SWAGMAN-Whatif, an interactive computer program to teach salinity relationships in irrigated agriculture

Managing salt-affected irrigated lands and marginally salinine irrigation water requires understanding the interactions among soil salinity, crop salt tolerances, soil physical properties, irrigation water quality, irrigation management, water table depth and quality, climate, and crop yield. An interactive computer program was developed to simulate interactions among the above factors. It shows how changing one factor impacts the others for a growing season. The user selects a climate, crop, and soil characteristics from menu lists, then sets the water table depth and quality, irrigation water quality, and develops an irrigation schedule. On execution, surface runoff, water table rise or fall, and the relative yield reductions due to overirrigation, underirrigation, and salinity are shown numerically for 1 yr. Soil water content, soil salinity, water table depth changes, and rain and irrigation events are also shown graphically. An IBM-compatible computer with a math coprocessor executes the program in 6 to 10 s. This is an educational tool designed to teach the concepts of salinity and irrigation management and is not an irrigation scheduling program nor a management tool. Two versions have been developed, one using metric units, southern hemisphere growing seasons, and Australian terminology; and a second using northern hemisphere growing seasons and U.S. units and terminology. The U.S. version also allows use of metric units. The program is supplied in executable code with a user guide, a soil salinity manual, and a salinity units conversion slide rule

Predicting salinization in a heavy clay soil subjected to a saline shallow water table

Salt increase in a heavy clay soil due to capillary rise was simulated by an analytical model and a numerical model. Predicted values were compared with experimental data. The analytical model was inadequate in predicting salinisation in a dynamic crop/soil system. When root growth was accounted for, the numerical model satisfactorily predicted salt increase in the soil profile

Models for estimating capillary rise in a heavy clay soil with a saline shallow water table

Shallow saline water tables underlie large areas of the clay soils in the Murray basin of Australia. Accurate estimation of capillary rise is important in formulating management strategies to avoid degradation of such soils. Measured capillary rise from a saline water table was compared with capillary rise estimated by three mathematical models of varying complexity and input requirement. A quasi steady state analytical model (QSSAM), a transient state analytical model (TSAM) and a numerical model (NM) were used. An undisturbed heavy clay soil core of 0.75 m diameter and 1.4 m deep was subjected to a static saline water table at 1.2 m from the surface. A wheat crop was grown on the core and the weekly capillary rise from the water table was measured. The electrical conductivity of a 1 : 2 soil : water extract was determined at 0.15 m depth intervals before and 21 weeks after the introduction of the saline water table. The QSSAM did not satisfactorily estimate the initial wetting of the subsoil and the estimated capillary rise was considerably lower than the measured values. Capillary rise estimated by the TSAM was reasonably close to the measured values, but the weekly rates fluctuated considerably. The NM estimated capillary rise quite satisfactorily throughout the experiment. Except near the soil surface, the electrical conductivity values estimated by the NM were close to the measured values. For estimating total capillary rise over large areas, the TSAM is preferred over the NM because of its fewer input requirements and shorter execution time

Understanding salt and sodium in soils, irrigation water and shallow groundwaters: A companion to the software program SWAGMAN-Whatif

Understanding Salt and Sodium in Soils, Irrigation Water and Shallow Groundwaters is a companion booklet to SWAGMANe-Whatif, a computer model that lets you see how salts, soils, water and water tables interact. SWAGMANkWhatif also lets you assess the effects of management practices that you might undertake in a particular area. This booklet gives background information to help you understand salts, sodium and their interactions with water and soils. It explains where sodium and salts come from, how to identify salt-affected soils, and gives instructions on taking soil and water samples for analysis. It also gives suggestions on how to reduce the harmful effects of salts and sodium, and tells you where to get advice in making reclamation and management decisions for each situation. Managing salt and sodium affected soils, together with waters used for irrigation, is complex. It is not possible to cover all technical aspects or possible treatment approaches in this booklet. Instead, we have given a simple overview of the major principles involved in diagnosing and managing salt and sodium affected soils and irrigation waters. It is difficult to summarise salt and sodium effects on soils and plants without using some technical terms, so a comprehensive glossary has been included

SWAGMAN-Whatif Software and User Guide

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Predicting salinization in a heavy clay soil subjected to a saline shallow water table

Salt increase in a heavy clay soil due to capillary rise was simulated by an analytical model and a numerical model. Predicted values were compared with experimental data. The analytical model was inadequate in predicting salinisation in a dynamic crop/soil system. When root growth was accounted for, the numerical model satisfactorily predicted salt increase in the soil profile

The impact of seasonal waterlogging on the depth-wise distribution of major and trace metals in the soils of the eastern Ganges basin

© 2020 Elsevier B.V. In the Ganges River basin, studies related to the depth-wise distribution of major and trace metals in these floodplain soils (seasonally waterlogged and non-water logged) have been limited thus far. This research attempts to address this gap in the current literature by geochemical and geostatistical analyses and assessment of soil pollution. Significant concentrations of major and trace metals in these soils could greatly impact the health of local communities. Soil samples were collected in the eastern Ganges basin from a shallow seasonally waterlogged (SWL) site and a shallow non-waterlogged (SNWL) site up to 3 m below ground level (mbgl) and a deep seasonally waterlogged (DWL, up to 14 mbgl) site. The soils were analysed to determine soil texture and the concentration of major oxides and trace metals with increasing depth. The average concentration of trace metals (Ba, Rb, V, Cr, Ni, As, Pb, Ga, Co, Cs, Nb, W) and major oxides (Al2O3, Fe2O3, K2O, MgO) are higher in the SWL soil than the SNWL soil. A higher concentration of metals generally occurred in the upper soil layers due to the adsorption of elements by the silt and clay fractions. Soil pollution assessment indicated that W, As, Sb and Cu are enriched in both the waterlogged and non-waterlogged soils, while Sn is enriched in the SNWL soil profile only. The values obtained for the geochemical indices, which were geoaccumulation index (Igeo), enrichment factor (EF), contamination factor (CF) and pollution load index (PLI), were relatively higher in the top layers for the SWL and DWL sites. Based on effects range-low (ERL) and effects range-median (ERM) values, the possibility of adverse biological effects caused by the metals is highest for Ni in the DWL site, Cr and Ni in the SWL site and Cu in the SNWL site. Pearson's correlation and principal component analysis (PCA) justify the role of soil texture, phyllosilicates, Fe-Mn oxyhydroxides and carbonates in the occurrence and distribution of metals in these soils. Seasonal waterlogging facilitates the dissolution and precipitation of oxides, hydroxides, carbonates and adsorption/desorption processes, leading to the accumulation and retention of more trace metals in the soil. This study implies that the silt and clay present in the vadose zone may act as a filter to protect local groundwater aquifers from metal contamination. This work provides insights on the behaviour of major and trace metals in the soil depth profile of seasonally waterlogged floodplain soil that is used for local agriculture