Medium-term impacts of poultry litter application on potentially toxic elements in soil under subtropical conditions in southern Brazil

Abstract

Poultry litter is widely applied as an organic fertilizer, yet concerns remain regarding the cumulative input and potential accumulation of potentially toxic elements (PTEs) in agricultural soils. This study evaluated the medium-term effects of repeated poultry litter application on pseudo-total concentrations and cumulative inputs of arsenic (As), cadmium (Cs), chromium (Cr), copper (Cu), nickel (Ni), and zinc (Zn) in an acidic dystrophic Red Latosol under subtropical conditions in southern Brazil. An eight-year field experiment (2011–2018) evaluated four annual poultry litter rates (0, 4, 8, and 12 t ha⁻ 1 ) combined with dolomitic limestone application under a randomized complete block split-plot design. Baseline soil characterization, cumulative PTE mass balance, and linear mixed-effects models were integrated to assess treatment responses and environmental relevance. Despite continuous inputs, no significant accumulation of As, Cd, Cr, Cu, or Ni was detected within the evaluated 0–20 cm soil layer, likely reflecting low cumulative additions relative to initial soil stocks and soil retention processes. In contrast, Zn showed significant dose-dependent accumulation in the surface layer (0–10 cm), consistent with its higher cumulative input from poultry litter. Dolomitic limestone application had no detectable effect on PTE dynamics during the evaluated period, probably due to the limited increase in soil pH. Although all PTE concentrations remained below Brazilian regulatory thresholds, cumulative Zn inputs represented the largest proportional increase relative to the initial soil pool, highlighting Zn as a sensitive indicator for monitoring repeated organic amendment applications. These findings emphasize the importance of combining baseline characterization, mass balance approaches, and continued monitoring to improve environmental risk assessments of organic waste reuse in subtropical agroecosystems.

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