Relationship between roots growth and forage biomass of native and cultivated grasslands of the flooding Pampa (Argentina).

In order to get correct vegetal production management it is necessary to study root growth as a component of the productive system. In native and cultivate grassland soils, root growth possibilities depends on the mechanic resistances they found for elongation. The objectives of this research were to determine seasonal density of root biomass of both native, with salt grass (Distichlis scoparia Kunth y D. spicata L.) and dallisgrass (Paspalum dilatatum Poir.) as major contributors, and cultivate grasslands with tall wheatgrass (Thinopyrum ponticum Podp.) and white clover (Trifolium repens L.) in a Natracualf soil of the Flooding Pampa and their relationship to biomass forage. In each treatment, native and cultivate grassland, 10 samples of 0.5 m2 were extracted and aboveground dry matter was estimated. In order to assess root biomass and its vertical density distribution samples were taken, by a cylindrical technique, from 4 layers 0-5, 5-15, 15-25 and 25-35 cm. A greater winter and spring tall wheatgrass biomass forage than native grassland biomass was determined. Differences are according to the greater 0-5 cm deep root biomass. Unlike cultivate grassland, the greater the studied depth the greater the correlations between roots density and forage biomass were in native grassland.

Key words: native grasslands, roots growth, roots biomass, forage, cultivate grasslands.