Abstract

TOLEDO, Diana Marcela et al. Indices and indicators of soil quality in natural and cultivated red soil systems. Cienc. suelo [online]. 2013, vol.31, n.2, pp.201-212. ISSN 1850-2067.

The objectives of this study were to determine soil quality (SQ) indicators, develop proper soil quality indices and apply the indices from the literature so as to assess their sensitivity in detecting the SQ changes caused by deforestation and agricultural use in Oxisols at Oberá (Misiones), where rainforests have been removed and replaced with annual and perennial crops. The experimental design was completely randomized with three treatments: tropical forest (S), corn crop under conventional tillage (Zea Mays L.) (M) and tea crop (Camellia sinensis L.) (T). Twelve plots were sampled from each treatment at 0-0,10; 0,10-0,20 and 0,20-0,30 m depths. The following variables were evaluated on the soil samples: respiration (RES), bulk density (Da), texture, pH, organic matter (MO), particulate organic matter (MOP), total nitrogen (Nt), and potentially mineralizable nitrogen (NPM). The following indices were determined: MOP/MO, NPM/Nt, NPM/MOP, MO/Li+Arc, MOP/RES, and the stratification ratios of soil organic carbon (COSr₁, COSr₂) and of nitrogen mineralization potential (NPMr₁, NPMr₂). All data were analyzed through ANOVA, means were separated by the LSD Test (p < 0,05), and a Pearson correlation was performed. Soil indicators Da, RES, MO, Nt and NPM, and indices NPM/Nt, MO/Li+Arc, NPM/MOP, IRC, IMC, COSr₁ and COSr₂ revealed statistical differences between soils under natural systems and cultivated soils. Indicators Da and RES, and index COSr₂ turned out to be more sensitive; they showed differences between perennial and annual cropping systems, the latter causing higher soil degradation. Even though further research is needed, the results obtained from this study would indicate that high quality soils have a stratification ratio COSr₁ >2 and COSr₂ >1,5; lower values would therefore suggest loss of SQ. The elaborated ratio MOP/RES showed differences in MOP quality and its cycling, indicating that in virgin soils and perennial cropping systems without removal of soil (T), the cycling is slower than in soils under annual crops (M).

Keywords : Soil quality; Indicators; Functional indices; Crops systems.

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