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Soil pore structure and soil water content are critical regulators of microbial activity and associated carbon dioxide (CO2) emissions. This study evaluated the impacts of soil bulk density and matric potential on carbon dioxide (CO2) emissions through modifications of total porosity, air-filled porosity, water retention, and gas diffusivity. Soil samples were manipulated into four bulk densities (1.0, 1.1, 1.2, and 1.3 Mg m−3) and ten matric potential levels (−1, −2, −3, −4, −5, −6, −7, −8, −9, and −10 kPa) in controlled soil cores. The results showed that lower bulk densities enhanced while higher densities suppressed CO2 emissions. Similarly, wetter matric potentials decreased fluxes, but emission increased with drying. Correlation and regression analyses revealed that total porosity (r = 0.28), and gravimetric water content (r = 0.29) were strongly positively related to CO2 emissions. In contrast, soil bulk density (r= −0.22) and matric potential (r= −0.30) were negatively correlated with emissions. The results highlight that compaction and excessive water content restrict microbial respiration and gas diffusion, reducing CO2 emissions. Proper management of soil structure and water content is therefore essential to support soil ecological functions and associated ecosystem services. [ABSTRACT FROM AUTHOR]

Soil moisture content and matric potential are two important parameters for determining soil water characteristic curve (SWCC), which has significant differences for different types of soils. The common method to determine SWCC under field condition is using two separated sensors to measure moisture content and matric potential of the tested soils. However, measurement error may occur due to soil spatial heterogeneity around two sensors. In this study, a novel composite sensor was designed to simultaneously measure soil moisture content, matric potential, and temperature. The composite sensor consists of a 32-bit MCU main control chip, relay switching module, dielectric measurement module for determining soil moisture content and matric potential, and temperature measurement module. The main MCU control chip measures soil moisture content, matric potential, and temperature through controlling the relay switching, and performs temperature correction as well. The performances of the composite sensor were tested for soil moisture content and soil matric potential measurements including monotonicity, calibration, volume of sensitivity, response time, etc. To test the monotonicity of the dielectric mode, the length of high frequency transmission line was gradually increased and the sensor output was recorded when the probes of soil moisture content and soil water potential were moistened from dry to saturation. The three modes, soil moisture content, soil matric potential and temperature were calibrated respectively using forest soil, farmland loam and sandy soil. To determine the volume of sensitivity of the soil moisture content mode, the probe of soil moisture content was installed in a soil sample. The soil sample was gradually removed layer by layer and meanwhile the output of the soil moisture content was recorded. When the output started to decrease, the radius of volume of sensitivity was determined by measuring the thickness of residual soil layer from surface to the probe. To determine the response time of soil moisture content and soil matric potential modes, the composite sensor probe was firstly dried and then put into a saturated soil sample. Meanwhile, the output of the soil moisture content and soil matric potential was recorded as time elapse. When the recorded output of each mode did not remarkedly change, the elapsed time was the response time. Experiments for sensor observation were conducted using forest soil, farmland loam and sandy soil under laboratory condition at 25 °C. The experimental results were compared with those measured using commercial instruments. The results showed that the composite sensor had a good monotonicity when measuring soil moisture content and matric potential in the range from dry to near saturation. After calibration, the composite sensor can determine soil moisture content, matric potential and temperature with high accuracies, achieving the determination coefficients larger than 0.98. The measurement ranges of volumetric soil water content and soil matric potential were 0%-40% and -1 500--15 kPa, respectively, which is feasible for most soil textures. The response time of the soil moisture content and soil matric potential was 450 ms and 150 s, respectively. The temperature coefficient of the circuit board of the composite sensor was yielded to correct the temperature induced output variation. The SWCCs of forest soil, farmland loam and sandy soil were determined using both the commercial instruments and the composite sensor during wetting and drying processes. The hysteresis between soil drying and wetting processes was also observed as expected. The Pearson correlation coefficients between the SWCCs measured by the two methods were larger than 0.96 during wetting and drying processes, i.e., 0.962 and 0.983 for the forest soil, 0.993 and 0.995 for the farmland loam, and 0.979 and 0.998 for the sandy soil. The composite sensor developed in this study can accurately determine soil water characteristic curves of different types of soils. [ABSTRACT FROM AUTHOR]

Carbon (C) substrates are critical for regulating denitrification, a process that results in nitrous oxide (N2O) and dinitrogen (N2) emissions from soil. However, the impacts of C substrates on concomitant soil emissions of carbon dioxide (CO2) and N2O under varying soil types and soil water contents are not well studied. Three repacked Pallic grassland soils, varying in texture and phosphorus (P) status, containing NO3−‐15N were held at three levels of matric potential (ψ, −3, −5 and −7 kPa), while receiving daily substrate additions (acetate, glucose and water control) for 14 days. The CO2 and N2O emissions were measured daily. Additionally, the N2O:(N2 + N2O) ratios were determined using 15N on days 3 and 14. Results showed that N2O emissions increased exponentially as soil gas diffusivity declined, and N2O peak emissions were higher with glucose than with acetate addition, with a range (± standard deviation) of 0.1 ± 0.0 to 42.7 ± 2.1 mg N m−2 h−1. The highest cumulative N2O emission (2.5 ± 0.2 g N m−2) was measured following glucose addition with a soil ψ of −3 kPa. In comparison with added glucose, acetate resulted in a twofold increase in N2 emissions in soils with relatively low gas diffusivities. The N2O:(N2O + N2) emissions ratios varied with substrate (glucose, 0.91; acetate, 0.81) on day 3, and had declined by day 14 under substrate addition (≤0.10). Cumulative CO2 emissions were enhanced with increasing soil gas diffusivity and were higher for soils amended with glucose (ranging from 22.5 ± 1.3 to 36.6 ± 1.8, g C m−2) than for those amended with acetate. Collectively, the results demonstrate that the increase of N2O, N2 and CO2 emissions and changes in the N2O:(N2 + N2O) ratio vary over time in response to C substrate type and soil gas diffusivity. Highlights: Co‐regulation of CO2 and N2O emissions was assessed for varying soil types and C substrates.Soil diffusivity explained concurrently cumulative N2O and CO2 emissions.Acetate enhanced N2O reduction to N2 in three grassland soils more than glucose.C substrate effects on soil N2O, N2 and CO2 emissions were soil type specific. [ABSTRACT FROM AUTHOR]

