Soil Moisture Potential Research Articles

Increase in Soil Moisture Reserves Due to the Formation of High Stubble Residues for the Accumulation of Snow Precipitation

The Orenburg region belongs to the dry-steppe regions with a sharply continental climate, the efficiency of crop production in which depends on the amount of precipitation. Due to the natural and climatic conditions of the region, precipitation in the form of snow is used irrationally, which leads to a decrease in the amount of potential soil moisture. Lack of moisture negatively affects the quality of crop production processes and the state of the soil itself. To solve this problem, it is proposed to implement measures for mechanized snow retention in agricultural fields. Technical and technological disadvantages of the classic mechanized snow retention are established. Negative components of the classical technology are the need for additional costs for winter events and the forced additional impact on the soil of heavy equipment. As a solution to the problem, it is advisable to accumulate snow on high stubble residues formed simultaneously with the process of harvesting grain crops. It was found that for the Orenburg region, taking into account the natural and climatic features, it is advisable to use a Reaper for two-phase harvesting of grain crops by a batch method with a device for the formation of high stubble residues. A dependence was established to determine the optimal share of the field area with stubble residues for effective snow retention. The optimal values of the interdependent parameters of the Reaper reel and the reel of the stubble residue formation device are revealed. The analysis of experimental field studies showed that the formed stubble residues allow accumulating the amount of snow, which increases the moisture reserves in the soil in the spring period by about two times. The feasibility study of the proposed solution showed the feasibility of its application and allowed us to establish the level of profit from the increase in yield due to an increase in the amount of moisture in the soil as a result of snow retention.

Insuring crops from space: the potential of satellite-retrieved soil moisture to reduce farmers’ drought risk exposure

Abstract Crop producers face significant and increasing drought risks. We evaluate whether insurances based on globally and freely available satellite-retrieved soil moisture data can reduce farms’ financial drought risk exposure. We design farm individual soil moisture index insurances for wheat, maize and rapeseed production using a case study for Eastern Germany. We find that the satellite-retrieved soil moisture index insurances significantly decrease risk exposure for these crops compared to the situation where production is not insured. The satellite-retrieved index also outperforms one based on soil moisture estimates derived from meteorological measurements at ground stations. Important implications for insurers and policy makers are that they could and should develop better suited insurances. Available satellite-retrieved data can be used to increase farmers’ resilience in a changing climate.

Relationships among soil factors and greenhouse gas emissions from furrow-irrigated Rice in the mid-southern, USA

The furrow-irrigated rice (Oryza sativa) production system has been developed as an alternative water conservation practice, but results in spatially variable soil conditions. No research has been conducted to relate greenhouse gas (GHG) production to soil and plant properties or environmental factors under furrow-irrigated rice in the mid-southern, USA. The objective of this field study was to evaluate relationships between methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) fluxes and emissions and global warming potential (GWP) and early season soil properties and environmental factors over two growing seasons (2018 and 2019) under furrow-irrigated rice on a silt-loam soil (Typic Albaqualf). Gas samples were collected weekly between planting and harvest from enclosed-headspace, static chambers and analyzed by gas chromatography. Methane fluxes were correlated with soil moisture (r = 0.18) and oxidation-reduction (redox) potential (r = −0.59), N2O fluxes were correlated with redox potential (r = 0.13), and CO2 fluxes were correlated with soil moisture (r = 0.29), redox potential (r = −0.27), and temperature (r = 0.09). Results suggested that environmental parameters like soil temperature, soil moisture, and redox potential can be included in management practices as controlling factors for production and release of GHG fluxes. Methane, and N2O, emissions were positively (0.36 < r < 0.78) and negatively (−0.33 < r < −0.54) correlated with numerous soil and plant properties. Significant multiple regression models predicting season-long CH4-C, N2O–N, CO2-C, and GWP from a suite of soil and plant properties were identified (0.49 < R2 < 0.78). Results demonstrated that numerous soil, plant, and environmental factors substantially control GHG production and release.

