Nitrogen use efficiency of maize hybrids released in different decades

MARIANA ROBLES; JAVIER DI MATTEO; ANIBAL CERRUDO; PABLO A. BARBIERI; ROBERTO RIZZALLI; FERNANDO ANDRADE

San Antonio, Texas

Congreso; ASA, CSSA, SSSA 2011 International Annual Meeting, San Antonio, Texas; 2011

ASA, CSSA, SSSA

Direct selection for grain yield in breeding programs has led to indirect improvement in secondary traits such as nitrogen use efficiency (NUE). NUE can be defined as grain production per unit of  nitrogen (N) available in the soil, including the fertilizer, and it has two components: nitrogen recovery efficiency (NRE=kg N uptake/kg N available in the soil) and nitrogen internal efficiency (NIE=kg grain /kg N uptake). An experiment was conducted at Balcarce (37º45?S, 58º18?W) during the 2009/2010 growing season in order to compare and evaluate NUE, NRE and NIE of hybrids released in different decades. Three hybrids (released in 1965, 1995 and 2010) were sown at 75000 pl ha-1 at two N levels: 0 and 150 kg ha-1 applied at sowing. Grain yield was determined at physiological maturity. Total aboveground biomass and N concentration in the shoot was measured at silking and at physiological maturity. Response to N fertilization was greatest in the 2010 hybrid and resulted in reductions in NUE and its components in all cultivars. NUE was significantly greater for the 1995 and 2010 hybrids compared to the 1965 one, at both N availabilities. NRE did not differ among hybrids during the vegetative stages. During grain filling, however, there was a trend toward a higher NRE in the modern hybrid at low N availability. NIE was superior for the 1995 and 2010 hybrids than for the 1965 one. Comparing the newest hybrid with the oldest one, both without N fertilization, NRE during the complete growing cycle increased 35% whereas NIE increased 38%. At high N availability, differences between hybrids in NUE were mostly explained by differences in NIE. Thus, hybrids released in different decades exhibited differences in NUE, which were most closely related to differences in NIE than to NRE.