Effect of Different Tillage Systems on Growth Indices and Yield of Zea mays L. (Corn Forage)

Introduction The maize as the oldest cultivated plant, is ranked second and first in terms of cultivated area and amount of production, in the world respectively. Although, researchers have improved the yield of corn by introducing new lines and hybrids, new genotypes alone cannot increase agricultural production, and it is necessary that appropriate and advanced agricultural techniques also be used to maximize corn yield. Maize is one of the most important crops in Golestan province, which is planted in more than 5000 hectares of agricultural land. In Golestan Province, different tillage systems are used for planting maize. Conservation tillage is a new and widespread method in this province, which many farmers use this method every year for cultivating their crops. The main objective of this study was to investigate the effects of different tillage systems on growth indices and yield of maize. Materials and Methods To study the effects of different tillage systems on qrowth indices and forage yield of corn, an experiment was conducted using a Nested design at Azadshahr city. Treatments included no-tillage, minimum-tillage and conventional tillage. Each treatment was carried out in a separate 30 × 50 m plot. Cultivar 770 was planted in all plots with row spacing of 75 cmand the distance between plants on the ridges was 14 cm. Sampling was done by a 1*1 m2 quadrate in six phenological stages of maize including two leaf-stage (9 days after planting), six-leaf stage (26 days after planting), flowering (55 days after planting), (71 days after planting), (85 days after planting) and 86 days after planting. At each stage, 15 quadrates were randomly sampled in each plot. Leaf area and dry weight, height of each plant and total fresh and dry weight of maize was measured at laboratory. Results and Discussion Net assimilation rate decreased following a quadratic equation in all treatments. Although the amount of NAR was estimated 13.5, 13.16 and 13.11 g.m-2.day-1 for conventional, minimum and no tillage, respectively but there was not significance different between the tillage systems in this regard. The maximum amount of NAR occurred at 17.3, 17.4 and 17.5 days after planting for conventional, minimum and no tillage, respectively. The value of this index at the end of the growing season (86 days after planting) was estimated as 0.41, 0.45 and 0.47 g.m-2.day-1 for conventional, minimum and no tillage, respectively. Relative growth rate decreased following a quadratic trend for all tillage systems. In conventional tillage, RGR declined from 0.24 g.g-1.day-1 at the beginning of the growing season to 0.01 g.g-1.day-1 at the end of the growing season. There was no difference between estimated RGR of the tillage systems both at beginning and at the end of growing season. Maximum crop growth rate occurred at 54 days after planting in all three tillage systems. The maximum value of CGR was estimated 41, 41 and 40 g.m-2.day-1 for maize in conventional, minimum and no tillage systems, respectively. CGR was estimated as 3 g.m-2.day-1 at the beginning of the growing season for all treatments; this index was estimated 15, 15 and 14 g.m-2.day-1 at the end of the growing season, for conventional, minimum and no tillage systems, respectively. Result showed that although tillage systems did not effect on dry weight of maize, forage yield of maize in conventional system (71 ton.ha-1) was significantly more than minimum (67 ton.ha-1) and no tillage (64 ton.ha-1) systems