Biochar-Improved Growth and Physiology of Ehretia asperula under Water-Deficit Condition

Ehretia asperula’s physiological responses to growth performance following oak-wood biochar application under water stress conditions (WSC) and no water stress conditions (non-WSC) were investigated in a pot experiment. Biochar (WB) was incorporated into the soil at concentrations of 0, 5, 10, 15, and 20 tons ha−1 before transplanting Ehretia asperula in the pots. One month after transplanting, Ehretia asperula plants were put under water stress by withholding water for ten days. Water stress significantly decreased the growth and physiology of Ehretia asperula. Under WSC, the application of WB at the concentrations of 15 and 20 tons ha−1 to the soil increased the plant height; number of leaves; fresh and dry weight of the roots, shoots, and leaves; Fv/Fm; chlorophyll content; leaf relative water content; and soil moisture as well as decreased the relative ion leakage. The application of WB enhanced drought tolerance in Ehretia asperula plants by lowering the wilting point. The findings suggest that WB application at the concentration of 15 tons ha−1 could be recommended for ensuring the best physiological responses and highest growth of Ehretia asperula plants.

Evaluation of Water Content in Soils of Žitný Ostrov from the Point of View of Its Exploitation for Biosphere

The lithospheric zone between the soil surface and the first ground water horizon, respectively the ground water table, has a character of three-phase system. It consists of solid phase having fine to rough disperse granularity. This creates a structure of porous environment with characters that can be physically determined. The water occurs in pores in different forms of state and its bond with solid phase. Its energetic bond is clearly quantified by means of moisture retention curve. The gas phase fills pores with the water up to the value of the full porosity, i.e. it fills the part of pores that is not saturated with water. Therefore, this lithospheric zone is called the soil aeration zone. The volume of water occurring in the soil aeration zone corresponds to the concentration of water in the framework of hydrological cycle components. This water serves as the water resource for the vegetation cover. The data used for calculation were particular soil types in the area, depth of ground water table, hydrolimits (wilting point, point of decreased availability, field water capacity) and aeration zone thickness. The water content in the soil aeration zone between hydrolimits field water capacity (FWC) and wilting point (WP) is the critical interval of water content for vegetation cover in a given locality. Water from this interval is available for the vegetation cover. This water has no properties of free water, and plants have to have a developed root system and such suction pressure, that is able to overcome the bond between water and soil. Calculated results were verified with the help of monitored water content. Both calculated and measured values of soil water content in the aeration zone show that the water content is affected by appurtenant soil type. The human activity in a landscape directly affects the dynamics of this water resource, either from quantitative or qualitative viewpoint. This affect is demonstrated by changes of the ground water regime, i.e. changes of ground water table and amplitude of its fluctuation. The paper brings results of water content evaluation in the soil aeration zone in the Žitný ostrov area.

Crop Response to Combined Availability of Soil Water and Its Salinity Level: Theory, Experiments and Validation on Golf Courses

The phenomenological expression showing crop yield to be directly dependent on water deficiency, under saline conditions, has encouraged a continued focus on salinity as a viable approach to increase crop yields. This work reassesses crop response to availability of saline soil water ASW in two stages (A) Develop a simple approach suggesting that permanent wilting point (WP) increases under high saline soil water tension and relative yield of Lettuce (Lactuca sativa L., var longifolia Lam., cv. Nevada) and maize (Zea Mays L., cv. Jubilee sweet) decrease. (B) Using a deterministic numerical soil water model to validate the theory on Bermuda grass of golf courses. The experimental plots were established in the North Negev, Israel (Sweet corn) and the Algarve, Portugal (Lettuce and Bermuda grass covering the golf courses). Sprinkler irrigation and line source techniques were used for water application, creating a saline gradient under a precise irrigation water distribution. Two salinity empirical models were tested (Mass and Hoffman MH and van Genuchten–Gupta vGG). Their empirical models were modified and instead of soil electrical conductivity of irrigation water (ECe) we used wilting point (WP) and RASW to follow the changes in relative yield. The validation was conducted with theoretical soil plant atmosphere water (SPAW) to predict the results on golf courses. It is concluded that an alternative S-shaped response model provides better fit to our experimental data sets. Modified MH model (Yr = Y/Ymax = a* (ASW–threshold’s constant) revealed that a single dimensionless curve could be used to express yield—salinity interference when represented by varying ASW. The vGG model: vGG can represent salt tolerance of most crops, by using varying wilting point of average root zone salinity, at which the yield has declined by 50%. The abscissa of both models was based on WP rather than the standard soil electrical conductivity (ECw). The correlation between the experimental data and WP or relative available soil water (RASW) was acceptable and, therefore, their usefulness for prediction of relative yield is acceptable as well. The objectives of this study were: 1. To develop a simple model describing the effect of salinity through soil water availability on crop production; 2. To replace the standard varying soil electrical conductivity ECe used by MH and vGG models by two soil parameters (at wilting point- θwp and at field capacity ϴfc) in order to describe the relationship between them and relative yield. 3. Validate the new model with respect to independent salinity on Golf courses and a mathematical deterministic model.

