Avaliação química do solo sob cultivo de eucalipto com 13 anos, recomendações de manejo e análise econômica para implantação de lavoura

Abstract

Soil chemical quality is a determining factor for the sustainability of agricultural systems and for the successful conversion of degraded forest areas into productive environments. Eucalyptus is a widely cultivated species of great economic importance in Brazil, and as a fast-growing forest species, it demands high nutrient uptake from the soil. In this context, the present study aimed to identify the main chemical constraints and propose a feasible soil management strategy for recovery and subsequent implantation of soybean cultivation, to assess the fertility of a soil previously cultivated with eucalyptus for 13 years, and to estimate the cost of inputs and seeds for the recommended cover crops. The study was conducted in Coronel Domingos Soares, Paraná State, where soil samples were collected from two depths (0–20 cm and 20–40 cm). Laboratory analyses were performed at the UTFPR Soil Laboratory – Pato Branco Campus, following official interpretation methodologies from the (SBSC/IAPAR, 2019; CQFS-RS/SC, 2016) fertilization and liming manuals. Based on the results, a fertility diagnosis was carried out and a corrective management plan was developed, including split applications of dolomitic lime, agricultural gypsum, phosphorus and potassium fertilization, and the implantation of cover crops. The results revealed a severely acidified soil, with extremely low pH (3,4–3,9), base saturation (V%) below 3%, high aluminum saturation, and critical levels of Ca, Mg, P, and K. The technical prescription included 18.7 t/ha of split-applied dolomitic lime and 1.5 to 3.0 t/ha of agricultural gypsum to correct acidity and supply Ca and Mg. Phosphorus correction was achieved using single superphosphate, while potassium fertilization was performed through split KCl applications, both complemented by the formulated fertilizer (04-30-10), totaling 120 to 150 kg/ha of P2O5 and 100 to 120 kg/ha of K2O. For physical and biological soil recovery, a cover crop mixture of black oat, forage radish, and brachiaria was proposed, promoting nutrient cycling, increasing organic matter, and reducing erosion. The cost estimation of inputs demonstrated technical and economic feasibility for soil recovery. It is concluded that although soil under eucalyptus may present significant chemical degradation when improperly managed, its restoration is achievable through careful corrective practices and strategic use of cover crops. The proposed management plan restores suitable conditions for soybean cultivation and reinforces that the “soil depletion” commonly attributed to eucalyptus is more closely linked to management practices than to the species itself.