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Estimation of the Exchangeable Sodium Percentage from the Sodium Adsorption Ratio for salt-affected soils in the High Valley (Bolivia)
Get PDFIn order to obtain a more cost-time efficient way to predict the Exchangeable Sodium Percentage (ESP) function to Sodium Adsorption Ratio (SARe) of salt-affected soils in the High Valley of Cochabamba (Bolivia), two regression models were generated: ESP= 0.972 SARe + 1.576 (R2=0.85, P 0.05). Both models are relatively similar in terms of performance and could be recommended to predict ESP from SARe in the High Valley. To improve the prediction, additional samples for modelling and data stratification in terms of sodicity might be necessary
Characterization of salt affected soils in the High Valley of Cochabamba Bolivia
Get PDFRehabilitation of salt-affected soils in the High Valley of Cochabamba - Bolivi
Random Forests to classify salt-affected soils from soluble salt ions
Get PDFeditorial reviewedSalt-affected soils are characterized by an excess of soluble salts and/or sodium. The widely used US Salinity Lab (USSL) classification considers the exchangeable sodium percentage (ESP), electrical conductivity (EC) and pH. Breiman and Cutler's random forests (RF) algorithm chooses the most voted class over all the trees at training time. The aim was to model and predict the USSL salt-term categories from soluble ions by applying RF model classification. Topsoil samples (110) were collected from the High Valley of Cochabamba (Bolivia) and were analyzed to measure the soluble cations (Na+, K+, Ca2+, Mg2+) and anions (HCO3–, Cl–, CO32–, SO42–), in addition to the required salinity parameters to classify the samples according to the thresholds: ESP of 5%, ECe of 4 dSm-1 and pH of 8.2. No samples matched in the saline category. The overall out-of-bag error was 17.4% and according to the confusion matrix, the class errors for normal, saline-sodic and sodic soil were 0.12, 0.00 and 0.36, respectively. The variables with higher estimated importance and also selected by RF backward elimination were: Na+, Cl–, Ca2+ and HCO3–. Additional sampling might be useful in order to reduce the errors and misclassifications, as well as to improve the selection of variables
Estimation of the Exchangeable Sodium Percentage as a function of the Sodium Adsorption Ratio for salt-affected soils in the High Valley of Cochabamba
Get PDFeditorial reviewedIn order to develop a more efficient cost-time alternative, to determine the sodicity of salt-affected soils, the objective of the study was to generate a regression model to predict the Exchangeable Sodium Percentage (ESP) from the Sodium Adsorption Ratio (SAR). Based on a database of 84 soil samples from the High Valley of Cochabamba, a linear model was generated: ESP = 0.9725 SAR + 1.5765 (R2=0.85). Subsequently, through a set of 18 samples and using T-test of paired samples between values of the predicted ESP and directly measured ESP, the efficiency of the generated model was verified with a value of p= 0.063, indicating that the values were not significantly different, however, the US Salinity Lab referential model was more efficient (p= 0.285). The generated model had a better fit for soils with CE<4 dS.m-1 and ESP <15%. To recommend the generated model, it is pertinent to increase its efficiency with additional samples, besides stratifying the analysis according to salinity/sodicity levels and texture of the soil.Con el fin de desarrollar una alternativa más eficiente en términos de tiempo y costo, para determinar la sodicidad de suelos afectados por sales, el objetivo del estudio fue generar un modelo de regresión para predecir el Porcentaje de Sodio Intercambiable (PSI), en función a la Relación de Adsorción de Sodio (RAS). A partir de una base de datos, de 84 muestras de suelo del Valle Alto de Cochabamba, se generó el modelo lineal: PSI = 0.9725 RAS + 1.5765 (R2=0.85). Posteriormente, a través de un conjunto de 18 muestras y empleando el análisis “prueba T” de muestras pareadas, entre valores del PSI estimado y PSI medido de forma directa, se verificó la eficiencia del modelo generado con un valor de p = 0.063 indicando que los valores de PSI estimados, no son significativamente diferentes de los valores de PSI medidos; no obstante, el modelo referencial del US Salinity Lab resultó más eficiente (p = 0.285). El modelo generado tuvo un mejor ajuste para suelos con CE<4 dS.m-1 y PSI <15%. Para recomendar el modelo generado, es pertinente incrementar su eficiencia con muestras adicionales, además de estratificar el análisis en función a los niveles de salinidad/sodicidad y textura del suelo
Gypsum and sulphur for remediation of a saline-sodic soil from the high valley of Cochabamba
Get PDFeditorial reviewedSaline-sodic soils have an excessive amount of soluble salts and sodium ion, respectively, thus negatively affecting the soil properties and physiology of the plant. The addition of chemical amendments and the leaching to displace sodium and soluble salts are conventional practices to remediate these soils. Two chemical amendments (agricultural gypsum and sulphur) with two levels (50% and 100%) according to the calculated requirement, to recover a saline-sodic soil from the High Valley of Cochabamba, based on pH, electrical conductivity (EC) and exchangeable sodium percentage (ESP), through a pot experiment under leaching conditions. The chemical amendments plus the leaching improved the Na+ and saline conditions of the initial soil (pH 9.6, EC 22.7 dS.m-1, ESP 69.7%). Agricultural gypsum was more effective than Sulphur