Effect of fertilizer nutrition and salicylic acid on yield and some biochemical traits of wheat under drought stress

Wheat (Triticum aestivum L.) is one of the most strategic crops for food, feed, and biofuel security worldwide. Drought stress is one of the most destructive environmental stresses that limit crop productivity worldwide. Drought stress causes a wide range of physiological changes and disturbances in metabolic processes. Environmental problems caused by the use of chemical fertilizers, production costs, and consumption costs are significant issues that require methods to increase crop production and improve sufficient food for the world's population. Today, the economic damage and destructive effects of the environment due to the excessive use of chemical fertilizers in agriculture are known worldwide, and it is obvious that a suitable alternative must be found for these fertilizers. Currently, biofertilizers are used as an alternative to chemical fertilizers based on the principles of sustainable agriculture and the stress tolerance of plants. Salicylic acid is a plant growth regulator that plays an important role in the plant protection system against biotic and abiotic stresses and can affect many physiological and biochemical processes.

In order to investigate the effect of biological and chemical fertilizers and foliar application of salicylic acid on wheat tolerance to drought stress experiment, a factorial split plot in the form of a randomized complete block design in the 2019-2020 crop year in the research farm of the Faculty of Agriculture of Lorestan University in three replications was performed. The Main plot includes irrigation levels in two levels: A1: without stress (100% of water requirement) and A2: drought stress (50% of water requirement) and sub-plots including fertilizer in five levels, including B0: use of 50% chemical fertilizer, nitrogen and phosphorus fertilizer (B1: use of 100% chemical fertilizer), B2: use of nitroxin biofertilizer with 50% chemical fertilizer, B3: use of mycorrhizal with 50% chemical fertilizer, B4: use of biological fertilizers nitroxin and mycorrhiza with 50% chemical fertilizer, and foliar application treatment at two levels (C1: foliar application with water and C2: foliar application with a concentration of 1 mM salicylic acid).

The results showed that drought stress caused a decrease in grain yield, leaf chlorophyll index (SPAD), and relative water content, as well as an increase in peroxidase, proline, and electrolyte leakage. Combined treatment of biofertilizer nitroxin and mycorrhiza with 50% chemical fertilizer caused an increase of 40.53%, 5.18%, 5.89%, 13.85%, 8.46%, and 8.90%, respectively, in grain yield, leaf chlorophyll index, grain zinc concentration, peroxidase, proline, relative water content of the leaf, and 6.29 % reduction of electrolyte leakage compared to the use of 50% chemical fertilizer. Also, salicylic acid foliar spray treatment caused an increase of 11.45%, 2.82%, 4.32%, 7.46%, 9.19%, and 8.02 % in grain yield, leaf chlorophyll index, grain zinc concentration, peroxidase, proline, relative water content of the leaf, and 18.11 % reduction of electrolyte leakage compared to no foliar spraying of salicylic acid. Combined fertilizer treatments of nitroxin and mycorrhiza with 50% chemical fertilizer and salicylic acid could reduce the effect of drought stress on the traits evaluated in this research.

Fertilizer application of nitroxin and mycorrhiza with 50% chemical fertilizer and salicylic acid foliar spraying could provide favorable conditions for the growth and better performance of the plant by improving the biochemical characteristics of the plant while increasing its resistance to drought stress conditions. In general, it can be concluded that the application of biological fertilizers nitroxin and mycorrhiza with 50% of chemical fertilizers and foliar spraying of salicylic acid can be an effective and alternative fertilizer to reduce the consumption of chemical fertilizers in the conditions of drought stress in Khorram Abad in the direction of sustainable agriculture. As a result, this treatment can be recommended to farmers in order to reduce the consumption of chemical fertilizers in wheat under drought -stress conditions.