Accurate determination of the water retention curve (WRC) of a soil is essential for the understanding and modelling of the subsurface hydrological, ecological, and biogeochemical processes. Volcanic ash soils with andic properties (Andosols) are recognized as important providers of ecological and hydrological services in mountainous regions worldwide due to their large fraction of small size particles (clay, silt, and organic matter) that gives them an outstanding water holding capacity. Previous comparative analyses of in situ (field) and standard laboratory methods for the determination of the WRC of Andosols showed contrasting results. Based on an extensive analysis of laboratory, experimental, and field measured WRCs of Andosols in combination with data extracted from the published literature we show that standard laboratory methods using small soil sample volumes (≤300 cm3) mimic the WRC of these soils only partially. The results obtained by the latter resemble only a small portion of the wet range of the Andosols' WRC (from saturation up to −5 kPa, or pF 1.7), but overestimate substantially their water content for higher matric potentials. This discrepancy occurs irrespective of site‐specific land use and cover, soil properties, and applied method. The disagreement limits our capacity to infer correctly subsurface hydrological behaviour, as illustrated through the analysis of long‐term soil moisture and matric potential data from an experimental site in the tropical Andes. These findings imply that results reported in past research should be used with caution and that future research should focus on determining laboratory methods that allow obtaining a correct characterization of the WRC of Andosols. For the latter, a set of recommendations and future directions to solve the identified methodological issues is proposed. [ABSTRACT FROM AUTHOR]

Root‐induced changes of soil hydraulic properties, that is soil water retention curve (SWRC) and unsaturated hydraulic conductivity (K(ψ)), depend on plant species and root density. This study aimed to investigate the effects of wheat roots and okra roots on both SWRC and K(ψ) of soil within an extended range of matric potential (−300 ~ 0 kPa) and to investigate the effects of root density of wheat (i.e. grass species) and okra (i.e. shrub species) on SWRC and K(ψ) of a loamy soil. The SWRC and K(ψ) of soil planted with wheat and okra were measured by the simplified evaporation method. Soil matric potential was measured directly by high‐capacity tensiometers. Different root densities were obtained by establishing different seeding densities in the soil. Meanwhile, root characteristics in planted soil were obtained using image analysis. The results showed that wheat‐ and okra‐planted soil had significantly larger volumetric water content (VWC) within the range of matric potential from −90 to 0 kPa than that of unplanted soil. Within the range of matric potential from around −300 to −90 kPa, the effects of wheat and okra roots on SWRC were not significant. The effects of wheat and okra roots on K(ψ) were not significant within the range of matric potential from around −300 to −10 kPa. Wheat‐planted soil with a root length density (RLD) of 10.04 cm cm−3 had larger values of VWC (ψ = 0, −33, −50 kPa) than those of wheat‐planted soil with RLD of 2.69 cm cm−3. The difference in hydraulic properties between okra‐planted soil and the two RLDs, 0.89 and 2.96 cm cm−3, was not significant. Okra roots were more effective in increasing saturated water content (θs) and field capacity (θfc) than wheat roots. This might be because okra roots are relatively coarser than wheat roots. Highlights: Effect of root density of wheat and okra on SWRC and K(ψ) was investigated.The K(ψ) of soil planted with wheat and okra was measured at matric potentials less than −100 kPa.Okra roots were more effective in increasing θs and θfc than wheat roots.Effect of wheat and okra roots on K(ψ) was not significant at matric potentials from −300 to −10 kPa. [ABSTRACT FROM AUTHOR]

Greenhouse growers must use water more efficiently. One way to achieve this goal is to monitor substrate moisture content to decrease leaching. A systems approach to irrigation management would include knowledge of substrate matric potentials and airfilled pore space (AS) in addition to substrate moisture content. To study the relationship between substrate moisture and plant growth, annual vinca (Catharanthus roseus L.) was subject to a 2 × 2 factorial combination of two irrigation treatments and two substrates with differing moisture characteristic curves (MCCs). A gravimetric on-demand irrigation system was used to return substrate moisture content to matric potentials of L2 or L10 kPa at each irrigation via injected drippers inserted into each container. Moisture characteristic curves were used to determine gravimetric water content (GWC), volumetric water content (VWC), and AS at target substrate matric potential values for a potting mix consisting of sphagnum moss and perlite and a potting mix consisting of sphagnum moss, pine bark, perlite, and vermiculite. At each irrigation event, irrigation automatically shut off when the substrate-specific weight of the potted plants associated with the target matric potential was reached. Irrigation was triggered when the associated weight for a given treatment dropped 10% from the targetweight.VWC and AS differed between substrates at similar matric potential values. Irrigating substrates toL2 kPa increased the irrigation volume applied, evapotranspiration, plant size, leaf area, shoot and root dry weight, and flower number per plant relative to irrigating to L10 kPa. Fafard 3B had less AS than Sunshine LB2 at target matric potential values. Plants grown in Fafard 3B had greater leaf area, shoot dry weight, and root dry weight. Leachate fraction ranged from0.05 to 0.08 and was similar across all treatment combinations. Using data from an MCC in conjunction with gravimetric monitoring of the container-substrate-plant system allowedAS to be determined in real time based on the currentweight of the substrate. Closely managing substrate matric potential and AS in addition to substrate water content can reduce irrigation and leachate volume while maintaining plant quality and reducing the environmental impacts of greenhouse crop production. [ABSTRACT FROM AUTHOR]

Compaction of the subsoil is an almost irreversible damage to the soil resource. Modern machinery exerts high mechanical stresses to the subsoil, and a range of studies report significant effects on soil functions. There is an urgent need for quantitative knowledge of soil strength in order to evaluate sustainability of current field traffic. The aim of this study was to identify the most important drivers of soil precompression stress, σ pc , and to develop pedotransfer functions for prediction of σ pc . We revisited previously published data on σ pc for a silty clay loam soil at a range of soil matric potentials. σ pc was estimated from the original stress-strain curves by a novel, numerical method for estimating the stress at maximum curvature, assumingly partitioning the curve into elastic and plastic sections. Multiple regression was used to identify the drivers best describing the variation in σ pc data. For the plough layer, σ pc increased with bulk density (BD), which explained 77% of the variation. For the subsoil layer just beneath the ploughing depth, the model best describing σ pc data included the drivers BD and pF, with pF defined as the log to the negative matric potential. The model was strongly significant with R 2  = 0.90. The same trend was found for three subsoil layers from 0.35–0.95 m depth, but the model accounted for only 16% of the variation in σ pc . A model involving samples from all soil layers and including BD, pF and soil clay content accounted for 38% of the variation. This model predicted σ pc to be constant at pF ~2 across soil clay contents for a given soil BD. For pF < 2, σ pc was predicted to be higher for sandy soils than for soils rich in clay. In contrast, σ pc increased with clay content for dryer conditions (pF > 2). Model predictions correlated well with measured data in two independent data sets from the literature. However, the predictions were approximately double those of one of the data sets. This may relate to the longer stress application used in laboratory compression tests for these data compared to the other calibration data set and to the procedure used in this study. We encourage further studies of the effect of stress application procedures in compression tests. The prediction equations established in this investigation have to be verified based on measurements of σ pc for a range of soil types, soil horizons and soil moisture conditions. [ABSTRACT FROM AUTHOR]

