Effect of nitrogen on yield and quality of Panicum maximum cvv. Mombasa and Tanzania in Northeast Thailand

Abstract

A field trial in Northeast Thailand during 2011-2012 compared the effects of nitrogen fertilizer, applied as urea in the wet season, on the growth and quality of Panicum maximum cvv. Mombasa and Tanzania. In the establishment year, increasing rates of nitrogen (0, 20, 40 and 60 kg N/ha every 40-45 days) (0-180 kg N/ha for growing period) progressively increased stem, leaf and total DM production (P < 0.05). At higher rates (80 and 100 kg N/ha or 240-300 kg N/ha for growing period), only total DM increased at the highest rate. In the second year, a rate of 20 kg N/ha every 40?45 days (80 kg N/ha for growing season) doubled the amount of DM compared with no nitrogen, and 80 kg N/ha every 40?45 days (320 kg N/ha for growing period) produced significantly higher stem, leaf and total DM yields than most other rates. The yield response (kg DM/kg N) decreased linearly (24.7 to 20.3 in 2011; 56.7 to 15.1 in 2012) from the lowest to the highest rate of nitrogen. In both years, increasing rates of nitrogen significantly increased CP and NDF concentrations in stems and leaves and ADF concentrations in stems. Mombasa produced 17 and 19% more leaf and 18 and 22% more total DM than Tanzania, in the first and the second year, respectively. Mombasa also produced 30% more stem DM than Tanzania in the second year. While Tanzania produced higher CP levels than Mombasa in the establishment year, in the second year, Tanzania had higher levels than Mombasa only when N rates of 80-100 kg N/ha were applied every 40?45 days (320-400 kg N/ha for growing period). Applying 60 kg N/ha every 40?45 days appears to be a reasonable compromise to achieve satisfactory DM yields in the wet sea-son (8,000 kg/ha first year and 12,000 kg/ha second year), leaf percentage of 68-70% and leaf CP concentrations above 7%.