Total Soil Moisture Content Research Articles

Impact of clod (aggregate) size on evaporation rate and soil moisture profile during the drying process

AbstractLarge clods (centimetres in size) can be formed by tillage in clayey paddy fields where upland crops are planted. These clods cause early water depletion near the soil surface, which decreases crop germination and emergence rates. Because of the difficulty in reducing clod size, desiccation damage to seeds can be avoided by adjusting the seeding depth based on the clod size‐dependent soil moisture profile. This study aimed to clarify the effect of clod size on (1) the evaporation rate (E) and soil moisture profile and (2) the mobility of soil water during the drying process. Evaporation experiments were conducted in an air‐conditioned greenhouse with natural light using cylindrical columns filled with artificially made clods 3 (L columns) and 1 cm (S columns) in diameter. We measured E, potential evaporation rate (PE), and total soil moisture content (wtot) throughout the experiment and the soil moisture profiles at the end of the experiment. The water diffusivity (Dw) and apparent vapour diffusion coefficient (dvap) were calculated as the mobility of soil water and water vapour, respectively. We found that wtot was lower in the L column than in the S column, although not at the onset of the experiment. At the end of the experiment, the soil moisture content was lower in the L column than in the S column throughout the soil layer. In contrast, E/PE was higher in the L column than in the S column throughout the experiment and even at the same wtot. Regarding mobility, Dw was slightly greater in the L column than in the S column in the soil moisture content range, where vapour movement could be greater than liquid water movement. In addition, the ratio of dvap to the diffusion coefficient of water vapour in soil was higher than unity in both columns and was 2.4–3.2 times higher in the L column than in the S column. In summary, larger clods caused a higher evaporation rate and lower soil moisture content, owing to the increased enhancement of water vapour movement probably induced by wind.

The influence of partial deforestation on moisture regime: sums of precipitation and total soil moisture content for the territory of Ukraine based on data of numerical experiment LUMIP

The paper is dedicated to the impact of partial deforestation on sums of precipitation and part/fraction or sums of precipitation intercepted by the canopy; total soil moisture content under condition of minimal anthropogenic influence for the territory of Ukraine. In this work used data from the Land Use Model Intercomparison Project (LUMIP), which is based on Global Climate Models (GCMs). The purpose of LUMIP is to reveal patterns of changes of climate characteristics due to gradual global deforestation with a trend approximately 1 % every year and its replacement on grass or pastures for period 1850—1899. This time span is considered as the pre-industrial. The next period, 1900—1929 is without changes in forest cover. For estimation of impacts of partial deforestation the methods of anomalies over the first 20-year period (1850—1869) was used with further application of 5-year running mean of climatic characteristics to smooth their interannual variability. Coefficients of linear correlation between running mean anomalies of specific characteristic and the percentage of forest cover in grid cells with averaging over latitudinal zones, linear trends and differences were estimated.
 Overally estimations have shown that the global partial deforestation doesn’t impact directly on of monthly total precipitation in the middle latitudes, particularly, in Ukraine. But gradual forest reduction decreases part or fraction of precipitation intercepted by the canopy in both cold and warm seasons with average trend up to –2,6....–1,5 %/10 years in latitudinal zones in specific grids, where forest cover was reduced. The maximal decline was up to –14.5 % in grids as the difference between the 50-year period of partial deforestation and the next 30-year period. Such an effect will causemore precipitation reaching the ground and most likely will influence surface runoff. Found, that it causes the increase in total soil moisture content with trend 0.1—4.9 %/10 years depending on month and climate model, but with most significant changes during summer and autumn seasons.
 Thus, the analysis of LUMIP data for Ukraine has revealed that the partial deforestation caused the decrease of fraction part/fraction of precipitation intercepted by the canopy. Most GCMs demonstrated that this reduction provoked the increase of total soil moisture content and also can cause changes in hydrological regime and provoke higher flood frequency and other related hydrometeorological hazards in the forest part of Ukraine.

