How to Retain Water in Soil Baby Diapers

Soil Water Retentivity

Soil water retention curves (SWRC), divers as soil water content equally a office of soil matric potential (Ψm), is a critical soil hydraulic property.

From: Advances in Agronomy , 2021

A review of time domain reflectometry (TDR) applications in porous media

Hailong He , ... Jialong Lv , in Advances in Agronomy, 2021

3.3.2 TDR-matric potential probe to determine soil water retention curves (SWRC)

Soil water retention curves (SWRC), divers every bit soil water content equally a function of soil matric potential ( Ψ _m), is a disquisitional soil hydraulic property. It is required to numerically simulate θ _five, water flow and solute transport, to schedule irrigation, and other soil and land direction endeavors (Wraith and Or, 2001). A multifariousness of straight measurement methods have been developed to mensurate SWRCs, including the hanging water column, pressure plate, tensiometers, centrifuge, dew betoken, thermal dissipation method, thermocouple psychrometer, VSA, and evaporation method (Cresswell et al., 2008; Dane and Hopmans, 2002; Klute, 1986; Romano and Santini, 2002; Scanlon et al., 2002). However, these methods vary in measurement range, accuracy, cost and portability. In situ, automatic and continuous measurement of SWRC is highly desirable, because dynamic changes in continuity of pore and pore-size distribution significantly affect the SWRC. Common ways to decide SWRC in situ requires paired water content and matric potential sensors. However, this approach suffers from errors associated with poor hydraulic coupling including unmatched spatiotemporal resolutions and incompatible measurement ranges. A probe that combines TDR with a tensiometer or with a fixed porous media (due east.thou., gypsum cake or porous ceramics) enables the simultaneous, automatic and continuous in situ measurement of SWRC values (i.e., water content and matric potential) in the same volume.

Vaz et al. (2002) coiled copper wires around the ceramic cup of a tensiometer (for matric potential measurement) to function as TDR for θ _v measurement (Fig. 15A ). Lungal and Si (2008) put a coiled TDR in a ceramic cup to make a coiled TDR matric potential probe (Fig. xvB). Whalley et al. (1994) and Baumgartner et al. (1994) used hollow stainless-steel tubes with a porous stainless-steel tip as TDR rods (Fig. 15C). The porous tip functioned every bit a tensiometer to measure soil water matric potential. The hollow TDR rod is continued with a pressure transducer arrangement to mensurate the soil matric potential effectually the porous tip. Nonetheless, Noborio et al. (1999) institute that almost of the TDR-matric potential methods were generally limited to the measurement range Ψ _m > − 0.085 MPa. Therefore, Noborio et al. (1999) combined TDR with a porous ceramic block (dental plaster) to simultaneously approximate matric potential, based on the θ _v of the porous cake, and θ _v of the soil (Fig. xvD). Their method extended the measurement range to − 1000 < Ψ _m < − 10 kPa. Or and Wraith (1999) arranged a set of commercially available porous ceramics plates along the axis of a TDR probe. More details of combined TDR with tensiometers or porous material are shown in Table 4.

Tabular array 4. Selected designs of time domain reflectometry (TDR) combined with matric potential probes.

No.	Source	TDR design	Matric potential sensing	Notes
1	Baumgartner et al. (1994)	2 rods: hollow stainless steel tubes, 13.i cm long, 3.9 mm i.d., vi.two mm o.d.	Stainless steel porous cup + pressure transducer	Vacuum pump was used to sample h2o in the hollow tube
ii	Whalley et al. (1994)	three rods: hollow aluminum tubes	Porous cup + rubber septum or force per unit area transducer	/
iii	Noborio et al. (1999)	2 stainless steel rods (1.6-mm bore, 25 mm apart and 51.4 mm long) soldered to 2 copper tubes (iii.2-mm bore, 5 mm apart and 50 mm long)	Porous media (gypsum block)	/
iv	Or and Wraith (1999)	3 rods: 150 mm long and 15 mm autonomously	Porous ceramic and plastic disks	0–−0.5 MPa
5	Wraith and Or (2001)	3 rods: 3.2-mm bore, 20 mm autonomously and 200 mm long	Previously characterized porous media (having like pore-size distribution with soils under measurement)	Using paired TDR probes
vi	Vaz et al. (2002)	Coiled TDR	/	/
vii	Lungal and Si (2008)	Coiled TDR	Porous media (ceramics)	0–−1.5 MPa
8	Moret-Fernández et al. (2008)	A zigzag copper rod (150-mm long, ii mm bore) vertically installed in a articulate plastic cylinder, half-dozen vertical copper rods (threescore-mm long, 2 mm diameter) arranged around the inner wall of the cylinder	Porous ceramic disks	0–−0.v MPa

