Efecto del manejo agrícola en parámetros físicos y químicos del suelo en diferentes agroecosistemas de la granja Santa Inés

Abstract

In recent years, agriculture has become an important pillar for society, generating changes in agro-ecosystems, which have led to changes in the landscape, as well as affecting the physical and chemical properties of agricultural soils, reflected in soil degradation, loss of biodiversity, emission of greenhouse gases into the atmosphere, global warming, and increased presence of extreme events. Ecuador, an eminently agricultural country, has not escaped this situation, since agriculture is the main source of employment, and constitutes a major axis in economic development and food security. Human activity in agricultural production has led not only to the exploitation of agricultural areas, but also to the use of virgin soils and vacant land. The research was developed with the objectives of demonstrating the incidence of the management of the productive system on physical and chemical parameters of soils subjected to different conditions at different depths of the soil (0-15, 15-30 and 30-45 cm) and to know the correlation force between the values of the physical properties and the values of the chemical properties at 0-15, 15-30 and 30-45 cm depth of soil in productive systems of the experimental farm Santa Inés, belonging to the Faculty of Agricultural Sciences, Technical University of Machala, El Cambio parish, Machala canton, in the province of El Oro, classified as Holdridge natural life zone within the very dry forest formation -Tropical (bms-T). The study is of an observational, transversal, prospective and analytical type. Five agrosystems were selected corresponding to productive areas of banana, forest, short cycle crops, pastures and cocoa, in which permanent sampling points were established completely at random and georeferenced. In the five PPMs, pits were made with a diameter of 60 x 60 cm, at three depths of the soil (0-15 cm, 15-30 cm and 30-45 cm) from where the samples were taken, which were homogenized to guarantee a representative sampling. The analytical determinations were made in the laboratory of soil, foliage and water, belonging to the Ecuadorian Agency for Quality Assurance of Agriculture (AGROCALIDAD) Tumbaco-Quito. In order to know if significant statistical differences between the means of the variables real density, clay, silt, sand, pH, MO, N, P, K, Ca, Mg, CIC and CE are presented or not, the analysis of variance (ANOVA) of an inter-group factor was used, previous verification of the requirements of independence of observations, normality of data and homogeneity of variances. In case of significant statistical differences between the different agricultural systems for each of the depths evaluated (0-15 cm, 15-30 cm and 30-45 cm), post-hoc tests, multiple range tests and comparisons were applied in order to establish between which treatments the differences or similarities are found. To establish if the physical properties of the soil are related in a linear way to the chemical properties of the soil, the hypothesis test was applied for the contrast and later to establish the type and strength of the correlation between the two variables (Pearson's correlation coefficient (r). The data were statistically processed with the SPSS version 24 statistical test package for Windows and an estimation reliability of 95% was used (α=0.05). In general, there is evidence of an influence of agricultural management and the type of crop used on the physical and chemical properties of the soil. For the case of real soil density at 0-15 cm depth, in pastures (1.76 g/ml) the lowest value was obtained, statistically equal to forest, cocoa and banana, but statistically different to corn (2.34 g/m), which shows that the intensification of the work is a condition for the increase of soil compaction. In the case of soil pH at 0-15 cm depth, values above 7 were obtained in all systems, although the lowest value was obtained for cocoa (7.20 g/ml), which is statistically equal to forest and banana, but statistically different to grass (7.81 g/ml) and corn (7.83 g/ml), which may be associated with the incorporation of organic waste into the soil. The behavior of organic matter in the soil showed that cocoa (3.71%) and forest (2.91%) reached the highest values, statistically different to corn (0.64%) and grass (1.80), which is attributed to the large amount of leaves, branches and stems that are generated that are incorporated into the soil by the activity of microorganisms. The cation exchange capacity shows that in corn (13.28 cmol/kg) the lowest values are reached, even below 20, which is statistically different from the rest of the productive systems, indicating that a continuous and intensive management of the soil causes a decrease in carbon sequestration, accompanied by a little incorporation of organic waste and a low fertility in the area. Correlation tests carried out show a significant correlation between real density and strong negative cation exchange capacity (p-value=0.008 and r=-0.64).