Evaluating long-term potential evapotranspiration and soil moisture dynamics at Shanghai City China

As the finical hub of China, the Shanghai metropolitan area is one of the most important regions on earth, which requires significant efforts in water, energy and resources management and supply. Ongoing dynamic changes in climate have posed large uncertainties in our ability to better quantify, estimate and predict future hydrological and ecological responses, including soil moisture dynamics and potential evapotranspirative demands. Given these significant implications, in this study, we focused on better understanding long-term dynamic trends in soil moisture and potential evapotranspiration at Shanghai with the Hargreaves equation and 1-Dimensional flow transport with Richard’s equation. We further tested how perturbations in temperature and precipitation patterns influence soil moisture and potential evapotranspiration responses. Our results suggested significant correlation between temperature and potential evapotranspiration as well as precipitation inputs and soil moisture. We believe these results can provide useful insights to help us better understand the hydrological responses at Shanghai to climate change.

MINIMUM NUMBER OF POINTS FOR A RELIABLE SOIL WATER RETENTION CURVE USING RICHARDS’ PRESSURE CHAMBER

The soil hydro-physical characteristics are very important for studies about soil water dynamics. The soil water retention curve it is a soil characteristic sometimes expensive and time consuming to be done and could be a problem for farmers. The numbers of points and its tension evaluated are normally choose arbitrarily. This study aimed to define the fewest pairs of soil moisture and water soil potential points which result in a reliable water retention curve in two different soils (sandy and clay). Using different tensions by suction table and Richards’ pressure chamber, nine replications were adjusted by van Genuchten's equation. Curves with 4, 5, 7, 8, 9, 10 and 13 points were studied and the curve with 13 points was adopted as standard. The obtained parameters for different pairs of soil moisture and their corresponding soil water potential were compared to the equivalent standard curve and submitted to analysis of variance (F test), and their values were compared by the Scott-Knott test (5% of probability). The curve with 7 points, using the tensions of 0; 40; 100; 300; 1,000; 5,000 e 15,000 hPa, was the lower number of points that did not showed statistical difference in any parameters of the model and the point with 15,000 hPa shown to be important and should be used on the combination of points to obtain a good adjustment.

Terrain wetness indices derived from LiDAR to inform soil moisture and corrosion potential for underground infrastructure

The external corrosion of cast iron water supply pipes has been associated with the availability of free moisture at the pipe wall. This is difficult to observe or measure for extensive pipe networks such as in major cities. A proxy is soil surface moisture content. This may be estimated using terrain wetness indices with highly accurate elevation data derived from airborne Light Detection and Ranging (LiDAR). Such information was obtained for several pipelines and compared with data from 6 cm deep soil moisture Theta Probe measurements along 12 pipeline transects. Additionally, all soil moisture data (in volumetric water content, %) were combined and separated by thresholds of transect means into low (<20%), medium (20%–35%) and high (>35%). Good correlations were obtained (R values 0.49–0.93, all with p value < 0.05). Higher R values were found for wetter conditions (above ~20%). The wetness indices were also found to relate to pipe-wall maximum pitting corrosion rates (mm/yr) when soil classifications were taken into account, with separate trends for clay, silty clay, sandy clay and sand. Some outliers were detected. These were all associated with pipes for which there is evidence of poor workmanship or quality during installation. In total, 25 catchments from inner city to coastal and lakeside suburbs as well as semi-rural regions were assessed. Results show the potential for terrain indices to indicate relative soil wetness in urban areas and thus potential for pipe failure. This is the first study of its kind. This also may assist water authorities to improve life prediction, management and replacement schedules for water supply pipelines and other underground assets.

