Management of cotton cultivars under variable plant densities using a plant growth regulator.

Author(s)

Graciela Decian Zanon

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2002-11-28

Examining board members

Ederaldo Jose Chiavegato; Jose Dias Costa; Enes Furlani Junior

• Advisor: Ederaldo Jose Chiavegato

Abstract

The purpose of this work was to study the phenological, morphological and productive behavior of cotton cultivars presenting different plant shapes under different spacing layouts managed with the use of plant growth regulator. The experiment was established in the experimental field of ESALQ/USP, Piracicaba, Sao Paulo, during the 2000/01 growing season and was arranged in a randomized block experimental design with subdivided plots and 4 replications. The plots represented spacing layouts of 0.76 and 1.01 m, subplots consisted of the IAC 23, DeltaOpal and CD 401 cultivars, while the sub-subplots were characterized by the use or absence of growth regulator. Six plants per plot were labeled and analyzed for the phenological phases (emergence, appearance of the first flower bud, anthesis of the first flower, opening of the first cotton boll) and field agronomical characteristics (plant height, stem diameter, number of vegetative and fruit branches, plant shape, number of cotton boll per plant and insertion height of the first fruit branch). The harvest early and raw cotton yield per hectare were determined considering the effective plot area. The agronomical lab characteristics (mass of 100 seeds, fiber percentage and cotton boll mass), as well as the fiber technological characteristics (length, length uniformity, maturity, strength, and micronaire) were analyzed using a sample of 20 bolls taken at random. Based on the results obtained, it can be concluded that there were no significant interactions among cultivars x spacing x growth regulator, as to cotton yield, harvest early, agronomical lab characteristics and fiber technological characteristics, except for stremgth. The analyzed cultivars, regardless of the plant shape, showed good adaptation to the variation in spacing layouts, as well as to the application of growth regulator, considering the analyzed characteristics. The field agronomical characteristics, such as plant height and stem diameter, generally decreased with the reduction in spacing and with the application of growth regulator, considering the most vigorous cultivars (IAC 23 and DeltaOpal). On the other hand, the cultivar presenting a more compact plant (CD 401) pattern was not influenced by spacing or use of growth regulator. (AU)