Effect of Various Nutritional Resources on Phytochemical Traits of Some Rice Varieties Under Drought Stress Conditions

A split-plot factorial experiment with randomized complete block design with three replications was performed at Dasht-e-Naz company located in Sari city, the Mazandaran province, Iran, in 2016 and 2017. It aimed to study the phytochemical properties of rice cultivars using different nutrients (chemical, organic) under drought stress. Three levels of stress, including drought stress at the beginning of tillering stage (15 days after transplanting), active grain filling period (end of flowering and the beginning of seed filling) and lack of stress (control) were the main causes of drought stress. Irrigation was stopped for two days, and re-irrigation was performed periodically after the appearance of hairy cleavage. The type of nutrition system was considered as the sub-factors in the factorial pattern in terms of four levels of vermicomposting and Azolla compost, in the quantities of 6 and 8 tons per hectare, respectively, humic acid (4.5 litres per thousand litres of water), the conventional chemical fertilizers (NPK), and two cultivars (Shirodi and the local Tarom). The maximum paddy seed yield was obtained in the non-stress condition using humic acid in the cultivars of shirodi and local Tarom. The maximum proline content was obtained in the drought stress condition in the retransition growth stage using the conventional fertilizer in the local Tarom cultivar. Maximum free radical scavenging and phenol content was obtained in drought stress conditions applied in the mobilization phase using humic acid in local Tarom rice. The overall results of the research suggested that humic acid increases the resistance of rice cultivars against drought due to the reduction of oxidative damage compared to the other fertilizers resources and enhances the paddy seed yield by affecting the phytochemical process.