DOCSLIB.ORG

Soil Salinity Measurement

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Soil Salinity Measurement Soil Salinity Measurement Dennis L. Corwin United States Department of Agriculture (USDA), Riverside, California, U.S.A. INTRODUCTION 20 million ha severely effected by salinity worldwide.[1] Because of these detrimental impacts, the measurement, The measurement of soil salinity is a quantification of the monitoring, and real-time mapping of soil salinity is total salts present in the liquid portion of the soil. The crucial to sustaining world agricultural productivity. measurement of soil salinity is important in agriculture because salinity reduces crop yields by 1) making it more difficult for the plant to extract water; 2) causing specific- METHODS OF SOIL ion toxicity; 3) influencing the soil permeability and tilth; SALINITY MEASUREMENT and/or 4) upsetting the nutritional balance of plants. A discussion of the basic principles, methods, and equipment Historically, five methods have been developed for for measuring soil salinity is presented. The concise determining soil salinity at field scales: 1) visual crop discussion provides a basic knowledge of the background, observations; 2) the electrical conductance of soil solution latest equipment, and current accepted methodologies for extracts orextracts athigher thannormal water contents; 3)in measuring soil salinity with suction cup extractors, porous situ measurement of electrical resistivity; 4) noninvasive matrix/salinity sensors, electrical resistivity, electromag- measurement of electrical conductance with EM; and most netic induction (EM), and time domain reflectometry recently 5) in situ measurement of electrical conductance (TDR). with TDR. Visual Crop Observation SOIL SALINITY: DEFINITION, EFFECTS, AND GLOBAL IMPACTS Visual crop observation is a quick and economical method, but it has the disadvantage that salinity Soil salinity refers to the presence of major dissolved development is detected after crop damage has occurred. inorganic solutes in the soil aqueous phase, which consist For obvious reasons, the least desirable method is visual of soluble and readily dissolvable salts including charged observation because crop yields are reduced to obtain soil þ þ þ2 þ2 2 2 2 species (e.g., Na ,K ,Mg ,Ca ,Cl , HCO3 ,NO3 , salinity information. However, remote imagery is increas- 22 22 SO4 ,andCO3 ), non-ionic solutes, and ions that ingly becoming a part of agriculture and potentially combine to form ion pairs. The predominant mechanism represents a quantitative approach to visual observation. causing the accumulation of salt in irrigated agricultural Remote imagery may offer a potential for early detection soils is loss of water through evapotranspiration, leaving of the onset of salinity damage to plants. ever increasing concentrations of salts in the remaining Downloaded by [University of California, Riverside Libraries] at 13:11 02 April 2015 water. Effects of soil salinity are manifested in loss of Electrical Conductivity of Soil stand, reduced plant growth, reduced yields, and in severe Solution Extracts cases, crop failure. Salinity limits water uptake by plants by reducing the osmotic potential making it more difficult The determination of salinity through the measurement of for the plant to extract water. Salinity may also cause electrical conductance has been well established for specific-ion toxicity or upset the nutritional balance of decades.[2] It is known that the electrical conductivity (EC) plants. In addition, the salt composition of the soil water of water is a function of its chemical composition. McNeal influences the composition of cations on the exchange et al.[3] were among the first to establish the relationship complex of soil particles, which influences soil per- between EC and molar concentrations of ions in the soil meability and tilth. Irrigated agriculture, which accounts solution. Soil salinity is quantified in terms of the total for 35%–40% of the world’s total food and fiber, is concentration of the soluble salts as measured by the EC of adversely affected by soil salinity on roughly half of all the solution in dS m2 1.[2] To determine EC, the soil irrigated soils (totaling about 250 million ha) with over solution is placed between two electrodes of constant 852 Encyclopedia of Water Science DOI: 10.1081/E-EWS 120010191 Copyright q 2003 by Marcel Dekker, Inc. All rights reserved. Soil Salinity Measurement 853 geometry and distance of separation.