Application of Mepiquat Chloride at Different Planting Densities in Cotton.

The cultivation of cotton was changed from small and medium producers to a new reality, based on a scale production model, characterized by high yield and intense use of inputs and mechanization. With the introduction of cultivars with favorable plant architecture for mechanized harvesting and resistant to many diseases that occur in the region, the cotton crop from the middle of 90´s start a new production cycle, with the rapid expansion of cultivated areas. The balance between vegetative and reproductive development of cotton is fundamental to the achievement of high yields. Because it is a plant with indeterminate growth habit, the adoption of techniques  or processes should corroborate with this balance.  In Brazil, since the 60’s, many papers with plant population and spacing in cotton, were developed.  The present work consists in a  field experiment with two application systems of growth regulator: a- conventional: two applications of 500 mL ha^-1 at 50 and 70 days after plant emergence and b- high division: six applications of 50, 100, 125, 175, 225 and 325  mLha^-1 at 20, 30, 40, 50, 60 and 70 days after emergence of cotton plants, with different  row spacings (0.38, 0.45, 0.76 and 0.90 m) and population densities (6, 8, 10:13 plants/m). The Experiment was conduced in a randomized completly blocks design, in the factorial system 4x4x2 with three replications. The cultivar was the FMT 701 in a oxysol, at the experimental farm of the São Paulo State University, located at Selvíria – MS, in the border of the northwest of São Paulo State and south of Mato Grosso do Sul, during the growing season of 2010/2011. This study aiming to evaluate the influence of the high division of cotton growth regulator on the agronomic characteristics and yield of the plant. It was evaluated that the vegetative development of cotton (height, length of the fifth, seventh, ninth and eleventh branch reproductive number of nodes of the stem, stem diameter and average number of reproductive branches and yield), analyzes of reproductive development of cotton (mass of 20 bolls, number of flower buds in the 5, 7, 9 and 11 branch and yield), physiology of cotton (SPAD reading and evaluation of the light intensity).   The results showed that the higher division system of the growth regulator provides the lower values of plant height , ninth branch length and number of nodes.  The higher values of plant height, stem diameter and branches length were obtained with the row spacing of 0,9m.  The light intensity was higher in the system with six applications of growth regulator and the row spacing of 0,9m.  The high contents of nitrogen were obtained in the higher division system of growth regulator. The high yields were verified in the row spacings of 0,45 and 0,9 m.  In the highest plant population (13 plants m^-1) the system of six applications of 1,0 L ha^-1 provides the higher value of yield for the cotton crop.