Direct response of tree growth to soil water and its implications for terrestrial carbon cycle modelling

Wood growth constitutes the main process for long-term atmospheric carbon sequestration in vegetation. However, our understanding of the process of wood growth and its response to environmental drivers is limited. Current dynamic global vegetation models (DGVMs) are mainly photosynthesis-driven and thus do not explicitly include a direct environmental effect on tree growth. However, physiological evidence suggests that, to realistically model vegetation carbon allocation under increased climatic stressors, it is crucial to treat growth responses independently from photosynthesis. A plausible growth response function suitable for global simulations in DGVMs has been lacking. Here, we present the first soil water-growth response function and parameter range for deciduous and evergreen conifers. The response curve was calibrated against European larch and Norway spruce in a dry temperate forest in the Swiss Alps. We present a new data-driven approach based on a combination of tree ring width (TRW) records, growing season length and simulated subdaily soil hydrology to parameterize ring width increment simulations. We found that a simple linear response function, with an intercept at zero moisture stress, used in growth simulations reproduced 62.3% and 59.4% of observed TRW variability for larch and spruce respectively and, importantly, the response function slope was much steeper than literature values for soil moisture effects on photosynthesis and stomatal conductance. Specifically, we found stem growth stops at soil moisture potentials of -0.47MPa for larch and -0.66MPa for spruce, whereas photosynthesis in trees continues down to -1.2MPa or lower, depending on species and measurement method. These results are strong evidence that the response functions of source and sink processes are indeed very different in trees, and need to be considered separately to correctly assess vegetation responses to environmental change. The results provide a parameterization for the explicit representation of growth responses to soil water in vegetation models.

MINING RESIDUE IN THE COMMERCIAL LIMESTONE BLENDING AND THE CHEMICAL ATTRIBUTES OF A LATOSOL

The limestone mining activity causes environmental impacts due to the generation of waste. However, the reuse of these residues has been investigated with the objective of improving soil fertility and acidity correction. The objective of this work was to evaluate the potential for using mining residues in the commercial limestone blending and in the chemical attributes of a dystrophic Red Yellow Latosol. The experiment was carried out in three steps: the first corresponded to the sampling and characterization of the residues in the tailings pile; the second was the combination and characterization of the new soil acidity correction agents as well as the selection of treatments based on the Neutralization Power and doses of soil acidity correction agetns (0.0; 0.5; 1.0; 2.0; 4.0 t ha-1); in the third step, a test of the incubation and calibration of the application doses of the soil acidity correction agents was performed. It was found that even with the raise in the levels of Ca2+ and Mg2+ in the correction agents, it was not possible to provide an optimal supply of nutrients to the soil, a fact explained by the low constant solubility of CaCO3 and MgCO3. However, the commercial limestone blending with tailing was efficient, as it had a significant effect on raising the pH and neutralizing the soil moisture potential.

The importance of volume changes in the determination of soil water retention curves on the East Slovakian Lowland

Estimation and application of water retention curves in heavy soils have own specifics. The reason for these specific properties is the composition of the high clay texture. This is manifested by volume changes of soil depending on moisture. Up to 40% change in the volume compared to the saturated state was recorded in the conditions of the East Slovakian Lowland. The results described in this work are based on research work carried out in the East Slovakian Lowland and represent an analysis of selected 42 samples out of a total of 250 samples in which laboratory measurements of soil water retention curves and volume changes were performed. Selected samples represent the localities Senné and Poľany. Volumetric changes were measured in a laboratory by measuring the dimensions of soil samples. Appropriate changes in the volume of soil samples should be measured when determining moisture retention curves. Neglecting this physical effect leads to a distorted determination of the water retention curves in heavy soils. In the laboratory measurement of water retention curves points, changes in the volume of the sample were measured in the range of 0.24–43.67% depending on the soil moisture potential during drainage. In the case of neglecting the effect of shrinkage during the drainage of samples, a certain error is occurring in the calculation of the volumetric moisture. The range of this error was 1–13% of volumetric moisture.

