Autor: Sbrissia, André Fischer; Chiavegato, Marilia Barbosa; Barreta, Daniel Augusto; Silva, Sila Carneiro da; Pittaro, Gabriela; Barbosa, Rodrigo Amorim

Balancing agricultural productivity with biodiversity conservation represents a significant challenge in grassland management.

This study aimed to determine the extent to which increasing nitrogen fertilization rates affect plant species diversity in frequently grazed multispecies pastures managed at heights designed to maintain light availability throughout the canopy. Despite management strategies specifically targeting light competition as a biodiversity loss mechanism, our three-year field experiment revealed significant diversity decline with increased nitrogen inputs. Shannon diversity index decreased by 7–16 % across treatments, with the most pronounced reductions occurring at higher nitrogen rates. Species composition analysis demonstrated that a single competitive grass species (Cenchrus clandestinus) accounted for over 70 % of leaf area index increases at elevated nitrogen levels, establishing competitive dominance despite controlled canopy height. Legume abundance decreased significantly with higher nitrogen rates, declining from 18.3 % at 100 kg N ha⁻¹ to 8.1 % at 300 kg N ha⁻¹ year⁻¹ , while forage production increased by 15.5 % when nitrogen rates doubled from 100 to 200 kg N ha⁻¹ year⁻¹ , with no significant gains at 300 kg N ha⁻¹ year⁻¹ . While the highest nitrogen rate reduced diversity immediately, moderate rates (200 kg N ha⁻¹ year⁻¹) showed progressive decline over the three-year period, indicating a dose-dependent temporal response. These findings reveal fundamental challenges for sustainable grassland intensification: conventional management approaches focusing solely on canopy structure are insufficient to prevent nitrogen-driven diversity loss, while the dose-dependent temporal patterns identify intervention windows enabling management strategies that could reconcile productivity and biodiversity.

Para ver el contenido completo, ingrese al repositorio institucional INTA Digital