Development and Evaluation of Pedotransfer Functions to Estimate Soil Moisture Content at Field Capacity and Permanent Wilting Point for South African Soils

This study was undertaken to develop new pedotransfer functions (PTFs) for the estimation of soil moisture content at field capacity (FC, at −33 kPa) and permanent wilting point (PWP, at −1500 kPa) for South African soils based on easily measurable soil physico-chemical properties. The new PTFs were developed using stepwise multiple linear regressions with the dependent variable (either FC or PWP) against clay, silt, sand and soil organic carbon (SOC) content from a total of 3171 soil horizons as the explanatory variables. These new PTFs were evaluated and compared with five well-established PTFs using a total of 3136 soil horizons as an independent dataset. The coefficient of determination (r2) values for the existing PTFs ranged from 0.65–0.72 for FC and 0.72–0.81 for PWP, whilst those developed in this study were 0.77 and 0.82 for FC and PWP, respectively. The root mean square error (RMSE) values for the well-established PTFs ranged from 0.052–0.058 kg kg−1 for FC and 0.030–0.036 kg kg−1 for PWP, whilst those developed in this study were 0.047 and 0.029 kg kg−1 for FC and PWP, respectively. These findings suggest that PTFs derived locally using a large number of soil horizons acquired from different agro-climatic locations improved the estimation of soil moisture at FC and PWP. Due to the range of conditions and large soil datasets used in this study, it is concluded that these new PTFs can be applied with caution in other regions facing data scarcity but with similar soil types and climatic conditions.

Effects of Wheat and Rapeseed Production on Soil Water Storage in Mongolian Rangeland

In recent years, Mongolia has witnessed an increase in not only wheat fields, which have been present for a long time, but also rapeseed fields. This has led to increasing concerns about soil degradation due to inappropriate cultivation. This study aims to determine the impacts of rapeseed production on soil water storage in Mongolia. The soil water content and matric potential were measured in wheat and rapeseed fields and adjacent steppe rangeland for five years, including crop production and fallow years, and the soil water storages in the fields were compared. The results demonstrated that the matric potential below the root zone in the rapeseed field and both rangelands was drier than the wilting point, whereas the potential in the wheat field was usually almost the same or wetter than this point. The comparison of the amount of soil water storage during the fallow year with that of the adjacent rangeland showed it to be 5–10% higher for the wheat field and almost equal for the rapeseed field. Field management must consider the fact that rapeseed fields use more water than is required by wheat fields and that less water is stored during fallow periods.

Biochemical changes in black oat plants in response to water deficit under different temperatures

The black oat (Avena strigosa Schreb.) stands out as a forage of great importance in Brazilian agriculture. However, the productivity and quality of this forage can be affected by abiotic factors, such as temperature and water availability, which affect the physiological processes and facilitate the accumulation of free radicals (reactive oxygen species - ROS). Thus, the objective of this study was to understand the biochemical changes in black oat plants subjected to water deficit at different temperatures. Experiments were conducted in a greenhouse in two experimental periods, which presented an average temperature of 20 °C and 24 °C, respectively. Black oat seeds, of the variety IAPAR 61, were sown in pots and the plants were irrigated for 60 days. After which, the pots were covered with plastic bags and the irrigation was suspended. The analyses were carried out in five periods of evaluation - M1: plants before the suspension of irrigation, M2: plants at the first wilting point, M3: three days after plastic removal and irrigation return, M4: four days after M3 and before the second suspension of irrigation, and M5: the second wilting point. The levels of total protein and malondialdehyde (MDA), and the activity of the enzymes catalase (CAT) and ascorbate peroxidase (APX), were analyzed. The experimental design was completely randomized, with six replications, in a factorial scheme of average temperature × water management × periods of evaluation, and the means were compared by Tukey’s test at 5%. In response to water deficiency and temperature increase, black oat plants increased their levels of total soluble proteins, and there was greater lipid peroxidation due to the increase in malondialdehyde content. There was no change in the activity of the enzymes catalase and ascorbate peroxidase under water deficit, and these activities decreased with increasing temperature.

