Evaluation of early corn and sunflower cultivars as a double cropping, San Clemente Area, seventh region grain yield, yield components, degree - days and other morphological characteristics

The seventh Region has normally been considered less adequate for double cropping; nevertheless, the great importance of wheat in the rotations of the zone and the present availability of corn and sunflower early hybrids induced to evaluate five corn hybrids and five sunflower in double cropping after wheat. The parameter measurements corresponded to yield, yield components, oil content, grain moisture, degree-days, plant and ear height, stalk diameter, number of leaves, foliar area index, leaf area of the ear and harvest index. The trial was established on december 29, 1988, at the Demonstrative Center "San Agustin de Aurora", San Clemente, Talca. The experimental design consisted of completely randomized blocks with four replications. Early corn and sunflower average yield were 89.7 and 22.7 q/ha, respectively. The sunflower cultivars were harvested with commercial grain moisture; conversely the corn hybrids did not reach this moisture level. In corn, the earliest hybrid was the T-277t with 58,5 days (624 DG) to flowering and 127,0 days (1.085 DG) from sowing to harvest. For sunflower, the earliest cultivar was S-246, with 58.00 days (828 DG) to flowering and P-6240 with 118.0 days (1.365 DG) from sowing to harvest; a statistically similar precocity degree, in the sowing to harvest period, had the cultivars S-246 and S-445. In relation to the other parameters studied; corn hybrid JX-127A reached the higher values of plant and ear height, stalk diameter, number of leaves per plant and foliar area index, its harvest index was 0.35 (2nd place). Among sunflower hybrids, P-6440 reached the highest values of plant height, stalk diameter, number of leaves per plant and foliar area index; harvest index was 0.19 (the lowest). Corn correlations coefficients were positive and highly significant between ear length and plant and ear height, number of leaves per plant and foliar area index. Sunflower showed positive and significant correlation between grain yield and plant height, stalk diameter and foliar area index. It was possible to observe a close association between yield, its components and the growth parameters. It was concluded that in the Talca zone corn early hybrids had a vegetative cycle longer than the one required for a double cropping, on the contrary, sunflower early cultivars presented a shorter life cycle