The Effect of Different Levels of Phosphorus and Zinc Spraying on Growth Properties, Oil Content and Biochemical Characteristics of Securigera securidaca

IntroductionOptimum nutrition of plants and reducing the effect of lack of important nutrients is one of the most effective factors on the production of all plants; so, it is one of the main pillars in improving the quantitative and qualitative attributes of the product. In order to achieve optimal yield with proper nutrition of the plant, each element must be provided to the plant sufficiently, and there must also be a balance between the absorbable amounts of elements in the soil. Securigera securidaca is one of the medicinal plants belonging to the Fabaceae family. There are many records about the traditional use of this plant and its seeds. Its seeds have antiparasitic, anticonvulsant, antihypertensive, antiulcer, analgesic, antioxidant, antiviral, antitumor and hypoglycemic effects have been reviewed. Considering the climatic conditions of Iran and its high potential in the production of medicinal plants and its economic justification; it is very necessary to pay attention to the nutrition of medicinal plants due to their different growth conditions with other crops and its effect on their growth and effective substances. Materials and MethodsIn this research, in order to evaluate the response of the Hatchet vetch plant (Securigera securidaca) to different levels of phosphorus and zinc foliar application, a factorial experiment was conducted in a randomized complete block design (RCBD) with two factors and three replications. The treatments include four levels of phosphorus (0, 50, 100 and 150 kg.h-1) and three levels of zinc foliar application during the flowering period (no foliar application as a control, foliar application: each two weeks once and once a week). Zinc foliar spraying was done with a concentration of 4 g per liter during before flowering to the formation of the pods (about one month), which was done twice and four times for the two-weekly and once-a-week treatments, respectively. This research was carried out in Mohammad Abad area of Jahrom city located in Fars province. The most important indicators of growth and yield were measured including: shoot number, length of main stem, number of pods per plant, number of seeds per pod, pod length and seed yield. Also, the most important biochemical characteristics of seed extract (flavon and flavonol, total flavonoid, total phenolic compounds, tannin content and antioxidant activity), oil percentage and seed oil yield were also measured.   Results and DiscussionBased on the results obtained from the variance analysis of the data, the effect of phosphorus and zinc on all measured traits was significant except for the number of seeds in pods and pod length. The results showed that the application of phosphorus alone was more effective than the combined application of phosphorus and zinc in increasing the number of stems, main stem length, seed yield, oil yield, the amount of flavonoids and antioxidant activity of Hatchet vetch plant seeds. The application of 50 kg of phosphorus increased the number of stems, the length of the main stem, the number of pods per plant, the yield of seeds, amount of phenolic compounds and oil yield of seed. While the use of 100 kg of phosphorus without the use of zinc was more effective in increasing the amount of flavonoid and antioxidant activity. However, the application of zinc was effective in increasing phenolic compounds, tannin content, oil percentage and seed yield. The interaction effect of the treatments showed that the highest seed yield (61.03 g.m-2) was related to 50 kg of phosphorus without zinc foliar spraying, while the lowest amount (32.01 g) was observed in 50 kg of phosphorus and zinc solution once a week treatment. The highest amount of total flavonoid (3.58 mg.g-1 dry weight) was found in the treatment of 100 kg of phosphorus without the application of zinc. While the lowest amount (1.11 and 1.24 mg) was observed in treatments without phosphorus (spraying zinc solution once every two weeks and once a week), respectively. In the treatments of 100 and 150 kg of phosphorus, increasing the frequency of zinc foliar spraying has reduced the amount of phenolic compounds in the seeds of this plant. Although this decrease is not significant statistically. Also, in the control, 50 and 150 kg of phosphorus treatments, increasing the frequency of zinc foliar spraying had no effect on the change of its antioxidant activity, while in the treatment of 100 kg of phosphorus fertilizer, increasing the frequency of zinc foliar spraying decreased the antioxidant activity of the seed extract of this plant. ConclusionsIn general, according to the conditions in this research, despite the differences that were seen in the measured traits in response to the amounts of phosphorus and zinc, the concentration of 50 kg of phosphorus and foliar spraying of zinc once every two weeks, in most of the traits were satisfactory compared to other treatments.