Abstract

LUJAN ACOSTA, María Gabriela; TOLEDO, Diana Marcela; CONTRERAS LEIVA, Stella Maris  and  GALANTINI, Juan Alberto. FOREST EXPANSION ON NATIVE GRASSLANDS IN AQUICS SOILS IN THE N-NORTHEAST OF CORRIENTES. Cienc. suelo [online]. 2022, vol.40, n.2, pp.137-148.  Epub Apr 21, 2023. ISSN 1850-2067.

In the N-NE of Corrientes province, forest expansion has mainly been aimed at displacing native grassland areas. The objective of this research was to determine whether this affects soils, and to what extent. We assessed the sensitivity of some soil indicators, built some functional indices and applied stratification ratios of carbon and nitrogen. The assay was carried out in Inceptisols of an aquic moisture regime. A completely randomized design was applied, with two treatments: native grassland (Pz) and Pinus sp (Pi) plantations. For each treatment, three plots were used, with five sampling sites. The soil samples were collected at depths of 0-0.10, 0.10-0.20, 0.20-0.30, and 0-1 m. The following soil properties were determined: bulk density (Da), texture, pH, soil respiration (RES), soil organic carbon (COS), total nitrogen (Nt) and potentially mineralizable nitrogen (NPM). Functional indices were applied, as well as the stratification ratios of organic carbon (COSr) and total nitrogen (NTSr). The results were analyzed through ANOVA, an LSD test (P<0.05) and a Pearson’s correlation test. Soils proved to be acidic and coarse-to-medium textured. Soil indicators and indices were sensitive enough to detect changes in soil quality. Lower values were observed, for COS (-15%), NT (-43,3%) and microbial activity (RES: -23.8%, NPM: -67.7%) at 0-0.10 m. A change was seen in the functioning of the system, in the NPM/RES, NPM/MO and NPM/NT indices. Grassland clearing, soil tillage and Pinus sp. plantation for more than 15 years significantly affected the system. For a sustainable production, it is thus imperative to fertilize when soils are originally poor, medium-to-coarse textured and of an aquic moisture regime, such as Inceptisols of the N-northeast of Corrientes province (Argentina). The resulting NPM may be used to adjust fertilization schemes in forested areas, as it is incorporated to the nutritional balance for this area and soil type.

Keywords : grassland clearing; Pinus sp. plantations; soil quality.

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