Response of Soil Moisture Regime of Relay Grass Pea (Lathyrus sativus L.) to Seed Priming and Foliar Fertilization in New Alluvial Zone of West Bengal

Background: Indian agricultural sector requires a huge consumption of total available water for the sake of optimum crop production. The modern era of water scarcity necessitates the escalation of water use efficiency of crops to secure higher portion of economic harvests per drop use of water in agriculture. Against this background, it is requires to introduce lesser water consuming crops like pulses, oilseeds etc with innovative and cost-effective agronomic interventions for the purpose of contributing towards conservation of more water. Methods: A field experiment was conducted at District Seed Farm, ‘A-B’ Block of Bidhan Chandra Krishi Viswavidyalaya, West Bengal, during subsequent winter seasons of 2017-18 and 2018-19 to evaluate the effect of seed priming with molybdenum and foliar fertilization on moisture utilization of relay grass pea, variety Ratan (Bio L-212) without irrigation, using seed priming with Ammonium molybdate and foliar spray of 2% Urea and 0.5% NPK (19:19:19) in different combinations. Result: Maximum water use efficiency of 16.65 and 14.80 kg ha-1 mm-1 in the respective years were recorded with seed priming combined with twice foliar spray of 0.5% NPK (19:19:19) with the highest yield and moisture consumption. Total soil moisture content was found to be an exponential function of dry aerial biomass, but shared a polynomial correlation with leaf area index at different growth stages of grass pea. However, water use efficiency exhibited strong and polynomial correlation with seed yield and stover yield of grass pea in both the years. The combination of seed priming with Ammonium molybdate @ 0.5 g kg-1 seed along with a twice foliar spray of 0.5% NPK (19:19:19) will be a profitable technology for the relay grass pea growers in new alluvial zone of West Bengal.

Development and validation of an operational multi-layered model for estimation of soil moisture at point-scale in South Africa

Data discontinuity is the major challenge that hinders the integrity of datasets from the sparse soil moisture monitoring networks in developing countries. In this study, a simplified, multi-layered soil water balance model to estimate daily soil moisture at point-scale from standard weather data and minimal physical soil properties was developed. The model requires values for soil water retentivity properties such as wilting point, field capacity and saturation of each soil layer. It also requires measurements or estimates of reference evapotranspiration (ETo ) in addition to rainfall as climate inputs. The developed model was evaluated using point-scale in-situ soil moisture measurements acquired over a minimum of two years from three well-calibrated stations representing different soil types and climatic conditions in South Africa. The results indicate that the proposed model was capable of estimating total soil moisture content at all three sites, with coefficient of determination (r 2) values greater than 0.84, index of agreement (d) values greater than 0.95 and root mean square error (RMSE) values less than 7.30 mm. The findings of this study suggest that the proposed model can be reliably used for daily estimation of soil moisture at point-scale using climate data and minimal soil physical properties, to fill in gaps, and to extend datasets in locations facing data-discontinuity.

The influence of the preceding crops on the soil moisture content under the spring soft wheat fields

The paper presents data on the influence of the preceding crops on the soil moisture content under the spring soft wheat fields in the conditions of the moderately dry steppe in Altai Krai. The wheat was sown after three different predecessors: legumes, row crops and fallows. The total soil moisture content in the one-meter layer had been decreased from the beginning to the end of the vegetation period. The preceding crops have a significant influence on this indicator. This must be taken into account for the development of technology for environmentally sustainable and efficient spring soft wheat production.

Response of Ecoenzymatic Stoichiometry to Soil Physicochemical Properties after Afforestation on Loess Hilly Region

Afforestation has significantly affected interactions between soil nutrients and microbial enzymes. To understand the detailed variations in extracellular enzyme activity and their link with soil nutrient availability after returning farmland (FL) to forest, soil samples were collected from FL and three afforested lands, Robinia pseudoacacia L. forest (RP), Caragana korshinskii Kom. forest (CK), and abandoned land (AL) in the Loess Hilly Region of northern China. The soil enzymes: β-glucosidase (BG), N-acetylglucosaminidase (NAG), alkaline phosphatase (AP), and leucine aminopeptidase (LAP); their stoichiometric ratios; and soil properties such as soil organic carbon, total nitrogen (TN), total phosphorus (TP), dissolved organic carbon, dissolved organic nitrogen, available phosphorus, soil moisture content (SMC), soil bulk density, and pH were measured. The BG activity showed similar trends as AP activity during afforestation, reaching the highest level in CK and showing a value 205% higher than that in FL. The NAG and LAP activities were not altered by afforestation; only the (NAG + LAP) : AP ratio decreased significantly by 44 to 60%. The BG : AP and (NAG + LAP) : AP ratios were strongly correlated with pH. Compared with other soil physicochemical properties, the soil moisture content greatly affected soil enzyme activity. The most relevant nutrients for the enzymes and stoichiometry were TN and TN : TP. Thus, our results suggest that soil enzyme activity and its stoichiometry are sensitive to changes in soil physical and chemical properties and total soil nutrients content, particularly pH, SMC, TN, and TN : TP.