in displacing Na+, reducing PSI by 34.4%. The amendments slightly reduced the pH. The leaching, as well the amendments, decreased EC by more than 50%. Three lixiviations were enough to remediate soil salinity and sodicity. However the reductions in EC, pH, and ESP values where significant, did not reach the thresholds defined by the “US Salinity Lab” salt-term classification.Los suelos salino-sódicos tienen una cantidad excesiva de sales solubles y del ion sodio, respectivamente, afectando negativamente las propiedades del suelo y la fisiología de la planta. La adición de enmiendas químicas además del lavado para desplazar el sodio y sales solubles, son prácticas convencionales para remediar estos suelos. Se evaluaron dos enmiendas químicas (yeso agrícola y azufre) con dos niveles (50% y 100%) según el requerimiento calculado, para recuperar un suelo salino-sódico del Valle Alto de Cochabamba en función al pH, conductividad eléctrica (CE) y porcentaje de sodio intercambiable (PSI), a través de un experimento en macetas bajo condiciones de lixiviación. Las enmiendas químicas más el lavado, mejoraron las condiciones sódicas y salinas del suelo inicial (pH 9.6, EC 22,7 dS.m-1, ESP 69.7%). El yeso agrícola fue más efectivo que el azufre para desplazar el Na+, reduciendo el PSI en 34.4%. Las enmiendas redujeron levemente el pH. El lavado, así como las enmiendas, disminuyeron la CE en más del 50%. Tres lavados fueron suficientes para remediar la salinidad y sodicidad del suelo. No obstante las reducciones en los valores de CE, pH y PSI fueron significativas; no alcanzaron los umbrales definidos en la clasificación del US Salinity Lab
Reclamation of a Saline-Sodic Soil with Organic Amendments and Leaching
Get PDFeditorial reviewedExcessive amounts of Na+ and soluble salts are characteristics of saline-sodic soils. Loss
of soil structure and osmotic stress in plants are negative effects of salinity-sodicity. This study evaluated the effect of cattle manure, biochar and tropical peat at 1 and 2% (w/w) with leaching, on the exchangeable sodium percentage (ESP), electrical conductivity (ECe) and pH of a saline-sodic soil from the High Valley of Cochabamba (Bolivia). The soil was placed in simulated soil columns and two lixiviations were applied. The initial values of soil were as follows: ESP of 66.6%, ECe of 20.5 dS m−1, and pH of 8.55. Results after leaching differed significantly (p = 0.05) among the interactions. Cattle manure at 2% was the most effective in reducing soil ESP to 27.6%, followed by the rest of the treatments. The three amendments at any level were efficient in lowering ECe below 4 dS m−1. Peat at 2% decreased the soil pH to 7.76. The superiority of cattle manure can be explained by the improvement of soil aggregation and leaching efficiency, through its OM and Ca2+ + Mg2+
contribution. Overall, cattle manure was superior in reclaiming the soil salinity-sodicity, and only the ECe threshold value from the US Salinity Lab classification was reached by any amendment, indicating that cattle manure, biochar or tropical peat with leaching, can be used to reclaim some saline-sodic soils
Organic amendments for the remediation of a saline-sodic from the High Valley of Cochabamba
Get PDFeditorial reviewedSalt-affected soils represent a critical problem in productive and ecological terms on the national and global scale. The objective of the study was to evaluate, for remediation purposes, the effect of four organic amendments (biochar, subtropical peat, bovine manure and poultry manure) with two application levels (1 and 2%) on a saline-sodic soil from the High Valley of Cochabamba. The evaluation was carried out in pots under leaching conditions. Organic amendments were effective in reducing soil ESP and EC. Application levels did not influence the effect on EC and pH. To reduce initial ESP by >80%, poultry manure was the most effective, followed by bovine manure and biochar in equal magnitude. To reduce >60% of the EC, all treatments were equally effective. The
pH decreased slightly with the amendments, except biochar. The evolution of leachates was consistent with the remediated soil and reflected marked reductions in the EC and SAR in the first-second and second-third leachate, respectively; as well as a slight increase in pH. The indicator crop confirmed the remediation effect in terms of survival.Los suelos afectados por sales, representan un problema crítico en términos productivos y ecológicos a escala nacional y global. El objetivo del estudio fue evaluar, con fines de remediación, el efecto de cuatro enmiendas orgánicas (biocarbón, turba subtropical, estiércol bovino y gallinaza), con dos niveles de aplicación (1% y 2%) en un suelo salino sódico del Valle Alto de Cochabamba. La evaluación se desarrolló en macetas bajo condiciones de lixiviación. Las enmiendas orgánicas fueron efectivas para reducir el PSI y la CE del suelo. Los niveles de aplicación no influyeron en el efecto sobre la CE y el pH. Para reducir el PSI inicial en >80%, la gallinaza fue más efectiva, seguida por el estiércol bovino y biocarbón en igual magnitud. Para reducir >60% de la CE, todos los tratamientos fueron igual de efectivos. El pH se redujo levemente con las enmiendas, excepto biocarbón. La evolución de los lixiviados fue consistente con el suelo remediado y reflejó reducciones marcadas en la CE y la RAS, con énfasis en el primer-segundo y
segundo-tercer lixiviado, respectivamente; así como un leve incremento en el pH. El cultivo indicador, confirmó el efecto remediador en términos de sobrevivenci
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