Frecuencia e intensidad de defoliación de Paspalum dilatatum Poiret y Paspalum quadrifarium Lamarck en campo natural y campo natural mejorado

The present essay aims to study the response in frequency and intensity of defoliation of Paspalum dilatatum Poiret and Paspalum quadrifarium Lamarck in natural rangelands and enhanced rangelands. In order to this, the morphogenetic characteristics and the response to defoliation of the mentioned species were evaluated. The study was carried out on the Experimental Station Mario A. Cassinoni from Faculty of Agronomy in Paysandú, coordinates 32º23’21,10” south latitude; 58º01’55,24” west longitude, on Brunosols typical Soils, belonging to San Manuel unit, which is developed over lodolites from Fray Bentos formation, during the period October 30^th to December 14^th of 2020. The experimental design consisted of randomized complete block design with three replicates. The treatments evaluated were natural grasslands and enhanced natural grasslands with 8 kg/ha of Trifolium pratense E116 and 6 kg/ha of Lotus tenuis Matrero with an application of 40 kg/ha de P₂O₅. Measurements were made on 30 tillers per plot, of the length (green portion) of the leaf and leaves were characterized weather they were in extension, completely extended, defoliated or senescent. These determinations on the marked tillers were made every two days on average, with a total duration of 15 days per block. Grazing pattern was expected to differ between species and also to be modified with the different treatments and during the grazing days. The obtained results showed that P. dilatatum had a greater number of leaves per tiller and P. quadrifarium presented a higher extension rate and leaf blade size, characteristics that where not modified through the different treatments. Grazing pattern, expressed through frequency and intensity of defoliation, differed between P. dilatatum, which was more intensely grazed, and P. quadrifarium, which was more frequently defoliated. The amount of grazing days did not modify frequency and intensity of defoliation during the grazing period, despite the reduction of forage allowance.