Photochemical activity of chloroplasts of isogenic lines (E genes) of soybean (Glycine max (L.) Merr.) under different periods of red-light irradiation

The effect of different periods of red-light (RL, 660 nm) irradiation of plants on the biomass, leaf area, chlorophyll content, level of the Hill reaction and photophosphorylation in short-day (SD) and photoperiodical neutral (PhPN) lines of soybean have been studied in vegetation experiments. The objects of study were the isogenic lines (E genes) of soybean (Glycine max (L.) Merr.), Clark variety. The SD (E1E2E3) and PhPN lines (e1e2e3) were used. The plants were grown in a vegetation chamber in the soil culture (black soil). Plants of SD and PhPN lines were grown in 9 vessels of three liters volume. 10–12 plants were grown in each vessel. The constant growing conditions were provided during the experiment: temperature – 20–24/17–20°С (day/night), soil moisture – 60–70 % of the total soil moisture content, intensity of illumination – 20 klx, photoperiod duration – 10 hours. After 4–5 weeks of vegetation (after the second true leaf formation), plants of each line in three vessels were irradiated for 30 minutes with low intensity red light at the beginning (experiment 1) or in the middle of the dark period (experiment 2). The light diodes emitting in the region of 630±10 nm were used for plant irradiation. Other plants in three vessels of each line, which were not illuminated by the red light, were used as a control group. It was shown that under the short day the SD line in the control group passed to flowering 43±1.8 days after germination and PhPN line – 44±2.2 days after germination. The red-light irradiation, both before the beginning and in the middle of night, caused a delay of the transition to flowering in the SD line by 5±1 and 7±2.2 days, respectively. In the PhPN line, changing flowering period due to RL was not established. In the SD line, activation of the phytochromes by RL before the dark period caused an increase of the biomass, leaf area, total chlorophyll content, reduction of potassium ferrocyanide and photophosphorylation by isolated chloroplasts per chlorophyll of one leaf. While interruption of the night by RL caused decrease of these parameters and Hill reaction intensity per 1 mg of chlorophyll. The effect of RL on the studied parameters in the PhPN soybean line has not been detected.

Assessing Aquacrop model for pearlmillet (Pennisetum glaucum) under in-situ water conservation in a rainfed semi-arid environment

AquaCrop (v4. 0) model has been commonly used to simulate the crop yield under irrigated environments, but this model has not yet been calibrated and validated for simulating the yield of pearlmillet (Pennisetum glaucum (L.) R. Br.) under in-situ water conservation. Thus, a three year (2011−13) field experiment was conducted at ICAR-Indian Agricultural Research Institute, New Delhi with six in-situ water conservation treatments,viz. trench-cum-bund (TCB: 20 cm depth of trench, 20 cm height of bund), bund (30 cm height), ridge-and-furrow (R&F: 15 cm height), skip-row (SR: 3:1) planting, basin-tillage (BT: 45 cm × 45 cm) and control (no-water conservation). Calibration of AquaCrop (v 4. 0) model for pearlmillet grain yield and total soil moisture content was done using experimental data of 2011 and validated separately for 2012 (deficit rainfall year) and 2013 (excess rainfall year) data. For the year (2012), absolute prediction errors of grain yield were 1.7, 8.7, 14.1, 14.9, 3.3 and 7.3% for BT, R&F, TCB, bunds, SR and control, respectively, whereas Nash Sutcliffe Efficiency, root mean square error and coefficient of determination were 0.95, 0.07 and 0.96, respectively during calibration period and 0.73, 0.15 and 0.93 during validation period of deficit year. Thus, model predictions were satisfactoryfor less rainfall (<600 mm) year. Coefficient of determination R2 (0.4 to 1.0) was better for soil moisture simulation during dry-spell periods and for BT practice. The validated AquaCrop model can be used for prediction of pearlmillet yield and soil moisture under different water conservation practices in a semi-arid environment.

