SILVA, M. B. R.; http://lattes.cnpq.br/3528552134688132; SILVA, Maria Betânia Rodrigues.
Résumé:
The physic nut (Jatropha curcas L.) is an oil producer plant; it belongs to Euphorbiaceae's
family, which is a native species from American continent, and that is being considered as an
alternative for biodiesel's production. This research had as objective to study the possible
effects of irrigation with wastewater from domestic sewage, under different levels of
evapotranspiration replacement, on the growth and development of physic nut, as well as the
effects of irrigation on soil chemical properties. The experiment was carried out in drainage
lysimeters under a protected area belonging to Universidade Federal de Campina Grande,
Technology and Natural Resources' Center of Academic Unit of Agricultural Engineering.
The experimental design had randomized blocks with four replications and it had studied five
levels of water's replacement - Nr (Nri = 0.25, Nr2 = 0.50, Nr3 = 0.75, = Nr4 = 1.00 and
Nrs = 1.25 of evapotranspiration - ETc), and a control treatment (T), in which the plants were
irrigated by potable water, and received 100% of ETc. The experimental unit was constituted
by two grown plants in separate lysimeters. The irrigations were performed according to a
frequency of two days; the water's volume applied in each treatment was determined by water
balance, based on the treatment Nr4 . The irrigation with wastewater allowed a best growth
and development of plants, especially at treatments without water stress. The variables of
growth (plants' height, stem diameter, number of leaves and leaf area) were affected by levels
of evapotranspiration in all studied periods, but were more intensely affected in leaf area.
Plants that were irrigated under the treatment of 1.25 of ETc presented the highest growth
rates. The maximum quantum efficiency of photosystem I I was influenced by the levels of
water's replacement of ETc only after 140 DAT (days after transplanting). The average
production of irrigated plants with wastewater exceeded the control treatment. There was an
increase of 648.80% in relation to average number of fruit clusters, 1515.61% in relation to
average weight of seeds, 1423.20% in relation to average weight of fruits and 976.39% in
relation to average number of fruits, between treatments Nri and Nr5 . The oil's content in
seeds varied with period and treatment, it was reaching the maximum value of 42%. The
variables of water balance, water's total consumption, crop's total evapotranspiration and
medium evapotranspiration, increased with increasing levels of soil's moisture. The
irrigation with sewage's effluent increased soil fertility, which resulted in higher
concentrations of N and P in the layer of 0-10 cm, and K, Ca, Mg and Na in the layer of 10-20
cm deep. The concentration of soil's salts varied with depth, it became more saline in the
deeper layers, including higher values of electrical conductivity of saturation's extract. In the
soil surface depth it was verified an increase in pH.