Combined Application of Potassium and Zinc Improves Water Relations, Stay Green, Irrigation Water Use Efficiency, and Grain Quality of Maize under Drought Stress

Maize (Zea mays L.) plays an important role in the global food security, but its production is threatened by climate change, especially drought stress. Potassium (K) and zinc (Zn) are considered useful to mitigate the negative consequences of drought stress in plants. Therefore, the objective of this two-year study was to identify the best combination of K and Zn application to improve the water relations, photosynthetic pigments, yield, irrigation water use efficiency (IWUE) and grain quality of maize sown under mild and severe drought stress conditions. The consisted of three drought stress levels viz. 1) well-watered as control (WW), 2) mild drought (MD) with 25 mm of potential soil moisture deficit (PSMD), 3) severe drought (SD) with 50 mm of PSMD and six K-Zn treatments: i.e. 125, 100 and 150 kg ha−1 K with 0 and 12 kg ha−1 Zn. The results indicated that K-Zn application improved the water relations and chlorophyll contents, biological yield and grain quality, irrespective of water stress treatment. The combined application of K-Zn under mild drought stress produced statistically same biological yield and grain quality as under well-irrigated without K-Zn fertilization and also produced compratively higher IWUE, biological yield and grain quality under sverer drought stress. Hence, the application of K at 150 kg ha−1 in combination with Zn at 12 kg ha−1 might be useful to improve the maize production and grain quality under drought stress. As IWUE was low in WW conditions, therefore, irrigation scheduling must be re-evaluated for optimum water use efficiency.

Soil moisture and matric potential – an open field comparison of sensor systems

Abstract. Soil water content and matric potential are central hydrological state variables. A large variety of automated probes and sensor systems for state monitoring exist and are frequently applied. Most applications solely rely on the calibration by the manufacturers. Until now, there has been no commonly agreed-upon calibration procedure. Moreover, several opinions about the capabilities and reliabilities of specific sensing methods or sensor systems exist and compete. A consortium of several institutions conducted a comparison study of currently available sensor systems for soil water content and matric potential under field conditions. All probes were installed at 0.2 m b.s. (metres below surface), following best-practice procedures. We present the set-up and the recorded data of 58 probes of 15 different systems measuring soil moisture and 50 further probes of 14 different systems for matric potential. We briefly discuss the limited coherence of the measurements in a cross-correlation analysis. The measuring campaign was conducted during the growing period of 2016. The monitoring data, results from pedophysical analyses of the soil and laboratory reference measurements for calibration are published in Jackisch et al. (2018, https://doi.org/10.1594/PANGAEA.892319).

Hydrophysical properties of sandy clay contaminated by petroleum hydrocarbon

The aim of the presented research was to assess the changes in hydro-physical properties of sandy clay under the influence of petroleum hydrocarbon contamination. An understanding of these changes is fundamental in the right remedial actions and for further use of soil. Laboratory tests of inherently wettable sandy clay showed that the petroleum hydrocarbon induced potential soil water repellency (SWR) of extremely repellent class at the contamination of 18 g kg−1. The relationship between soil water potential (pF) and SWR determined by the WDPT test for given hydrocarbon contamination, i.e., 6, 12, 18, 30, 100 g kg−1, showed that the critical soil moisture value (CSMC) corresponds to the pF = 1.0 ÷ 1.5. Soil retention characteristic (pF) showed that an increase in hydrocarbon contamination from 0 to 100 g kg−1 caused a reduction of total available water for plants from about 0.19 to 0.06 cm cm−3. At the same time, in the pF = 1.5 ÷ 2.0 range, intensive soil pore drainage was observed. Statistically, significant effect of hydrocarbon contamination and soil moisture potential on SWR was found. Soil hydrophobicity limits the addition of soil retention, because a significant part of the precipitation can be transformed by surface runoff. The carried out tests showed that at a hydrocarbon contamination of 30 g kg−1, total rainfall amount 14 mm with an intensity of 2 mm h−1 was transformed into a surface drain in approx. 40%. The conducted studies demonstrate the adverse impact of hydrocarbon contamination on the soil’s hydro-physical properties. The soil water retention reduction and launching of the surface outflow, as a result of limiting the water penetration process resulting from SWR, change the agrohydrological conditions of the contaminated area. It can result as the imbalance of the flow of energy and matter in the ecosystem. The scenarios of environmental effects, among others, depend on the type of soil, the degree of its pollution, the type of ecosystem, and supporting activities undertaken by man. It should be taken into account that the increasing frequency of drought occurrence associated with climate change is conducive to the phenomenon of SWR regardless of the reasons for its occurrence.