The moisture migration from unfrozen region to freezing front is the main factor that causes frost heave during soil freezing, it is generally believed that the energy difference between two positions in soil drives the liquid water migrate to frozen region and leads water redistribution when soil freezing. However, limited by technical means, the matric potential measurement in frozen soil is still an open problem. In this study, the relationship between matric potential, soil water content and frost heave was investigated by using the newly introduced pF meter matric potential sensor and the 5TM water content sensor that could liquid water content and matric potential in one-dimension saturated soil freezing. The results showed the temperature field change caused the change of the liquid pore water phase into the ice, led the destruction of the initial energy equilibrium in different position of the soil sample, and then caused the liquid water migrated from high potential area to a relatively low potential area. During the freezing experiment, we found that the 16-cm depth of the soil sample began to freeze when the experiment had been conducted for 4 hours, and the freezing was from top to deep soil. When the experiment had been conducted for 4 hours, the freezing arrived at 10-cm depth of the soil sample, and the frozen depth kept unchanged. After the experiment，the water content in 10-14 cm of the soil sample could reach as high as about 55%, and at the 6 cm soil sample height, the liquid water content in the unfrozen region reduced to 25.8%, which supported the moisture movement upwards to the upper part of the soil sample. The frost heave process of saturated soil could be divided into 3 stages: 1) In 0-4 h, the frost heave amount was smaller; 2) In 4-60 h, the frost heave amount increased rapidly and the segregation ice began to grow, the moisture migration process were active; 3) The growth of segregation ice tended to stabilize and the liquid water stopped migrating to the freezing front; Similarly, the soil matric potential would have response to the change of the liquid water content and the moisture migration during the freezing process. In the early stage of freezing, the liquid water content in frozen region decreased, and the soil matric potential below the freezing front lasted for 0. When the freezing had been conducted for 20 h, the soil matric potential near the upper cooling plate reached about -1 000 kPa, and the soil matric potential in 14, 12, 10 cm of the soil samples was –55, –47.5, –30.2 kPa, respectively. When the freezing rate slowed down and the segregation ice began to grow, the liquid water tended to migrate upward, meanwhile, the soil matric potential below the freezing front decreased continuously, which were due to the liquid water migration from the unfrozen region to the frozen region. Results supported the moisture migration required 2 conditions: the matric potential difference between 2 positions in soil and the sufficient time. After the experiment, the distribution of the water content in the soil was consistent with that of the segregation ice lens. In the frozen region, the liquid water content was approximately linear with the temperature gradient, and in unfrozen region, the liquid water content was related to the amount of migrated moisture, but not related to the temperature gradient. The results provide an experimental basis for understanding frost heave mechanism and the establishment of frost heave model. [ABSTRACT FROM AUTHOR]

In greenhouses, reducing water consumption by increasing water efficiency is of high interest. To reach this goal, predictive models of soil-plant-atmosphere water transfer could be helpful. However, such models have been mainly developed for open field conditions, and very few models exist for greenhouse plants grown in pots. Moreover, most of these models were implemented under well-watered conditions, but very few are available under water restriction. The aim of this study is to develop an integrated soil-plant-atmosphere water balance model applied to potted plants grown in greenhouses, to predict plant transpiration under different restrictive irrigation regimes. Implementing such a model requires an accurate estimation of stomatal resistance R s under water restriction conditions. R s is then used in the Penman-Monteith model to evaluate transpiration. To establish the model parameters, an experiment was conducted for sixteen weeks inside a greenhouse with ornamental plants (New Guinea Impatiens) grown in containers on shelves. Well-watered and water restriction conditions were applied. The peat matric potential, radiation, temperature and humidity were continuously recorded, while R s was measured and transpiration was assessed every half-hour from 8:00 am to 8:00 pm 10, 11, 12, 14, and 16 weeks after planting. The resulting model was first validated against experimental measurements during the twelfth week of the experiment. It displayed good correlations for both the instantaneous data and integrated total transpiration. Different scenarios of irrigation reduction (frequency x volume) were tested and the results indicated real potential for water use reduction. Indeed, by reducing water application by 50% and by applying one irrigation per day, transpiration was not affected. [ABSTRACT FROM AUTHOR]

Monitoring soil water status is a well-known method to efficiently control irrigation in order to optimally meet plant water requirements and at the same time avoid unproductive water losses through deep percolation. A common approach is to keep soil water status within a certain range that is defined via soil-specific unsaturated hydraulic parameters. In this study, water content and matric potential were monitored in a soil profile in a vineyard. The soil hydraulic properties required for irrigation control were determined by water retention analyses using a pressure plate apparatus, and estimated by means of pedotransfer functions. While the soil matric potential sensors delivered calibrated absolute values, their range was limited and soil water dynamics were not always reflected properly. The soil water content probe, on the other hand, properly illustrated soil water dynamics, but the readings were possibly inaccurate as no onsite calibration was executed. Furthermore, the determined unsaturated hydraulic parameters differed considerably depending on the applied method. Alternatively, a modified approach was applied. It was based on measurements of a sensor pair in a representative depth and should combine the advantages of both sensors types. The respective thresholds for irrigation management were determined based on sensor data using in-situ soil water retention functions. The main advantages were that neither field calibration of soil water content sensors nor laborious soil analyses were required. Furthermore, data interpretation was more plausible compared to the standard approach. Due to the reduced sensor setup and the omitted soil sampling and analyses, the modified approach represented a practical and economical alternative as basis for irrigation control. [ABSTRACT FROM AUTHOR]