The matric potential tin can be estimated from either permittivity or water content. Noborio et al. (1999) related TDR-measured permittivity of the gypsum to the soil h2o matric potential as:

(36) $ɛ_{gyp} = ɛ_{res} + (ɛ_{sat} - ɛ_{res}) \cdot {[\frac{1}{{(1 +| α \cdot ψ_{m})}^{p}}]}^{q}$

where ɛ _gyp, ɛ _sat and ɛ _res are permittivity of gypsum and permittivity at saturation and residual water contents, respectively; α, p and q are calibration constants. The dielectric constant of gypsum and soil were determined as:

(37) $ɛ_{gyp} = {(\frac{L_{a}}{L})}^{2}$

where 50 _a is the apparent probe length and L is the probe length. The TDR waveforms at different matric potential values are shown in Fig. 16. Noborio et al. (1999) showed that the Ψ _thousand -θ relationship determined past the TDR probe embedded in porous ceramic was comparable to the human relationship determined past traditional pressure level-plate appliance.

Or and Wraith (1999) used the van Genuchten (1980) model to establish the relationship between TDR-measured water content and ceramic-measured matric potential (Fatás et al., 2013)

(38) $θ_{five} = [(θ_{sabbatum} - θ_{res}) {[\frac{ane}{i + {(αψ)}^{due north}}]}^{m}] + θ_{res}$

where n is the pore-size distribution parameter, m = 1 −(1/n), is the scale factor related to air-entry point or bubbling pressure (kPa), and θ _sabbatum and θ _res are the saturated and residue volumetric water contents of the ceramic plates, respectively. The equation parameter for each TDR-matric potential probe are derived from pressure jail cell calibration measurements.

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Quantifying and Managing Soil Functions in Globe'south Critical Zone

Southward. Rousseva , ... S.A. Banwart , in Advances in Agronomy, 2017

Abstract

Near of soil functions depend straight or indirectly on soil water retentiveness and transmission, which explains their importance for many environmental processes inside Globe's Critical Zones. Soil hydraulic properties are essential in irrigation and drainage studies for endmost water residual equation, for predicting leaching of nutrients, for water supply to plants, and for other agricultural and environmental applications. Soil hydraulic backdrop reflect the structure of the soil porous system comprising pores of different geometry and sizes. This investigation comprises a detailed analytical study of soil hydraulic properties and climate conditions at 18 methodologically selected sites in Damma Glacier, Slavkov Forest, Marchfeld, and Koiliaris Critical Zone Observatories of SoilTrEC projection. The local moisture regimes were assessed on a long-term footing by the Newhall model. The experimental information for soil water content at dissimilar potentials were used for assessing water storage capacity, pore size distribution, parameters of fitted retention curve equation, curve slope at the inflection betoken, and water permeability characteristics of each soil horizon. The differences of soil water retention and manual characteristics—as cardinal properties describing soil structure—were explained past the unlike stages of soil profile evolution, parent materials, organic matter content, and land apply histories.

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Organic Carbon Sources and Nitrogen Direction Improve Biomass of Hybrid Rice (Oryza sativa 50.) under Nitrogen Scarce Condition

Amanullah , ... Shah Fahad , in Advances in Rice Research for Abiotic Stress Tolerance, 2019

22.ane.three Importance of Soil Organic Affair in Rice Production

SOM plays four important ecosystem roles: resistance to soil erosion, soil water retention, soil fertility, and soil biodiversity. Stable and productive soils having a sufficient amount of organic matter affect the resilience of farms to cope with the effects of climate change ( Paris Understanding, 2015). Nigh one.2 billion metric tons of carbon could be stocked every year in agricultural soils which represents an annual rate of iv% (IPCC, 2014). Crop production in Africa, Asia, and South America could increase by millions every year, by increasing SOM by one metric ton per hectare (Lal, 2006). Agricultural land utilize is subjected to a variety of pressures today, as demands for food, animate being feed, and biomass production increment (Tsiafouli, 2016). Therefore, sustainable agricultural management such as incorporation of dissimilar organic sources in soils are urgently needed to enhance crop production nether multiple cropping systems (Amanullah et al., 2015a, Amanullah and Khalid, 2016; Amanullah and Hidayatullah, 2016). Maintaining organic carbon-rich soils, restoring and improving degraded agricultural lands and, in full general terms, increasing the soil carbon, play an important role in addressing the three-fold challenge of food security, adaptation of nutrient systems and people to climate change, and the mitigation of anthropogenic emissions (Paris Agreement, 2015).