[4] At constant soil-solution extractor or directly in the field by using in potential, the current is inversely proportional to the situ, imbibing-type porous-matrix salinity sensors. solution’s resistance. The measured conductance is a There are serious doubts about the ability of soil consequence of the solution’s salt concentration and the solution extractors and porous matrix salinity sensors (also electrode geometry whose effects are embodied in a cell known as soil salinity sensors) to provide representative constant. The electrical conductance is a reciprocal of the soil water samples.[6 –8] Because of their small sphere of resistance (Eq. 1): measurement, neither extractors nor salt sensors ade- quately integrate spatial variability;[9 –11] consequently, ECt ¼ k=Rt ð1Þ Biggar and Nielsen[12] suggested that soil solution samples where EC is the EC of the solution in dS m2 1 at are “point samples” that can provide qualitative measure- t ment of soil solutions, but not quantitative measurements temperature t (EC), k is the cell constant, and Rt is the 2 1 unless the field-scale variability is established. Further- measured resistance at temperature t. One dS m is equivalent to 1 mmho cm2 1. more, salinity sensors demonstrate a response time lag that Customarily, soil salinity has been defined in terms of is dependent upon the diffusion of ions between the soil laboratory measurements of the EC of the saturation solution and solution in the porous ceramic, which is affected by 1) the thickness of the ceramic conductivity extract (ECe), because it is impractical for routine purposes to extract soil water from samples at typical cell; 2) the diffusion coefficients in soil and ceramic; and 3) the fraction of the ceramic surface in contact with field water contents. Partitioning of solutes over the three [13] soil phases (i.e., gas, liquid, and solid) is influenced by the soil. The salinity sensor is generally considered the least desirable method for measuring EC because of its soil–water ratio at which the extract is made, so the ratio w low sample volume, unstable calibration over time, and must be standardized to obtain results that can be applied [14] and interpreted universally. Commonly used extract ratios slow response time. other than a saturated soil paste are 1:1, 1:2, and 1:5 soil– water mixtures. Soil salinity can also be determined from the Electrical Resistivity measurement of the EC of a soil solution (ECw). Theoretically, EC is the best index of soil salinity Because of the time and cost of obtaining soil solution w extracts, developments in the measurement of soil EC because this is the salinity actually experienced by the have shifted to the measurement of the soil EC of the bulk plant root. Nevertheless, ECw has not been widely used to express soil salinity for various reasons: 1) it varies over soil, referred to as the apparent soil electrical conductance the irrigation cycle as the soil water content changes and 2) (ECa). The apparent soil EC measures the conductance methods for obtaining soil solution samples are too labor, through not only the soil solution but also through the solid and cost intensive at typical field water contents to be soil particles and via exchangeable cations that exist at the practical for field-scale applications.[5] For disturbed solid–liquid interface of clay minerals. The techniques of samples, soil solution can be obtained in the laboratory electrical resistivity, EM, and TDR measure ECa. Electrical resistivity methods introduce an electrical by displacement, compaction, centrifugation, molecular adsorption, and vacuum- or pressure-extraction methods. current into the soil through current electrodes at the soil surface and the difference in current flow potential is For undisturbed samples, ECw can be determined either in the laboratory on a soil solution sample collected with a measured at potential electrodes that are placed in the vicinity of the current flow (Fig. 1). These methods were Downloaded by [University of California, Riverside Libraries] at 13:11 02 April 2015 developed in the second decade of the 1900s by Conrad Schlumberger in France and Frank Wenner in the United States for the evaluation of ground electrical resis- tivity.