Yield components are useful for characterizing the impact of crop management parameters on cranberry yield and are known to be influenced by irrigation management. This study was conducted to evaluate the potential contribution of cranberry yield components to maximizing yield, and the influence of the soil water tension threshold used to initiate irrigation (SWT I ) on those components. During the 2011 and 2012 growing seasons, tensiometers were installed at three production sites in Quebec to test SWT I values ranging from 5.5 to 10.0 kPa. Sites were cropped to cranberries to evaluate the impact of these irrigation treatments on yield components. The four most important cranberry yield components related to final yields were, in order of importance, the number of marketable berries per quadrat ( B M /Q ), the number of uprights per quadrat ( U/Q ), the number of marketable berries per upright ( B M /U ), and the marketable fruit set ( B M /F ). Significant reductions in B M /Q , B M /U and B M /F were observed when SWT I varied from 8.5 to 10.0 kPa while a reduction in U/Q was associated with a SWT I of 5.5 kPa. A SWT I ranging from 7.0 to 8.0 kPa significantly improved the principal yield components. [ABSTRACT FROM AUTHOR]

The study aims to propose a methodology for estimating the water retention curve for soils of the State of Rio Grande do Sul, by using artificial neural networks. For the development of the research it was assembled a database with information available in the literature, texture and structure of soils of Rio Grande do Sul. The modeling was developed using the software Matlab, where the networks were trained with different architectures, varying the numbers of neurons in the input layer and the hidden layer. The efficiency of the network was analyzed graphically by the ratio 1:1 between the estimated versus the observed data by means of statistical indicators. It was observed from the results that the architecture with best predictive performance was the 4-24-7, with index classification of "great" performance. Thus it can be inferred that the use of neural networks to estimate the water retention curve of the soil is a tool with high predictive ability which will bring great contribution to the agricultural sector. [ABSTRACT FROM AUTHOR]

The availability of soil water, and the ability of plants to extract it, are important variables in plant research. The matric potential has been a useful way to describe water status in a soil–plant system. In soil it is the potential that is derived from the surface tension of water menisci between soil particles. The magnitude of matric potential depends on the soil water content, the size of the soil pores, the surface properties of the soil particles, and the surface tension of the soil water. Of all the measures of soil water, matric potential is perhaps the most useful for plant scientists. In this review, the relationship between matric potential and soil water content is explored. It is shown that for any given soil type, this relationship is not unique and therefore both soil water content and matric potential need to be measured for the soil water status to be fully described. However, in comparison with water content, approaches for measuring matric potential have received less attention until recently. In this review, a critique of current methods to measure matric potential is presented, together with their limitations as well as underexploited opportunities. The relative merits of both direct and indirect methods to measure matric potential are discussed. The different approaches needed in wet and dry soil are outlined. In the final part of the paper, the emerging technologies are discussed in so far as our current imagination allows. The review draws upon current developments in the field of civil engineering where the measurement of matric potential is also important. The approaches made by civil engineers have been more imaginative than those of plant and soil scientists. [ABSTRACT FROM PUBLISHER]

Abstract: In saline soils, microbial activity may be reduced by low matric (low water content) and low osmotic potential (presence of salts) but little is known about the impact of the relative contribution of matric and osmotic potential to water potential (sum of matric and osmotic potential) on microbial activity and biomass. A laboratory incubation experiment was conducted using a non-saline sandy loam; different osmotic potentials (−0.30 to −3.24 MPa) were achieved by adding different amounts of NaCl. After pre-incubation for 14 days, subsamples of these treatments were dried to achieve different contributions of matric potential (8–73%) and osmotic potential (27–92%) to water potential which ranged between −0.57 and −4.57 MPa. All treatments were amended with 20 g kg−1 pea residues to increase nutrient supply; carbon dioxide (CO2) emission was measured over 14 days. Microbial biomass C and K2SO4-extractable C were measured at the end of the experiment. Cumulative CO2–C (mg g−1 soil) was significantly (p < 0.05) lower at water potential −4 MPa than at water potential −1.5 MPa. Above water potential −4 MPa, cumulative CO2–C significantly decreased with increasing percentage contribution of osmotic potential to water potential, particularly if the contribution of osmotic potential was >50%. In contrast, K2SO4-extractable C and microbial biomass C were little affected by water potential above −4 MPa. Only at water potential −4 MPa, cumulative CO2–C and microbial biomass C were affected by matric potential and its contribution to water potential; that is when the soils are very dry. Our results show that cumulative CO2–C was more sensitive to decreasing water potential or the contributions of osmotic and matric potential than microbial biomass C. This suggests that not only water potential but also the contribution of osmotic and matric potential should be taken into account to understand microbial activity and growth in saline soils. [Copyright &y& Elsevier]

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Abstract: Compaction of tilled layers under the single effect of rainfall or irrigation was called slumping. Slumping affects strongly root development and plant biomass production. It has been observed in different soil types, but sandy soils appear particularly prone to this physical degradation. Our objectives in this study were (i) to measure in the field the changes in soil structure and water status simultaneously, (ii) to study the effects of rainfall and management practices on slumping, and (iii) to propose a conceptual model for sandy soil slumping. An experimental site was selected in Northeast Thailand and we studied the effect of tillage depth and initial water content on slumping dynamic. Plots (9m×15m each) were tilled at (i) two depths (20 and 40cm, called S and D respectively) in dry conditions, (ii) at 20cm depth in dry or wet conditions (called Y and W respectively). These plots were submitted to natural rainfall for 20 or 61 days to get different total rainfall amounts (114 and 212mm respectively). In addition, smaller plots (0.24m2 each) were used for experimental flooding irrigation (similar to measured rainfalls, i.e. 100 and 200mm). Soil bulk density, soil surface elevation, soil water content and matric potential were measured. A decrease in soil elevation was observed in all treatments. In the absence of erosion it was interpreted as a loss of porosity which resulted from slumping. Bulk density increased in all layers of the tilled profile (from 1.38 to 1.57gcm−3). In the surface layer (0–5cm) this increase was systematically higher compared to deeper layer. No significant difference in final bulk density was found between the S and W treatments, and between the Y and W treatments. Bulk density increased more rapidly in the Y and W treatments than in the S and D treatments, even though the cumulative rainfall was lower. After the flooding experiments, bulk density was higher than after natural rainfall despite similar amounts of water added to the soil. [Copyright &y& Elsevier]

