Levels Of Soil Compaction Research Articles

Selection approaches to the variation of responses to soil compaction stress among maize hybrids (Zeamays L.)

AbstractSoil compaction stress can strongly affect plant growth, development and productivity. Effects of different levels of soil compaction were investigated in 18 maize hybrids during field and greenhouse experiments. Maize hybrids in the field experiments were subjected to low (L) or high (H) and in the greenhouse experiments to low (L: 1.10) and high (C: 1.60 g cm−3 soil) soil compaction level. Differences between maize hybrids grown under non‐stress and stress conditions were found in a decrease in grain yield (GY), grain number (GN), weight of 1,000 grain (W‐1000), seedling dry matter (DM), emergence (EM), plant height (H), leaf area (LA) and leaf greening (SPAD). Stress susceptibility index (SSI), geometric mean productivity index (GMP) and tolerance index (TI) were evaluated by determining the effects of low (L) or high (H) soil compaction levels on grain yield (GY) or dry matter of the above‐ground part (DM). The values of SSI, GMP and TI enabled us to rank the tested hybrids with respect to their susceptibility to soil compaction stress. SSI and TI made it possible to identify maize hybrids resistant and sensitive to soil compaction stress. Changes in growth traits were greater in the hybrids with high SSI and TI. Correlation coefficient (r) between stress susceptibility index (SSI) of maize hybrids in the field and greenhouse experiment was high and statistically significant. This observation may indicate that genetically determined susceptibility to soil compaction stress in maize hybrids was similar throughout ontogenesis.

Effect of Soil Compaction and Application of Lime and Gypsum on Soil Properties and Yield of Soybean

ABSTRACT Lime and gypsum application is one strategy for correcting soil acidity and improving soil fertility. However, soil compaction in no-till systems can influence these dynamics. This study aimed to assess the effect of lime and gypsum application under different soil compaction levels on soybean yield and soil chemical attributes. The application of lime and gypsum under artificial compaction levels and the movement of exchangeable calcium (Ca2+), magnesium (Mg2+), potassium (K+), and soil pH were monitored in the 0–0.05, 0.05–0.10, 0.10–0.20, and 0.20–0.40 m soil layer depths. Soybean grain yield was not influenced by the gypsum and lime applications and artificial compaction levels. In the 0.05–0.1, 0.1–0.2, and 0.2–0.4 m soil layers, the exclusive surface application of lime was effective in increasing the soil pH. Ca2+ and Mg2+ carbonates had low solubility and mobility in the soil; however, a rapid reaction to the surface over a relatively short period was observed. K+ concentration in the 0–0.05 m soil layer did not vary after the gypsum and lime applications. Therefore, the superficial application of lime is effective in acidity correction in no-till systems when the soil is not compacted.

Вплив щільності будови та вологості ґрунту на продуктивність інтенсивного та напівінтенсивного сортів ячменю ярого

Goal. To determine the influence of agrophysical parameters of arable soil layer on the productivity of spring barley varieties of different types of intensity under conditions of application of mineral fertilizers on the example of typical deep low humus deep-boiling heavy loam on loess-like loam chernozem of the Left Bank part of Forest-steppe of Ukraine. Methods. Laboratory-analytical, laboratory-model, field (small-area), mathematical-statistical, computational. Results. The improvement of conditions of germination, development, and increase of biological mass of cultivars of the studied culture at soil density and humidity at the level of 1.2 g/cm3 and 80% of the lowest moisture content (LMC) in comparison with compacted soil is established. The optimal values of structure density and soil moisture are determined, which ensure the maximum biomass of intensive variety of spring barley Vzirets: 1.2 g/cm3 and 100% of LMC (at the application of 90 kg/ha of the active substance (a.s.) of nitrogen, phosphorus and potassium fertilizers); semi-intensive variety Zdobutok: 1.2 g/cm3 and 80% of LMC (at the application of 45 kg/ha of nitrogen and phosphorus fertilizers, and 90 kg/ha of potassium fertilizers). In the course of field research, a decrease in the use of nutrients from the soil was revealed: nitrogen by 4.0% — for intensive and 2.0% — for semi-intensive varieties; phosphorus — by 3.4 and 4.7%; potassium — by 10.7 and 6.3%, respectively, at a high (1.4 g/cm3) level of compaction compared to its low (1.0 g/cm3) level. Under the same conditions, a decrease in the yield of spring barley grain was revealed: intensive variety — by 25, semi-intensive — by 22%. Conclusions. According to the results of experimental studies, the complex influence of soil moisture and compaction levels was revealed and their optimal parameters were established for growing intensive and semi-intensive varieties of spring barley, which achieved their maximum yield in soil fertilization.