Low organic matter content in soils under different cropping systems in semi-arid climates is the major cause of decline in crop productivity and smallholders income (Amanullah and Khalid, 2016; Amanullah and Hidayatullah, 2016; Amanullah et al., 2016). The low crop productivity and depletion of SOM are the consequences of mod rice (Oryza sativa L.) based cropping systems (Biswas and Sharma, 2008; Patil, 2008; Yadav, 2008). Low organic matter in these soils cause depletion of essential plant nutrients, thereby, decreasing soil fertility and yield in different field crops (Amanullah and Inamullah, 2016a,b; Amanullah et al., 2016). Awarding of different SOM sources (east.g., creature manures and plant residues) in various forms (fresh, dry, composts, biochar, ash, etc.,) increase ingather productivity, grower'due south income, soil fertility, and ameliorate wellness (Amanullah, 2016a,b, 2017, presentations in Tehran and Rome, respectively).

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Harnessing ecosystem services from biological nitrogen fixation

Sipho T. Maseko PhD , ... Felix D. Dakora PhD , in The Role of Ecosystem Services in Sustainable Food Systems, 2020

N contribution past legume encompass crops

The inclusion of legumes as comprehend crops in cropping systems can accrue multiple benefits which include soil water retention, control of pests and weeds, reduced runoff and soil erosion, memory, and reduced leaching of North, improved P supply and cycling, increased soil organic carbon, and enhanced soil aggregate stability ( Zheng et al., 2018; Hallama et al., 2019). A hairy vetch-wheat cover crop system combined with N fertilization markedly reduced Northward loss in conservation agriculture without affecting yield (Shelton et al., 2018). A contribution past Crotalaria ochroleusa was not significant when used as a cover crop with biomass incorporation into the soil (Souza et al., 2018). Based on 65 studies in the Us and Canada, Marcillo and Miguez (2017) legumes used as winter cover crops increased maize yields through provision of sufficient North to crops grown in rotation, thus reducing inputs such as chemic fertilizers (Magdoff and Weil, 2004), equally a outcome of increased Northward in soils (Wayman et al., 2015). Despite these marked positive furnishings of leguminous encompass crops in cropping systems, in Southern Africa small-scale farmers are unable to tap these benefits because of uncontrolled bush fires, also as the combined practice of crop and livestock farming, where livestock are allowed into farmers' fields for feed.

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Agro-waste-derived silica nanoparticles (Si-NPs) every bit biofertilizer

Ng Lee Chuen , ... Aziz Ahmad , in Valorization of Agri-Food Wastes and Past-Products, 2021

43.vi Fertilizers

Other than being adult as fertilizer, the Si-NPs also have a few other advantages, which include improved soil water retentiveness chapters and remediation of heavy metals or hazardous materials in polluted soil. Silicon nanoparticles with unique physiological characteristics are being aimed toward alleviating diverse biotic and abiotic stresses in plants. Recently, the application of Si with nanotechnology has been gaining broad attention in agriculture, specially toward promoting plant growth and development, for constructive pest direction, affliction and weed control, nanoparticles as delivery agents, nanozeolite for soil water retention, nanosensors for soil monitoring, etc. (run across Fig. 43.ii).

The impact of Si in enhancing plant growth, and productivity on a wide range of food crops has been reported, peculiarly nether unfavorable and stressed conditions (Ma & Yamaji, 2006; Balakhnina & Borkowska, 2012; Tubana et al., 2016; Yassen, Abdallah, Gaballah, & Zaghloul 2017). In plants, Si has been reported to improve nutrient imbalance, reduce mineral toxicities, enhance the mechanical strength of constitute tissues, and ameliorate resistance to various biotic and abiotic stresses (Hattori et al., 2005; Ng, Anuar, Jong, & Elham 2016; Tripathi et al., 2017). Nanoparticles exhibit greater surface area-to-weight ratio with various shapes being reported to display various properties over the bulk material (Feizi, Moghaddam, Shahtahmassebi, & Fotovat, 2012; Shen, 2017). For instance, the spread of nanosized Si in the ground is reported to be more secure due to its small size, thus enabling the rice establish to absorb more Si from the roots or leaves (Amrullah, Sopandie, Sugianta, & Junaedi, 2015). The furnishings of Si-NPs in promoting seed germination, plant growth, plant wellness, and productivity are summarized in Table 43.2. The liquid forms of Si-NPs-formulated fertilizer could be directly applied equally foliar application and/or dispensed on soil (blanching). Through foliar contact, the Si-NPs can readily enter the plant prison cell and exist accumulated in different plant parts (Chen, Zhang, Zhao, Huang, & Liu 2018; Sun et al., 2016). This can subsequently stimulate changes in metabolism and facilitate various photosynthetic activities (Rastogi et al., 2019). Still, plants' responses toward nanoparticles depend on physicochemical backdrop, application methods, plant variety, and growth stages, likewise as h2o and nutrients availability (Tabular array 43.ii).