[16,17] The electrode configuration is referred to as a Wenner array when four electrodes are equidistantly spaced in a straight line at the soil surface with the two outer electrodes serving as the current or transmission electrodes and the two inner electrodes serving as the potential or [18] Fig. 1 Schematic of electrical resistivity of four electrodes (the receiving electrodes. The depth of penetration of the electrical current and the volume of measurement increase Wenner array configuration). C1 and C2 represent the current electrodes, P1 and P2 represent the potential electrodes, and a as the inter-electrode spacing, a, increases. For a represents the inter-electrode spacing. Modified from Rhoades homogeneous soil, the soil volume measured is roughly and Halverson.[15] Pa 3. There are additional electrode configurations that are 854 Soil Salinity Measurement frequently used, as discussed by Burger,[16] Telford considerably
Load more

Recommended publications
  • Soil Salinity in Agricultural Systems: the Basics
    Soil Salinity in Agricultural Systems: The Basics Jeffrey L. Ullman Agricultural & Biological Engineering University of Florida Strategies for Minimizing Salinity Problems and Optimizing Crop Production In-Service Training, Hastings, FL March 26, 2013 What is salt? What is Salt? . Salts are more than just sodium chloride (NaCl) . Salts consist of anions and cations . In terms of soil and irrigation water these generally include: Cations Anions Sodium Na+ Chlorides Cl- 2+ 2- Magnesium Mg Sulfates SO4 2+ 2- Calcium Ca Carbonates CO3 - Bicarbonates HCO3 What is Salt? . Other salts in agriculture + Potassium (K ) - Nitrate (NO3 ) Boron (B) • Often as boric acid (H3BO3, often written as B(OH)3) • Can form salts such as sodium borate (borax; Na2B4O7) Photo: Georgia Agriculture What is Salt? H O(l) NaCl(s) 2 Na+(aq) + Cl-(aq) (aq) indicates that Na+ and Cl- are hydrated ions Sodium sulfate Magnesium carbonate Source: Averill and Eldredge (2007) Types of Salts Some common salts NaCl Sodium chloride Table salt (halite) CO 2- 3 KCl Potassium chloride Muriate of potash Na+ 2- NaHCO3 Sodium bicarbonate Baking soda (nahcolite) SO4 - Cl CaSO4 Calcium sulfate Gypsum + K CaCO3 Calcium carbonate Calcite 2+ Ca MgSO Magnesium sulfate Epsom salt (epsomite) Mg2+ 4 K2SO4 Potassium sulfate Sulfate of potash (arcanite) HCO - 3 Glauber’s salt (thenardite Na SO Sodium sulfate 2 4 and mirabilite) Gypsum Calcite Thenardite Sources of Salt . Dissolution of parent rock material . Irrigation water . Saline groundwater . Fertilizers . Manure . Seawater intrusion Photo: J. Ullman Saline Soils . Accumulation of salts known as salination . Can occur in diverse types of soil with different physical, chemical and hydrologic properties Photo: USDA-NRCS Saline Soils .
    [Show full text]
  • Soil Salinity Type Effects on the Relationship Betweenthe Electrical
    sustainability Article Soil Salinity Type Effects on the Relationship between the Electrical Conductivity and Salt Content for 1:5 Soil-to-Water Extract Amin I. Ismayilov 1, Amrakh I. Mamedov 2,* , Haruyuki Fujimaki 2 , Atsushi Tsunekawa 2 and Guy J. Levy 3 1 Institute of Soil Science and Agrichemistry, Azerbaijan National Academy of Sciences (ANAS), Baku AZ1073, Azerbaijan; [email protected] 2 Arid Land Research Center, Tottori University, Tottori 680-0001, Japan; [email protected] (H.F.); [email protected] (A.T.) 3 Institute of Soil, Water and Environmental Sciences, ARO, Rishon LeZion 7505101, Israel; [email protected] * Correspondence: [email protected] Abstract: Soil salinity severely affects soil ecosystem quality and crop production in semi-arid and arid regions. A vast quantity of data on soil salinity has been collected by research organizations of the Commonwealth of Independent States (CIS, formerly USSR) and many other countries over the last 70 years, but using them in the current international network (irrigation and reclamation strategy) is complicated. This is because in the CIS countries salinity was expressed by total soluble salts as a percentage on a dry-weight basis (total soluble salts, TSS, %) and eight salinity types − 2− − + (chemistry) determined by the ratios of the anions and cations (Cl , SO4 , HCO3 , and Na , Ca2+, Mg2+) in diluted soil water extract (soil/water = 1:5) without assessing electrical conductivity (EC). Measuring the EC (1:5) is more convenient, yet EC is not only affected by the concentration Citation: Ismayilov, A.I.; Mamedov, but also characteristics of the ions and the salinity chemistry.
