Abstract
The determination of biomass flows can assist on improving pasture fertilization techniques, contributing to identify the best management methods and, in relation the use of fertilizers. Nitrogen deficiency in pastures can reduce forage production. On the other hand, there is an environmental concern on nitrogen (N) losses when this nutrient is used in excess and this concern guides the search for new grazing systems that optimize its use. Leaf biomass flow, intensity and frequency of defoliation were evaluated in Alexandergrass ( Urochloa plantaginea (Link) Hitch) fertilized with Zero, 100, 200 or 300 kg/hanitrogen (N) as urea. The grazing method was put and take stocking in order to keep the forage mass at 3,000 kg/haDM. The experimental animals were Angus heifers with an initial age of 15 months and body weight of 241.5±5 kg. The experimental design was completely randomized following a repeated measure arrangement, with four treatments and variable number of experimental units. The highest growth of leaf blades was achieved with 100 kg/haN. Senescence and intake flows and defoliation intensity were similar among the N levels used. The frequency of return to the same tiller (days) was influenced by N levels and evaluation periods. Our findings recommend the use of 100 kg/ha N in Alexandergrass pasture.
Highlights
Pastures are the most practical and economical way to feed cattle and sustain the livestock production in Brazil
We evaluated the biomass flow, defoliation intensity and frequency on Alexandergrass pasture fertilized with Zero, 100, 200 or 300 kg of nitrogen (N)/ha as urea
Calves were kept in paddocks with similar forage mass (FM; 2,969 ± 82 kg/ha dry matter (DM); P=0.6398)
Summary
There is an environmental concern on nitrogen losses (N) when this nutrient is used in excess and this concern guides the search for new grazing systems that optimize its use. In Southern Brazil, the Alexandergrass (Urochloa plantaginea (Link) Hitch) has been studied as a forage species because it occurs spontaneously in areas cultivated with summer crops, having favorable characteristics for grazing (OLIVEIRA NETO et al, 2013). Studies involving the use of nitrogen in Alexandergrass pasture indicated a positive response of this forage to this nutrient (ADAMI et al, 2010; SARTOR et al, 2014). In addition to the leaf biomass flows, knowledge of defoliation patterns (intensity and frequency) can provide information to minimize losses of leaf tissues by senescence. The intensity and frequency of removal of leaf blades are important factors determining the plant canopy structure and can determine the plant response to the action of herbivore
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