Table 43.two. Awarding of Si-NPs on plant growth, institute health, and productivity.

Si-NPs source; size and purity (%)	Method and amount used	Mode of actions on institute	References
Nano-SiO_two; rice husk; 50 nm; >99.9	Basis awarding; NA	Nano-SiO₂ enhanced seed germination rate (100%) of corn than conventional Si sources, increased (doubled) colony of bacterial population and food value of soil.	Karunakaram et al. (2013)
Nano-SiO₂; commercial (Evonik Industries, Germany); 12 nm	Seeds formation; eight g/Fifty	Nano-SiO₂ significantly improved the lycopersicon esculentum (Lycopersicum esculentum Mill.) seed germination rate, germination fourth dimension, germination alphabetize, and seed vigor index and bulb biomass.	Siddiqui and Al-Whaibi (2013)
Nano-SiO₂; rice husk; xx–40 nm; 99.97	Combined with Pseudomonas fluorescens as footing application; 5, x, and fifteen kg/ha	Nano-SiO_ii enhanced foliage roughness, hardness, phenolic activity and hence reduces the stress by the suppression of responsive enzymes in maize hybrid seeds (Zea mays Fifty.; TIP TOP)	Rangaraj et al. (2014)
Nano-SiO_two; rice husk; NA	Basis application; 0.09, 0.23, 0.45, 0.68. 0.9 ppm at 10, 25, fifty, 75, and 100 kg/ha	Nano-SiO₂ significantly improve the rice (IR64) morphological traits (plant peak, length of root and leaves) rice institute biomass.	Amrullah et al. (2015)
Mesoporous Si-NPs; chemic; xx nm	Seed germination; 0, 200, 500, 1000, 2000 mg/L	Si-NPs significantly increased photosynthetic activity, seed formation, institute biomass, total protein and chlorophyll content of wheat and lupin	Sunday et al. 2016
Oligochitosan–nano-SiO_ii; rice husk; 10–30 nm	Foliar spraying; fifty mg/L–50 mg/L, r	Oligochitosan–nanosilica equally foliar awarding significantly improved soybean seed yield.	Phu, Du, Tuan, and Hiean (2017)
Mesoporous nano- SiO_two; Chemic; xx–150 nm	100, 200, 300, and 400 mg/mL	Love apple: early on blight (Alternaria solani). Mesoporous Nano- SiO_ii significantly inhibited the growth of A. solani and increased plant peak, fresh and dry out weight.	Derbalah et al. (2018)
Mesoporous Nano- SiO_two; twenty nm;	Pineapple plantlets were sprayed until runoff; 0.5 mg/mL	Mesoporous nano- SiO₂ significantly improved pineapple (Ananas comosus L.) resistance to Phytopthora cinnamomi by preventing lesion enlargement and improving root growth of infected plants.	Lu et al. (2019)

Diverse studies have indicated that Si-NPs directly promote plant growth by enhancing total poly peptide content, photosynthesis activeness, chlorophyll pigment content (Dominicus et al., 2016), seed germination rate (Siddiqui and Al-Whaibi, 2013), and morphological/physiological structures (Rangaraj et al., 2014). Indirect impacts of Si-NPs have been reported to exist associated with an increase in soil nutrient and microbial population and mitigation stresses (Amrullah et al., 2015; Derbalah, Shenashen, Hamza, Mohamed, & El-Safty 2018; Lu, Zhang, Wen, Wu, & Tao, 2002, 2019; Rangaraj et al., 2014; Triphati et al., 2017). The impacts of Si-NPs were also hypothesized to strengthen physiological barriers against pathogen infection, thus increasing the plants' resistance. Mesoporous Si-NPs (normally 20 nm) in plants accept been observed to be taken by the root system through apoplastic and symplastic pathways, and translocating to the aerial parts of the plants via xylem before getting deposited in the cell walls (Lord's day et al., 2016). Interestingly, degradation in the prison cell walls is therefore indicated in the beingness of an affinity with the cell wall components (Luyckx Hausman, Lutts, & Guerriero 2017), which tin can act as a physiological barrier against possible pathogen infection. Nevertheless, studies on the interaction mechanisms of nanoparticles with biological systems in plants at the molecular level remain scarce, especially activity of nanoparticles on cellular structures (Jha & Pudake, 2018).