Pedotransfer functions (PTFs), predicting the soil water retention curve (SWRC) from basic soil physical properties, need to be validated on arable soils in Norway. In this study we compared the performance of PTFs developed by Riley (1996), Rawls and Brakensiek (1989), Vereecken et al. (1989), Wosten et al. (1999) and Schaap et al. (2001). We compared SWRCs calculated using textural composition, organic matter content (SOM) and bulk density as input to these PTFs to pairs of measured water content and matric potential. The measured SWRCs and PTF input data were from 540 soil horizons on agricultural land in Norway. We used various statistical indicators to evaluate the PTFs, including an integrated index by Donatelli et al. (2004). The Riley PTFs showed good overall performance. The soil specific version of Riley is preferred over the layer specific, as the latter may introduce a negative change in water content with increasing matric potential (h). Among the parameter PTFs, Wosten's continuous PTF showed the overall best performance, closely followed by Rawls&B and Vereecken. The ANN-based continuous PTF of Schaap showed poorer performance than its regression based counterparts. Systematic errors related to both particle size and SOM caused the class PTFs to perform poorly; these PTFs do not use SOM as input, and are therefore inappropriate for soils in Norway, being highly variable in SOM. The PTF performance showed little difference between soil groups. Water contents in the dry range of the SWRC were generally better predicted than water contents in the wet range. Pedotransfer functions that included both SOM and measured bulk density as input, i.e. Wosten, Vereecken and Rawls&B, performed best in the wet range. [ABSTRACT FROM AUTHOR]

Abstract: Microbial communities exist and are active in a complex 3-D physical framework which can cause a variety of micro-environments to develop that are more or less suitable for microbial growth, activity and survival. If there is a significant microbial biogeography at the pore scale in soil, then the relationship between microbial diversity and ecosystem function is likely to be affected by micro-environmental variations at the pore scale. In this laboratory study we show that there is a significant pore-scale microbial biogeography by labelling microbial communities in different pore size classes of undisturbed soil cores with 13C-labelled fructose (a soluble, labile substrate). This was achieved by adding the substrate solution to the samples at different matric potentials (−100 kPa, −3.15 kPa and −1 kPa; placing the substrate in pores with maximum diameter of 0.97, 9.7 and 97 μm, respectively) and incubating the samples for two weeks. The mineralisation of soil organic carbon and fructose was measured as CO2 and 13C–CO2, respectively, in the jar headspace throughout the incubation. At the end of incubation we analysed the total microbial community structure using PLFA. The structure of microbial communities in different pore size classes was measured by PLFA stable isotope probing. Total PLFA profiles suggested that there was little effect of the incubation conditions on microbial community structure. However, labelled PLFA profiles showed that microbial community structure differed significantly among pore size classes, the differences being due primarily to variations in the abundance of mono-unsaturated lipids (Gram-biomarkers) and of the fungal biomarker (C18:2(9,12)). This is the first evidence for a significant microbial biogeography at the pore scale in undisturbed soil cores. [ABSTRACT FROM AUTHOR]

Abstract: The soil solution influences the soil stability in different ways: via water content as due to drainage menisci contract particles, and via the chemical composition including different ions in different amounts. While the first aspect was at least examined on the mesoscale, the second aspect remains widely unexplored when it comes to the influence of single ions on the microscale of soils. Previously published papers indicate a higher soil stability under the influence of potassium that cannot be explained only by its positive effect on plant growth and the enhanced shrinkage and swelling processes caused thereby. Parameters derived from rheological measurements can be used to examine the influence of soil solution in different compositions and matric potentials on soil microstructure. The rheological parameters were obtained by means of an amplitude sweep test where soil samples are subjected to oscillating forces with increasing deflection. From the sample''s resistance towards this deformation storage modulus G′ and loss modulus G″ are derived, representing elastic and plastic deformation, respectively. Characteristic stability values of the moduli curves are the end of the linear viscoelastic (LVE) range indicating irreversible deformation and the yield point indicating flow. Additionally, the maximum shear stress during the test was used to characterize the maximum resistance of the sample against deformation. In our investigations we found higher soil stability on the microscale with higher ion concentration and more negative matric potentials. With potassium chloride the LVE range extended and the yield point shifted to higher deformation and stress values. Consequently, the influence of potassium chloride resulted in a higher stability of the microstructure based on the storage and loss modulus as well as the shear stress. With increasing ion concentrations in the soil solution a further increase in microstructural strength was detected. Regarding the influence of matric potential both the shear stress at the end of the LVE range and the maximum shear stress increased with more negative matric potentials, because a higher drainage intensity resulted in higher effective stresses caused by stabilising menisci, cemented bonds due to precipitation of salts and increased number of contact areas between particles. Additionally, the yield point attained higher values for storage and loss modulus, respectively. [Copyright &y& Elsevier]

Anticipated increases in precipitation intensity due to climate change may affect hydrological controls on soil N2O fluxes, resulting in a feedback between climate change and soil greenhouse gas emissions. We evaluated soil hydrologic controls on N2O emissions during experimental water table fluctuations in large, intact soil columns amended with 100 kg ha−1 KNO3-N. Soil columns were collected from three landscape positions that vary in hydrological and biogeochemical properties ( N= 12 columns). We flooded columns from bottom to surface to simulate water table fluctuations that are typical for this site, and expected to increase given future climate change scenarios. After the soil was saturated to the surface, we allowed the columns to drain freely while monitoring volumetric soil water content, matric potential and N2O emissions over 96 h. Across all landscape positions and replicate soil columns, there was a positive linear relationship between total soil N and the log of cumulative N2O emissions ( r2= 0.47; P= 0.013). Within individual soil columns, N2O flux was a Gaussian function of water-filled pore space (WFPS) during drainage (mean r2= 0.90). However, instantaneous maximum N2O flux rates did not occur at a consistent WFPS, ranging from 63% to 98% WFPS across landscape positions and replicate soil columns. In contrast, instantaneous maximum N2O flux rates occurred within a narrow range (−1.88 to −4.48 kPa) of soil matric potential that approximated field capacity. The relatively consistent relationship between maximum N2O flux rates and matric potential indicates that water filled pore size is an important factor affecting soil N2O fluxes. These data demonstrate that matric potential is the strongest predictor of the timing of N2O fluxes across soils that differ in texture, structure and bulk density. [ABSTRACT FROM AUTHOR]