PHYTOHORMONAL REGULATORY MECHANISM OF THE ONTOGENESIS OF HETERODERIDES’ ACTIVATION AND SYNCHRONIZATION

Studies using the developed device confirmed the attractive properties of the aquatic extracts of host plants, as well as the high trophic receptivity of the invasive larvae of cyst nematodes. The greatest stimulation of the release and active migration of larvae from cysts was observed when phytoncids were introduced by cultivated host plants at a distance of 2.5–5 cm from the object of study at an optimal humidity of 60–70% of the total soil moisture content. At the same time, the aqueous extracts of the roots of the initial phases of plant growth and development compared to the extracts of the subsequent organogenesis phases were the most attractive. We believe that the larvae react most to the increased content of phytohormones, cytokinins, because their synthesis in comparison with other growth activators mainly occurs in the root system of plants. Nematode isolation of enzymes in plant tissue causes a high content of phytohormones, which are catalysts for the formation of new young roots, thereby providing optimal conditions for the invasion and development of next-generation larvae. Certain stimulating effect was also shown by extracts from other plant organs, which indicates the integrity of the flow of all physiological processes in the plant organism. Due to the genetically fixed mechanism of activation and suspension of physiological processes, a clear synchronization of the ontogenesis of cyst nematodes in accordance with the organogenesis of host plants has been noted. Since the development of heteroderides occurs only in one plant populated by them, sedentary phytoparasites react sensitively to changes in the biochemical composition of the plant organism, due to biological aging or adverse factors of different nature, causing their pathology. The perennial cyclical nature of the development of sedimentary nematodes in accordance with the organogenesis of typical host plants caused the formation of their population adaptation.

Performance and sensitivity of the DSSAT crop growth model in simulating maize yield under conservation agriculture

With the practice of conservation agriculture (CA) soil water and nutrient dynamics are modified by the presence of a mulch of crop residues and by reduced or no-tillage. These alterations may have impacts on crop yields. The crop growth model DSSAT (Decision Support Systems for Agrotechnology Transfer) has recently been modified and used to simulate these impacts on crop growth and yield. In this study, we applied DSSAT to a long-term experiment with maize (Zea mays L.) grown under contrasting tillage and residue management practices in Monze, Southern Province of Zambia. The aim was (1) to assess the capability of DSSAT in simulating crop responses to mulching and no-tillage, and (2) to understand the sensitivity of DSSAT model output to input parameters, with special attention to the determinants of the model response to the practice of CA. The model was first parameterized and calibrated for the tillage treatment (CP) of the experiment, and then run for the CA treatment by removing tillage and applying a mulch of crop residues in the model. In order to reproduce observed maize yields under the CP versus CA treatment, optimal root development in the model was restricted to the upper 22 cm soil layer in the CP treatment, while roots could optimally develop to 100 cm depth under CA. The normalized RMSE values between observed and simulated maize phenology and total above ground biomass and grain yield indicated that the CA treatment was equally well simulated as the CP treatment, for which the model was calibrated. A global sensitivity analysis using co-inertia analysis was performed to describe the DSSAT model response to 32 model input parameters and crop management factors. Phenological cultivar parameters were the most influential model parameters. This analysis also demonstrated that in DSSAT mulching primarily affects the surface soil organic carbon content and secondly the total soil moisture content, since it is negatively correlated with simulated soil water evaporation and run-off. The correlations between the input parameters or crop management factors and the output variables were stable over a wide range of seasonal rainfall conditions. A local sensitivity analysis of simulated maize yield to three key parameters for the simulation of the CA practice revealed that DSSAT responds to mulching particularly when rooting depth is restricted, i.e., when water is a critical limiting crop growth factor. The results of this study demonstrate that DSSAT can be used to simulate crop responses to CA, in particular through simulated mulching effects on the soil water balance, but other, often site-specific, factors that are not modeled by DSSAT, such as plough pan formation under CP or improved soil structure under CA, may need to be considered in the model parameterization to reproduce the observed crop yield effects of CA versus CP.