The effects of Si-NPs accept been shown to exist plant species-dependent and Si-NPs' size tin significantly affect their uptake in plants (Table 43.two). Slomberg and Schoenfisch (2012) have reported Si-NPs (at 200 nm) to be transported into the root of Arabidopsis thaliana without indication of whatever phytotoxic effects. Nevertheless, the toxicity effects of Si-NPs were reported when applied as foliar spray at high concentration (Suriyaprabha, Karunakaran, Yuvakkumar, Rajendran, & Kannan, 2014; Yassen et al., 2017). The toxicity bear on may be attributed to the element of group i pH of Si-NPs and nutritional imbalance problems (Slomberg & Schoenfisch, 2012). Nonetheless, the optimum distribution and uptake of nanoparticles in plants greatly depends on the optimum pH and concentration of the surfactant (Jha & Pudake, 2018; Sun et al., 2014). Experiments conducted earlier on foliar spray of micronutrients on different fruit crops showed they imparted significant responses which improved yield and quality of fruits (Lalithya, Bhagya, Bharathi, & Hipparagi 2014). However, there is however a lack of report on Si-NPs application in agronomics through foliar applications. The effects and advantages of Si assimilation through the leaves on the performance of rice were studied past using potassium silicate (Buck, Korndörfer, Nolla, & Coelho, 2008). Coating formation on the leaves subsequently spraying potassium silicate indicated that the sparse film that formed strengthened the cuticle activity and acted as a mechanical barrier to pathogen penetrations (Menzies, Bowen, & Ehret, 1992). Moreover, soluble Si was reported not to directly touch on the infection by Sphaerotheca aphanis, but tin induce changes in the chemical limerick in the cuticle layer which tin can inhibit conidia germination and consequently command the proliferation of a illness (Kanto, Miyoshi, Ogawa, Maekawa, & Aino, 2004). Therefore a decrease in the rate of a plant'due south defence biochemical reaction tin occur (Cadet et al., 2008). The unique physicochemical properties of Si-NPs have certain advantages that can be applied as foliar spray for superior absorption and uptake by plants. However, many studies undertaken have clearly indicated the advantages of Si-NPs in agricultural applications with optimum utilization either alone or in combination with others to promote growth, health, and productivity.

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Influence of Topography on Soil Properties

Igor V. Florinsky , in Digital Terrain Analysis in Soil Science and Geology (Second Edition), 2016

9.4 Word

It is obvious that soil wet content depends not only on topography, only also on some physical and hydraulic characteristics of soils, such as soil texture and soil h2o retentiveness ( Lin, 2012). However, spatial distribution of these parameters also depends on morphometric variables (Moore et al., 1993; Pachepsky et al., 2001) because they are, in one mode or another, controlled by the intensity and direction of gravity-driven overland and intrasoil ship of substances.

Notice that the spatial distribution of moisture in a soil layer may sometimes depend on characteristics of subsurface topography, that is, the meridian surface of parent rocks. Amongst these are dense, water poor or impermeable rocks (eg, clays, granites). In such cases, topographic variables of the elevation surface of the C horizon may play similar roles as those of the state surface (Florinsky and Arlashina, 1998; Freer et al., 2002; Chaplot and Walter, 2003; Chaplot et al., 2004; Kim, 2009) (Fig. ix.1).

Finally, we should annotation that the influence of topography on soil properties depends on the management or tillage practice, for instance, naught cultivation versus conventional tillage (Farenhorst et al., 2003; Senthilkumar et al., 2009). Nigh of the works dealing with relationships between topography and soil backdrop in agricultural landscapes accept been conducted in Canada, the United States, and Australia on fields tilled over a 50- to 150-year period without dramatic modifications of the state surface and soil cover. This may exist ane reason why high correlations accept been systematically observed for the system "topography-soil" in agrolandscapes. A stiff, long-term agricultural load can seriously reduce the topographic control of soil backdrop (Venteris et al., 2004; Samsonova et al., 2007).

Results of the author's studies of topographic influence on soil wet tin can be found in Section 10.3 and Chapter 12.

