EFICIENCIA DE UTILIZACIÓN DEL NITRÓGENO DE DOS HÍBRIDOS DE MAÍZ EN FECHAS DE SIEMBRA CONTRASTANTES

CAVIGLIA, OP; MELCHIORI, RJM.; PAPAROTTI, OF

Rosario, Argentina

Congreso; VII Congreso Nacional de Maíz; 2005

Nitrogen (N) utilization efficiency (EUN), also termed N physiological use efficiency, can be defined as the amount of plant material, grain yield (EUNg) or biomass (EUNB), per unit of N uptake at maturity. Factors affecting N or B partitioning, as sowing date or hybrid, could lead to important variations in EUN. The objective of this work was to evaluate the effect of two contrasting sowing dates in two hybrids differing in biomass partitioning. Experiments were carried out in two growing seasons (2002-2003 and 2003-2004, hereafter seasons 1 and 2) in Paraná, Argentina (31º50´ S). Treatments were a combination of two factors: sowing dates (FS; optimum, mid September, and late, late December) and hybrids (DK752MGCL and DK682MGCL). Plots were laid out in a complete randomized block design with a factorial arrangement . Crops grew under irrigation and were well N- and P-supplied. Grain yield ranged from 8.4 to 13.6 t. ha-1, and was modified by sowing date (p<0.0001 and p<0.002; seasons 1 and 2, respectively) and hybrid (p<0.004) in season 1. EUNg was affected mainly by the hybrid (p<0.0001; p<0.009) and, to a lesser extent, by the FS*Hybrid interaction. Thus, DK682 had 22-17% higher EUNg than DK752 in optimum sowing dates but only 9-3% higher EUNg in the late dates. EUNg was positively associated with both harvest index (IC) (p<0.0001; p<0.002) and N harvest index (ICN) (p<0.0001; p<0.03) and negatively with N grain concentration (p<0.01; both seasons). In turn, ICN was negatively related to N in aboveground plant excluding grain (Nrest), suggesting the relevance of remobilization from vegetative organs to increase EUNg. IC or ICN could be useful, in consequence, as traits to seek hybrids with improved EUNg.