SIQUEIRA, E. C.; http://lattes.cnpq.br/5420335048712215; SIQUEIRA, Eliezer da Cunha.
Résumé:
Upland cotton (Gossypium hirsutum L. r. latifolium Hutch) under irrigation is one of the main
agricultural alternatives for the semi-arid the Brazilian Northeast. Considered as tolerant to
salinity, it makes possible the use of salt affected soils and of the waters considered inadequate
for sensitive crops, as well as, the possibility to produce colored fibers, a product "
environmental correct". This in absence of need for artificial coloration does not pollute the
environment. The objective of present research was to study the effects of different salinity
levels and composition of the irrigation water on the germination, growth and yield of the
upland cotton (Gossypium hirsutum L. r. latifolium Hutch) - line CNPA 2002/26 - Dark Brown
Cluster. For this, an experiment was conducted under greenhouse conditions at Embrapa -
Cotton, Campina Grande - PB, using as substrate a Neossolo regossol of sandy loam texture,
initially classified as non saline. The experiment was conducted during the period of April to
September of 2003 in a 6 x 2 factorial scheme using completely randomized design with three
replications. The effects of 6 of water salinity levels -ECw (2.0, 3.5, 5.0, 6.5, 8.0 and 9.5 dSm"1)
and 2 irrigation water compositions with Na/Ca ratios (9.5/0.5 and 6.0/4.0) in chloride forms,
were studied. The variables analyzed were germination and growth (plant height, number of
leaves, leaf area, dry weight of the aerial part total plant and root weight), physiological indexes
(absolute and relative growth and ratio of leaf area) and production variables (number of
capsule and it's mean weight). The obtained results showed no abrupt alterations of the soil pH
with the treatments and in spite of leaching; there was increase of the electrical conductivity of
soil (EC) at the end of experiment and reduction of the water consumption by the plant,
indicating that the plants suffered water stress induced by the high saline levels. The results
also showed that the growth variables were more sensitive than the production variables and, in
a general way, the salinity levels were more xxx to plants than the composition the irrigation
water. Although the significant effects of the salinity levels were observed on most of the
variables analyzed, the results showed an appreciable yield decrease for salinity levels higher
than 6.5 dSm"1. The average yield obtained with the level of ECw 8.0 dS m"1 was 37.81 % of
that obtained with the level of 2.0 dSnf1. Thus, preliminarily, the cotton line used in the present
study is tolerant to the salinity.