Abstract
The aim of the present study was to evaluate the agronomic traits in the pre- and post-grazing and the nitrogen use efficiency of Piatã grass that was subjected to nitrogen fertilization throughout the seasons of the year. The experiment was performed in a randomized block design with four treatments (0, 150, 300, and 450 kg ha−1 N). Grazing was performed with sheep when the forage canopy reached 95% light interception up to 20 cm height of post-grazing. The pre-grazing forage mass of the Piatã grass showed a behavior (p < 0.05) linear to nitrogen fertilization, with higher and lower values in spring and winter, respectively. The post-grazing forage mass responded linearly (p < 0.05) to nitrogen fertilization, with an increase of 43.12% for the dose of 450 kg ha−1 N in relation to pastures without nitrogen fertilization. When the non-fertilized pasture was compared with the highest nitrogen dose, a reduction of 21.79% dead tissue was observed in the post-grazing forage mass. The highest nitrogen use efficiency was obtained with the dose of 450 kg ha−1 N. The forage mass production of the Piatã grass in the pre- and post-grazing conditions are positively influenced by nitrogen fertilization and the seasons of the year, with lower values in winter.
Highlights
To make competitive the use of pasture as a forage resource for the feeding of ruminants, it is necessary to use the pasture adequately in order to ensure production and harvest efficiency [1].studies that are conducted based on the physiology and ecology of forage grasses are extremely important [2,3,4].Based on the ecophysiological management of grasses, when the forage canopy reaches 95% light interception (LI), the maximum forage accumulation rate is maintained, while there is sufficient leafAgriculture 2020, 10, 337; doi:10.3390/agriculture10080337 www.mdpi.com/journal/agricultureAgriculture 2020, 10, 337 area to intercept almost all incident light [5]
The grazing intensity of Piatã grass was obtained from the results presented by [15], who used LI as a parameter of grazing frequency
These results were similar to those that were reported by [18], who evaluated the effect of nitrogen doses (0, 125, 250, 375, and 500 kg ha−1 N) on the productive characteristics of the Brachiaria brizantha cv
Summary
To make competitive the use of pasture as a forage resource for the feeding of ruminants, it is necessary to use the pasture adequately in order to ensure production and harvest efficiency [1].studies that are conducted based on the physiology and ecology of forage grasses are extremely important [2,3,4].Based on the ecophysiological management of grasses, when the forage canopy reaches 95% light interception (LI), the maximum forage accumulation rate is maintained, while there is sufficient leafAgriculture 2020, 10, 337; doi:10.3390/agriculture10080337 www.mdpi.com/journal/agricultureAgriculture 2020, 10, 337 area to intercept almost all incident light [5]. Based on the ecophysiological management of grasses, when the forage canopy reaches 95% light interception (LI), the maximum forage accumulation rate is maintained, while there is sufficient leaf. LI and, in response to competition for light, the plant initiates an intense stem elongation process, leading newer leaves to be positioned above the older leaves under conditions of full light. This leads to reduced leaf accumulation and increased accumulation of stems and dead material, with an increase in the amount of tissues without photosynthetic (senescent) tissues [6]. [7] demonstrated that the optimal point for interrupting the regrowth of pastures subjected to cutting regimes would be the one with the highest average rate of forage accumulation and nutritional quality
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