Effect of Water Stress at Different Growth Stages and Amino Acid Foliar Application on Seed Yield and Water Use Efficiency of Castor Bean (Ricinus communis L.)

• Baidaa Abd Lafteh Salem and Ahmed Yassin Hassan

  Author

A field experiment was conducted at the Field Crops Research Station, College of Agriculture, University of Diyala, during the 2025 season to study the effects of water stress and amino acid Foliar Application on seed yield and water-use efficiency in castor bean plants. A randomized complete block design (R.C.B.D.) with a split-plot arrangement and three blocks was used. The first factor was the application of water stress stages, which included the first water stress stage, implemented after the plant had six vegetative leaves on May 11, 2025, and lasting for 30 days of vegetative growth; the second water stress stage, implemented after the first stage on June 10, 2025, at the same water stress level (60% of the prepared irrigation), also lasting for 30 days of vegetative growth; and a control irrigation treatment (100% of the prepared irrigation) without water stress. The second factor was the application of four amino acid concentrations (0, 1, 2, and 3 ml L⁻¹) in two applications, 15 days apart. The results showed that the irrigation treatment without water stress was superior in leaf area, fresh weight of the plant, number of capsules, weight of 300 seeds, seed yield, and water use efficiency, with values ​​of (20.34 cm², 88.90 g, 55.25 capsules per plant, 309.08 g, 117.54 g, and 0.040  kg ha⁻¹ ) respectively. In contrast, the spray treatment with a concentration of 3 ml L⁻¹ of amino acids was superior in leaf area, fresh weight of the plant, number of capsules, seed yield per plant, and water use efficiency, with values ​​of 113.76 cm², 300.11 g, 54.00 capsules per plant, 20.26 g, and 0.042 kg ha⁻¹ respectively, except for the weight of 300 seeds, which was superior with a 2 ml L⁻¹ spray, reaching 87.81 g . The interaction between irrigation without water stress and Foliar Application with a concentration of 3 ml L^-1 of amino acids also showed a significant improvement in seed yield, reaching 25.00 g. plant^-1

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