The effect of foliar application of iron and zinc fertilizers on some agronomic traits of Lallemantia iberica L. under post anthesis water deficit

Among various non-biological stresses, drought stress is the most important factor that has limited production in the agricultural sector of the country (Akhzari and Pessarakli, 2016). Today, the supply of oilseeds for the extraction of vegetable oils needed for various industrial, edible, medicinal and cosmetic uses is one of the basic needs of the current population growth (Beynam, 2015). Balangu (Lallemantia iberica L.) is an annual, herbaceous and drought-resistant plant belonging to the mint family (Lamiaceae). With medicinal-oil properties, it is considered a multi-purpose plant in agriculture (Hendawy et al., 2015). In order to check and predict the phenological stages of the planted plants in an area, the relationship between the phenological stages and the thermal factor should be considered. For this purpose, thermal units of growth degree days (GDD) are used to check the amount of heat needed to pass each growth stage of plants (Kumari et al., 2020). In plants under drought stress, where the absorption of nutrients through the root faces a problem due to the decrease in soil water volume, the absorption of micronutrients such as iron and zinc can be effective through foliar spraying. (Rafique et al., 2015). In the conditions of lack of water resources, like what is happening in our country, it is necessary to change the agricultural pattern towards planting plants adapted to dry land, as well as ways to increase yield per unit area. Therefore, the purpose of this research was to investigate the development of Balangu planting and the role of foliar application of iron and zinc micronutrients on phenology and the adjustment of stress effects.

This research was conducted in the research farm of Razi University of Agriculture and Natural Resources, Kermanshah during two consecutive years (2017-2018 and 2018-2019) as a split-plot-factorial experiment in the form of a basic randomized complete block design with three replications. The experimental treatments include: irrigation (Water deficit after flowering and Normal) in the main plots, foliar spray factors (zero, four and eight per thousand concentrations of iron and zinc sulfate) and foliar application time (at the beginning of the vegetative and reproductive growth stage) were factorially placed in sub-plots. The seeds (native population of Songhor region of Kermanshah province) were planted manually at a depth of two centimeters and with a density of 400 plants per square meter in a row at the first appropriate time in late March of 2017 and 2018. Application of nitrogen, phosphorus and potash fertilizers was based on need. Dehydration stress was applied by stopping irrigation from the time of full flowering (opening of 50% of flowers).

The results showed that, with the application of water stress, the seed yield and oil yield decreased by 24% and 17%, respectively, and the oil percentage increased by 8% compared to the treatment without water stress. Also, water deficit stress reduced the number of days and heat requirement to maturity by 10 days and 275 growth days degree, respectively. The greatest increase in oil yield compared to the treatment without foliar spraying (control) was related to the 4 and 8 per thousand zinc foliar treatments in reproductive stage and under stress conditions, which increased these traits from 339 and 283 respectively in conditions Lack of stress and water deficit stress increased to 539 and 513 kg/ha. The greatest effect of iron and zinc foliar application treatments on increasing plant height and the number of days and heat requirement to maturity stage was related to 4 and 8 per thousand iron and zinc foliar application in the vegetative growth stage.

In the present study, it can be concluded that the Balangu having adaptability, suitable production, relatively short growth period and matching the length of the growth period with the rainfall of the study area, and it can be considered as a common plant for rotation in this region. Foliar application of iron and zinc micronutrient elements should be used by farmers to moderate the effects of water deficit stress, taking into account its small and economical amounts.