Producción estivo - otoñal de un campo natural del noreste sometido a niveles crecientes de sombra

The present work was carried out to evaluate the summer - autumn production of a natural field in the northeast of the country subject to increasing levels of artificial shade. The experiment was carried out in the department of Cerro Largo - Uruguay, on the EEBR site from November 2020 to July 2021. The experimental design proposed was in complete randomly blocks, with 4 repetitions and 5 treatments, which were a natural field control in full sun, 35, 50, 65 and 80% interception of solar radiation by shade mesh. The management carried out consisted of four forage cuts, the first with sheep and the remaining three with a self-propelled mower. It was found that as light availability decreased, the efficiency in the use of radiation of plants increased. Forage growth was evaluated for each period between samplings and the corresponding daily growth rate. In turn, for each cut, height and the available and remaining dry matter, the disappeared dry matter and the percentage of harvest were determined. The ground cover was studied for both the available dry matter and the remaining of each cut. The botanical composition present in the available dry matter from each cur was also evaluated. At all evaluation times, forage production was higher while the radiation interception was higher, in this way the maximum production occurred in the treatment with 80% interception and the minimum in the treatment on natural field with full sun. Regarding the ground cover in the available forage, it was found that the control treatments presented the lowest percentage of green cover and the highest percentage of dry remains, while the treatments with radiation interception obtained a better green/dry ratio in the available forage. The botanical composition also varied according to the interception of the radiation, in shaded treatments a change in the balance between winter/summer grasses was recorded compared to treatments on natural field in full sun. It is concluded that the different levels of solar radiation had effects both on forage production and on soil cover and the botanical composition of a natural field in the northeast of the country.