    [Show full text]
  • Status of Soil Salinity in California
    it a major item in his joint presentation percent of construction, operation, and Although progress has been made, the to Congress and meeting with former maintenance costs. Basin states see the need for expanded President Nixon in 1972. In 1975, the Forum recommended wa- salinity control to maintain the numeric ter quality standards for salinity, includ- Proposed solutions criteria. Bills now before Congress would ing numeric criteria of 723 mg/L below authorize five additional salinity control The salinity problem has the potential to Hoover Dam, 747 mg/L below Parker units to be constructed by the Depart- cause lengthy legal and political battles Dam, and 879 mg/L at Imperial Dam. ment of the Interior, give the US. De- between the Upper and Lower Basin Their proposal also called for prompt partment of Agriculture specific author- states. The Lower Basin wants to pre- construction of the salinity control units ity for a program of on-farm Colorado vent salinity increases that would result authorized by P.L. 93-320, construction River salinity control measures in coop- from further upstream development; Up- of additional units upon completion of eration with local landowners, and pro- per Basin states are concerned that the planning reports, implementation of on- vide for 25 percent of the construction salinity issue could prevent future in- farm water management practices to costs to be paid by the Basin states. creases in their water use. control salinity, limitations on industrial In other efforts to control the river’s The states began to work together and municipal discharges, use of saline salinity, the Basin states have adopted a and with the federal government in the water for industrial purposes, and the policy calling for a no-salt return from late 1960s, and in the early 1970s several inclusion of the salinity components of industrial discharges and limiting the steps were taken to deal with the prob- water quality management plans devel- incremental increase permitted from lems.
    [Show full text]
  • Chapter No. 06 Definition, Classification and Characteristics of Salt Affected Soils
    Chapter No. 06 Definition, classification and characteristics of salt affected soils The salt-affected soils occur in the arid and semiarid regions where evapo- transpiration greatly exceeds precipitation. The accumulated ions causing salinity or alkalinity include sodium, potassium, magnesium, calcium, chlorides, carbonates and bicarbonates. The salt-affected soils can be primarily classified as saline soil and sodic soil. S. Characteristics Saline (Alkaline) Saline – Sodic Sodic (Alkali) No. 1. pH < 8.5 > 8.5 > 8.5 2. EC > 4.0 dSm-1 > 4.0 dSm-1 < 4.0 dSm-1 3. Salt Concentration > 0.2 % > 0.2 % < 0.2 % 4. ESP%* < 15.0% > 15.0% > 15.0% 5. SAR** < 13.0 > 15.0 > 15.0 6. Dominant Cation Ca2+, Mg2+, K+ Ca2+, Mg2+, K+, Na+ Na+ - 2- - - 2- - 2- - 7. Dominant Anion Cl , SO4 , NO3 Cl , SO4 , NO3 , CO3 , HCO3 2- - CO3 , HCO3 8. Soil Structure (Soil Flocculated Flocculated De flocculated particles) 9. Infiltration Good God Poor 10. Drainage Good God Poor 11. Nomenclature Solenchalk - Solentz (White alkali) (Black alkali) * Exchangeable Sodium Percentage (ESP) Exchangeable Na+ (in milli equi./100 g Soil) ESP = X 100 Total CEC (in milli equi./100 g Soil) ** Sodium Adsorption Ratio (SAR) [Na+] SAR = [Ca2+] + [Mg2+] / 2 Saline soils :- Saline soils defined as soils having a conductivity of the saturation extract greater than 4 dS m-1 and an exchangeable sodium percentage less than 15 Saline soils defined as soils having a conductivity of the saturation extract greater than 4 dS m-1 and an exchangeable sodium percentage less than 15. The pH is usually less than 8.5.
