Development and analysis of the Soil Water Infiltration Global database

In this paper, we present and analyze a novel global database of soil infiltration measurements, the Soil Water Infiltration Global (SWIG) database. In total, 5023 infiltration curves were collected across all continents in the SWIG database. These data were either provided and quality checked by the scientists who performed the experiments or they were digitized from published articles. Data from 54 different countries were included in the database with major contributions from Iran, China, and the USA. In addition to its extensive geographical coverage, the collected infiltration curves cover research from 1976 to late 2017. Basic information on measurement location and method, soil properties, and land use was gathered along with the infiltration data, making the database valuable for the development of pedotransfer functions (PTFs) for estimating soil hydraulic properties, for the evaluation of infiltration measurement methods, and for developing and validating infiltration models. Soil textural information (clay, silt, and sand content) is available for 3842 out of 5023 infiltration measurements ( ∼ 76%) covering nearly all soil USDA textural classes except for the sandy clay and silt classes. Information on land use is available for 76% of the experimental sites with agricultural land use as the dominant type ( ∼ 40%). We are convinced that the SWIG database will allow for a better parameterization of the infiltration process in land surface models and for testing infiltration models. All collected data and related soil characteristics are provided online in *.xlsx and *.csv formats for reference, and we add a disclaimer that the database is for public domain use only and can be copied freely by referencing it. Supplementary data are available at https://doi.org/10.1594/PANGAEA.885492 (Rahmati et al., 2018). Data quality assessment is strongly advised prior to any use of this database. Finally, we would like to encourage scientists to extend and update the SWIG database by uploading new data to it

BIOPHYSICAL CONTROLS ON RHIZOSPHERE DYNAMICS

Soil structure directly determines important soil physical properties including porosity, hydraulic conductivity, water retention, and mechanical strength. It also indirectly influences almost all biological and chemical processes that occur in soil. Conversely, the development, stability, and dynamics of soil structure are dictated by the very physical, chemical, and biological processes that occur within the structured soil. There is ample empirical evidence showing the effectiveness of wetting and drying in the presence of organic matter in soil aggregation and stabilization. However, the mechanisms that bond the particles together under this process need more investigation. The goal of this dissertation was to understand and develop quantitative description of the role of wetting and drying cycles in presence of exudates in the formation and stabilization of soil aggregates within the rhizosphere.In this dissertation, I (a) developed a new, easy and rapid method to measure the carbohydrate and total carbon concentrations using UV spectrophotometry, (b) examined whether the association between plant root and bacteria exudates with neutral sand particles occurred and defined the mechanism of this association, (c) developed a conceptual/mathematical model describe the soil aggregation mechanism in presence of exudates under multiple wetting and drying cycles, (d) examined the mechanisms that affect rhizosphere water dynamics and whether these dynamics are a result of the osmotic potential induced by root exudates or the soil structure modification that occurred because of these exudates, and (e) developed a mathematical model to quantitatively describe the experimental results of the effect of water potential induced by root exudates on water evaporation rate.This dissertation presented a framework for in-depth understanding on how wetting and drying cycles in the presence of exudates promote soil aggregation and stabilization within the rhizosphere. It also advanced our understanding of the benefits of presence of root exudates in the rhizosphere on water retention and evaporation rate and provided the right-scale physics for high resolution computational modeling of water dynamics around the plant roots and root water uptake

BIOPHYSICAL CONTROLS ON RHIZOSPHERE DYNAMICS

Soil structure directly determines important soil physical properties including porosity, hydraulic conductivity, water retention, and mechanical strength. It also indirectly influences almost all biological and chemical processes that occur in soil. Conversely, the development, stability, and dynamics of soil structure are dictated by the very physical, chemical, and biological processes that occur within the structured soil. There is ample empirical evidence showing the effectiveness of wetting and drying in the presence of organic matter in soil aggregation and stabilization. However, the mechanisms that bond the particles together under this process need more investigation. The goal of this dissertation was to understand and develop quantitative description of the role of wetting and drying cycles in presence of exudates in the formation and stabilization of soil aggregates within the rhizosphere.In this dissertation, I (a) developed a new, easy and rapid method to measure the carbohydrate and total carbon concentrations using UV spectrophotometry, (b) examined whether the association between plant root and bacteria exudates with neutral sand particles occurred and defined the mechanism of this association, (c) developed a conceptual/mathematical model describe the soil aggregation mechanism in presence of exudates under multiple wetting and drying cycles, (d) examined the mechanisms that affect rhizosphere water dynamics and whether these dynamics are a result of the osmotic potential induced by root exudates or the soil structure modification that occurred because of these exudates, and (e) developed a mathematical model to quantitatively describe the experimental results of the effect of water potential induced by root exudates on water evaporation rate.This dissertation presented a framework for in-depth understanding on how wetting and drying cycles in the presence of exudates promote soil aggregation and stabilization within the rhizosphere. It also advanced our understanding of the benefits of presence of root exudates in the rhizosphere on water retention and evaporation rate and provided the right-scale physics for high resolution computational modeling of water dynamics around the plant roots and root water uptake

