Agronomic performance of mayze hybrids under application of prohexadione-calcium and nitrogen topdressing

: The use of prohexadione-calcium (ProCa) is a management alternative to mitigate greater predisposition to vegetative growth. The objective of this study was to evaluate the use of ProCa in combination with two doses of nitrogen fertilizer in cover, in the morphophysiological and productive performance of corn hybrids. Experiments were performed with corn hybrids AS1757 VTPRO3 and AG9025 VTPRO3 , in a randomized block design, factorial 2×2, with four replications. The treatments consisted of the application of nitrogen fertilizer in cover, 1x and 2x the recommended dose, and in the absence or presence of the application of ProCa. The single effect of ProCa on the hybrid AS1757 VTPRO3 increased the SPAD index by 20%; in the AG9025 VTPRO3 hybrid there was a reduction of 8.6 cm in the height of ear insertion and increments of 2.2 mm in the stem diameter. The application of ProCa with 2x N ha -1 increased, on average, 8.2% the number of leaves of the AS1757 VTPRO3 hybrid compared to the application to 1x N ha -1 . There is single effect of ProCa on morphophysiological characteristics in the tested hybrids, but without affecting its grain yield. The use of ProCa in association with 2x N ha -1 does not mitigate the vegetative growth in the genotypes, sown late in the South of Brazil.