Avaliação da toxicidade da ureia no solo para colêmbolos Folsomia candida e enquitreideos Enchytraeus crypticus

Abstract

The use of chemical fertilizers, particularly to achieve high agricultural productivity, has raised concerns about their environmental impacts. Nitrogen is widely applied in the form of urea, which, when in contact with soil, can affect soil invertebrates-organisms essential for maintaining agroecosystems and providing various ecosystem services. To assess the effects of chemical substances on soil, edaphic organisms such as the collembolan Folsomia candida and the enchytraeid Enchytraeus crypticus are commonly used in ecotoxicological assays and are considered model organisms for this type of study. Given the limited understanding of the effects of chemical fertilization on edaphic organisms, this study aimed to evaluate the impact of different doses of nitrogen fertilizer urea on the reproductive development of F. candida and E. crypticus. Chronic toxicity tests were conducted with these species in natural Brazilian soil (Neossolo Quartzarênico) following standardized methodologies: NBR ISO 11267 for F. candida and ISO 16387 for E. crypticus. The organisms were exposed to soil containing increasing concentrations of urea dissolved in water: 0 (distilled water), 0.1, 0.2, 0.4, 0.8, and 1.6 g of urea per kilogram of dry soil (g/kg). The water volume was standardized at 60% of the soil's water-holding capacity (WHC) for all treatments. Collembolans were exposed for 28 days, while enchytraeids were exposed for 21 days. The results showed that from a concentration of 0.8 g/kg, significant reductions in reproduction were observed for both test organisms. However, differences in responses were noted at lower concentrations, where 0.1 and 0.2 g/kg significantly increased the reproduction of E. crypticus but had no significant effect on F. candida. The concentrations estimated to cause 20% (EC20) and 50% (EC50) effects on the E. crypticus population were 0.4614 g/kg and 0.5226 g/kg, respectively. For F. candida, the estimated values were 0.3692 g/kg for EC20 and 0.9861 g/kg for EC50. Considering that field application rates often exceed the concentrations that caused toxicity to these organisms, understanding urea-soil interactions with edaphic organisms is crucial to prevent negative impacts on soil quality.