English

Abstract

This two year study aims to verify the necessity of splitting nitrogen (N) fertilization by assessing the effect of different N fertilization strategies (split and not split), on cultivated Tifton 85 (Cynodon spp.) accumulation rate and total dry matter (DM) production, as well as quantifying the levels of nitrate (NO3) in Red Dystrophic Oxisol. Research was carried out at the experimental unit of the Agronomic Institute of Paraná (IAPAR), Pato Branco - PR, in 2011/2012 and repeated in 2012/2013. Experimental treatments were replicated four times using a split plot randomized block design. Main plots consist of accumulated days of evaluation. In the split plot, the N-levels (0, 100, 200 and 300 kg ha-1) were applied following different N-fertilization strategies (applied all at once or split into two or four applications). Tifton 85 total DM production increased as N-levels increased in both years up to 300 kg ha-1. The highest total DM production (16.1 Mg ha-1) was achieved in the second period with 300 kg ha-1 of N, regardless of N-management. Low N-recovery and N-use efficiency were observed in the first experimental period due to the previous shortage of N-fertilization. This is probably because the soil-microbe population immobilized the N applied in the first experiment period. In this case, splitting N-fertilization resulted in greater DM accumulation. After N-fertilization in the second experimental period, on the other hand, there was no response to splitting N-doses. The lack of response to the N-fertilization strategies indicates a soil-microbes plant system stabilization, which resulted in smaller N-immobilization, greater N-recovery and greater N-use efficiency by the Tifton. Furthermore, splitting small rates of N (less than 200 kg ha-1) reduces fodder N-concentration in the initial growth phase, which could impair performance of plant growth and reduce plant protein content. Fodder dry mass more than double at the highest nitrogen level, although, there were no effects regarding to the nitrogen management, inferring that both option may be used.    Key words: Cynodon spp., forage production, nitrogen management, soil-plant interaction.