Efficiency of urea with urease and nitrification inhibitors in the production of bermuda grass fodder

Resumo

The adoption of strategies aimed at a more efficient use of nitrogen (N) and ontaining hig yields are important to satisfy the demand for food for animals and humans. The Tifton 85 Bermuda grass (Cynodon spp.) is a crop with high productive potential and may be used to create hay, but its culture requires elevated doses of nitrogen. In this sense, the objective of this experiment was to evaluate, in field conditions, the growth and production of Tifton 85 Bermuda grass according to nitrogen doses with urea containing urease and nitrification inhibitors for two agricultural years — eight cycles of forage growth. The treatments were evaluated in a randomized complete block design with three repetitions in a 3x5 factorial scheme. Treatments were: I) urea; II) urea + triamide N-(n-Butyl) thophosphoric (NBPT) urease inhibitor; and III) urea + nitrification inhibitor 3,4-Dimethylpyrazole phosphate (DMPP) with N rates (0, 40, 80, 120 and 160 kg ha-1 of N) applied after each growth period. Then, the study proceeded to estimate forage dry mass and N concentrations in dry mass for each of the growth cycles and their sum, as well as the apparent N recovery. N critical levels were set when relative production reached 90%. The use of urease (NBPT) or nitrification (DMPP) inhibitors did not improve the efficiency of urea regarding growth and production of Tifton 85 Bermuda grass. The appropriate dose of nitrogen for Tifton 85 Bermuda grass in a hay production system is 40 kg per ton of dry mass produced in each growth period.