Adilson Nunes da Silva1, Evandro Luiz Schoninger Sr.2, Halan Vieira de Queiroz Tomaz3, Lucas Peres Miachon Sr.4, Paulo C. Ocheuze Trivelin Sr.2 and Klaus Reichardt5, (1)Crop Science, ESALQ, University of Sao Paulo, Piracicaba, Brazil (2)Stable Isotope Laboratory, CENA, University of Sao Paulo, Piracicaba, Brazil (3)Crop Science, ESALQ, University of Sao Paulo, Piracicaba, SP, Brazil (4)Soil Science, ESALQ, University of Sao Paulo, Piracicaba, Brazil (5)CENA/USP, University of Sao Paulo, Piracicaba, Brazil
The response of corn plants and the correlation between shoot variables in response to the nitrogen fertilization is an important issue for yield maximization. A corn experiment was conducted under field conditions, from 2011 to 2012, in Piracicaba/SP, Brazil.Treatments were sidedressing with N-urea at different growth stages (V4, V6, V8, V10 and V12), including a control. The following variables were analyzed: photosynthetic rate (PR) and stomatal conductance (SC) in a fully developed leaf of each plant with an Infra Red Gas Analyzer (IRGA, mod. Li-cor 6400 (USA)) evaluated at V14 phenological stage; plant height (PH) and leaf area (LA) evaluated at flowering and the nitrogen content in grains (NCG) evaluated after harvesting. The design was in randomized blocks with four replicates. Data were subjected to variance analysis using the F test (p<0.05), LSD test for mean comparison and Pearson correlation test to verify the possible correlation between variables. There were significant differences, in relation to treatments, only for PH and NCG. For the other variables, treatments did not provide significant differences. For PH, treatments differed only from the control. The application of nitrogen sidedressing on the V6 growth stage, provided the highest average for NCG. Positive correlations were observed between NCG and PH, LA and SC. NCG showed the highest correlation with LA, showing that the greater the leaf area more nitrogen will be absorbed by the plant and a higher N concentration is found in grain. This is also observed for the variable PH. The third positive correlation was observed between NCG and SC, most likely due to constant transpiration performed by stomata, which caused the flow nitrogen rise from roots to shoots.