Abstract
High stocking rate livestock management has determined the decline of native species of high forage value as Bromus auleticus Trin ex Nees in the Campos region of the Rio de la Plata grasslands. The species has some agronomic and ecological characteristics that define it as of high potential to be reintroduced in degraded natural grasslands. However, Bromus auleticus has not been sufficiently described, since commercial seeds and information regarding the establishment phase are scarce. Two field experiments were carried out in 2013 and 2014, reintroducing Bromus auleticus into native grasslands in the Basaltic region, aiming to evaluate the impact of sowing density in the forage productivity and their seasonal distribution. The treatments consisted of different sowing densities: 20, 40, 60 and 80 kg ha-1 and one control treatment. Considering the management and the evaluated period (4 years for experiments 2013, and 3 years for experiments 2014), different sowing densities did not modify the forage production in any of the plantings for the evaluated period and compared to the control. However, the use of sowing densities of 40 kg ha-1 or higher allowed modifying the seasonal distribution of forage production with a better contribution in autumn-winter, and more stable production throughout the year.
Highlights
In the Campos biome region, overgrazing is one of the main causes of ecosystem degradation(1)
The PAW remained equal to or greater than 60%, in the 120 days after the establishment of Experiment 2013 (E2013), except in August, which was around 30%
In Experiment 2014 (E2014), the PAW remained above 80% in most of the period between sowing and 120 days after sowing, and unlike in E2013, the PAW in the first summer was lower than 30%, in February and March
Summary
In the Campos biome region, overgrazing is one of the main causes of ecosystem degradation(1). Natural fields are repeatedly exposed to overgrazing, especially when coinciding with periods of low forage growth (for example winters or severe droughts). In both natural and cultivated pastures, seasonal variations in forage production are related to fluctuations in temperature, humidity, radiation, and grazing pressure(2)(3)(4). In the autumn-winter period, forage production is minimal due to low temperatures and frosts that induce the physiological dormancy of the dominant native C4 grasses in most natural grasslands(4)(5). Overgrazing under these conditions can lead to a reduction in pasture growth(6) and species diversity(7). The reintroduction of winter perennials together with the addition of nutrients and the management of the pasture with strategic breaks and control of the forage supply would allow the productive recovery of fields degraded by overgrazing, especially in the autumn-winter period(8)(9)(10)(11)
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