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CONDITIONERS

R.E. Sojka , ... Westward.J. Orts , in Encyclopedia of Soils in the Environment, 2005

Early Use of Mineral and Organic Materials

This article provides a brief history of early on and traditional conditioner technologies and and so focuses on recent developments in inexpensive and highly effective synthetic conditioner materials and utilise strategies. Organic conditioners take more often than not been applied to increase infiltration and soil water retention, promote aggregation, provide substrate for soil biological activity, improve aeration, reduce soil force, and resist compaction, crusting, and surface sealing. The effects of organic conditioners frequently occur bimodally. That is, some furnishings, such as improved infiltration and water retention, are evident immediately upon soil incorporation, whereas other furnishings, such as improved aggregation, depend on chemical and biological processes over time.

Mineral conditioners are oftentimes used to bear on soil chemical processes also every bit soil physical processes. Lime, for example, raises soil pH. Gypsum or lime is often used to increase base saturation, or reduce the exchangeable sodium percent (ESP) of retained cations. Considering the divalent calcium ion has a compact hydrated radius, it also promotes flocculation of clays and increases amass stability. These effects help to reduce particle dispersion and detachment – which reduce erosion and surface sealing. Similarly, the calcium ion promotes flocculation and aggregation. These effects tin be particularly important in arid soils with low soil organic matter (SOM) contents. The physical properties of such soils are frequently impaired when the exchange complex is dominated by the sodium ion, which has a much larger hydrated radius, and thus impedes flocculation and aggregation and favors dispersive phenomena. The physical benefits of calcium addition in low SOM saline soils provide for improved leaching of salts and removal of sodium, especially nether irrigated weather.

Mineral conditioners are especially important for the management of arid or tropical soils where high temperatures promote rapid bio-oxidation of incorporated organic material. A diverseness of other strategies are used with mineral conditioners to exploit soil physicochemical processes, straight or indirectly improving soil physical and/or chemical status. While the uses of lime and gypsum have ancient origins, another interesting arroyo in recent decades has been the use of various oxides of iron to promote aggregation in depression-organic-matter soils. In the 1970s researchers added iron oxides to increase aggregate stability of soils and found peak assemblage at a two% addition charge per unit, with aggregation favored past acidic weather condition. Others in the 1980s found promising results for addition of ferrihydrite compounds to calcareous soils, with the germination of weak quasicrystalline structures. Recent work shows potential for adding ferric hydrides to low-organic-matter soils for structure comeback and wind erosion resistance. Ferric hydrides are common h2o-handling and industrial process waste products.

Soil conditioner research to the nowadays has explored the use of many naturally occurring organic and mineral materials, agronomical and industrial waste products, or by-products of other processes. Materials that have been used as conditioners accept included crushed rock, footing coal, gypsum (mined or from ground plasterboard), wood chips, bark, sawdust, food-processing wastes, cheese whey, various manures, composts of manures and/or other organic materials, and, as discussed more fully beneath, a broad range of constructed polymer materials, including copolymers of synthetic and naturally occurring substances. All these materials have shown varying capacities to modify soil conditions or soil processes.

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Livestock Production and Its Touch on on Nutrient Pollution and Greenhouse Gas Emissions

Grand. Sakadevan , Thousand.-L. Nguyen , in Advances in Agronomy, 2017

4.three Livestock and Soil Physical and Chemical Characteristics

The binding of soil particles with organic matter into aggregate is the major physical feature of soils that influence its function and suitability as a medium for found growth and regulate the motility of air, water and nutrient in the soil, water retention, and physical environment for active microorganisms and found roots (Cuttle, 2009). Global climate change alters rainfall regimes with the possibility of increased occurrence of droughts and higher frequencies of extreme rainfall events during the crop growing season. The spatial and temporal variability of rainfall increased the frequency of wetting and drying cycles which is likely to affect soil water content (Harper et al., 2005). The presence of grazing animate being further accelerates the wetting and drying cycles (Cuttle, 2009). The resultant drying and wetting of soil is expected to modify soil structure through the physical processes of shrink–swell (Carter and Stewart, 1996) and affect water infiltration and GHG emissions under grazing systems.

Soils with big clay contents (> 60%) shrink as they dry and bully when they get wet again, forming large cracks and fissures. Cleft formation results in rapid and direct movement of h2o and solutes (nutrients, metals, and dissolved organic matter) from surface soil to the unsaturated zone through bypass or preferential catamenia leading to possible losses of nutrients and water pollution from soil root zone which is generally available to plants (Nguyen et al., 1998; Rounsevell et al., 1999). Dry soil atmospheric condition for longer periods of the year would besides result in intensification of wet upland grazing areas due to livestock concentration (Rounsevell et al., 1996). When the soil becomes wet, information technology is subjected to structural amending nether the influence of grazing animals, and this amending increases with increasing soil h2o content (Mulholland and Fullen, 1991). This modify in soil water content associated with soil wetting and drying cycles and livestock grazing affects a number of soil processes including hydrology and vegetation growth. Soil structural alterations associated with grazing animals including compaction, pugging, and poaching (Bilotta et al., 2007).