    [Show full text]
  • Managing Soil Salinity Tony Provin and J.L
    E-60 3-12 Managing Soil Salinity Tony Provin and J.L. Pitt* f your soil has a high salinity content, the plants ing may cause salts to accumulate in both surface growing there will not be as vigorous as they would and underground waters. The surface runoff of these Ibe in normal soils. Seeds will germinate poorly, dissolved salts is what gives the salt content to our if at all, and the plants will grow slowly or become oceans and lakes. Fertilizers and organic amendments stunted. If the salinity concentration is high enough, also add salts to the soil. the plants will wilt and die, no matter how much you water them. Effects of salts on plants Routine soil testing can identify your soil’s salinity As soils become more saline, plants become unable levels and suggest measures you can take to correct to draw as much water from the soil. This is because the specific salinity problem in your soil. the plant roots contain varying concentrations of ions (salts) that create a natural flow of water from the soil Salinity and salt into the plant roots. The terms salt and salinity are often used inter- As the level of salinity in the soil nears that of the changeably, and sometimes incorrectly. A salt is sim- roots, however, water becomes less and less likely to ply an inorganic mineral that can dissolve in water. enter the root. In fact, when the soil salinity levels are Many people associate salt with sodium chloride— high enough, the water in the roots is pulled back into common table salt.
    [Show full text]
  • Methods of Analysis Soil Sampling
    Soil Sampling and Methods of Analysis Second Edition ß 2006 by Taylor & Francis Group, LLC. In physical science the first essential step in the direction of learning any subject is to find principles of numerical reckoning and practicable methods for measuring some quality connected with it. I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely in your thoughts advanced to the state of science, whatever the matter may be. Lord Kelvin, Popular Lectures and Addresses (1891–1894), vol. 1, Electrical Units of Measurement Felix qui potuit rerum cognoscere causas. Happy the man who has been able to learn the causes of things. Virgil: Georgics (II, 490) ß 2006 by Taylor & Francis Group, LLC. Soil Sampling and Methods of Analysis Second Edition Edited by M.R. Carter E.G. Gregorich Canadian Society of Soil Science ß 2006 by Taylor & Francis Group, LLC. CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2008 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works Printed in the United States of America on acid-free paper 10 9 8 7 6 5 4 3 2 1 International Standard Book Number-13: 978-0-8493-3586-0 (Hardcover) This book contains information obtained from authentic and highly regarded sources.
    [Show full text]
  • Saline and Alkali Soils Are Soils That Saline Soil
    282 YEARBOOK OF AGRICULTURE 1957 gions of an arid or a scmiarid climate. Under humid conditions, the soluble salts originally present in soil materials and those formed by the weathering of Saline and minerals generally are carried down- ward into the ground water and are transported ultimately by streams to Alkali Soils the oceans. In arid regions, leaching and trans- C. A. Bower and Milton Fireman portation of salts to the oceans is not so complete as in humid regions. Leach- Saline and alkali conditions ing is usually local in nature, and solu- ble salts may not be transported far. lower the productivity and This occurs because there is less rain- value of large areas of agri- fall available to leach and transport the salts and because the high evapo- cultural land in the United ration and plant transpiration rates States—an estimated one- in arid climates tend further to con- centrate the salts in soils and surface fourth of our 29 million acres waters. of irrigated land and less ex- Weathering of primary minerals is the indirect source of nearly all soluble tensive acreages of nonirrigated salts, but there may be a few instances crop and pasture lands. in which enough salts have accumu- lated from this source alone to form a Saline and alkali soils are soils that saline soil. Saline soils usually occur in have been harmed by soluble salts, places that receive salts from other consisting mainly of sodium, calcium, locations; water is the main carrier. magnesium, chloride, and sulfate and secondarily of potassium, bicarbonate, RESTRICTED DRAINAGE usually con- carbonate, nitrate, and boron.
