Investigation of the effect of irrigation regime and foliar application of ZnSO4 and MnSO4 on yield, some physiological and phenological characteristics of safflower (Carthamus tinctorius L.) in Saravan climatic conditions

The use of low irrigation regimes by saving water consumption can help as a water management solution to increase the cultivated area and also determine the optimal cultivation pattern. The importance of oil products such as safflower has increased in recent years in the world. In general, safflower is produced in relatively dry marginal lands with low input. Efforts are being made to improve the yield and seed quality of this plant through the development of new genotypes and agricultural practices around the world. But the fact is that drought also affects the growth and performance of this plant. Zinc plays an important role in seed and biomass production, chlorophyll production, pollination process and even plant germination.

The purpose of this experiment was to investigate different levels of irrigation regime and foliar application of zinc and manganese sulfate in the research farm of Saravan Education Complex as a split plot in a randomized complete block design with three replications. The main plot included full irrigation, cut-off of irrigation at the stem stage and cut-off of irrigation at the flowering stage, and the sub-plot included three levels of foliar application with zinc sulfate (three per thousand), manganese sulfate (three per thousand) and without foliar application (control). The harvest was done manually, depending on the time of full processing, from the end of May to the beginning of June 2019. In order to evaluate the yield, the plants were harvested after removing the margins and after beating and separating the seeds, the yield was measured. The dry matter of plant leaves was also measured by collecting the leaves of three plants in each plot; Thus, by placing the collected leaves in an oven at 75°C for 48 hours and calculating the average leaf weight of three plants, the leaf dry matter was obtained. Analysis of data variance was done using SAS software (9/1 version) and mean comparisons were done at the five percent probability level using the LSD test.

The results showed that the cut-off of irrigation in the stem and flowering stages reduced number of days up to heading, number of days up to 50% flowering and the number of days up to maturity irrigation than full irrigation. Also, interruption of irrigation in stem and flowering stages compared to full irrigation conditions significantly reduced RWC and significantly increased electrolyte leakage. Foliar application with zinc sulfate compared to manganese sulfate and no foliar application caused a significant increase of 0.53 and 2.31 percent in number of days to heading, 1.71 and 2.54 percent in number of days up to 50% flowering and 0.52 and 1.64 percent number of days up to maturity, respectively. Foliar application of zinc sulfate and manganese sulfate significantly increased RWC and decreased significantly electrolyte leakage compared to no foliar application. At each level of irrigation regime, foliar application significantly increased seed yield, which was more effective in zinc sulfate treatment than manganese sulfate.

In general, full irrigation and foliar application of zinc sulfate is recommended for safflower cultivation in Saravan climate. In general, the cut-off of irrigation in the stages of stem growth and flowering caused a sharp decrease in grain yield in safflower plants compared to full irrigation conditions. Considering the high ambient temperature in the study area, it seems that the risk of under-irrigation in safflower cultivation in this area is very high and therefore it is recommended to carry out full irrigation in safflower cultivation in this area. Also, due to the alkalinity of the soil in dry areas and the non-absorbability of zinc and manganese elements by the plant and the positive effects of these elements in relation to the defense and photosynthesis system of the plant (especially zinc sulfate), foliar spraying with zinc sulfate for safflower in conditions Saravan weather is recommended.