CAMBIOS EN EL PATRON DE CRECIMIENTO POR EFECTO DE LA REFERTILIZACION NITROGENADA TARDIA EN DIFERENTES JERARQUIAS DE PLANTAS

GVOZDENOVICH JJ; MELCHIORI RJM; CAVIGLIA OP

Rosario, Argentina

Congreso; VII Congreso Nacional de Maíz; 2005

Delayed N-fertilization oriented to efficient use of new diagnostic tools, like remote sensors, could affect growth dynamics differentially between plant hierarchies (i.e. dominated and dominant plants). The objective of this work was to evaluate the effect of delayed and at sowing N-fertilization on growth dynamics of dominated and dominant plants. One experiment was carried out at Paraná, Argentina (31º 50´ S) during 2004/05 growing season. Treatments were a combination of two factors: a) N rate at sowing (0 and 140 kg N ha-1) and b) delayed N-fertilization (control, at V8 and at V12). A non-destructive method based on allometric relationship was used to estimate shoot biomass at different growth stages on 20 consecutive, tagged, plants. At maturity plants were harvested and grain yield per plant (RTOpl), total shoot biomass and total kernel number were recorded. Plants located in 33 and 67th percentile of biomass distribution were considered dominated and dominant, respectively. Growth rate per plant (TCP) was estimated as a ratio between accumulated biomass around silking (V13 and R3) and duration of that period. Delayed N-fertilization increased TCP in dominated plants, even in treatments well fertilized at sowing, however delayed fertilization had a little effect on RTOpl and harvest index. In the other hand, dominant plant increased their harvest index and RTOpl but not their TCP. Greater biomass at the onset of critical period in dominant plants in contrast to dominated ones would be a key issue involved in that response. Kernel number per unit of TCP was lower (p<0.0001) in dominated plants, suggesting an additional effect on the kernel set other than the reduction in TCP.