Effect of different types of soil tillage for sunflower on some soil physical characteristics. Part I: soil moisture

The investigation was carried out during 2014–2016 in the land of General Toshevo town in the South Dobrudzha region on slightly leached chernozem soil type. The effect of the types of soil tillage for sunflower given bellow was followed: ploughing at 24–26 cm, chisel-plough at 24–26 cm, disking with disk harrow at 10–12 cm and direct sowing (no-tillage) on the soil moisture content. Based on bulk density, wilting point and the determined soil moisture content the plant-available water was calculated. The additional soil tilths of the areas subjected to ploughing, chisel-ploughing and disking with disc harrow included double spring pre-sowing cultivation with harrowing. To destroy the emerging weeds in the variant with direct sowing, a total herbicide was applied. The soil moisture content was evaluated during three main stages of sunflower development: emergence, flowering and technical maturity. The investigated parameter was determined for each of the studied layers – 0–10, 10–20, 20–30, 30–40 and 40–60 cm. In years with normal amounts of rainfalls, no significant differences in the soil moisture under the different ways of soil tillage were observed. Conventional ploughing and tillage without turning of the soil layer contributed to accumulation of more moisture and to higher moisture storage down the soil profile under heavy and intensive rainfalls. Tillage without turning of the soil layer, minimal and no tillage maintained more and better soil moisture in years with limited precipitation and in periods of drought.

Tracking Changes on Soil Structure and Organic Carbon Sequestration after 30 Years of Different Tillage and Management Practices

Long-term field trials are essential for monitoring the effects of sustainable land management strategies for adaptation and mitigation to climate change. The influence of more than thirty years of different management is analyzed on extensive crops under three tillage systems, conventional tillage (CT), minimum tillage (MT), and no-tillage (NT), and with two crop rotations, monoculture winter-wheat (Triticum aestivum L.) and wheat-vetch (Triticum aestivum L.-Vicia sativa L.), widely present in the center of Spain. The soil under NT experienced the largest change in organic carbon (SOC) sequestration, macroaggregate stability, and bulk density. In the MT and NT treatments, SOC content was still increasing after 32 years, being 26.5 and 32.2 Mg ha−1, respectively, compared to 20.8 Mg ha−1 in CT. The SOC stratification (ratio of SOC at the topsoil/SOC at the layer underneath), an indicator of soil conservation, increased with decreasing tillage intensity (2.32, 1.36, and 1.01 for NT, MT, and CT respectively). Tillage intensity affected the majority of soil parameters, except the water stable aggregates, infiltration, and porosity. The NT treatment increased available water, but only in monocropping. More water was retained at the permanent wilting point in NT treatments, which can be a disadvantage in dry periods of these edaphoclimatic conditions.

Analiza fizikalnih lastnosti šotnega substrata

<p>Peat substrate is the main substrate for plant production, mainly for the cultivation of vegetable seedlings and ornamental plants. Peat has good water retention properties, low mass, low pH and is free from diseases and pests. The water retention properties are particularly important for optimizing irrigation and thus water consumption in plant production. We investigated the water retention properties of unused and used peat substrate and various mixtures with additives, as well as the occurrence of water repellency, as this influences water absorption into the substrate. Unused peat substrate and different mixtures retained between 3.4 % and 18.4 % more water than the used substrate. The daily water losses are lower for the used substrates that initially contain lower water content at full saturation. At tensions between 10 and 33 kPa, the unused peat substrate contained between 25 % and 32 % water. The wilting point (WP) for unused peat substrate (tension between 300 and 1500 kPa) was between 15 and 18 %. Peat substrate has a wide interval of field capacity and the transition from the field capacity to wilting point is fast (change in water content between 7 % and 10 %). After drying, the water repellency of both unused and used peat substrates increased.</p>

Comparison of the physical properties of soils belonging to different reference soil groups

Soil properties can be influenced by long-term agricultural management practices as described in pedological literature. In this study, selected physical properties (particle density and bulk density, total porosity, maximum capillary water capacity, minimum air capacity, field capacity, permanent wilting point and available water capacity) of topsoils from different reference soil groups (Cambisols, Luvisols, Fluvisols, Chernozems and Phaeozems, Leptosols, Stagnosols and Gleysols) were sampled and analysed in the years 2016–2017. The topsoil samples were taken from points of so-called S (specific) soil pits to be sampled from the General Soil Survey of Agricultural Soils (GSSAS) which was accomplished in the years 1961–1970. In addition, some of the properties were also compared with those measured during the GSSAS. Recognising the properties, only the particle density, the maximum capillary water capacity, the permanent wilting point and the available water capacity of the topsoil of the individual soil groups were statistically significantly (P &lt; 0.05) different. A comparison of the physical properties with those analysed after more than 40 years was performed, the bulk density increased and the total porosity decreased in the topsoil of the major part of the studied soil groups.