Analysis of the Effects of Different Snow Cover Mulches on Spatio-temporal Variationsof Farmland Soil Moisture

<abstract> <b><i>Abstract. </i></b> We investigated the influence of snow cover on soil moisture in a seasonally frozen area in northern China. To do this, we performed a field test during one freeze-thaw cycle with four treatments of the test area: bare land, normal snow cover, compacted snow cover, and thick snow cover. Soil moisture depth, liquid moisture depth, frost depth, temperature, solar radiation, and other meteorological data were measured to obtain a comprehensive analysis. One-way ANOVA with Duncan‘s multiple ranges test was used to evaluate significant differences between soil moisture among all four treatments. The results demonstrated that the different snow cover treatments led to significantly different levels of soil moisture. Soil moisture accumulation area appeared obvious temporal and spatial distribution differences. However, snow cover effectively inhibited large magnitude temporal and spatial variations of the soil liquid moisture content. The feedback adjustment capability of the total soil moisture content showed that shallow profiles were more affected by different snow cover treatments than deep profiles. The compacted snow treatment was most effective for conserving soil moisture in shallow soil and improving the liquid moisture content of deep soil.

4D ground-penetrating radar during a plot scale dye tracer experiment

Flow phenomena in the unsaturated zone are highly variable in time and space. Thus, it is challenging to measure and monitor such processes under field conditions. Here, we present a new setup and interpretation approach for combining a dye tracer experiment with a 4D ground-penetrating radar (GPR) survey. Therefore, we designed a rainfall experiment during which we measured three surface-based 3D GPR surveys using a pair of 500MHz antennas. Such a survey setup requires accurate acquisition and processing techniques to extract time-lapse information supporting the interpretation of selected cross-sections photographed after excavating the site. Our results reveal patterns of traveltime changes in the measured GPR data, which are associated with soil moisture changes. As distinct horizons are present at our site, such changes can be quantified and transferred into changes in total soil moisture content. Our soil moisture estimates are similar to the amount of infiltrated water, which confirms our experimental approach and makes us confident for further developing this strategy, especially, with respect to improving the temporal and spatial resolution.

An RCM multi-physics ensemble over Europe: multi-variable evaluation to avoid error compensation

Regional Climate Models are widely used tools to add detail to the coarse resolution of global simulations. However, these are known to be affected by biases. Usually, published model evaluations use a reduced number of variables, frequently precipitation and temperature. Due to the complexity of the models, this may not be enough to assess their physical realism (e.g. to enable a fair comparison when weighting ensemble members). Furthermore, looking at only a few variables makes difficult to trace model errors. Thus, in many previous studies, these biases are described but their underlying causes and mechanisms are often left unknown. In this work the ability of a multi-physics ensemble in reproducing the observed climatologies of many variables over Europe is analysed. These are temperature, precipitation, cloud cover, radiative fluxes and total soil moisture content. It is found that, during winter, the model suffers a significant cold bias over snow covered regions. This is shown to be related with a poor representation of the snow-atmosphere interaction, and is amplified by an albedo feedback. It is shown how two members of the ensemble are able to alleviate this bias, but by generating a too large cloud cover. During summer, a large sensitivity to the cumulus parameterization is found, related to large differences in the cloud cover and short wave radiation flux. Results also show that small errors in one variable are sometimes a result of error compensation, so the high dimensionality of the model evaluation problem cannot be disregarded.