Compaction reduces soil pore space and permanently removes air and water from the soil leading to mechanical disruption of soil amass, reducing aggregate stability, increasing the bulk density and penetration resistance of the soil, and creating anaerobic conditions in the soil (Abdalla et al., 2009; Donkor et al., 2002; Mwendera and Mohamed Saleem, 1997). Equally the drainage is impeded due to poaching, the soil becomes decumbent to surface runoff and erosion leading to sedimentation and water quality problems downstream (Mulholland and Fullen, 1991).

Soil infiltration tin can be reduced by up to lxxx% under the influence of grazing. For instance, Trimble and Mendel (1995) reviewed the touch on of livestock on soil infiltration and showed that it tin can be decreased from approximately fifty mm/h on lightly grazed to 25 mm/h on heavily grazed lands. Similarly, Heathwaite et al. (1990) showed that infiltration chapters was reduced past 80% and surface runoff increased past 12 times on heavily grazed compared to ungrazed pastures. In Alberta, Canada, the bulk density and penetration power of soil were significantly greater by 15% and 17% in short duration grazing with iv.16 animal unit of measurement months per hectare compared to continuous grazing with 2.08 animal unit of measurement months per hectare, suggesting that the duration of grazing influences the characteristics of the soil (Donkor et al., 2002). Studies carried out in tallgrass prairie pastures showed that for ungrazed pasture the largest infiltration was 29.v cm/day for a dirt loam soil and 27.five for a silt loam soil, while the grazing treatments had lower infiltration irrespective of soil types (Daniel et al., 2002). In northern Red china, soil characterization nether grazed and ungrazed systems has shown that the bulk density significantly increased under grazing (Zhou et al., 2010).

Changes in soil physical characteristics tin influence the processes affecting soil processes and nutrient transformations by altering soil moisture, soil redox potential, and found uptake processes (Bilotta et al., 2007; Di et al., 2001). For case, in both temperate and tropical regions the presence of grazing animals significantly increased soil erosion nether pastures (Hamza and Anderson, 2005). The National Land and Water Resources Audit in Australia has found that soil erosion from native pastures (with grazing) in the northern region of Commonwealth of australia accounts for 76% of continent's total soil erosion, and across these grazing lands the rate of soil loss is several times greater than the soil formation (NLWRA, 2001). As many every bit 100 million ha of rangeland is considered highly erodible in the United states of america (USDA-NRCS, 1992). Improved technologies and grazing management practices can help reduce impacts of soil concrete and chemical characteristics on soil erosion. For instance, in the United States, soil erosion losses from crop lands have been reduced from 1.2 1000000 tons per year in 1992 to 960 1000000 tons per year in 2007 (NRCS, 2010).

Inside the context of agricultural productivity the most obvious chemical characteristics influenced by grazing are nutrients (nitrogen and phosphorus) that have a straight and positive effect on plant growth and SOM, a determinant for soil quality. SOM, the precursor to soil sustainability, is an of import role of the labile (reactive) puddle which also determines the power of soil to retain water and nutrients. Studies have shown that soil organic C and North, and microbial biomass C and North increased or at least remain stable under grazed pastures compared to soils in croplands (Grace et al., 1998). Grazed pastures provide a quick way to build carbon by growing perennial plants continuously throughout the year and minimize disturbances to soil compared to cropping (Kirkegaard et al., 2007). Land management practices such as conservation agriculture (minimum or no cultivation, crop rotation, cover crops, mulching, integration of livestock with cropping, and the introduction of legumes) that influence SOM are important for enhancing soil concrete and chemical characteristics and minimizing livestock impacts on state degradation.

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Quantifying and Managing Soil Functions in Globe's Critical Zone