Моделирование резания грунта при различных углах атаки лемеха рабочего органа стоечного рыхлителя методами фрактального анализа

The level of soil compaction is influenced by physical and mechanical properties, climatic conditions, the amount of annual precipitation, the type of cultivated crops, and other factors. Excessive compaction of the soil impairs water permeability and air access to the roots, resulting in reduced crop yields, increased soil erosion, reduced fertilizer efficiency, which leads to an increase in the cost of material and technical resources for tillage. Therefore, it is important to solve this problem with minimal energy and material costs. Such a solution is the loosening of the soil, which can be done naturally and with the help of mechanical loosening. (Research purpose) The research purpose is in evaluating the effectiveness of loosening the soil with a U-shaped ripper at different angles of the ploughshare using fractal analysis methods, which is necessary to reduce additional loads during further soil treatment. (Materials and methods) A dirt channel with a special cart was used to consider physical models of meliorative machines and specialized working equipment. (Results and discussion) Author conducted six experiments in a soil tray for each corner of the ploughshare separately. Nineteen ground sections were made. The structure of the soil before and after treatment depends on the mode of operation of the ripper model and the design features of its working bodies. (Conclusions) The more energy is spent on the treatment of homogeneous areas, the more the soil structure changes. To quantify the structural changes in the nature of the cultivated soil, we used its fractal characteristics, in particular, the fractal dimension. The soil sections have fractal properties, and, accordingly, fractal methods can be used for their analysis. The article proves the applicability of fractal methods in the analysis of the quality of tillage and the degree of its loosening.

Tree preservation during construction: An evaluation of a comprehensive municipal tree ordinance

In the United States, urban forests represent 35 % of all urban land cover, and deliver benefits to nearly two-thirds of the population. As global urban populations continue to rise, however, redevelopment is continually reported as a major factor in reduced canopy cover. While urban trees provide us with measurable benefits when adequately maintained, their costs when not cared for remains poorly understood. In order to safeguard the benefits that urban forests provide, municipalities have begun to introduce ordinances with the intention to protect and manage trees within their community. The aim of this study was to better understand the condition and survival outcomes of residential trees intended to be preserved through a municipal tree preservation ordinance. The results of this study found that a comprehensive tree preservation ordinance can successfully protect tree and soil health during and after residential development occurs. This is evident through an overall preservation rate of nearly 75 %, having found no correlation between proximity to newly developed foundation and observed tree condition or mortality, and the discovery of healthy soil compaction levels within tree protection areas and the critical root zones of preserved trees. Collaborative research as demonstrated by this project can help both academics and professionals gain a better understanding of how to best manage their own urban forests.

Precrops alleviate soil physical limitations for soybean root growth in an Oxisol from southern Brazil

