Root decomposition in Urochloa decumbens pastures fertilized with increasing nitrogen doses or intercropped with Calopogonium mucunoides

Cropping systems may affect root decomposition and our objective was to evaluate chemical characteristics and root decomposition in signal grass 'Basilisk' [Urochloa decumbens (Stapf) R.D. Webster] pastures under different cropping systems. A split-split plot scheme, with four cropping systems (0, 50, 100 kg·ha−1 of N, and intercropping with calopo (Calopogonium mucunoides Desv.) in the plots (paddocks), two experimental periods (2019/2020 and 2020/2021) in the split-plots, and nine incubation times (4, 8, 16, 32, 64, 128, 256, and 512 days) in the split-split plots, in a randomized block design with two replications was used. Root biomass was not affected (p > 0.05) by cropping systems (7.4 t ha−1 on average). Before incubation, ADIN-TN (acid detergent insoluble nitrogen in total nitrogen) concentration was affected by cropping systems and C concentration was affected by interaction cropping systems x period. The remaining biomass had a loss total of 28% (1st ) and 30% (2nd ) after 512 d. N concentration was higher in the 1st period, resulting in a lower carbon: nitrogen ratio. Higher lignin concentration was observed for 0 kg·ha−1 of N (1st ) and 50 kg·ha−1 of N (2nd ). The ADIN concentration was higher in 100 kg·ha−1 of N than others systems. The lignin: N and lignin: ADIN ratios decreased over time. Although the root litter decomposition was not affected by the cropping systems, a potential average input of 18.6 kg·ha−1 of N was observed after 512 days.