Phenotypic response of corn genotypes to different agrotechnical management

Corn (Zea mays L.) is one of the highest yield crops. Brought in Romania about 300 years ago, our country comes up to the largest corn-growing states with 2.3-2.5 million hectares/year, in EU being recognized as the largest maize grower. The biological material used by Romanian farmers has different origin, thus its agronomic performance is often reduced due to the application of improper management measures. Corn grain yield has significantly increased in the hybrid era and the increase in the number of plants per unit area is suggested as one of the main contributors to yield improvement. In modern maize hybrids, field yield increases with plant density until a maximum population is reached, according to the growing environment and after this maximum, field yield declines. Plant density in farmer’s field is considered a very important stress factor, since competition between different plant species or between different maize hybrids is very strong and reaction of the genotype to this competition can influence yield potential. Four commercial hybrids were studied at four different sowing densities. Greatest grain yields were recorded at the highest sowing densities. Three of the studied hybrids reach the highest yield at the 90,000 pl ha-1 and one at 80,000 pl density. Ear weight is directly affected by the plant density for all the studied hybrids, causing a decrease of this character with the progressive increase of plant density, reaching values between 148.17 g on the first hybrid at 90,000 plants ha-1 and 213.16 on fourth hybrid at 60,000 plants density. Ear length touched values between 15.08 cm at the fourth hybrid by 90,000 plants ha-1 to 19.27 cm for third hybrid at 60,000 plants ha-1. As a main yield component, weight of grains per ear is also influenced by increasing of plant density. The lowest grains yield / maize ear was on Hybrid 1 at 90,000 pl ha-1 (129.26 g) and the biggest value was recorded on Hybrid 4 at 60,000 plants density (197.30 g). The values of yield efficiency (~ 90%) suggest the superior genetic value of the studied maize hybrids even in increasing plant competition conditions.