Efficacy of copper foliar spray in preventing copper deficiency of rainfed wheat (Triticum aestivum L.) grown in a calcareous soil

Abstract

Field experiments were conducted to evaluate the response of rainfed wheat (Triticum aestivum L.) to foliar copper (Cu) application in correcting Cu deficiency in calcareous soils. Two native soil Cu contents were tested in successive growing seasons. The soil “1” contained 0.35 mg kg−1 of Cu (Diethylenetriamine Pentaacetic Acid extraction). It was evaluated during the 2016-17 season. The soil “2” contained 0.61 mg kg−1. It was studied during the 2017-18 season. The rainfall amount was around 289 mm and 429 mm, respectively, for 2016-17 and 2017-18 seasons. For the soil “1”, the Cu treatments were: control, 0.2%, 0.4%, 0.6%, 0.8%, and 1%. For the soil “2”, the Cu tested levels were: control, 0.01%, 0.03%, 0.05%, 0.1%, and 0.2%. Cu was applied at the early boot growth stage in the sulfate form. The results showed that the response of grain yield to Cu foliar feeding was not related to the tested native soil Cu content. A significant grain yield increase, due to Cu spray, was revealed during the rainfall season (429 mm) in soil “2”. This increase was around 8% at 0.018% of Cu compared to control. However, Cu foliar application higher than 0.03% induced leaf damage. The Cu content of flag leaf and kernels showed a linear response to Cu supply. Flag leaf Cu content was around 5 mg kg−1 in control and exceeded 30 mg kg−1 at Cu application over than 0.03%.