Effect of nylon mulch and some plant growth regulators on water use efficiency and some quantitative traits in onion (Allium cepa cv.) under water deficit stress

Abstract

In order to investigate the effects of plant growth regulators (PGRs) and mulch on some traits of onion under water deficit stress, a split-factorial experiment based on Randomized Complete Block Design with three replications was conducted in Iran in 2016 and 2017. The main plot consisted of water deficit stress treatment at three levels (100%, 80% and 60% of water requirement), and sub-plots consisted of a dark nylon mulch application and an unmulched control, and PGRs six levels (zero, salicylic acid 0.5 mM, methyl jasmonate 5 and 7.5 mM, and 24-epibrasinolide 0.5 and 1 mM, respectively). Final yield under water deficit stress (60% water requirement) decreased by 30% compared to control (100% water requirement). On the other hand, the use of plastic mulch increased the yield by 29%. Interaction of water deficit stress and PGRs on leaf number, fresh and dry weight of plant, plant height, bulb length and diameter, early yield and final bulb yield were significant and the effect of regulators was mainly effective in severe water deficit conditions. The highest crop yield of 52.55 ton per hectare was obtained from 1 micromolar brassinolide treatment under non-stress conditions which had a 9% increase compared to control under non-stress conditions and 28% increase compared to control under severe water deficit stress.