The impact of soil compaction on soybean root growth and grain yield can be alleviated by the presence of biopores and root channels in the soil profile. We hypothesize that cover crops (ruzigrass and oats) are better than grain crops (wheat and maize) to reduce the soil physical limitation to soybean root growth. We aimed to identify which precrops have higher potential to reduce the mechanical and water stresses resulting from soil compaction and soil desegregation, and to enhance soybean (Glycine max L) root growth and yield in an Oxisol (Rhodic Eutrudox), with clayey soil texture. Soybean was grown after four precrops (ruzigrass, oats, wheat, or maize), under four soil compaction levels [soil chiselling (MTC), no-tillage (NT), NT additionally compacted with four passes of a tractor (NTCT), and NT additionally compacted with eight passes of a grain harvester (NTCH)]. Soil physical attributes (bulk density, macroporosity, water-filled pore space and soil penentration resistance) in the soil profile (0−50 cm) and soybean components (grain yield, cumulative root length density and root dry mass) were investigated. Soil physical attributes were improved over time due to the combined effects of natural wetting-drying cycles and biopores created by the roots of precrops. Ruzigrass increased soybean root biomass and length density, mainly at deeper soil layers of compacted treatments (NTCT and NTCH). The rate of increase of soybean root length density in the soil profile was higher after ruzigrass cultivation in comparison with maize and oats. Soil compaction effects on grain yield were partially (NTCH) or totally (NTCT) alleviated after two years and ruzigrass intensified the mitigation process. Ruzigrass also resulted in higher soybean yields in comparison with maize, whereas NTCH and MTC reduced yields in approximately 400 kg ha−1 (∼13 %) compared to NT and NTCT. Soil strengthening was more evident after ruzigrass and oats cultivation than maize or wheat cropping. Soil compaction in clayey Oxisols can be alleviated over time as a result of root channels provided by precrops combined with natural wetting-drying cycles. Among the evaluated precrops, ruzigrass is of particular interest, as it provides the most suitable soil physical environment for soybean root growth and grain yield. In contrast, chiselling was demonstrated to be a non-viable strategy to mitigate soil physical constraints for root growth and grain yields.

MicroRNA-based markers as a tool to monitor the barley (Hordeum vulgare L.) response to soil compaction

Plants are often exposed to adverse environmental conditions that can significantly interfere with their genomic response. Soil compaction induced by heavy field machinery represents a major problem for crop production mainly due to restricted root growth and penetration into soil and therefore reduced water and nutrient uptake by the plants. Tested hypotheses were to declare whether the plant‘s genome responds to soil compaction and whether the microRNA-based markers are suitable to determine this response. A long term field scale experiment was established in 2009 where different levels of soil compaction are researched from the soil and crop point of view. The analyzed barley (Hordeum vulgare L.) plants were collected during the growing season in 2019. The effect of soil compaction was analysed by four different DNA-based markers corresponding to miRNA sequences of dehydratation stress-responsive barley miRNAs (hvu-miR156, and hvu-miR408) and nutrition-sensitive markers (hvu-miR399 and hvu-miR827), within the leaf, stem and root tissues of barley plants. Our preliminary data support hypotheses that plant genome response was tissue-specific due to significant induction of the biomarkers to dehydratation and nutrition stress. The most affected part of the plant by dehydration, were roots and lack of nutrient supply was most pronounced on leaves.

Evaluating Soil–Root Interaction of Hybrid Larch Seedlings Planted under Soil Compaction and Nitrogen Loading

Although compacted soil can be recovered through root development of planted seedlings, the relationship between root morphologies and soil physical properties remain unclear. We investigated the impacts of soil compaction on planted hybrid larch F1 (Larix gmelinii var. japonica×L. kaempferi, hereafter F1) seedlings with/without N loading. We assumed that N loading might increase the fine root proportion of F1 seedlings under soil compaction, resulting in less effects of root development on soil recovery. We established experimental site with different levels of soil compaction and N loading, where two-year-old F1 seedlings were planted. We used a hardness change index (HCI) to quantify a degree of soil hardness change at each depth. We evaluated root morphological responses to soil compaction and N loading, focusing on ectomycorrhizal symbiosis. High soil hardness reduced the total dry mass of F1 seedlings by more than 30%. Significant positive correlations were found between HCI and root proportion, which indicated that F1 seedling could enhance soil recovery via root development. The reduction of fine root density and its proportion due to soil compaction was observed, while these responses were contrasting under N loading. Nevertheless, the relationships between HCI and root proportion were not changed by N loading. The relative abundance of the larch-specific ectomycorrhizal fungi under soil compaction was increased by N loading. We concluded that the root development of F1 seedling accelerates soil recovery, where N loading could induce root morphological changes under soil compaction, resulting in the persistent relationship between root development and soil recovery.

