The study effect of potassium, zinc and boron foliar application on canopy temperature, physiological traits and yield of two bread wheat cultivars under optimum and late planting dates

To study the effect of potassium, zinc and boron foliar application on physiological traits and yield of two bread wheat cultivars under optimum and late planting dates, An experiment was conducted as split-split plot based on randomized complete blocks design with 20 treatments and 3 replications in Ramhormoz city in farming year 2015-16. The experimental factors were included planting date in two levels: optimum (November 21) and late (January 5) as the main factor, nutrients foliar application in five levels: (water as a control, potassium, zinc, boron and combination potassium zinc boron (each 3 lit.h-1)) as the sub factor and two cultivars of bread wheat Pishtaz and Chamran 2 as the sub-sub factor. Solutions for foliar application were prepared by using potassium (21%), zinc-chelate (7.5%) and boron (5%). Traits measured were included leaf chlorophyll content, flag leaf relative water content, cell membrane stability, maximum quantum efficiency of PSII (Fv/Fm) and leaf proline content. The results showed that with delay in planting all above traits except leaf proline content decreased significantly due to terminal heat stress. However, the delay in planting was increased canopy temperature. Potassium, zinc and boron foliar application separately and in combination reduced harmful effects caused by the delay in planting on the traits leaf chlorophyll content, flag leaf relative water content, cell membrane stability index, maximum quantum efficiency of PSII (Fv/Fm), leaf proline content and grain yield in both wheat cultivars. As well as, foliar application these nutrients reduced canopy temperature of wheat cultivars under both optimum and late planting dates. Despite the lack of significant differences in Pishtaz and Chamran 2 wheat cultivars in canopy temperature, cell membrane stability index, maximum quantum efficiency of PSII (Fv/Fm), leaf proline content and grain yield, these cultivars showed a more appropriate response to the zinc separate application and potassium zinc boron combined application in both optimum and late planting dates, respectively. Chamran 2 cultivar under water foliar application conditions (control) indicated more yield than the Pishtaz cultivar in both planting dates. Measured physiological traits Pishtaz and Chamran 2 wheat cultivars showed improvement as a result of potassium, zinc and boron application in both planting dates. In general can be used from potassium, zinc and boron foliar application and their combined application as appropriate management strategy to reduce canopy temperature, improve physiological traits and reduce the negative effects of delay in planting date on bread wheat in Ramhormoz city.