Engineering challenges of warming

Observations reveal recent Arctic warming, but future societal impacts are poorly understood. Now research identifies potential abrupt thaw-driven soil moisture shifts, with consequences for northern development including more intense wildfires and rainfall.

A geospatial method for estimating soil moisture variability in prehistoric agricultural landscapes.

Prehistoric peoples chose farming locations based on environmental conditions, such as soil moisture, which plays a crucial role in crop production. Ancestral Pueblo communities of the central Mesa Verde region became increasingly reliant on maize agriculture for their subsistence needs by AD 900. Prehistoric agriculturalists (e.g., Ancestral Pueblo farmers) were dependent on having sufficient soil moisture for successful plant growth. To better understand the quality of farmland in terms of soil moisture, this study develops a static geospatial soil moisture model, the Soil Moisture Proxy Model, which uses soil and topographic variables to estimate soil moisture potential across a watershed. The model is applied to the semi-arid region of the Goodman watershed in the central Mesa Verde region of southwestern Colorado. We evaluate the model by comparing the Goodman watershed output to two other watersheds and to soil moisture sensor values. The simple framework can be used in other regions of the world, where water is also an important limiting factor for farming. The general outcome of this research is an improved understanding of potential farmland and human-environmental relationships across the local landscape.

MicroclimUS: hourly estimates of historical microclimates for the United States of America with example applications.

Microclimatic data are required for many problems in pure and applied ecology. This data includes aboveground convective and radiative conditions as well as soil temperature and moisture. In cold regions, the connection between above- and belowground microclimates via snow cover is also critically important. Here I describe a data set of hourly microclimates for the continental United States, simulated from the years 1979 to 2017 across a grid of 2,287 locations approximately 60km apart. The data were generated with the NicheMapR microclimate model, driven by 0.04° gridded daily meteorological forcing data (air temperature, wind speed, humidity, solar radiation, air pressure, and rainfall). The aboveground microclimate variables include horizontal plane solar radiation, solar zenith angle, sky temperature (from which downwelling longwave radiation can be computed), air temperature, relative humidity, and wind speed at 1 and 200cm height, and snow depth. The belowground variables include soil temperature, pore humidity, soil moisture, and soil water potential for 0, 2.5, 5, 10, 15, 20, 30, 50, 100, and 200cm belowground. The computations are for four shade levels (0%, 50%, 75%, and 90%). The predictions are validated against detailed soil temperature, soil moisture, and snow observations and show enhanced performance over existing microclimatic data for the United States. The data set can be used for a wide variety of applications, including the computation of heat and water budgets of organisms, the potential for vegetation growth, and the computation of stress and growth indices. The use of daily forcing data also allows assessments of the consequences of extreme events including heat waves and drought. Example applications are provided for computing plant growth potential, lizard egg development and body temperature, and mammalian energy and water requirements. No copyright or proprietary restrictions are associated with the use of this data set other than citation of this Data Paper.

On the uncertainty of initial condition and initialization approaches in variably saturated flow modeling

Abstract. Soil water movement has direct effects on environment, agriculture and hydrology. Simulation of soil water movement requires accurate determination of model parameters as well as initial and boundary conditions. However, it is difficult to obtain the accurate initial soil moisture or matric potential profile at the beginning of simulation time, making it necessary to run the simulation model from the arbitrary initial condition until the uncertainty of the initial condition (UIC) diminishes, which is often known as “warming up”. In this paper, we compare two commonly used methods for quantifying the UIC (one is based on running a single simulation recursively across multiple hydrological years, and the other is based on Monte Carlo simulations with realization of various initial conditions) and identify the warm-up time twu (minimum time required to eliminate the UIC by warming up the model) required with different soil textures, meteorological conditions and soil profile lengths. Then we analyze the effects of different initial conditions on parameter estimation within two data assimilation frameworks (i.e., ensemble Kalman filter and iterative ensemble smoother) and assess several existing model initializing methods that use available data to retrieve the initial soil moisture profile. Our results reveal that Monte Carlo simulations and the recursive simulation over many years can both demonstrate the temporal behavior of the UIC, and a common threshold is recommended to determine twu. Moreover, the relationship between twu for variably saturated flow modeling and the model settings (soil textures, meteorological conditions and soil profile length) is quantitatively identified. In addition, we propose a warm-up period before assimilating data in order to obtain a better performance for parameter and state estimation.