Spin-up behavior of soil moisture content over East Asia in a land surface model

This study presents an investigation of the spin-up behavior of soil moisture content (SMC) and evapotranspiration (ET) in an offline Noah land surface model (LSM) for East Asia, focusing on its interplay with the Asian monsoon. The set of 5-year recursive runs is conducted to properly assess the spin-up behavior of land surface processes and consists of simulations initialized with (1) a spatially uniform soil moisture, (2) NCEP GDAS soil moisture data, and (3) ECMWF ERA-Interim soil moisture data. Each run starts either after or before the summer monsoon. Initial SMCs from GDAS and ERA-Interim data significantly deviate from the equilibrium state (spin-up state) with the given input forcing even though the same equilibrium is reached within 3-year spin-up time, indicating that spin-up of land surface process is necessary. SMC reaches the equilibrium much quickly when (1) the consistent LSMs have been used in the prediction and analysis systems and (2) the spin-up simulation starts before the onset of heavy rainfall events during summer monsoon. For an area with heavy monsoon rainfall, the total column SMC and ET spin up quickly. The spin-up time over dry land is about 2–3 years, but for monsoon rainfall area decreases dramatically to about 3 months if the spin-up run starts just before the onset of monsoon. Further scrutiny shows that the spin-up time is well correlated with evaporative fraction given by the ratio between the latent heat flux and the available energy at the land surface.

From Near-Surface to Root-Zone Soil Moisture Using Year-Round Data

Passive microwave remote sensing may provide quantitative information about the water content of a shallow near-surface soil layer. However, the variable of interest for applications such as short- and medium-term meteorological modeling and hydrological studies over vegetated areas is the root-zone soil moisture, which controls plant transpiration. Because near-surface soil moisture is related to root-zone soil moisture through diffusion processes, assimilation algorithms may enable one to retrieve the total soil moisture content from observed surface soil moisture. A variational assimilation method is applied to a new dataset obtained over a fallowland in southwestern France in 1997 and 1998. The new database includes continuous automatic measurements of water content within the top 6-cm soil layer during a 17-month period from January 1997 to May 1998. Once calibrated, the Interactions between Soil, Biosphere, and Atmosphere (ISBA) surface scheme is able to simulate properly the measured surface variables and the root-zone soil moisture. It is shown that, knowing the atmospheric forcing (including the precipitation), four observations of the surface soil moisture spread out over a 9-day period are enough to retrieve the total soil water content by inverting ISBA and that only two observations are required during rainless periods.

A parameterization of snowpack and frozen ground intended for NCEP weather and climate models

Extensions to the land surface scheme (LSS) in the National Centers for Environmental Prediction, regional, coupled, land‐atmosphere weather prediction model, known as the mesoscale Eta model, are proposed and tested off‐line in uncoupled mode to account for seasonal freezing and thawing of soils and snow‐accumulation‐ablation processes. An original model assumption that there is no significant heat transfer during redistribution of liquid water was relaxed by including a source/sink term in the heat transfer equation to account for latent heat during phase transitions of soil moisture. The parameterization uses the layer‐integrated form of heat and water diffusion equations adopted by the original Eta‐LSS. Therefore it simulates the total ice content of each selected soil layer. Infiltration reduction under frozen ground conditions was estimated by probabilistic averaging of spatially variable ice content of the soil profile. Off‐line uncoupled tests of the new and original Eta‐LSS were performed using experimental data from Rosemount, Minnesota. Simulated soil temperature and unfrozen water content matched observed data reasonably well. Neglecting frozen ground processes leads to significant underestimation/overestimation of soil temperature during soil freezing/thawing periods and underestimates total soil moisture content after extensive periods of soil freezing.

Retrieving the Root-Zone Soil Moisture from Surface Soil Moisture or Temperature Estimates: A Feasibility Study Based on Field Measurements

Abstract The bulk soil water content must be estimated accurately for short- and medium-term meteorological modeling. A method is proposed to retrieve the total soil moisture content as well as the field capacity from observed surface parameters such as surface soil moisture or surface temperature. A continuous series of micrometeorological and soil water content measurements was obtained in southwestern France over a fallow site in 1995. In addition, the database includes measurements of the surface temperature and soil moisture profiles within the top 5-cm soil layer. The surface soil moisture measurements are available twice a day during two 30-day intensive observing periods in spring and autumn 1995. Once calibrated, the ISBA (Interactions between Soil, Biosphere, and Atmosphere) surface scheme is able to properly simulate the measured surface variables and the bulk soil moisture. Then an assimilation technique is applied to analyze the field capacity and the total soil water content from the surface...

The Canadian Forest Fire Weather Index System as a predictor of total soil moisture content as estimated by the Thornthwaite water balance

Weather data from Upsala and Atikokan, Ontario, were used to determine the Canadian Forest Fire Weather Index System values and to calculate the soil moisture for two soil types using the Thornthwaite water balance. The Duff Moisture Code and the Drought Code were found to give excellent correlations with the total soil moisture content under most weather patterns.

