Benefits of liquid urea and a microbial catalyst on biomass and the nutritional value of Mombasa grass

During 2019, an experiment was conducted at the Agricultural Experiment Station in Isabela (Puerto Rico) on an Oxisol with previously well-stablished stands of cv. Mombasa. This experiment assessed the effects of a microbial catalyst (MC) and liquid urea 22-0-0 (LU) at a rate of 168 kg ha-1 (in split applications), a mixture of LU+MC and a control on aboveground biomass, root biomass, nutritional value, nitrogen use efficiency and soil parameters on cv. Mombasa at 35-day (d) harvests during six harvests. The study was established in a completely randomized design with four replicates. The effects of LU and MC on belowground (root) biomass were determined by collecting samples in 1 m2 to determine the yield and chemical composition. Soil samples were collected at 15 cm depth using a soil corer at the first and 6th harvest from each plot to assess organic carbon (OC), total nitrogen (TN), pH, macronutrients, and cation exchange capacity (CEC). The results showed that aboveground biomass doubled using LU (2369 kg DM ha-1) compared to the control and MC (1100 kg DM ha-1). Crude protein (CP) was 10.1 % using LU. Neutral Detergent fiber was 70 % for the control, 74.2 % when LU was used, and around 40 % for acid detergent fiber (ADF) for any treatment. Overall, there were no significant effects of treatments on OC and organic matter percentages, P, N, Ca, Mg, and CEC. In conclusion, LU is an excellent source of N for Mombasa, but shorter harvest frequencies may be required to improve the fiber quality of Mombasa.