Some aspects of soil shrinkage and the effect of cracking upon water entry into the soil.

1954 ◽  
Vol 5 (2) ◽  
pp. 279 ◽  
Author(s):  
GB Stirk
Keyword(s):  
Soil Water ◽  
Soil Aggregates ◽  
Water Entry ◽  
Water Withdrawal ◽  
Natural Soil ◽  
Structural Development ◽  
Continuous Irrigation ◽  
Suitable Index ◽  
Water Contents ◽  
Soil Water Contents

The shrinkage of natural soil aggregates that accompanies water withdrawal has been examined. Four main stages operate: (1) structural shrinkage, (2) normal shrinkage, (3) residual shrinkage, (4) no shrinkage: The pF ranges over which these stages operate and the fraction that they constitute of the total shrinkage has been measured for a range of soils. The influence of structure and texture upon shrinkage was assessed. These affect both the shrinkage phase and the range over which it operates. Structural development affects shrinkage markedly, giving a very different shrinkage pattern from that found for puddled soil or remoulded soil blocks. The difference in porosity between a natural aggregate and a puddled block of the same soil corresponding to a definite pF value is suggested, therefore, as a means of assessing the degree of structural development in the soil. It provides a suitable index for assessing the rate of structure improvement under various ameliorative treatments. The influence of cracking in increasing the rate of water entry into fine textured soils is discussed. In the particular cases of irrigated soils, where soil water contents are maintained at relatively high levels (above wilting point), it seems that cracking may not have progressed sufficiently to compensate for the low inherent permeability of such soils. Cultivation of the surface soil to form a mulch before irrigation tends to eliminate any contribution to conduction by the smaller cracks which are present at higher soil water contents. Large increases in permeability, due to the presence of gross soil cracks, are attained only when water contents are reduced to levels which are not practicable in continuous irrigation culture.

Implications of root exudates on the formation of rhizosheaths

2020 ◽  
Author(s):  
Riffat Rahim ◽  
Adrian Haupenthal ◽  
Eva Kroener
Keyword(s):  
Rheological Properties ◽  
Soil Water ◽  
Root Exudates ◽  
Plant Root ◽  
Soil Aggregates ◽  
Aggregate Stability ◽  
Adhesion Properties ◽  
Drying And Wetting Cycles ◽  
Water Contents ◽  
Soil Water Contents

<p>Root exudates stimulate microbial activity and functions as a binding and adhesive agent that increases aggregate stability in the rhizosphere. The exudates produced from plant roots and microorganisms in the rhizosphere play a significant role in the formation of rhizosheath. Rhizosheaths comprises the soil that adheres to the roots with the help of root hair and mucilage even when it is removed from the surrounding soil. Low surface tension and great viscosity stabilize soil aggregates in surrounding root and develop rhizosheath formation. To our knowledge, no investigations are made on the influence of root exudates in soil rhizosheath formation, although it is well documented the formation and stabilization of rhizosheath of maize plants under various soil water contents but the influence of root exudates on the rhizosheath formation associated with other rheological properties is still missing. Such knowledge will greatly enhance the understanding of how rhizosheath is formed under different root and seed exudates and the effect of their physiochemical properties on the adhesion properties of mucilage will be studied in this project.</p><p>The aim of this study is to provide the first combined quantitative data on how root and seed exudates of different plants affect rhizosheath formation. We hypothesized that mucilage will contribute to the formation of rhizosheaths.  For this, we will use the mucilage of chia seeds which acts as a modelled plant root mucilage and mix it with soil in five different concentrations. After preparing the soil with mucilage, artificial roots (flax cords) will be incorporated in this soil and after drying and wetting cycles roots will be removed and the mucilage adhesion, simulation and rheological properties will be investigated under various soil water contents, soil texture, soil type, and soil compaction.</p><p><strong>Key words:</strong></p><p>                   Rhizosheath, mucilage, drying and wetting cycles and soil structure</p><p> </p>

scholarly journals The Effect of Irrigation Rate on the Water Relations of Young Citrus Trees in High-Density Planting

2021 ◽  
Vol 13 (4) ◽  
pp. 1759
Author(s):  
Said A. Hamido ◽  
Kelly T. Morgan
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Soil Salinity ◽  
Planting Density ◽  
Stem Water Potential ◽  
Irrigation Rate ◽  
Biological Stress ◽  
Stem Water ◽  
Water Contents ◽  
Soil Water Contents