We developed a simulation model for terrestrial sites including sensible heat exchange between the atmosphere and ground surface, inter- and intra-layer heat conduction by rock and soil, and short wave and long wave radiation. Water fluxes included snow melt, freezing/thawing of soil water, soil capillary flow, and vapour flows among atmosphere, soil,and snow. The model accounted for 96-99% of variation in soil temperature data. No long-term temporal trends in soil temperature were apparent. Soil water vapour concentration in thawed surface soil in summer often was higher than in frozen deeper soils, leading to downward vapour fluxes. Katabatic winds caused a reversal of the usual winter pattern of upward vapour fluxes. The model exhibited a steady state depth distribution of soil water due to vapour flows and in the absence of capillary flows below the top 0.5 cm soil layer. Beginning with a completely saturated soil profile, soil water was lost rapidly, and within a few hundred years approached a steady state characterized by dry soil (,0.5% gravimetric) down to one metre depth and saturated soil below that. In contrast, it took 42 000 years to approach steady state beginning from a completely dry initial condition. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate adult emergence and duration of the pupal stage of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), and emergence of the fruit fly parasitoid, Diachasminiorpha longicaudata (Ashmead), under different moisture conditions in four soil types, using soil water matric potential. Pupal stage duration in C. capitata was influenced differently for males and females, In females, only soil type affected pupal stage duration, which was longer in a clay soil. In males, pupal stage duration was individually influenced by moisture and soil type, with a reduction in pupal stage duration in a heavy clay soil and in a sandy clay, with longer duration in the clay soil. As matric potential decreased, duration of the pupal stage of C. capitata males increased, regardless of soil type. C. capitata emergence was affected by moisture, regardless of soil type, and was higher in drier soils. The emergence of D. longicaudata adults was individually influenced by soil type and moisture factors, and the number of emerged D. longicaudata adults was three times higher in sandy loam and lower in a heavy clay soil. Always, the number of emerged adults was higher at higher moisture conditions. C. capitata and D. longicaudata pupal development was affected by moisture and soil type, which may facilitate pest sampling and allow release areas for the parasitoid to be defined under field conditions. [ABSTRACT FROM AUTHOR]

The aim of this paper was to analyse water dynamics in the soil from tensiometer data in two different plots, one with bare soil and another with geotextiles and grass, correlating the information generated in the study concerning biotextile efficiency in soil moisture maintenance, which is essential to vegetation development and to the recovery from and control of erosion. Tensiometers were installed on the bare soil and grass plots at different depths (15, 30, 80 and 120 cm), and the respective readings were taken with a digital tensimeter. Water dynamics inside the soil can be demonstrated by matric potential data from pressure differences. A large difference between the bare soil and grass plots was demonstrated by matric potential medium values at depths of 15, 30, 80 and 120 cm during monitoring. [ABSTRACT FROM AUTHOR]

Abstract: Trenbolone acetate (TBA) is a synthetic androgenic steroid hormone administered as a subcutaneous implant for growth promotion in beef cattle. The primary metabolite excreted in manure from implanted cattle is 17α-trenbolone with lesser amounts of 17β-trenbolone and trendione also present. At 22°C and favorable moisture conditions in a controlled laboratory environment, trenbolone degrades to trendione in a few hours; however, these conditions are often not what exist in the field. Therefore, aerobic degradation rates of 17α-trenbolone, 17β-trenbolone and trendione were determined in a sandy soil and silty clay loam under a range of temperature and water availability combinations that may be expected in the field. A first-order exponential decay model was used to estimate rates and generally resulted in good model fits to the data. Degradation rates decreased with decreasing water availability (i.e., more negative soil matric potential) and decreasing temperature. However, when water availability was substantially reduced (−1.0MPa), hotter temperatures (35°C) significantly reduced trenbolone degradation rates. Once temperature was low enough to limit microbial activity, no further changes were observed with decreasing matric potential. Trendione also exhibited similar moisture and temperature dependent degradation, but persisted longer than the parent trenbolone. The latter was discussed in light of extracellular versus intracellular enzymatic degradation and sorption. Half lives at colder temperatures (5°C) even under favorable moisture conditions were 2–3d for the trenbolone isomers and approached 10d for trendione. [Copyright &y& Elsevier]

Abstract: The functional relation between the decline in the rate of a physiological process and the magnitude of a stress related to soil physical conditions is an important tool for uses as diverse as assessment of the stress-related sensitivity of different plant cultivars and characterization of soil structure. Two of the most pervasive sources of stress are soil resistance to root penetration (SR) and matric potential (ψ). However, the assessment of these sources of stress on physiological processes in different soils can be complicated by other sources of stress and by the strong relation between SR and ψ in a soil. A multivariate boundary line approach was assessed as a means of reducing these complications. The effects of SR and ψ stress conditions on plant responses were examined under growth chamber conditions. Maize plants (Zea mays L.) were grown in soils at different water contents and having different structures arising from variation in texture, organic carbon content and soil compaction. Measurements of carbon exchange (CE), leaf transpiration (LT), plant transpiration (PT), leaf area (LA), leaf+shoot dry weight (LSDW), root total length (RTL), root surface area (RSA) and root dry weight (RDW) were determined after plants reached the 12-leaf stage. The LT, PT and LA were described as a function of SR and ψ with a double S-shaped function using the multivariate boundary line approach. The CE and LSDW were described by the combination of an S-shaped function for SR and a linear function for ψ. The root parameters were described by a single S-shaped function for SR. The sensitivity to SR and ψ depended on the plant parameter. Values of PT, LA and LSDW were most sensitive to SR. Among those parameters exhibiting a significant response to ψ, PT was most sensitive. The boundary line approach was found to be a useful tool to describe the functional relation between the decline in the rate of a physiological process and the magnitude of a stress related to soil physical conditions. [Copyright &y& Elsevier]

