Predictive analysis of pH response to aglime in a Salvadorian field

Abstract

Constant misuse of fertilizer and bad agriculture practices lead to a decrease of soil pH, affecting fertility conditions for crop production. In El Salvador, calcium hydroxide is the cheapest source of aglime to correct this problem. However, since this compound is caustic, there is controversy about its effects in the short term. In this study, a predictive analysis of response of an agricultural field to this kind of treatment was performed by collecting 120 samples of 250 grams of dry soil at different positions across a rice field, recording its coordinates and general characteristics in order to create a Kriging model of the spatial variability by the use of a Geographic Information System (GIS). The initial value of acidity was included in the data. To each sample, 100 ml of distilled water and 0.5 grams of calcium hydroxide were added and mixed, then measuring pH after 15 minutes and again after 48 hours, in order to create a spatial variability model of the resulting acidity of the soil through the time. The results indicated that a violent caustic reaction occurs during the first minutes after the treatment, reaching temporally high alkaline values, but descending to its final value after 48 hours. Acidity values could be increased by the treatment in no more than 1 unit in the pH scale, depending on the type of soil.