Efecto de la fertilización nitrógeno-fosfatada sobre el crecimiento otoño-invernal y la absorción de fósforo en tepes de un pastizal natural.

Abstract

The effect of fertilization with triple superphosphate and ammonium sulfate on the botanical composition and thy matter production in pods of a pasture of naturalized species was studied during an autum-winter period. The fertilizer-P was labelled with 32 P in an attempt to determine cause affect relationships between fertilizer-P recovery and changes in botanical composition. Blocks of soil having undisturbed plant cover were excavated and kept at field capacity in wooden boxes, they were fertilized with 0, 90, 180 or 360 kg N/ha and 0, 45 or 90 kg P2 O5 /ha in a factorial design. The boxes were harvested at 56, 92 and 134 days after the fertilization, and plant cover was divided in five fractions: Gaudinia fragilis-Lolium multiflorum, Paspalum dilatatum-Stenotaphrum secundatum, legumes, forbs and graminoids. The fertilization with both nutrients increased the proportion of Gaudinia-Lohum and decreased that of the other fractions. Thy matter accumulation was increased thrice by both fertilizers applied together, but each one did not have any effect by itself The recovery of 32P was greatest from the Gaudinia-Lolium fraction with respect of the others but, in fact, it did not explain the predominance of the Gaudinia-Lolium fraction as a result of P-fertilization.