Brazil and New Zealand. The methods are widely used to detect compaction and are well-suited for monitoring changes in compaction status, particularly in relation to weather extremes. VESS proved useful in distinguishing grazing vs wheel compaction in the UK and Brazil by permitting detection of layers at different depths within the topsoil zone. The depths of compact layers are important for scoring management decisions for soil improvement. However the use of scores as limiting thresholds in different soil types needs the support of further soil measurements and/or additional visual assessments of soil and crop. VSA and VESS were also used to estimate the risk of significant soil emissions of nitrous oxide where compaction damage was present and rates of mineral N fertiliser were high. Visual assessments also have the potential to assess the risk of surface water runoff and nutrient loss. The potential role of soil colour was shown for the further development of visual evaluation techniques for a soil carbon storage index. Visual soil evaluation techniques also provide a useful visual aid for improving soil awareness in groups of stakeholders, helping the exchange of knowledge and ideas for innovation in agriculture.
•On a purpose-built experimental slope, use of quality green compost could increase vegetation cover of grass by up to 20 times.•Surface applications of quality green compost produced a greater ...effect than incorporation to 10cm depth.•Compost alone did not affect cohesion or angle of friction of the amended soil.•Increased soil cohesion from root reinforcement at 5cm depth quadrupled on slopes with 300tha−1 added compost.
Vegetation such as grasses and shrubs can improve slope stability, reducing the risk of shallow failures once roots have permeated soil to enhance cohesion. However, establishment of vegetation is hindered by poor soil fertility, frequently a characteristic of disturbed soils used in engineering projects. We evaluated whether compost could improve the rate of vegetation establishment and hence soil mechanical reinforcement by plant roots and therefore protect against shallow failures. Over 1200t of material was formed into a slope 40m long×15m wide, with an experimental soil slope angle of 20°. Washings from recycled mineral fill were used for the surface soil. Five amendment treatments were replicated three times in strips of 1.5m by 8m in a randomised block design on this slope; treatments were a no compost control, standard compost addition at a rate of 35tha−1 and a high level compost amendment at 300tha−1, applied either to the surface or incorporated into the topsoil to 10cm.
Thirteen weeks after planting an amenity grass mix, vegetation cover increased up to 6 times compared to the control for 35tha−1 surface applied compost and similarly 20 times for 300tha−1 compost that had been surface applied. Root length density was about 3kmm−3 with no added compost and about 30kmm−3 for 300tha−1 added compost. At 35tha−1 compost, peak shear stress of the vegetated soil at 5cm depth was not affected, but it almost doubled with 300tha−1 compost compared to no amendment. Cohesion from plant roots was 8.1kPa for 300tha−1, in comparison to 2.1kPa for no amendment and 2.3kPa for 35tha−1 compost. Whereas surface application resulted in better vegetation cover, there were no differences in peak shear stress between plots with surface application or incorporation of compost. This study provided experimental evidence in the field that compost improvement to soil fertility has a positive impact on soil stabilisation by plant roots.
Green roofs, defined as roofs of buildings that are partially or completely covered with vegetation planted in a growing medium can provide multiple sustainability benefits. There is potential to ...increase the sustainability benefits of green roofs by using recycled construction materials for green roof construction.
This study investigates the viability of using recycled aggregates in the substrate mix for extensive green roofs where a ‘carpet’ of plants is supported by lightweight growing media (substrate) overlying a drainage layer. We investigated the adequacy of recycled inert construction waste as a growth medium, the drainage properties of the substrate mix containing recycled materials as well as its susceptibility to erosion and resistance to sliding when placed on a slope.
In this laboratory study we compared the establishment, development and performance of both grass and sedum model green roofs under simulated rainfall and found that the substrate mix containing recycled construction waste materials was adequate in supporting plant growth, was resistant to erosion and slippage and capable of providing good drainage. When vegetated, the ‘green roof’ can provide attenuation of the drainage water with magnitude depending on the type and percentage of vegetation cover.
We attempt to put the results of this small scale laboratory investigation on extensive green roofs into the wider perspective of sustainability benefits offered by the green roofs.