The availability and proper irrigation scheduling of water are some of the most significant limitations on citrus production in Florida. The proper volume of citrus water demand is vital in evaluating sustainable irrigation approaches. The current study aims to determine the amount of irrigation required to grow citrus trees at higher planting densities without detrimental impacts on trees’ water relation parameters. The study was conducted between November 2017 and September 2020 on young sweet orange (Citrus sinensis) trees budded on the ‘US-897’ (Cleopatra mandarin x Flying Dragon trifoliate orange) citrus rootstock transplanted in sandy soil at the Southwest Florida Research and Education Center (SWFREC) demonstration grove, near Immokalee, Florida. The experiment contained six planting densities, including 447, 598, and 745 trees per ha replicated four times, and 512, 717, and 897 trees per ha replicated six times. Each density treatment was irrigated at 62% or 100% during the first 15 months between 2017 and 2019 or one of the four irrigation rates (26.5, 40.5, 53, or 81%) based on the calculated crop water supplied (ETc) during the last 17 months of 2019–2020. Tree water relations, including soil moisture, stem water potential, and water supplied, were collected periodically. In addition, soil salinity was determined. During the first year (2018), a higher irrigation rate (100% ETc) represented higher soil water contents; however, the soil water content for the lower irrigation rate (62% ETc) did not represent biological stress. One emitter per tree regardless of planting density supported stem water potential (Ψstem) values between −0.80 and −0.79 MPa for lower and full irrigation rates, respectively. However, when treatments were adjusted from April 2019 through September 2020, the results substantially changed. The higher irrigation rate (81% ETc) represented higher soil water contents during the remainder of the study, the lower irrigation rate (26.5% ETc) represents biological stress as a result of stem water potential (Ψstem) values between −1.05 and −0.91 MPa for lower and higher irrigation rates, respectively. Besides this, increasing the irrigation rate from 26.5% to 81%ETc decreased the soil salinity by 33%. Although increasing the planting density from 717 to 897 trees per hectare reduced the water supplied on average by 37% when one irrigation emitter was used to irrigate two trees instead of one, applying an 81% ETc irrigation rate in citrus is more efficient and could be managed in commercial groves.

MITIGATION YIELD SCALED METHANE EMISSION FROM RICE GROWN IN WATER STRESS CONDITIONS WITH BIOCHAR AND SILICATE AMENDMENTS

2021 ◽  
Author(s):  
MUHAMMAD ASLAM ALI ◽  
SANJIT CHANDRA BARMAN ◽  
MD. ASHRAFUL ISLAM KHAN ◽  
MD. BADIUZZAMAN KHAN ◽  
HAFSA JAHAN HIYA
Keyword(s):  
Water Stress ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Field Capacity ◽  
Saturated Soil ◽  
Rice Grain ◽  
Standing Water ◽  
Water Contents ◽  
Soil Water Contents

Climate change and water scarcity may badly affect existing rice production system in Bangladesh. With a view to sustain rice productivity and mitigate yield scaled CH4 emission in the changing climatic conditions, a pot experiment was conducted under different soil water contents, biochar and silicate amendments with inorganic fertilization (NPKS). In this regard, 12 treatments combinations of biochar, silicate and NPKS fertilizer along with continuous standing water (CSW), soil saturation water content and field capacity (100% and 50%) moisture levels were arranged into rice planted potted soils. Gas samples were collected from rice planted pots through Closed Chamber technique and analyzed by Gas Chromatograph. This study revealed that seasonal CH4 emissions were suppressed through integrated biochar and silicate amendments with NPKS fertilizer (50–75% of the recommended doze), while increased rice yield significantly at different soil water contents. Biochar and silicate amendments with NPKS fertilizer (50% of the recommended doze) increased rice grain yield by 10.9%, 18.1%, 13.0% and 14.2%, while decreased seasonal CH4 emissions by 22.8%, 20.9%, 23.3% and 24.3% at continuous standing water level (CSW) (T9), at saturated soil water content (T10), at 100% field capacity soil water content (T11) and at 50% field capacity soil water content (T12), respectively. Soil porosity, soil redox status, SOC and free iron oxide contents were improved with biochar and silicate amendments. Furthermore, rice root oxidation activity (ROA) was found more dominant in water stress condition compared to flooded and saturated soil water contents, which ultimately reduced seasonal CH4 emissions as well as yield scaled CH4 emission. Conclusively, soil amendments with biochar and silicate fertilizer may be a rational practice to reduce the demand for inorganic fertilization and mitigate CH4 emissions during rice cultivation under water stress drought conditions.

scholarly journals Effect of Nano-Carbon on Water Holding Capacity in a Sandy Soil of the Loess Plateau

2017 ◽  
Vol 21 (4) ◽  
pp. 189-195 ◽  
Author(s):  
Beibei Zhou ◽  
Xiaopeng Chen
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Loess Plateau ◽  
Sandy Soil ◽  
Water Retention ◽  
Soil Mixture ◽  
Cumulative Infiltration ◽  
Nano Carbon ◽  
Water Contents ◽  
Soil Water Contents

The poor water retention capacity of sandy soils commonly aggregate soil erosion and ecological environment on the Chinese Loess Plateau. Due to its strong capacity for absorption and large specific surface area, the use of nanocarbon made of coconut shell as a soil amendment that could improve water retention was investigated. Soil column experiments were conducted in which a layer of nanocarbon mixed well with the soil was formed at a depth of 20 cm below the soil surface. Four different nanocarbon contents by weight (0%, 0.1%, 0.5%, and 1%) and five thicknesses of the nanocarbon- soil mixture layer ranging from 1 to 5 cm were considered. Cumulative infiltration and soil water content distributions were determined when water was added to soil columns. Soil Water Characteristic Curves (SWCC) were obtained using the centrifuge method. The principal results showed that the infiltration rate and cumulative infiltration increased with the increases of nanocarbon contents, to the thicknesses of the nano carbon-soil mixture layer. Soil water contents that below the soil-nano carbon layer decreased sharply. Both the Brooks-Corey and van Genuchten models could describe well the SWCC of the disturbed sandy soil with various nano carbon contents. Both the saturated water content (θs), residual water content (θr) and empirical parameter (α) increased with increasing nano carbon content, while the pore-size distribution parameter (n) decreased. The available soil water contents were efficiently increased with the increase in nanocarbon contents.