Shifting mineral and redox controls on carbon cycling in seasonally flooded mineral soils

Abstract. Although wetland soils represent a relatively small portion of the terrestrial landscape, they account for an estimated 20 %–30 % of the global soil carbon (C) reservoir. C stored in wetland soils that experience seasonal flooding is likely the most vulnerable to increased severity and duration of droughts in response to climate change. Redox conditions, plant root dynamics, and the abundance of protective mineral phases are well-established controls on soil C persistence, but their relative influence in seasonally flooded mineral soils is largely unknown. To address this knowledge gap, we assessed the relative importance of environmental (temperature, soil moisture, and redox potential) and biogeochemical (mineral composition and root biomass) factors in controlling CO2 efflux, C quantity, and organic matter composition along replicated upland–lowland transitions in seasonally flooded mineral soils. Specifically, we contrasted mineral soils under temperature deciduous forests in lowland positions that undergo seasonal flooding with adjacent upland soils that do not, considering both surface (A) and subsurface (B and C) horizons. We found the lowland soils had lower total annual CO2 efflux than the upland soils, with monthly CO2 efflux in lowlands most strongly correlated with redox potential (Eh). Lower CO2 efflux as compared to the uplands corresponded to greater C content and abundance of lignin-rich, higher-molecular-weight, chemically reduced organic compounds in the lowland surface soils (A horizons). In contrast, subsurface soils in the lowland position (Cg horizons) showed lower C content than the upland positions (C horizons), coinciding with lower abundance of root biomass and oxalate-extractable Fe (Feo, a proxy for protective Fe phases). Our linear mixed-effects model showed that Feo served as the strongest measured predictor of C content in upland soils, yet Feo had no predictive power in lowland soils. Instead, our model showed that Eh and oxalate-extractable Al (Alo, a proxy of protective Al phases) became significantly stronger predictors in the lowland soils. Combined, our results suggest that low redox potentials are the primary cause for C accumulation in seasonally flooded surface soils, likely due to selective preservation of organic compounds under anaerobic conditions. In seasonally flooded subsurface soils, however, C accumulation is limited due to lower C inputs through root biomass and the removal of reactive Fe phases under reducing conditions. Our findings demonstrate that C accrual in seasonally flooded mineral soil is primarily due to low redox potential in the surface soil and that the lack of protective metal phases leaves these C stocks highly vulnerable to climate change.

New insights into the thermal regime and hydrodynamics of the early Late Cretaceous Arctic

AbstractThe Arctic is warming faster than anywhere else of comparable size on Earth, impacting global climate feedbacks and the Arctic biota. However, a warm Arctic is not novel. The Late Cretaceous fossil record of the region enables a detailed reconstruction of polar environmental conditions, and a thriving extinct ecosystem, during a previous 'hothouse’ global climate. Using leaf form (physiognomy) and tree ring characteristics we reconstruct Cenomanian to Coniacian polar thermal and hydrological regimes over an average annual cycle at eight locations in NE Russia and northern Alaska. A new high spatial resolution (∼1 km) WorldClim2 calibration of the Climate Leaf Analysis Multivariate Program (CLAMP) yields results similar to, but often slightly warmer than, previous analyses, but also provides more detailed insights into the hydrological regime through the return of annual and seasonal vapour pressure deficit (VPD), potential evapotranspiration (PET) estimates and soil moisture, as well as new thermal overviews through measures of thermicity and growing degree days. The new results confirm the overall warmth of the region, particularly close to the Arctic Ocean, but reveal strong local differences that may be related to palaeoelevation in the Okhotsk–Chukotka Volcanogenic Belt in NE Russia. While rainfall estimates have large uncertainties due to year-round wet soils in most locations, new measures of VPD and PET show persistent high humidity, but with notably drier summers at all the Arctic sites.

