Crescimento e desenvolvimento do pinhão-manso irrigado com águas salinas sob ambiente protegido.

Abstract

Physic nut it is an oleaginous plant and at the moment researched to biodiesel production. Between April and October of 2007, an experiment was installed and carried out in greenhouse, of the Natural Resources and Technology Center of the Federal University of Campina Grande, PB with objective of study the effects of the irrigation water salinity on the growth and development of physic nut, also verify saline impacts of irrigation water on the soil at the end of research. The plants grown in drainage lysimeters (200 L) with 230 kg of soil properly fertilized, no-saline, no-sodic. The treatments consisted of five levels of electrical conductivity of the irrigation water - CEw (0.6; 1.2; 1.8; 2.4 and 3.0 dS m"1, at 25 °C). The experimental design was in randomized block with 4 replications; each replication represented by mean of 2 plants cultivated in lysimeters separates. Saline solutions were obtained starting from the salts NaCl, CaCl2.2H20 and MgCl2.6H20, in the proportion 7:2:1 among the ions Na+:Ca++:Mg++. The plants were irrigated every 2 days. Vegetative stage was long 94 days with crop coefficient (kc) of 0.50; the beginning of stages flowering, frutification and maturation happened to the 94, 132 and 150 days after sowing - DAS; At 163 DAS, the plants height, the stem diameter, the number of leaves and the leaf area were lineally affected with reductions of 3.78, 7.35, 9.75 and 17.74%, respectively, for unitary increase of ECw. Number of fruits, biomass of fruits and of seeds of first bunch, as well as the quantum efficiency of photosystem II (Fv/Fm) were not affected by irrigation water salinity. Even ECw of 1.80 dS m"1. The number of bunches and number of fruits per plant were not affected, therefore 1.80 dS m"1, was considered as the threshold salinity for those variables. The variables of water balance, total consumption of water, total evapotranspiration of culture and the medium evapotranspiration were reduced in about 43% between 0.60 and 3.00 dS m"1 (approximately 18% for each dS m"1). After the irrigations, among 37 and 163 DAS (126 days of duration), was verified lineal increment accentuated in the concentrations of soluble ions CI", Na+, CaH, and Mg+ + with the increase of ECw; however, for the averages of electric conductivity of saturation extract - CEse (2.12 dS m" '), of sodium adsorption relationship - SAR ([6.22 mmol L"']1/2)= of exchangeable sodium percentage - ESP (7.22%) and of pH (5.37), was verified absence of process of soil salinization and sodification.