Y. Wang , ... Due south.A. Banwart , in Advances in Agronomy, 2017

4.two The Role of Soil Construction on Subsurface Lateral Flow Generation

The selected soil properties exercise not show meaning differences betwixt the 2 agroecosystems (Table 1), considering the short antecedent menstruation for the differing agricultural practices and the small dimensions of the experimental plots. Therefore, the reduced subsurface lateral flow in AF could not be attributed to soil texture, just to altered soil structure and the resulting changes in hydraulic properties. Forests can retain more than infiltrated water within soil profiles during rainfall (Bruijnzeel, 2004; Myers, 1983), every bit a office of the reservoir part of trees described in the literatures (Bruijnzeel, 2004; Myers, 1983). Mapa (1995) found higher soil water retention at any given water potential at all of the studied depths in reforested soils than in cultivated and grassland soils. For our inquiry fields, the lab-determined soil water memory was higher for the 015–0.twenty m soil depth in AF compared to MC and not different for the deeper soil layers between the two agroecosystems (Jing et al., 2008; Wang et al., 2013) (Fig. 9). However, at 0.two–0.9 thousand depth, the estimated van Genuchten parameter values using inverse modeling describe a water retention curve with lower h2o retention at lower soil matric potentials in AF than in MC. This is despite greater h2o retention in AF at most-saturation soil matric potentials (Fig. ix). These results indicate that the changed soil water retention curve cannot explain the increased water memory chapters and the reduced subsurface lateral flow in AF. The saturated hydraulic electrical conductivity was greater at the 0.2–0.9 grand depths compared to the pinnacle and deep soil layers in both agroecosystems (Table 2), suggesting presence of macropores at the 0.ii–0.9 m depths. In AF, the subsurface after flow may exist retarded due to the deeper root system, which may take not merely intensified the structural connectivity through macropores in vertical management, just as well reduced the structural connectivity in the lateral management. As if the subsurface lateral period was retarded in AF, quick preferential catamenia would be quicker due to more macropores compared to MC. This would then generate a temporary water table over the impermeable layer generates (Fig. 4). Therefore, the increased water retention capacity in AF tin can be explained past the raised water table due to the presence of macropores and the reduced subsurface lateral flow.

In that location are few studies on the effect of land use on soil hydraulic properties in the lateral direction. The furnishings may exist related to the development of soil micro- and mesopores due to the presence of fine roots or increased inputs of soil carbon as below-footing biomass and exudates, which promote the germination of large soil aggregates (Bogner et al., 2010; Mapa, 1995; Nair et al., 2010). Many studies have shown anisotropy of soil structure and hydraulic properties at mural scale (Bottinelli et al., 2016; Jing et al., 2008; Soracco et al., 2010). The effects of macropores on the reduced subsurface lateral period is indirectly reflected by the time filibuster of modeled top flow rate compared to the observed values in different soil layers for both agroecosystems, merely which is more profound in AF than in MC (Fig. 5). The weaker goodness of fit in AF is likely due to the altered macropore system (Fig. vi), which is not represented by the contradistinct soil water retentivity curve in the Hydrus-2D model.

To isolate the furnishings of soil structure change on the generation of subsurface lateral flow from the result of antecedent soil moisture, a numerical experiment with Hydrus-2nd was performed under the virtual status of the same ancestor soil matric potential along the hillslope. The two agroecosystems showed a similar increasing trend with increasing constructive rainfall intensity (the amount of infiltration h2o) in terms of the temporal water table and the subsurface lateral catamenia and no relation in terms of the soil water storage (Fig. 8). These results suggest that the effect of antecedent soil moisture or its related evapotranspiration can be ruled out as the reason for the reduced subsurface lateral flow in AF compared to MC. That is, the reduced subsurface lateral flow in AF is attributed to the increased tree canopy interception (or reduced infiltration) and the altered soil construction, which controls the anisotropy of soil hydraulic backdrop in vertical and lateral directions. Therefore, further studies are needed to elucidate the mechanisms how the tree root system shapes the anisotropy of soil hydraulic backdrop and consequently controls hillslope subsurface hydrological processes in Earth's CZ.

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CAPILLARITY

D. Or , 1000. Tuller , in Encyclopedia of Soils in the Environment, 2005

Hysteresis

The amount of liquid retained in a porous medium is not uniquely defined by the value of the matric potential merely is also dependent on the 'history' of wetting and drying. This phenomenon, known as hysteresis, is closely related to various aspects of pore geometry, capillarity, and surface wettability. The macroscopic manifestation of hysteresis in soil water retention (or soil water characteristic) is rooted in several microscale mechanisms, including: (1) differences in liquid–solid contact angles for advancing and receding water menisci ( Figure 14a), which is accentuated during drainage and wetting at different rates; (2) the 'ink bottle' result resulting from nonuniformity in shape and sizes of interconnected pores, as illustrated in Effigy 14b, whereby drainage of the irregular pores is governed by the smaller pore radius r, and wetting is dependent on the larger radius R. Additional effects stem from pore angularity; (3) differences in air-entrapment mechanisms; and (iv) swelling and shrinking of the soil under wetting and drying, respectively. From early observations to the present, the part of individual factors remains unclear, and hysteresis is a bailiwick of ongoing research.

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Source: https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/soil-water-retention

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