Evaluation of soil salinity and sodicity using electromagnetic conductivity imaging

<p>In order to prevent further soil degradation, it is important to understand the processes controlling salinization. Salt related problems in soils can refer to an excess of soluble salts (saline soils), a dominance of exchangeable sodium in the soil exchange complex (sodic soils), or a mixture of both situations (saline-sodic soils). These categories are important because the impacts and management vary accordingly. Traditional soil sampling methods –which require boreholes for soil sampling and analysis– difficultly lead to a comprehensive answer to this problem. This is because they cover only small and localized sites and may not be representative of the soil properties at the management scales. Furthermore, they are highly time and work consuming, resulting in costly surveys. Geophysical techniques such as electromagnetic induction (EMI) provide enormous advantages compared to soil sampling because they allow for in-depth and non-invasive analysis, covering large areas in less time and at a lower cost.</p><p>EMI surveys were performed in several regions in Portugal with historic soil salinity and sodicity problems to evaluate the salinization risk. We inverted field apparent conductivity data (σ<sub>a</sub>) in order to obtain electromagnetic conductivity images (EMCI) of the real soil electrical conductivity (σ) in depth. We evaluated the potential of EMCI in the estimation of soil salinity, sodicity, and other soil properties over large areas across regions with a very different range of salinity and sodicity.</p><p> </p><p><strong>Acknowledgments</strong></p><p>This work was developed in the scope of SOIL4EVER “Sustainable use of soil and water for improving crops productivity in irrigated areas” project supported by FCT, grant no. PTDC/ASP-SOL/28796/2017.</p><p> </p>

Soils of Thotapalli Major Irrigation Project of North-Coastal Andhra Pradesh: Characterization and Classification

Six representative pedons from Devarapalli (P1), Gujjangivalasa (P2), Patikivalasa (P3), Gangada (P4), Aamiti (P5) and Maddivalasa (P6) villages belonging to ayacut of Thotapalli major irrigation project of North-Coastal Andhra Pradesh were studied. Pedons 1, 2 and 5 were developed from granite-gneiss, while pedons 3, 4 and 6 had their parent legacy with granite-gneiss mixed with calcareous murrum. The soils of P1 and P2 were moderately deep to very deep having argillic horizon while cambic sub-surface diagnostic horizon was noticed in P3, P4 and P5. Deep and wide surface cracks and slickensides close enough to intersect were observed in P4 and P6. The pedons P1, P2, P3 and P5 had sandy loam to sandy clay loam texure and it was clay loam to clay in cultivated plains (P4 and P6). The soils were low to medium in organic carbon content. The CEC ranged from 6.4 to 32.5 cmol (p+) kg-1 and the soil exchange complex was dominated by calcium followed by magnesium, sodium and potassium. The ratio of CEC/ clay was low in P2, medium in P1, P3 and P5 and high in P4. Devararapalli pedon was classified as Typic Haplustalfs, Gujjangivalasa as Typic Haplustults, Patikivalasa and Amiti as Typic Haplustepts, Gangada as Vertic Haplustepts and Maddivalas as Chromic Haplusterts.

Acid rain and soil

A summary of important chemical properties of soil is given and the way in which acid rain may affect these properties is discussed. Acid rain may suppress microbiological decomposition and nitrification processes, thus influencing the nutrient status of soils. It has also been found that soil organic matter is less soluble in more acid solutions. Changed nutrient availability patterns are predicted in a low pH environment and enhanced leaching of essential elements from the soil exchange complex has been observed. Increased solubility of potentially toxic elements such as aluminium may also occur from soils which have been exposed to acidified rainfall.

EFFECT OF NITROGEN ON CESIUM-137 IN SOILS AND ITS UPTAKE BY OAT PLANTS

In an experiment designed to show the effects of time of addition of NH4 relative to Cs-137 and of NH, compared with NO3, the results showed conclusively that NH4 caused higher Cs-137 concentrations in oats than did the NO3 form of N at low soil K contents. The results were less conclusive for soils to which K had been applied. When NH4 was applied before Cs-137, in most instances the Cs-137 concentration was higher than when Cs was applied before NH4 without added K. When K was added, however, the trends were for the most part the reverse. Thus NH4, K and Cs-137 in the soil interact for sites on the soil exchange complex and the amount of Cs-137 taken up by the plant is a function of this interaction.Liming of one acid soil consistently increased the Cs-137 concentration and uptake, whereas in another acid soil the effects of liming were less consistent.