Compactación del suelo y su efecto en el crecimiento vegetativo de soja, maíz y guandú

Soil compaction affects root growth and crop yield. The objective of this work was to evaluate the development of soybean (Glycine max (L.) Merr.), corn (Zea mays L.) and pigeon pea (Cajanus cajan (L.) Millsp) crops in different soil densities. The experimental design was completely randomized, with treatments arranged in a 3 x 4 factorial scheme, with three crops (soybean, corn and pigeon pea) and four soil densities (0.9; 1.19, 1.39 and 1.59 g cm-3), with 4 replications. The experimental units consisted of PVC tubes with 20 cm diameter and 48.5 cm height, divided into sections: A (0-10 cm), B (10-13.5 cm), where the compaction was simulated and C (13.5-48.5 cm), respectively. ANAVA was used at 5% probability and where there was significance, Tukey test performed mean comparison. Plant height was determined at 30, 60 and 75 days, plant diameter, weight of green and dry matter, root area and root dry weight. Corn showed the highest values in the evaluated parameters of the aerial part. There was a significant difference between the soil compaction levels in plant height at 75 days with the highest soil density. In terms of area and dry weight of roots, they were higher in maize in sections A and B. Soil density negatively affected the dry weight of roots in section B, being higher with soil density of 1.19 g cm-3 (5.37 g pot-1) and smaller with density 1.59 g cm-3 (4.79 g pot-1). In section C soil density did not affect dry matter of soybean roots and pigeon pea, but decreased in corn. Soil compaction mainly affects the root development of corn, compared to soybean and pigeon pea

Impact of soil compaction on the engineering properties of potato tubers.

A study on a 30 hm2 field was conducted to assess the variability in soil compaction and to investigate its effect on the engineering properties of potato tubers in terms of tuber shape and key dimensions (length, width and thickness) and resistance to penetration, rupture and shear forces. Three soil compaction levels were spatially correlated with the engineering properties of potato tubers through linear regression and ANOVA test. The three compaction levels included a low level (C1) ranging between 1.2-1.9 MPa, a medium level (C2) with compaction levels between 2.0-2.3 MPa and a high level (C3) ranging between 2.4-2.9 MPa. Results revealed that there were no significant changes in the key tuber dimensions corresponding to the variability in soil compaction. However, inverse linear relationships were observed between soil compaction and the key tuber dimensions with R2 values of 77%, 97% and 96% for length, width and thickness, respectively. Similarly, the soil compaction was shown to have no effect on the tuber resistance to compression and shear force. In contrast, the tuber resistance to penetration was significantly affected by soil compaction (p>F = 0.0012). Keywords: compaction, potato tubers, precision agriculture, potato engineering properties DOI: 10.25165/j.ijabe.20201302.4818 Citation: Edrris M K, Al-Gaadi K A, Hassaballa A A, Tola E, Ahmed K A M. Impact of soil compaction on the engineering properties of potato tubers. Int J Agric & Biol Eng, 2020; 13(2): 163–167.

Effect of compaction and soil moisture on the effective permeability of sands for use in methane oxidation systems

Effective gas permeability is an important parameter in the design of methane oxidation systems, governing diffusive oxygen ingress and the spatial spread of landfill gas. The influences of soil texture, compaction, soil moisture and the resulting air filled porosity on the gas permeability were researched by performing pressure loss experiments on two loamy sands, currently in use as methane oxidation layer material. These experiments mimicked the influence of the intrinsic soil properties, the construction method (compaction) and the local climate (soil moisture) on the soils’ permeability. In both soils, effective and specific permeability were strongly impacted by the level of soil compaction, whereas increasing moisture contents had little effect in one of the soils, only reducing effective permeability when a certain threshold was exceeded. In the other soil, structure-forming processes induced by the addition of water led to an increase in both effective and specific permeability with increasing moisture. It is concluded that the spatial spread of the landfill gas in the gas distribution layer is predominantly affected by texture and compaction of the overlying methane oxidation layer. In terms of methane oxidation system design, the choice of material and construction method have more impact on gas permeability than seasonal changes in soil moisture in moderate climates. Furthermore, air filled porosity on its own is not adequate to estimate the effective permeability of loamy sand for methane oxidation layers. Further research should address the estimation of effective gas permeability based upon soil texture, bulk density and soil moisture combined.