Assessment of the Effect of Irrigation with Treated Wastewater on Soil Properties and on the Performance of Infiltration Models

An alternative strategy for saving limited water resources is using treated wastewater (TWW) originating from wastewater treatment plants. However, using TWW can influence soil properties owing to its characteristics compared to conventional water resources. Therefore, assessing the effect of TWW on soil properties and soil water infiltration is crucial to maintain sustainable use of TWW and to increase the water use efficiency of the precious irrigation water. Moreover, several studies were carried out to assess the performance of infiltration models. However, few studies evaluate infiltration models under the use of treated wastewater. Therefore, this study aims to assess the effect of TWW irrigation on soil properties after 2 and 5 years and to evaluate five classical infiltration models with field data collected from soil irrigated by treated wastewater for their capability in predicting soil water infiltration. This study revealed that using TWW for irrigation affects significantly on soil properties after 2 and 5 years. The soil irrigated with TWW had significantly higher electrical conductivity, organic matter, sodium adsorption ratio, cation exchange capacity, and lower soil bulk density compared to control. The basic infiltration rate and cumulative infiltration decreased significantly compared to control (60.84, 14.04, and 8.42 mm hr−1 and 140 mm, 72 mm, and 62 mm for control, 2, and 5 years’ treatments, respectively). The performance of the infiltration models proposed by Philip, Horton, Kostiakov, Modified Kostiakov, and the Natural Resources Conservation Service was evaluated with consideration of mean error, root mean square error, model efficiency, and Willmott’s index. Horton model had the lowest mean error (0.0008) and Philip model had the lowest root mean square error (0.1700) while Natural Resources Conservation Service had the highest values (0.0433 and 0.5898) for both mean error and root mean square error, respectively. Moreover, Philip model had the highest values of model efficiency and Willmott’s index, 0.9994 and 0.9998, respectively, whereas Horton model had the lowest values for the same indices, 0.9869 and 0.9967, respectively. Philip model followed by Modified Kostiakov model were the most efficient models in predicting cumulative infiltration, while Natural Resources Conservation Service model was the least predictable model

Assessment of the Effect of Irrigation with Treated Wastewater on Soil Properties and on the Performance of Infiltration Models

An alternative strategy for saving limited water resources is using treated wastewater (TWW) originating from wastewater treatment plants. However, using TWW can influence soil properties owing to its characteristics compared to conventional water resources. Therefore, assessing the effect of TWW on soil properties and soil water infiltration is crucial to maintain sustainable use of TWW and to increase the water use efficiency of the precious irrigation water. Moreover, several studies were carried out to assess the performance of infiltration models. However, few studies evaluate infiltration models under the use of treated wastewater. Therefore, this study aims to assess the effect of TWW irrigation on soil properties after 2 and 5 years and to evaluate five classical infiltration models with field data collected from soil irrigated by treated wastewater for their capability in predicting soil water infiltration. This study revealed that using TWW for irrigation affects significantly on soil properties after 2 and 5 years. The soil irrigated with TWW had significantly higher electrical conductivity, organic matter, sodium adsorption ratio, cation exchange capacity, and lower soil bulk density compared to control. The basic infiltration rate and cumulative infiltration decreased significantly compared to control (60.84, 14.04, and 8.42 mm hr−1 and 140 mm, 72 mm, and 62 mm for control, 2, and 5 years’ treatments, respectively). The performance of the infiltration models proposed by Philip, Horton, Kostiakov, Modified Kostiakov, and the Natural Resources Conservation Service was evaluated with consideration of mean error, root mean square error, model efficiency, and Willmott’s index. Horton model had the lowest mean error (0.0008) and Philip model had the lowest root mean square error (0.1700) while Natural Resources Conservation Service had the highest values (0.0433 and 0.5898) for both mean error and root mean square error, respectively. Moreover, Philip model had the highest values of model efficiency and Willmott’s index, 0.9994 and 0.9998, respectively, whereas Horton model had the lowest values for the same indices, 0.9869 and 0.9967, respectively. Philip model followed by Modified Kostiakov model were the most efficient models in predicting cumulative infiltration, while Natural Resources Conservation Service model was the least predictable model

Effect of hydrogel on corn growth, water use efficiency, and soil properties in a semi-arid region