    [Show full text]
  • Chapter 12 Leaching and Rootzone Salinity Control
    CHAPTER 12 saimr nil LEACHING AND ROOTZONE SALINITY CONTROL failles E. Ayars, Glenn J. Hoffman, and Dennis L. Corwin ll',sful water management for salinity control depends on ade­ leJching, which takes place whenever irrigation and rainfall exceed r; ca pacity to store infiltrated wat r within the crop's rootzone. In dregions, rainfall normaLly results in enough leaching to flush salt dl' rootzone. In subhumid and drier regions, irrigation water that the crop's water requirements may need to be applied to ensure 'Jle leaching. Depending on the salinity control needed, leaching ur continuously or at intervals of a few weeks to a few years. (TOP'S water requirement and salinity control must be prime con­ allon in places where salinity poses a hazard. Proper irrigation the soil's water deficit without a wasteful and potentially harmful l mps need water from irrigation and rainfall to control soil salin­ mJucing drainage (leaching). As discussed in this chapter, leaching r'move enough salt to prevent it from accumulating in the rootzone th crop's salt-tolerance level. Chemical reactions in the soil affect i!1uun t of salt leached, which may be greater than, equal to, or less t\1t.' amount of salt added by irrigation water. 'amount of irrigation water needed to meet the crop's water require­ r~'3 n be calcula t d from a wat balance of the crop rootzone. The !low' of water into the crop's rootzone are irrigation, rainfall, and Jrd now from the groundwater. The depths of each are expressed in 371 372 AGRICULTURAL SALINITY ASSESSM E T AND MANAGEMENT equations as OJ, 0" and Og' respectively.
    [Show full text]
  • Soil Salinity: Effect on Vegetable Crop Growth. Management Practices to Prevent and Mitigate Soil Salinization
    horticulturae Review Soil Salinity: Effect on Vegetable Crop Growth. Management Practices to Prevent and Mitigate Soil Salinization Rui Manuel Almeida Machado 1,2,* and Ricardo Paulo Serralheiro 1,3 1 ICAAM— Instituto de Ciências Agrárias e Ambientais Mediterrânicas; Universidade de Évora, Pólo da Mitra, Apartado 94, 7006-554 Évora, Portugal 2 Departamento de Fitotecnia, Escola de Ciência Tecnologia, Universidade de Évora, Pólo da Mitra, Apartado 94, 7006-554 Évora, Portugal 3 Departamento de Engenharia Rural, Escola de Ciência Tecnologia, Universidade de Évora, Pólo da Mitra, Apartado 94, 7006-554 Évora, Portugal; [email protected] * Correspondence: [email protected] Academic Editors: Arturo Alvino and Maria Isabel Freire Ribeiro Ferreira Received: 11 January 2017; Accepted: 26 April 2017; Published: 3 May 2017 Abstract: Salinity is a major problem affecting crop production all over the world: 20% of cultivated land in the world, and 33% of irrigated land, are salt-affected and degraded. This process can be accentuated by climate change, excessive use of groundwater (mainly if close to the sea), increasing use of low-quality water in irrigation, and massive introduction of irrigation associated with intensive farming. Excessive soil salinity reduces the productivity of many agricultural crops, including most vegetables, which are particularly sensitive throughout the ontogeny of the plant. The salinity −1 threshold (ECt) of the majority of vegetable crops is low (ranging from 1 to 2.5 dS m in saturated soil extracts) and vegetable salt tolerance decreases when saline water is used for irrigation. The objective of this review is to discuss the effects of salinity on vegetable growth and how management practices (irrigation, drainage, and fertilization) can prevent soil and water salinization and mitigate the adverse effects of salinity.