Abstract: Hydropedological processes affect soil water and nutrient transport and cycling. This study evaluated the impact of hydropedological properties on soil N availability and corn (Zea mays L.) growth in three areas within the same field representing distinguishing but typical mid-Atlantic (USA) landforms. These areas included: a depressional area (Site A), a steep (14%) slope area (Site B), and a flood plain area with 1% slope (Site C); different soil types (Hagerstown, Opequon, and Melvin series, respectively); and varying hydrological features (soil water content, matric potential, and subsurface flow) in a Ridge and Valley agricultural landscape. A small-plot replicated study was conducted in each of these three areas, including four blocks of two N treatments (NH4NO3) applied to corn at planting (0 and 150kgNha−1). Soil and above-ground plant biomass samples were collected during the growing season and grain yield was determined at harvest. Site A had the greatest mean grain yield (fertilized: 8.5Mgha−1; control: 4.5Mgha−1) and above-ground plant biomass (at physiological maturity or PM, fertilized: 11.7Mgha−1; control: 7.1Mgha−1), probably due to the fine-textured (>19% clay) and low saturated hydraulic conductivity (Ksat<0.3cmmin−1) soil with good water and N holding capacity. In contrast, Site B had the smallest grain yield (fertilized: 6.9Mgha−1; control: 3.5Mgha−1), which corresponded to the smallest inorganic soil N content due to its thin Ap1 (10cm) and Ap2 (21cm) horizons, greater Ap1 horizon Ksat (1.61cmmin−1), and shallow lateral subsurface flow at the steep soil–bedrock interface (0.4m below the surface). Despite the greater inorganic soil N content at Site C, the above-ground plant biomass (at PM, fertilized: 7.0Mgha−1; control: 6.2Mgha−1) and grain yield (fertilized: 7.1Mgha−1; control: 4.5Mgha−1) were less than observed at Site A and probably resulted from the low soil water content during the growing season, which also corresponded to greater solar radiation (564kw hm−2), coarser texture (>20% sand), and deep subsurface lateral convergent flow (0.7m below the surface). Understanding these types of relationships between corn response to N fertilizer and hydropedological features will improve N management decisions for corn production. [Copyright &y& Elsevier]

The effects of temperature and water potential on nitrification were investigated in two Iowa soils treated with Stay-N 2000. The soils were incubated at 10, 20, and 30 °C after soil water potentials of -1, -10, or -60 kPa were applied to each soil. A first-order equation was used to calculate the maximum nitrification rate (K max), duration of lag period (t'), period of maximum nitrification (Δt), and termination period of nitrification (t s). The highest K max were 18 and 24 mg kg-1 d-1 nitrate (NO3 -)-nitrogen (N), respectively, at 30 °C and -10 kPa in both the Nicollet (fine-loamy, mixed, superactive, mesic Aquic Hapludoll) and Canisteo (fine-loamy, mixed, superactive, calcareous, mesic Typic Endoaquoll) soils and reduced to 4 and 16 mg kg-1 d-1 NO3 --N when Stay-N 2000 was added. The extension of t' due to the addition of Stay-N 2000 was as high as 7 d in the Nicollet soil at 10 °C and -1 kPa and as little as 2 d in the Canisteo soil at 20 °C and -10 kPa. [ABSTRACT FROM AUTHOR]

Soil solution composition changes with time and distance from the root surface as a result of mass flow, diffusion, plant nutrient uptake and root exudation. A model system was designed, consisting of a root compartment separated from the bulk soil compartment by a nylon net (30 μm mesh size), which enabled independent measurements of the change of soil solution composition and soil water content with increasing distance from the root surface (nylon net). K+ concentration in the rhizosphere soil solution decreased during the initial growth stage (12 days after planting, DAP). Thereafter K+ accumulated with time, due to mass flow as the dominating process. The extend of K+ accumulation depended on the initial fertiliser application. As K+ concentrations in soil solution increase, not only as a result of transport exceeding uptake, but also as a result of decreasing soil water content, it is hypothesised that K concentration in soil solution is not the only trigger for the activity of K transporters in membranes, but ABA accumulation in roots induced by decreasing soil matric potentials may add to the regulation. A strong decrease of rhizosphere pH with time is observed as a result of H+ efflux from the roots in order to maintain cation-anion balance. In addition the K+ to Ca2+ ratio was altered continuously during the growing period, which has an impact on Ca2+ uptake and thus firmness of cell walls, apoplast pH, membrane integrity and activity of membrane transporters. The value of osmotic potential in the rhizosphere soil solution increased with time indicating decreasing soil water availability. Modelling approaches based on the data obtained with the system might help to fill in the time gaps caused by the low temporal resolution of soil solution sampling method. [ABSTRACT FROM AUTHOR]

The recent increase of irrigation practices in forage cactus crops makes appropriate irrigation management criteria necessary. In this study, the morphological and yield characteristics of forage cactus cultivars were evaluated for some soil-based irrigation management criteria. Five experiments were carried out simultaneously under semiarid conditions in a randomized block design, with forage cactus cultivars Orelha de Elefante (OE), IPA-Sertânia (IPA), Doce (DC), Gigante (GG), and Orelha de Onça (OO). For each cultivar, irrigation management was performed using four upper thresholds of matric potential (−0.2, −0.33, −1, and −3 atm), as well as a non-irrigated (rainfed) treatment. Forage cactus crop yield was evaluated after 12 months and responded positively and similarly to irrigation management using any of the thresholds, with a significant increase in the cladode area and, overall, a positive effect on growth and yield parameters. Very high irrigation water productivity up to 75 kg m−3 was obtained especially in the −3 atm threshold treatment, whereas an increase of the threshold potential caused a sharp reduction of water productivity. We conclude that irrigation management of forage cactus grown in semi-arid climates is highly beneficial and that unconventionally low matric potential thresholds may be used. • Upper matric potential thresholds for forage cactus irrigation were investigated. • Even with low thresholds, irrigation resulted in significant yield increase of cactus. • A low threshold of −3 atm resulted in a very high water productivity. • Recommended thresholds for forage cactus irrigation are unconventionally low. [ABSTRACT FROM AUTHOR]

Maize (Zea mays L.) plants parasitized by the root hemi-parasitic angiosperm, Striga hermonthica (Del.,) Benth., consistently display a range of symptoms similar to those found in droughted plants. The mechanisms by which these changes occur are largely unknown. However, S. hermonthica has unusually high rates of transpiration, and stomata which are relatively insensitive to water deficit. Consequently, it has often been suggested that the parasite might cause a severe depletion of the available water in the host's rooting zone. To determine whether the lower stomatal conductance and retarded growth of infected plants could be a result of parasite-induced water deficit, we have monitored the matric potential of the growth medium, water use, growth and stomatal conductance of infected vs. uninfected maize plants. Host plant height and stomatal conductance of parasitized plants were significantly lower than those of control plants from 31 or 37 d after planting (d.a.p.) respectively. However, there was no indication of an increase in the rate of water depletion in the rooting zone of infected plants until approx. 63 d into the parasitic association. In fact, from 39 until 59 d.a.p. infected plants used less water than uninfected control plants, probably the result of the plants having fewer expanded leaves during part of this period, combined with the lower stomatal conductance exhibited by the infected plants from day 37 onwards. Leaf RWC of infected plants was unchanged in comparison with that of uninfected plants, therefore the change in stomatal conductance was not a response to dehydration of the leaf tissue. Our results indicate that parasitism by S. hermonthica does not cause an increase in water uptake/use in the host until well after most of the symptoms of infection have become fully established. It is highly unlikely, therefore, that the observed effects on the host are primarily due to soil water deficit. [ABSTRACT FROM AUTHOR]

