Aspectos de la nutrición nitrogenada de Paspalum notatum Flugge, en respuesta a fuentes de nitrógeno e inhibición de nitrificación.

Abstract

A greenhouse experiment was made to study the effects of NH4 or NO3 (single vs, split, 3x) application on growth and nitrogen (N) assimilation of Paspalum nota-turn Fhi,gge Light and temperature conditions over the experimental period (20 days) had a more pronounced effect on seasonal patterns of dry matter accumulation than either N-carrier or application procedures. Nitrate-reductase activity was higher for plants that received NO3 in split applications, and lower for plants under NH4 in a single application. Amides were not detected in the soluble-N pool NO3 accumulated most in the roots of Paspalum, while the rhizomes showed higher accumulation of amino-N. The highest free-N levels (NO3-N + amino-N) were found in roots plus rhizomes: 73%, 70%, 76%and 57%of the total free-N, for NO3 (single), NO3 (split), NH4 (single) and NH4 (split) applica-tions, respectively. Protein-N however, accumulated most (62%, 57%, 56% and 65% of total Protein-N respectively, for the 4 treatments) in leaves. A negative relationship was found between total free-N and total dry weight (r = 0.984*) and leaf-free-N and total dry weight (r = 0.978*) of the plants. The data also indicate that the split application of N-SERVE (nitrification inhibitor) was more effective than the sole application. The highest free-N (NO3-N + amino-N) in roots plus rhizomes suggests that these organs could act as buffer zones, by keeping excess NH4 or NO3 from reaching the shoots, thus avoiding disturbances in the N-metabolism in the leaves.