Deep blade loosening increases root growth, organic carbon, aeration, drainage, lateral infiltration and productivity

All cultivated soils are prone to rapid reconsolidation when wet, particularly structurally unstable soils. This predisposes them to waterlogging, slow and limited infiltration, rapid drying, and poor establishment, growth and production of crops. Field-scale research was undertaken to develop soil management and/or engineering practices that will maintain a stable, loose tilth with aeration, drainage and infiltration properties that prevent waterlogging, enhance infiltration and increase crop production.The effects of deep ripping plus gypsum, permanent raised beds (PRB), deep blade loosening at 250 mm depth (DBL) and no-tillage crop establishment (NT) were studied in controlled traffic regimes on rainfed and irrigated crops. The DBL treatment severs roots at about 250 mm depth and loosens without inverting the overburden. Experiments were undertaken from 1997 to 2011 on winter waterlog-prone unstable sandy loam over clay soils in Western Australia, on an unstable fine sandy clay loam in Pakistan and on a self-mulching clay in Queensland. All sites were operated on a field scale as part of the commercial operations of collaborating farmers. Root zone soil conditions were monitored with measurements (0–400 mm) of bulk density, tilth porosity, hydraulic conductivity, perched water table depth, root mass, organic carbon, total nitrogen and moisture profiles. Irrigation applications and crop yield were also recorded.Bulk density data on all experimental sites showed reconsolidation of the tilth created by deep ripping with or without gypsum in the NT treatment occurred substantially within one growing season. The reconsolidated NT treatment in Western Australia also had low hydraulic conductivity, air-filled porosity values of only two to 4% at a soil moisture potential of −250 mm (PRB height) and suffered long duration waterlogging events. The DBL-PRB treatment on these soils remained largely unconsolidated, had larger hydraulic conductivity, an air-filled porosity at −250 mm moisture potential of ≥10%, and did not suffer waterlogging. Modelling using drainage theory showed that DBL-PRB could be as wide as three metres and easily drain saturated beds within two days, thus precluding waterlogging.Root mass in the 0–400 mm in DBL-PRB treatment was, on average, seasonally 31% greater than the NT treatment. This increase in root mass is shown to have produced increases of 48% in soil organic carbon and 34% in total soil nitrogen content, and, over 19 cropping seasons with six different types of crop, the DBL-PRB treatment produced an annual average increase in grain yield of 23% over that of the NT treatment.The DBL-PRB treatment also substantially increased the amount and rate of lateral infiltration. Irrigation wetting fronts were both measured and predicted by infiltration theory to reach the centre of 2 m wide DBL-PRB in one third to one half of the time taken in NT-PRB.DBL practice has the potential to stabilise a deepened tilth in all soil types through the conservation of the structure and mass of enhanced root growth, which increases soil organic carbon, total soil nitrogen and crop productivity, as well as preventing waterlogging and improving irrigation efficiency.

Interception and soil water relation in Norway spruce stands of different age during the contrasting vegetation seasons of 2017 and 2018

Interception, soil moisture and soil water potential were observed in four Norway spruce stands of different age in two subsequent vegetation seasons 2017 and 2018. Vegetation season 2018 can be characterized as being abnormally hot and dry with only 66% of precipitation in comparison with normal conditions. The interception of spruce increased with the stand age and its dimensions, ranging between 16 and 48% in 2017 and in the majority of stands even increasing in 2018. The soil moisture significantly decreased during the vegetation season 2018, with soil water potential close to the permanent wilting point (–1.5 MPa) for a substantial part of the monitored period. Differences between individual stands were observed in terms of the soil water potential (SWP) development which does not follow the interception patterns suggesting that the stand transpiration is a driving factor responsible for the soil water budget. In all stands, with the exception of the oldest one, the SWP of the upper soil horizon was less than 1.5 MPa for more than 80 days. In such extreme conditions the drought would negatively influence any Norway spruce stand regardless of its age or structure.