Efecto de la modificación del ph sobre la lixiviación de cationes en columnas de suelos calcáreos de la provincia de El Oro.

Abstract

The soil is considered an indispensable natural environment for life, and according to research carried out by several scientists, various crops can be grown with adequate productivity standards. Lime soils present a problem for some crops, since having a high pH causes the appearance of iron chlorosis, and consequently leaf yellowing, decreased production, etc. Ferrous sulfate monohydrate (SFM) was used to correct the pH of the limestone soils studied. This product usually contains a high percentage of iron (15-30%) and sulfuric acid (18%), these being its two main components. The objective of this research was to determine the evolution of the soil reaction (pH), electrical conductivity (C.E.), Calcium (Ca++), Magnesium (Mg++), Sodium (Na+) and Potassium (K+) in water leached in columns of different calcareous soils of El Oro Province after the application of ferrous sulfate monohydrate (SFM). The research was carried out in 4 farms located in El Oro Province. Soil samples were taken at depths of 0 - 15, 15 - 30, 30 - 45 and 45 - 60 cm; later the samples were homogenized to guarantee their representativeness and then they were sent to the Soil, Plant Tissues and Water Laboratory of the Litoral Sur Experimental Station of INIAP, located at Km. 26 via Durán Tambo, Virgen de Fátima parish, Yaguachi canton, Guayas province, for soil cation determinations. To determine whether or not there are significant statistical differences between the means of the variables soil reaction (pH), electrical conductivity (C.E.), Calcium (Ca++), Magnesium (Mg++), Sodium (Na+) and Potassium (K+) according to the different treatments, an intergroup factorial ANOVA test was carried out. Tukey's post-hoc tests were then performed to determine in which treatments the significant differences were present. Data processing was performed with the statistical program SPSS version 25 test for Windows 10 with a reliability of 95%, that is, a significance level α=0.05. Through the statistical analyses studied in the variables Soil reaction (pH), Electrical conductivity (C.E.) and Potassium (K+) significant differences were presented in at least one treatment. From the data obtained, it can be concluded that the soils studied owe their pH value to calcium salts (Ca++), which dominate the entire hydrochemical process. Ca++ began with an average value of 186.03 mg L-1, which after the SFM applications presented an average value of 164.72 mg L-1. Mg++ presented significant changes in this research, starting with an average value of 111.56 mg L-1, and after the application of the different SFM treatments ended with an average value of 85.90 mg L-1, showing that clays with a high calcium component are probably not the ones that predominate in the chemical and hydrochemical processes. The K+ starting with an average value of 113.77 mg L-1 and ending with an average value of 112.13 mg L-1 after the SFM applications, is practically independent of the process established in this research, suggesting that the position of the exchange in the clays, where it is located, is not altered by the process of attack with SFM, at least at the doses used here. Na+ at high doses is the most affected, since it started with an average value of 54.25 mg L-1 and after the SFM applications it ended up with an average value of 66.17 mg L-1, due to the fact that it will be displaced from its adsorption positions after a certain pH point and with this its values will increase. The use of SFM not only lowers the pH, due to Ca++ leaching in soils that have it in excess, but also does not affect the ion exchange process, such as K+, which is necessary for proper plant nutrition. From the data obtained it could be concluded that these calcareous soils owe their pH value to salts of the calcium ion, which dominates the whole hydrochemical process.