SEED SIZE, SOWING DEPTH AND MAIZE INITIAL GROWTH AT TWO SOWING DATES

Maize is highly dependent on plant population to reach high grain yields. The crop stand definition is affected by several factors such as seed size, sowing depth and planting date. This work was carried out aiming to evaluate the impact of contrasting seed sizes and sowing depths on plant emergence and maize initial growth at two planting dates. The trial was performed in square boxes, measuring 1,2m wide and 0,3m high, under natural radiation conditions. Two planting dates were tested: 01/29/2003 and 03/26/2004. A 4 x 2 completely randomized factorial design was used at each planting date. Four sowing depths were evaluated: 2,5 cm, 5,0 cm, 7,5 cm and 10,0 cm. Two seed sizes were assessed: large (mass of 1,000 grains of 451.2g) and small (mass of 1,000 grains of 245,2). The percentage and speed of plant emergence were estimated during the stand establishment period. Plant height and shoot dry mass were determined at the harvesting day. Plants were harvested when they had four to five expanded leaves. A variance analysis was used to assess the data. Average data were compared through the Duncan’s Test at 5% probability level. The increase in sowing depth from 2,5 cm to 10,0 cm decreased the percentage of plant emergence when maize was sown at the end of March. Seed size did not affect the percentage and speed of plant emergence, regardless of sowing depth or planting date. Plants derived from large seeds were taller and heavier than those originated from small seeds. Endosperm stored compounds were more important to accelerate the plant initial growth after emergence than to define the quantity of emerged seedlings