LIMA, G. S.; http://lattes.cnpq.br/0683441338403298; LIMA, Geovani Soares de.
Abstract:
In semiarid areas of the Northeast of Brazil, the salt concentrations that affect the
growth and development of plants vary and the effects on crops depend, among
other factors, on both the concentration total and the ionic composition of water
utilised in irrigation. In this context, in this study the emergence, growth, physiology,
production of castor bean cv. BRS Energia and the possible impacts on soil chemical
properties were evaluated. The experiment was conducted in drainage lysimeters
under greenhouse conditions using an Eutrophic Ultisol of sandy loam texture, in the
municipality of Campina Grande-PB, during the period from November, 2013 to
February, 2014. Six water salinity combinations were studied (S1 - Control; S2 - Na+;
S3 - Ca+2; S4 - Na++Ca+2; S5 - K+ and S6 - Na++Ca+2+Mg+2), in a randomized block
design with four replications, each plot was composed of five plants, totaling 120
experimental units.In control (S1), the plants were irrigated with water of electrical
conductivity (ECw) of 0.6 dS m-1, and the other treatments (S2, S3, S4, S5 and S6)
water used was prepared with different cations, all in the chloride formand ECw of
4.5 dS m-1. During the experiment, the plants were irrigated daily and the volume of
water applied was estimated by the water balance in the root zone, observing the
volume applied and drained in the previous irrigation, plus a leaching fraction of 0.10.
At 20 and 40 days after sowing (DAS), the growth and gas exchange was evaluated,
and at 60 and 80 DAS only the growth variables were determined, and from 70 DAS
started the harvest of the racemes.The emergence and growth of castor bean are
more sensitive to ECw compared to the cationic nature of water, and the smallest
reduction occurs in plants irrigated with water containing potassium in comparison to
other types; The high concentrations of sodium in irrigation water cause greater
reduction in water status resulting in severe damage to cell membrane integrity;
calcium ion is the largest contributor to the osmotic adjustment in this species, as the
lowest electrolyte leakage was observed in this treatment, in both the periods studied; the cationic nature of the irrigation water causes changes in photosynthetic
activity of castor bean 'BRS Energia', and its effects increse with exposure time of
stress; therefore increasing the efficiency of water use in plants irrigated with water
containing potassium, represented one of the mechanisms of adaptation to salt
stress although severe reduction in production of castor bean were observed. The
adoption of leaching fraction of 0.10 was not enough to prevent soil salinization and
resulted in increase in electrical conductivity of saturation extract ECes and
exchangeable sodium percentage (ESP) in all treatments including control higher
values being observed in treatments irrigated with water of 4.5 dS m-1 were used.