Sustainable Covers for Uranium Mill Tailings, USA: Alternative Design, Performance, and Renovation

2009 ◽  
Author(s):  
William J. Waugh ◽  
Craig H. Benson ◽  
William H. Albright
Keyword(s):  
Water Balance ◽  
Soil Water ◽  
Department Of Energy ◽  
Test Facility ◽  
Sagebrush Steppe ◽  
Natural Soil ◽  
Structural Development ◽  
Percent Cover ◽  
Mill Tailings ◽  
Uranium Mill Tailings

The U.S. Department of Energy Office of Legacy Management is investigating alternatives to conventional cover designs for uranium mill tailings. A cover constructed in 2000 near Monticello, Utah, USA, was a redundant design with a conventional low-conductivity composite cover overlain with an alternative cover designed to mimic the natural soil water balance as measured in nearby undisturbed native soils and vegetation. To limit percolation, the alternative cover design relies on a 160-cm layer of sandy clay loam soil overlying a 40-cm sand capillary barrier for water storage, and a planting of native sagebrush steppe vegetation to seasonally release soil water through evapotranspiration (ET). Water balance monitoring within a 3.0-ha drainage lysimeter, embedded in the cover during construction, provided convincing evidence that the cover has performed well over a 9-year period (2000–2009). The total cumulative percolation, 4.8 mm (approximately 0.5 mm yr−1), satisfied a regulatory goal of <3.0 mm yr−1. Most percolation can be attributed to the very wet winter and spring of 2004–2005, when soil water content exceeded the storage capacity of the cover. Diversity, percent cover, and leaf area of vegetation increased over the monitoring period. Field and laboratory evaluations several years after construction show that soil structural development, changes in soil hydraulic properties, and development of vegetation patterns have not adversely impacted cover performance. A new test facility was constructed in 2008 near Grand Junction, Colorado, USA, to evaluate low-cost methods for renovating or transforming conventional covers into more sustainable ET covers.

Diffusivity and sorptivity determination at different soil water contents from horizontal infiltration

Geoderma ◽  
2019 ◽  
Vol 338 ◽  
pp. 88-96 ◽  
Author(s):  
Rafael Villarreal ◽  
Luis A. Lozano ◽  
Esteban M. Melani ◽  
María Paz Salazar ◽  
María Florencia Otero ◽  
...  
Keyword(s):  
Soil Water ◽  
Horizontal Infiltration ◽  
Water Contents ◽  
Soil Water Contents

Soil water contents for tillage: A comparison of approaches and consequences for the number of workable days

2019 ◽  
Vol 195 ◽  
pp. 104384 ◽  
Author(s):  
Peter Bilson Obour ◽  
Thomas Keller ◽  
Johannes L. Jensen ◽  
Gareth Edwards ◽  
Mathieu Lamandé ◽  
...  
Keyword(s):  
Soil Water ◽  
Water Contents ◽  
Soil Water Contents

scholarly journals An empirical model for describing the influence of water content and concentration of sulfamethoxazole (antibiotic) in soil on the total net CO2 efflux

2020 ◽  
Vol 68 (4) ◽  
pp. 351-358
Author(s):  
Miroslav Fér ◽  
Radka Kodešová ◽  
Barbora Kalkušová ◽  
Aleš Klement ◽  
Antonín Nikodem
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Solution Treatment ◽  
Soil Microbial Activity ◽  
Soil Samples ◽  
Co2 Efflux ◽  
The Impact ◽  
Water Contents ◽  
Soil Water Contents

AbstractThe aim of the study was to describe the impact of the soil water content and sulfamethoxazole, SUL, (antibiotic) concentration in soil on the net CO2 efflux. Soil samples were taken from topsoils of a Haplic Fluvisol and Haplic Chernozem. Soil samples were packed into the steel cylinders. The net CO2 efflux was measured from these soil columns after application of fresh water or SUL solution at different soil water contents. The experiments were carried out in dark at 20°C. The trends in the net CO2 efflux varied for different treatments. While initially high values for water treatment exponentially decreased in time, values for solution treatment increased during the first 250–650 minutes and then decreased. The total net CO2 effluxes measured for 20 hours related to the soil water content followed the second order polynomial functions. The maximal values were measured for the soil water content of 0.15 cm3 cm−3 (Haplic Fluvisol with water or solution, Haplic Chernozem with solution) and 0.11 cm3 cm−3 (Haplic Chernozem with water). The ratios between values measured for solution and water at the same soil water contents exponentially increased with increasing SUL concentration in soils. This proved the increasing stimulative influence of SUL on soil microbial activity.

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