Zum vegetativen wachstum von weinreben in abhängigkeit von pedohydrologischen und klimatischen faktoren: Ergebnisse einer vergleichsstudie an zwölf testparzellen im Südbadischen weinbaugebiet

Summary On the relationship between the vegetative growth of vines and pedohydrological and climatic factors Results of a study comparing 12 test sites situated in the vine-growing area of Sudbaden (SW-Germany) During the growing periods of 1972 and 1973, investigations in twelve test sites were carried out, each having vines of the ‘Rulander’ variety and were situated in the viticultural areas of Breisgau, Kaiserstuhl-Tuniberg and Markgraflerland (Sudbaden). In order to obtain a broad variation in the soil moisture content as well as in climatic differentiation, the test sites were chosen on 1) loess, which had been consolidated and terraced to a large extent (Kaiserstuhl, Tuniberg, Vorbergzone), 2) limestone and marl mixed with loess (Markgraflerland), 3) volcanic weathering material (Kaiserstuhl) and 4) a mixture of sand and gravel from the lower terrace (Oberrheinebene). Each experimental site had 30 genetically homogenous vines of the ‘Rulander’ variety (Pinotgris). During the growing periods (hydrological summer half-years 1972 and 1973), topoclimatic and pedohydrological factors, (atmospheric and soil temperature, evaporation of a ceramic disk according to CZERATZKI, total soil water and the actual available soil moisture in the profile of the main root zone) were measured either continuously, or at weekly and fortnightly intervals. The following vegetative factors in vine development were ascertained: weight of pruning wood and topping foliage (from which the vegetative production is determined) as well as the length of three internodes. Grain size and pore space distribution were plotted for characteristic sites. In order to ascertain the soil water actually available to the plants, the total soil moisture content, measured by means of a neutron probe, was reduced by subtracting the amount of bound water, which had been diverted, according to the methods developed by HARTGE (1969) and RENGER (1972) . The air capacity of soil was derived from the pore space distribution. By means of statistical evaluation, multiple linear regression and correlation calculations are discussed, taking into consideration the most significant dependent variables for ‘vegetative growth’ (weight of pruning wood and topping foliage, length of the 3 internodes of segment no. 6, and the vegetative production) in biological and hydrological relation to the abovementioned climatic and pedohydrological factors. The following relations were detected: 1) Evaporation of the ceramic disk according to CZERATZKI has, generally, the most influence; therefore, with increased evaporation, the weight of pruning wood and topping foliage and consequently vegetative growth is reduced, and the length of the three internodes of segment no. 6 is shortened. 2) In both experimental years, the effectiveness of soil water proved to be the second most important influence. Increased soil water content available to plants produced an increased vegetative growth of the vines. In the relatively dry year of 1972, a greater significance in the effectiveness of soil water was noticed. With the increased soil moisture in th year 1973, the soil water was of less significance. Therefore, the effect of the air capacity of the soil on vine is indicated. Attention is drawn to further coherence between vegetative growth strength and yield development and consequently the wine quality.

Soil water relations and relative turgidity on leaves in the wheat crop

Trials were conducted in 1961 and 1962 at Wagga in southern New South Wales to investigate the yield physiology of the wheat crop. Various cultural treatments were applied to a single variety (Heron). The increases in evapotranspiration and associated reductions in total soil moisture content caused by early sowing, by heavier fertilizer applications, and to a lesser extent by a heavier rate of sowing were reflected in an increased plant moisture stress (reduced leaf relative turgidity) at a given time in the spring. At a given stage of development, however, relative turgidity was not much affected by time of sowing, and in fact post-flowering plant moisture stress increased with later sowing. There were only small treatment effects on the estimated depth and density of rooting. Relatively little water was extracted by crops from below 40 in.; dense crops reduced the soil moisture content throughout the root zone to less than the –15 bar value. Leaf relative turgidity at sunrise showed a consistent inverse relationship to soil moisture content in the root zone. Leaf turgidity (sunrise) was maintained at 100% until root zone moisture levels approached the –15 bar value.