Effect of use of biological fertilizers and superabsorbents on the agronomic characteristics of castor plant (Ricinus communis L.) under water deficit stress conditions

The castor bean (Ricinus communis L.), is an oilseed of relevant economic and social importance. From its seeds is extracted an oil of excellent properties, having wide use as industrial input and several applications. It is cultivated since the times of the ancient civilizations, the castor bean is a rustic plant, resistant to drought, belonging to the family of Euphorbiaceae, Drought stress, in addition to the negative effect on yield, causes or exacerbates other stresses, especially the stress of nutrient deficiencies for the plant. The purpose of this investigation was study effect of irrigation levels and Superabsorbents and biofertilizers on the agronomic properties of castor oil.

This experiment was conducted in West Azarbaijan Agricultural Research and Education Center, Orumieh- Iran at 2018-2021 crop season. Field experiment was carried out by a split plot design based on completely randomized block design with three replications. The first factor included Four levels (70, 100, 130 and 160 mm of evaporation pan),in the main plot and Sub-factor includes application of biofertilizer combination in four levels (Azospirillium, Citrobacter, combination of application of Azospirillium in Citrobacter and control without fertilizer) and superabsorbent in two levels (superabsorbent consumption and non-superabsorbent consumption) as factorial were placed in sub-plots. In this study, plant height, main length cluster, capsules number per plant, seeds number per plant, thousand kernel weight, biological yield, grain yield harvest index, oil percent and oil yield were measured. Also Traits were analyzed by using SAS 9.2 software and means comparison was tested by least significant difference (LSD).

The results of analysis of variance showed the effect of irrigation, biofertilizer and superabsorbent treatments at the level of 1% probability on plant height, number of seeds per plant, main cluster length, number of capsules per plant, 1000-seed weight, biological yield, grain yield, harvest index Oil percentage, oil yield, castor oil were significant. Also, the interaction effect of biosorbent and superabsorbent on plant height, number of seeds per plant, main cluster length and oil yield at the level of 5% probability and on grain yield, harvest index at the level of 1% probability was significant. The results showed that irrigation treatment after 160 mm of evaporation pan reduced plant height, number of seeds per plant, length of main cluster, number of capsules per plant, 1000-kernal weight, biological yield, grain yield, harvest index, oil percentage and oil yield in comparison with irrigation treatment after 70 mm by 7.62, 5.26, 12.19, 5.25, 5.86, 3.38, 9.50, 6.10, 2.38 and 11.83 percent, respectively. Among the biofertilizer treatments, seed inoculation with Citrobacter was able to increase the number of capsules, 1000-seed weight, biological yield and oil percentage compared to the control treatment by 5.5, 17.28, 2.74 and 8.50%, respectively. Among the interaction treatments, the highest plant height (165.21 cm), main cluster length (23.55 cm), grain yield (1137.61 kg ha-1), harvest index (20.72%) and oil yield (597.91 kg ha-1) was allocated to superabsorbent treatment and inoculation with Citrobacter.

In this study, by exacerbation of water stress, all agronomic traits were reduced. It can be concluded that water deficit stress reduces the amount of photo assimilate and transfer of these substances by disrupting the photosynthesis process, and thus grain yield and yield components as well as oil percentage and oil yield are affected, Therefore, in order to achieve maximum economic yield in castor, irrigation should be done with a regular plan and the plant should not face long periods of drought as much as possible. In this study, the use of biological fertilizers, especially citrobacter, both individually and in combination with supergene had a positive effect on increasing grain yield and grain yield components, oil content and oil yield. Therefore, the use of these materials to improve the economic performance of castor oil is recommended.