Comportamento de genótipos de algodoeiro anual (Gossypium hirsutum L. r. latifolium Hutch) em regime de irrigação.

Abstract

The principal objective of this research was t o study the performance of six upland cotton {Gossypium hirsutum L.r. latifolium Hutch.) genotypes under irrigated conditions. The experiment was conducted on an alluvial medium textured soil of Irrigated Perimeter "Engenheiro Arcoverde", Condado, Paraíba, during the period of May t o September 1983. A random block design with six replications was adopted for the experiment. The experimental plots consisted of four rows o f 5m with a spacing of lm between them. The observations were made only on plants belonging to two central rows. The treatments consisted of the following genotypes of upland cotton: 'CNPA 78-SME4', 'SU 0450-8909', 'BR 1', 'CNPA 76-6873; 'CNPA 77-149' and 'IAC 17'. The planting was done on May 12, 1983 with a density of 68,000 plants/ha. After 22 and 56 days of planting, 30 kg N/ha in the form of ammonium sulphate was a pplied . The irrigations were applied when the plants showed the first symptoms of wilting between 9:00 and 10:00 a.m., and the amount of water applied was determined on the basis o f water content of soil. A furrow irrigation method was utilized in the present study and water was conducted to the plots through gated pipes. In a l l 387.00mm of water through 5 irrigations was applied and during the period of experiment 59.1mm of rainfall was also registered. The cotton bolls were collected after 111 and 126 days of planting. The genotypes 'CNPA 76-6873', 'BR1' and 'SU 0458909' showed superior plant height, stem diameter and number of leaves in relation to other genotypes. The cotton genotypes presented an average period of 42 and 91 days for flowering and first boll openning, resDectively. The genotypes 'CNPA 78-SME4 'and'lAC 17' showed the highest cotton boll and seed weight while for the yield the genotypes studied presented the following decreasing order: 'CNPA 76-6873,'SU 0450-8909', 'BR 1', 'IAC 17', 'CNPA 78-SME4' and'CNPA 77-149'. Although the yields of genotypes studied varied from 3218 to 4551 kg/ha, the analys is of variance did not reveal statistical differences, however significant differences among the genotypes were observed for the agronomic and technological characteristics except fibre uniformity. The genotype ' IAC 17'presented highest, lint percentage while genotype'CNPA 78-SME4 ' produced best fibre length and resistance which may comercially be considered as extra long and highly resistant fibre . The genotype'CNPA 77-149*presented the lowest micronaire index and differed statistically from genotype'CNPA 76-68731 The genotypes studied , principally'CNPA 76-6873'and 'SU 0450-8909'showed promising yields in relationto normally obtained under rainfed conditions in northeast of Brazil thereby confirming the viability of upland cotton under irrigated conditions.