Soil compaction impacts soybean root growth in an Oxisol from subtropical Brazil

Soil mechanical impedance, hypoxia and water stress are the main soil physical causes of reduced root growth, but they are rarely included in root growth models. The aim of this work was to study the impact of soil compaction on soybean root growth in an Oxisol using extensive field data as well as a mechanistic model that is sensitive to soil physical conditions. Soybean was cultivated under field conditions in a Rhodic Eutrodox in four treatments. The treatments consisted of three soil compaction levels (no-tillage system, areas trafficked by a tractor, and trafficked by a harvester) and soil chiselling management (performed in an area previously cultivated under no-tillage). Soil structural properties (soil penetration resistance, bulk density, total porosity, macroporosity and microporosity), root system parameters (root length density, root dry mass and root anatomy) and crop production components (grain yield, shoot dry biomass) were determined for the four treatments down to 50 cm soil depth. A mechanistic model, sensitive to mechanical and hydric stresses, was applied to simulate soybean root growth. The model was able to simulate the interaction between the soil physical conditions and soybean root growth. Soil compaction differentiated vertical root distribution according to a stress reduction function impeding root elongation. Consequently, root growth was influenced by soil physical conditions during the cropping season, and simulated root length density showed strong agreement to measured data. Soybean grain yield was reduced due to both compaction (caused by harvester traffic) and excessive loosening (promoted by chiselling) relative to the no-tillage system. Soil physical attributes (i.e., soil bulk density, penetration resistance, macroporosity and microporosity) were only weakly correlated with grain yield and root growth. This may be due to the fact that those soil physical attributes are static properties that do not represent the dynamics of mechanical and hydric stresses during the growing season. Soil compaction changed the anatomy, shape and size of roots. Moreover, cortex cells were deformed in the secondary root growth stage. In the compacted soil, mechanical impedance had a major effect on root growth, while in the loose soil, the matric potential (water stress) represented the major soil physical limitation to root growth. Soil chiselling increased the root length density, but it reduced the grain yields due water stress. The study showed that soybean root growth was successfully modelled with respect to soil physical conditions (mechanical impedance, hypoxia and water stress) for different compaction levels of a Rhodic Eutrudox.

Implications on food production of the changing water cycle in the Vietnamese Mekong Delta

The Mekong Delta is sinking and shrinking due to excessive groundwater withdrawal for growing agricultural and other uses, coupled to reduced flow of water and sediments caused by upstream dams, growing upstream water uses and riverbed mining, reduced replenishment of aquifers, soil compaction, infrastructural extension, and thermo-steric sea level rise. Salinization of soil and aquifers, depletion of aquifers, constraints to fish migration, increased pollution, reduced flow of nutrients, deterioration of the coastal mangrove belt, general degradation of the ecosystem, and loss of emerged land, make the production of food from agriculture and fisheries more difficult, while also limiting the availability of clean fresh water for domestic uses. The subsidence generated by excessive groundwater withdrawal is more than one order of magnitude larger than the thermo-steric sea level rise. Particularly relevant is also the effect of the reduced flow of water, and sediments caused by upstream dams and growing upstream water uses. These drivers are changing the low-lying Mekong Delta, with dramatic impacts on food security expected by as early as 2050, and the possible complete disappearance of the Mekong delta as we know by 2100. While technological developments and enforcement of mitigation and adaptation strategies expected to overcome the most part of the short term issues, with production from aquaculture actually expected to dramatically rise to 2050, but contemporary reduced growth, if not reduction in the agricultural output, these measures may not be enough by 2100. The current rates of development, in both economy and population, are, not sustainable.

INFLUENCE OF SOIL COMPACTION LEVELS ON COWPEA PRODUCTION

Cowpea, a short-cycle legume with large production in the North and Northeast regions, has its productive potential limited by edaphic characteristics and degradation processes of soil physical quality, such as compaction. This process may interfere with plant development and productivity by restricting root system growth, aeration, water and nutrient availability. The objective of this work was to analyze the interference of different levels of compaction in the soil physical characteristics, root growth, development of the aerial part and productivity of cowpea. The experiment was conducted in a greenhouse following a completely randomized design with a control (control) and four levels of soil compaction, with four replications. Each experimental unit was composed of PVC tubes composed of a 0.05-m layer of gravel, cotton fabric and a 0.04-m layer of soil. The different levels of compaction were obtained using a proctor socket and a wooden base. Based on the value of penetration resistance (PR) of 1.00 MPa, soil reached the macroporosity considered as critical theresohold for soil aeration. Results indicate that the higher the PR of the soil, the lower the development of the root system and the aerial part. The productive aspects of cowpea presented better results in plants grown in soils with a level of resistance to penetration close to 0.8 MPa.