Most countries, particularly those in arid and semi-arid regions, are grappling with important agricultural production issues that influenced by rapid population growth and limited water resources. The application of soil additives to improve soil properties and water usage productivity has sparked the most attention, particularly in arid and semi-arid environments. The goal of this study was to assess the effect of hydrogel on soil physical properties and plant growth parameters using sandy and silty clay loam soils. Laboratory experiments were implemented using ten different concentrations of hydrogel based on the percentage of the added hydrogel (0, 0.02, 0.04, 0.07, 0.09, 0.11, 0.16, 0.22, 0.27 and 0.33% (w/w) hydrogel/soil) to assess its effect on soil physical and hydraulic properties. Moreover, a greenhouse pot experiment was conducted using four hydrogel concentrations of 0, 0.25, 0.5, and 1% (w/w) on Zea mays as a model plant to assess its effect on plant growth parameters. Results revealed that the greatest improvement in soil aggregate percentage was 35% with 0.27% hydrogel concentration whereas, 0.33% hydrogel concentration increased the soil available water by 49%. Moreover, water use efficiency was increased from 13% to 41% for sandy soil and from 35% to 67% for silty clay loam soil. In addition, when compared to the control, both soils' water use efficiency and corn growth rose. In agriculture, hydrogel can improve soil physical properties while also boosting water use efficiency and plant development parameters in dry and semi-arid areas

Molecular Characterization of Tomato (Solanum lycopersicum L.) Accessions under Drought Stress

Exploring the genetic diversity among plant accessions is important for conserving and managing plant genetic resources. In the current study, a collection of forty-six tomato accessions from Jordan were evaluated based on their performance and their morpho-physiological, in addition to molecularly characterizing to detect genetic diversity. Tomato accessions seedlings were exposed to drought stress with 70% field capacity and 40% field capacity under field conditions in Jordan. Drought stress had significantly negatively influenced the dry root weight, fresh root weight, root growth rate, fresh shoot weight, dry shoot weight, and shoot growth rate. Moreover, proline content showed a highly significant increase of 304.2% in response to drought stress. The analysis of twenty morphological characters revealed a wide range of variations among tomato accessions. Accessions were screened with fourteen SSR primers; six primers were informative to explain the genetic diversity. Based on resolving power, primers LEct004 and LEat018 were most significant with all 46 accessions. Interestingly, polymorphic information content (PIC) values ranged from 0.00 (Asr2 marker) to 0.499 (LEct004), which confirms that the SSR markers are highly informative. Our findings provide new insights into using informative molecular markers to elucidate such wide genetic variation discovered in our collections from Afraa and Abeel (the southern part of Jordan). Interestingly, the SSR markers were associated with genes, e.g., LEat018 with ACTIN_RELATED PROTEIN gene, the LEct004 with the HOMEOBOX PROTEIN TRANSCRIPTION FACTORS gene, and Asr2 with ABA/WDS. Moreover, the AUXIN RESPONSE FACTOR8 gene was associated with the LEta014 SSR marker and the LEta020 with the THIOREDOXIN FAMILY TRP26 gene. Therefore, the genetic diversity analysis and functional annotations of the genes associated with SSR information obtained in this study provide valuable information about the most suitable genotype that can be implemented in plant breeding programs and future molecular analysis. Furthermore, evaluating the performance of the collection under different water regimes is essential to produce new tomato varieties coping with drought stress conditions

Evaluating the Impact of Pre-Anthesis Water Deficit on Yield and Yield Components in Triticale (X Triticosecale Wittmak) Genotypes under Controlled Environmental Conditions

The purpose of this study was to measure the impacts of pre-anthesis drought during reproductive stages (GS31 and GS39) on triticale (X Triticosecale wittmak) yield and yield components. Four triticale genotypes (2 Local, and 2 from the USA) were exposed to pre-anthesis drought stress at both of stem elongation stage (B-treatment) and flag leaf emergence stage (C-treatment). Grain yield was not affected by pre-anthesis stress. Under no stress conditions (A-treatment), a strong correlation between grain yield and the number of grains per plant and plant height was detected. Under B-treatment, yield was negatively correlated with spike length and under C-treatment, yield was positively correlated with the number of grains per plant. The number of grains per plant, thousand grain weight, and harvest index were also not affected by drought stresses. This implied that the tested genotypes were drought tolerant since they form a large number of tillers, and when subjected to pre-anthesis drought it helps the plants to cover the soil surface and reduce water evaporation. JU and S1 showed fast pre-anthesis growth (early flowering cultivars) which makes them favored for further breeding. while N1 and N2 had slow pre-anthesis growth (late flowering cultivars) which enabled them to store more photosynthate pre-anthesis, which might compensate for the pre-anthesis drought effect on them