Assessment of changes in secondary metabolites and growth of saffron under organic fertilizers and drought

Abstract

Saffron (Crocus sativus L.) as the most expensive spice, needs low water for growth. However, its yield reduces under drought and nutrient stresses. A two-year field experiment was aimed to evaluate the improvement of saffron growth and quality by nutrition supply on drought conditions in 2018 and 2019. Irrigation regimes were included control (field capacity) and drought (66% depletion of soil water). Fertilizer treatments were included control (without fertilizing), chicken manure, chemical fertilizer, 25% chicken manure + 75% chemical fertilizer (Ch25M75), 50% chicken manure + 50% chemical fertilizer (Ch50M50), and 75% chicken manure + 25% chemical fertilizer (Ch75M25). Drought reduced the saffron growth characteristics, chlorophyll content, relative water content (RWC), and yield. On the contrary, the amount of proline and soluble carbohydrates (SC) increased. However, the content of crocin, picrocrocin, and safranal increased by drought. Mineral nutrition deficit reduced the saffron growth characteristics, yield, and secondary metabolites content under both irrigation regimes. The combined use of chemical fertilizers and chicken manure was more effective in improving the growth and biochemical traits of saffron in both irrigation regimes than using them alone. The greatest saffron growth was acquired by replacing 75% of chemical fertilizer with chicken manure. However, the highest quality of saffron was obtained when the share of chemical fertilizer was higher than chicken manure (3:1). Therefore, reducing chemical fertilizer and using chicken manure instead is recommended to improve the yield and quality of saffron in drought conditions.