Graph-analytical optimization of the transverse vertical cross-section of a contact zone between soil and an elastic wheeled mover

The intensification of agricultural production under modern conditions implies the use of super-powerful mobile technical means, which leads to an increase in the levels of technogenic impact on soil and, consequently, deteriorates its fertility. Therefore, the most acute issue related to current agricultural production is aimed at resolving the task on improving the operational indicators of wheeled running systems of mobile technical means. This necessitates an analytical study into the processes of soil deformation under the elastic motors of mobile wheeled agricultural machinery. We have proposed a procedure of the graph-analytical step-by-step modeling of the process of soil deformation under pneumatic tires of mobile agricultural equipment taking into consideration the changing shape of an elastic tire sheath. Using appropriate graphic models makes it possible to explore, in stages, the process of soil compaction inside the profile of the track it formed. It has been found that in the contact area «deformed soil – the surface of an elastic wheeled mover of the mobile vehicle» the highest level of compaction is observed in the soil layer, which is directly in contact with the elastic mover. The depth of the recompacted soil layer on the «track bottom» depends on the dimensions of a tire of the wheeled mover and does not exceed the value of 0.075 width of the tire. The highest soil compaction level is observed in the area directly adjacent to the gauge. It has been established that the most dangerous design of a pneumatic tire, in terms of soil overcompaction in the track, is the shape of an elastic tire sheath that is described by the curve of the Cassini oval with four points of inflection. We have outlined distinctive features of recommendations to determine the operational values of tire working pressure depending on specific physical-mechanical and agro-technological properties of soil and the character of performed technological operations

Predicting the dry bulk density of soils across Denmark: Comparison of single-parameter, multi-parameter, and vis–NIR based models

Dry bulk density (BD) is a key soil physical property, characterizing the level of soil compaction and controlling flow and transport of fluids and solutes. In this study, predictive BD models were developed from 2462 BD measurements of mineral soils representing both top- and subsoil horizons across Denmark. Three types of BD models were compared: (i) single-parameter based on soil organic carbon (SOC), (ii) multi-parameters based on SOC, soil texture and depth, and using multiple linear regression (MLR), and (iii) visible–near infrared spectroscopy (vis–NIRS) based, using the spectral information and partial least squares regression (PLSR). Also, three machine learning techniques (random forest (RF), regression rules (RR), and artificial neural networks (ANN)) were applied for multi-parameter and vis–NIRS based models to potentially improve predictions. BD models were calibrated on 70% of dataset and validated on the remaining 30%. Single-parameter models with SOC had the lowest predictive potential and were not able to predict BD above 1.62 g cm−3. Machine learning using RF, RR and ANN on soil properties resulted in significantly higher prediction accuracies (RMSE ≤ 0.11 g cm−3 and R2 ≥ 0.60) than MLR (RMSE = 0.12 g cm−3 and R2 = 0.41) and SOC-based models. The relative importance of variables was obtained from the multi-parameter models with SOC and clay as the most important variables. The prediction accuracies MLR and vis–NIRS did not differ but were better than SOC-based models, suggesting that vis–NIRS could be a cost- and time-efficient alternative to pedotransfer functions that generally require determination of one or more soil properties for developing the calibration models. Decomposing the spectral data into principal components and using selected components as inputs for RF, RR and ANN improved the model performances only for RF models. Instead and in perspective, combining techniques by supplementing spectral data with readily available soil information and using machine learning techniques may further improve BD predictions.