The physical behaviors of water in the interface are the fundamental to discovering the engineering properties and environmental effects of aqueous porous media (e.g., soils). The pore water pressure (PWP) is a key parameter to characterize the pore water state (PWS) and its phase transition in the micro interface. Traditionally, the water in the interface is frequently believed to be uniform, negative in pressure and tensile based on macroscopic tests and Gibbs interface model. However, the water in the interface is a non-uniform and compressible fluid (part of tensile and part of compressed), forming a spatial profile of density and PWP depending on its distance from the substrate interface. Herein, we introduced the static and dynamic theory methods of non-uniform water based on diffuse interface model to analyze non-uniform water state dynamics and water density and PWP. Based on the theory of non-uniform water, we gave a clear stress analysis on soil water and developed the concepts of PWS, PWP and matric potential in classical soil mechanics. In addition, the phase transition theory of non-uniform water is also examined. In nature, the generalized Clausius-Clapeyron equation (GCCE) is consistent with Clapeyron equation. Therefore, a unified interpretation is proposed to justify the use of GCCE to represent frozen soil water dynamics. Furthermore, the PWP description of non-uniform water can be well verified by some experiments focusing on property variations in the interface area, including the spatial water density profile and unfrozen water content variations with decreasing temperature and other factors. In turn, PWP spatial distribution of non-uniform water and its states can well explain some key phenomena on phase transition during ice or hydrate formation, including the discrepancies of phase transition under a wide range of conditions [Display omitted] • Soil water is spatial non-uniform in property depending on distance from substrate surface. • A novel static and dynamic theory analysis of non-uniform water were introduced. • Concepts of pore water pressure and matric potential in soil mechanics were developed. • In nature, the generalized Clausius-Clapeyron equation is consistent with Clapeyron equation. • Pressure spatial non-uniform can well explain key issues on phase transition in cold regions. [ABSTRACT FROM AUTHOR]

• Friability values depend on method of calculation and matric potential. • Clay loam soil was more affected by water quality due to higher clay content. • Friability decreased at air-dry condition for all of aggregate/clod sizes. • Dispersible clay was affected by water quality and influenced friability. Soil salinisation and sodification are two principal processes in arid and semi-arid regions which have been irrigated with poor-quality waters. A laboratory experiment was carried out to study the effect of soil texture, salinity (EC) and sodicity (SAR) of irrigation water and matric potential on soil friability. Intact soil aggregates/clods with different size ranges of 4–8, 8–15, 15–20, and 20–40 mm were collected from two texturally-different soils of sandy loam (SL) and clay loam (CL). Undisturbed soil samples were also taken for determination of soil water contents at matric potentials (h) of –30, –100, –200, and −400 kPa. All of the soil samples were subjected to five wetting/drying cycles using twelve different water quality treatments, combinations of four levels of EC (0.2, 1, 6, and 10 dS m−1) and three levels of SAR [1, 5 and 12 (meq L−1)1/2]. The tensile strength of aggregates/clods was determined by the indirect Brazilian test. Then, the soil friability was calculated by employing three methods of coefficient of variation (F 1), ranking order (F 2), and volume-dependence (F 3). The results showed that the F values varied considerably depending on the friability calculation method and matric potential. Soil friability was not affected by the treatments at the wet range because of the dominant effect of high water content on soil mechanical behavior; whereas soil aggregates/clods of 4–8, 8–15 and 15–20 mm at h of −400 kPa showed the highest friability. Soil friability decreased with an increase in SAR and increased with an increment in EC at low matric potentials (i.e., –200 and −400 kPa) due to the negative and positive effects of sodium and soluble ions on soil microstructure, respectively. The effects of SAR on soil stability, dispersion clay and tensile strength and as a consequence on soil friability was more pronounced at low EC values. Results showed more influence of water quality (EC and SAR) in clay loam than sandy loam soil due to its higher clay content. Comparison of the F values with well-known classification revealed that F 1 and F 2 were about 2–4 orders of magnitude higher than F 3 , especially for aggregates size ranges of 4–8 and 8–15 mm at h of –200 and −400 kPa and air-dry condition; and the coefficient of variation and ranking order methods were more acceptable and reliable than the volume-dependence method for characterizing the soil friability. [ABSTRACT FROM AUTHOR]

• A soil penetrometer resistance (PR) model was developed and validated. • PR was estimated from relative bulk density, matric potential, and depth. • The model has a simplified form and fewer parameters than previous models. • The model provided more accurate PR results than previous models. Soil penetrometer resistance (PR), an indicator of soil strength, is often used to denote the force that roots need to exert to penetrate the soil. In this study, we propose an empirical model, which has a simplified form and fewer parameters than the previous ones, to estimate PR from relative bulk density, matric potential of soil water, and soil depth. The model was established by using field measurements of PR , bulk density, water content, and laboratory water retention data at various soil depths in a long-term tillage experiment during maize growing season in 2017. Relative bulk density was determined from soil texture, bulk density, and organic matter content. Model performance was evaluated by comparing the predictions from the new model against those obtained from four earlier models using independent field data collected from four soils of different textures in 2015, 2018 and 2019. The root mean square error of the new model ranged from 0.358 to 0.879 MPa, significantly lower than that of the other four models (0.404–2.689 MPa), indicating that the new model could be applied to estimate PR for a wide range of soil textures with improved accuracy. [ABSTRACT FROM AUTHOR]

Abstract: To study bacterial behavior under varying hydration conditions similar to surface soil, we have developed a system called the Pressurized Porous Surface Model (PPSM). Thin liquid films created by imposing a matric potential of −0.4MPa impact gene expression and colony development in Pseudomonas putida. [ABSTRACT FROM AUTHOR]