Morphogenesis and structure of Tifton 85 cultivated in subtropical climate and fertilized with nitrogen

The experiment evaluated the morphogenesis and structure of Tifton 85 ( Cynodon spp. ) cultivated in subtropical climate and fertilized with nitrogen (N). The experiment was a completely randomized design with four levels of N (Zero; 75; 150 or 225 kg ha -1 ) in nine replicates per area. The experimental animals were Suffolk female lambs. The grazing method was continuous to maintain the sward height at 15 cm ± 10%. The stem expansion increased by 0.000027 cm degree-days -1 to each kg N applied (linear model). According to nonlinear model, the highest stem expansion (0.0226 cm degree-days -1 ) was observed with the use 220.1 kg ha -1 N. The leaf lifespan fitted a linear regression model, with increase of 50 degree-days leaf -1 , comparing the levels zero and 225 kg ha -1 of N. According to nonlinear regression model, the longest leaf lifespan (407.1 degree-days) was observed with the use 208.8 kg ha -1 N. With the maintenance of sward height at approximately 15 cm, we recommended to use 200 kg ha -1 N in Tifton 85 cultivated in subtropical climate.