Temporal and spatial variation of infiltration in urban green infrastructure

AbstractInfiltration is the primary mechanism in green stormwater infrastructure (GSI) systems to reduce the runoff volume from urbanized areas. Soil hydraulic conductivity is most important in influencing GSI infiltration rates. Saturated hydraulic conductivity (Ksat) is a critical parameter for GSI design and post‐construction performance. However, Ksat measurement in the field is problematic due to temporal and spatial variability and measurement errors. This review paper focuses on a comparison of methods for in‐situ Ksat measurement and the causes of temporal and spatial variations of Ksat within GSI systems. Automated infiltration testing methods, such as the Modified Philip–Dunne (MPD) and SATURO infiltrometers, show promise for efficient Ksat measurements. Soil Ksat values can change over time and substantially vary throughout a GSI, which can be attributed to multiple factors, including but not limited to temperature changes, soil composition and properties, soil compaction level, plant root morphology and distribution, biological and macrofauna activities in the soil, inflow sediment characteristics, quality of infiltrating water, and measurement errors. There is evidence that infiltration rates in vegetated urban GSI systems are sustained given an appropriate GSI design, reasonable concentration of suspended sediments in the inflow runoff, and routine maintenance procedures. These observations indicate that clogging can be counteracted by processes that tend to increase the soil hydraulic conductivity (e.g., plant root and biological activities). This self‐sustainability underlines that infiltration‐based GSI systems are a reliable long‐term stormwater management solution. Recommendations on how to incorporate the temporal changes of Ksat in GSI design and on obtaining a spatially‐representative Ksat for the GSI design are presented.

Mechanical and Hydric Stress Effects on Maize Root System Development at Different Soil Compaction Levels.

Soil mechanical resistance, aeration, and water availability directly affect plant root growth. The objective of this work was to identify the contribution of mechanical and hydric stresses on maize root elongation, by modeling root growth while taking the dynamics of these stresses in an Oxisol into consideration. The maize crop was cultivated under four compaction levels (soil chiseling, no-tillage system, areas trafficked by a tractor, and trafficked by a harvester), and we present a new model, which allows to distinguish between mechanical and hydric stresses. Root length density profiles, soil bulk density, and soil water retention curves were determined for four compaction levels up to 50 cm in depth. Furthermore, grain yield and shoot biomass of maize were quantified. The new model described the mechanical and hydric stresses during maize growth with field data for the first time in maize crop. Simulations of root length density in 1D and 2D showed adequate agreement with the values measured under field conditions. Simulation makes it possible to identify the interaction between the soil physical conditions and maize root growth. Compared to the no-tillage system, grain yield was reduced due to compaction caused by harvester traffic and by soil chiseling. The root growth was reduced by the occurrence of mechanical and hydric stresses during the crop cycle, the principal stresses were mechanical in origin for areas with agricultural traffic, and water based in areas with soil chiseling. Including mechanical and hydric stresses in root growth models can help to predict future scenarios, and coupling soil biophysical models with weather, soil, and crop responses will help to improve agricultural management.

Soil physical and hydraulic properties in the Donato stream basin, RS, Brazil. Part 1: Spatial variability

ABSTRACT The processes of water flow and water storage in the soil are directly associated with its hydraulic properties, which may vary significantly in space. Therefore, this study aimed to perform a spatial analysis of saturated hydraulic conductivity and the parameters of the soil water retention curve in the Donato basin, located in the municipality of Pejuçara, in the northwest region of the state of Rio Grande do Sul, Brazil, with geographic coordinates between 28º 25’ 34” S and 53º 40’ 30” W, and 28º 24’ 50” S and 53º 41’ 30” W, 590 m of altitude. Undisturbed soil samples (total of 55) were collected from August to November of 2012. The results have demonstrated larger variability for hydraulic conductivity and for the parameter α of the retention curve, and allowed identifying that the high spatial heterogeneity of the studied variables could be associated with factors such as climate, land use and land cover, sampling errors, sampling grid density and also the level of soil compaction.

Soil compaction enhances the impact of microwave heating on seedling emergence

An innovative microwave-based process to control invasive species in the field is currently under development. We investigated the effect of soil compaction levels under three microwave treatment pairings of power and duration (2kW4 min, 2kW8min and 4kW4 min), on seedling emergence of a diverse seed bank and three major invasive species in Europe (bohemian knotweed, giant goldenrod and jimsonweed). When soil was compacted, the number of seedling emergences of dicotyledons was significantly reduced by the 2kW4 min treatment. Furthermore, while some dicotyledon and giant goldenrod’s seedling emergences were observed respectively in plain soil in the 4kW4 min and 2kW4 min treatments, no seedling was recorded in compacted soil for the same treatments. Our results suggest that compacting soil increases the efficiency of microwave heating on seeds. Soil compaction level should therefore be considered in the design of the final microwave-based process.