    [Show full text]
  • Vadose Zone Characterization and Monitoring Current Technologies, Applications, and Future Developments
    3 Vadose Zone Characterization and Monitoring Current Technologies, Applications, and Future Developments Boris Faybishenko Contributors: M. Bandurraga, M. Conrad, P. Cook, C. Eddy-Dilek, L. Everett, FRx Inc. of Cincinnati, T. Hazen, S. Hubbard, A.R. Hutter, P. Jordan, C. Keller, F.J. Leij, N. Loaiciga, E.L. Majer, L. Murdoch, S. Renehan, B. Riha, J. Rossabi, Y. Rubin, A. Simmons, S. Weeks, C.V. Williams INTRODUCTION NEEDS FOR VADOSE ZONE CHARACTERIZATION AND MONITORING Vadose zone characterization and monitoring are essential for: • Development of a complete and accurate assessment of the inven- tory, distribution, and movement of contaminants in unsaturated- saturated soils and rocks. • Development of improved predictive methods for liquid flow and contaminant transport. • Design of remediation systems (barrier systems, stabilization of buried wastes in situ, cover systems for waste isolation, in situ treat- ment barriers of dispersed contaminant plumes, bioreactive treat- ment methods of organic solvents in sediments and groundwater). • Design of chemical treatment technologies to destroy or immobilize highly concentrated contaminant sources (metals, radionuclides, explosive residues, and solvents) accumulated in the subsurface. 133 134 VADOSE ZONE SCIENCE AND TECHNOLOGY SOLUTIONS Development of appropriate conceptual models of water flow and chemical transport in the vadose zone soil-rock formation is critical for developing adequate predictive modeling methods and designing cost- effective remediation techniques. These conceptual models of unsatu- rated heterogeneous soils must take into account the processes of preferential and fast water seepage and contaminant transport toward the underlying aquifer. Such processes are enhanced under episodic natural precipitation, snowmelt, and extreme chemistry of waste leaks from tanks, cribs, and other surface sources.
    [Show full text]
  • Measuring Soil Salinity
    Measuring soil salinity Viti-note Summary: Salinity is a measure of the concentration Salinity in the root zone often comes of soluble salts in the soil. The most from a saline watertable; therefore the • Method common salt is sodium chloride: however, subsoil, and possibly a deeper level soil • Interpreting results others include bicarbonates, sulphates sample, should also be measured. and carbonates of calcium, potassium • Useful conversions and magnesium. Some salts are useful, Method e.g. many fertilizers are in a salt form, but too much salt of any kind is detrimental 1. Take three surface soil and three to plants and other organisms. subsoil samples from each site (as described in points 1-5 the Taking soil Vitis vinifera varieties are moderately samples activity guide in this Vitinote tolerant of salinity (i.e. high total salts). series). Make sure surface soil and However, a concentration of salts in the subsoil are not combined so that they root zone that is too high can damage can be analysed separately. plant health and reduce crop yields. A very high concentration of soluble salts 2. Crush large aggregates and remove can kill vines. Measurement of soil salinity any gravel so that you have a fine mix is generally used to determine the salt to test. status of a soil, particularly if vines are 3. Make sure to refer to instrument showing salt toxicity symptoms. It is instructions and periodically calibrate also used to gauge the impact on soils your EC meter. irrigated with saline water, particularly in 4. Unscrew jar lid and fill the lid level combination with deficit irrigation.
    [Show full text]
  • An APLD Guide to Sustainable Soils
    An APLD Guide to Sustainable Soils We Define Landscape Design www.apld.org 1 APLD is committed to the principles of sustainability as the foundation for our collective landscape design practice. Healthy, appropriate soils, sustainably generated and maintained, are key to a strong, diverse ecosystem and are essential for a successful planting design. The Properties of Soil Soil has physical, chemical and biological properties, all combining to provide exquisite complexity for supporting plant life. Physical Properties of Soil The physical components of soil include liquids, The mineral solids are sand, silt, and clay, usually gases, and mineral and organic solids. mixed in varying concentrations that define the texture of the soil. The largest particles are sand, followed by silt and clay, in that order. The comparative sizes of the particles are shown below. U.S. Dept. of Agriculture National Resources Conservation Service U.S. Dept. of Agriculture National Resources Conservation Service 2 There are twelve main classes of soil texture, ranging The organic solids are carbon-based and derive from from blends of the mineral solids, with a combination the decaying remains of plant and animal life in the of approximately equal parts silt and sand, no more soil. They contribute to the structure of the soil by than 20% clay, and some organic solids being among working with clay to encourage the development the best types of soils. The diagram below illustrates of soil aggregates and cement the particles, thus the 12 main soil textures. stabilizing soil structure. Organic solids also improve the ability of the soil to hold water.
    [Show full text]