To penetrate soil, a root requires pressure to expand the cavity it is to occupy and to overcome root‐soil friction. We quantified these two pressures and showed that the root‐soil friction can be a ...substantial component of root penetration resistance. This provides evidence suggesting that modifying root‐tip traits has potential to improve plant performance.
To penetrate soil, a root requires pressure both to expand the cavity it is to occupy, σn, and to overcome root–soil friction, σf. Difficulties in estimating these two pressures independently have limited our ability to estimate the coefficient of soil–root friction, μsr. We used a rotated penetrometer probe, of similar dimensions to a root, and for the first time entering the soil at a similar rate to a root tip, to estimate σn. Separately we measured root penetration resistance (PR) Qr. Root PR was between two to four times σn. We estimated that the coefficient of root–soil friction (μsr) was 0.21–0.26, based on the geometry of the root tip. This is slightly larger than the 0.05–0.15 characteristic of boundary lubricants. Scanning electron microscopy showed that turgid border cells lined the root channel, supporting our hypothesis that the lubricant consisted of mucilage sandwiched between border cells and the surface of the root cap and epidermis. This cell–cell lubrication greatly decreased the friction that would otherwise be experienced had the surface of the root proper slid directly past unlubricated soil particles. Because root–soil friction can be a substantial component of root PR, successful manipulation of friction represents a promising opportunity for improving plant performance.
Soils with biological crusts that consist of fungal hyphae, bacteria and other small organisms usually resist erosion. However, the processes by which soil organisms stabilise air-dry aggregates ...against wind erosion are not well understood. We used saprotrophic fungi to examine some of these processes in a sandy clay loam (Hypercalcic Calcarosol). Soil aggregates, wetted with distilled water or glucose solution, were inoculated with one of six fungi, and incubated in darkness at 24 °C for 7 d in petri dishes under sterile conditions. Abrasion resistance (taken as resistance to wind erosion), tensile strength of soil, hot-water extractable carbohydrates (HWEC), dispersion index, pH, and hyphal length density (HLD) were each measured across all treatments. In all treatments, stability (abrasion resistance) and tensile strength, were positively related to HLD. Such relationships have not been reported elsewhere. All fungi enlarged the aggregates of the soil by cross-linkage and entanglement of particles, but with different processes, or different intensity of the processes, between species (for the same amount of substrate). The skins seen in scanning electron micrographs of stabilised soil were probably extracellular polysaccharides also produced by the fungi. We propose that the ductile failure of disks of soil, particularly those inoculated with Mucor sp., under tensile stress was due to movement of enmeshed particles, whereas the brittle failure of disks of soil inoculated with the other fungal species was due to metabolites or dispersed clay on the surface of the hyphae which limited deformation.
► Growth of fungal hyphae in soil is related to abrasion resistance of soil. ► Different fungi aggregate different amounts of soil for the same amount of substrate. ► Different fungi hold aggregates together in different ways.
Background and aim: Soil structure is an important indicator of the quality of soil, but detecting the early signs of soil degradation from soil structure is difficult. Developing precise instruments ...able to diagnose soil structure quickly is therefore critical to improve management practices. Here, the objective is to develop an instrument analysing the roughness of surfaces resulting from the fracture of soil cores, and to test the instrument’s ability to detect changes in soil structure cause by crop type and tillage. We have designed and constructed a 3D laser profilometer suitable for analysing standard soil cores. The 3D soil profiles were first assembled into a 3D surface using image analysis before roughness indicators could be computed. The method was tested by analysing how soil surface roughness was affected by crop varieties (barley and bean) and tillage (conventional tillage and no tillage). Results showed the method is precise and could reliably detect an influence of crop type and tillage on the roughness indicator. It was also observed that tillage reduced the difference in soil structure between the different cultures. Also, the soil in which barley grew had significantly lower roughness, irrespective of the tillage method. This could indicate that the roughness indicator is affected by biopores created by the root system. In conclusion, roughness indicators obtained from the fracture of soil cores can be easily obtained by laser profilometry and could offer a reliable method for assessing the effect of crop types and soil management on soil quality.
PDF
