Carbon and Nitrogen Balance in an Oxisol Influenced by Sewage Sludge and Mineral Fertilization

Abstract

ABSTRACT Most conventional agricultural production systems have difficulty maintaining carbon (C) and nitrogen (N) stocks in soils. However, the use of organic sources in fertilization, such as sewage sludge, can reverse these processes of degradation of soil organic matter. The objective of this study was to evaluate C and N stocks and balance in organic matter fractions of a Oxisol under pineapple after fertilization with sewage sludge and mineral fertilizers. A randomized block experimental design was used with four replications in a 2 × 2 factorial arrangement, corresponding to two pineapple cultivars (‘Vitória’ and ‘Smooth Cayenne’) and two fertilization tips (sewage sludge and mineral fertilizers). Soil samples were collected at the depths of 0–20, 20–40, and 40–60 cm to characterize the stocks of total organic carbon (TOC), total nitrogen (TN), labile carbon (LC), carbon in the fulvic acid fraction (FAF), in the humic acid fraction (HAF), and in the humin fraction (HUM), and the humification index (HI). Fertilization with sewage sludge increased the carbon and nitrogen stocks in the labile and stable fractions of the soil compared to the soil that received only mineral fertilization and compared to the condition at the beginning of cultivation. The increase in the TOC stock was 8 t ha−1, with accumulated storage of 148 t ha−1 in the 0–60 cm depth. The TN stock increased 2 t ha−1, with accumulated storage of 15 t ha−1 in the 0–60 cm depth. Therefore, fertilization with sewage sludge contributed to the agricultural sustainability of the soil.