Effect of seed priming and spraying with melatonin on growth and yield characteristics of soybean (Glycine max L.Meer.) grown under salt stress

• Sawsan Sameer Abed1 Abdullah Hassn Mohammed1*

  Author

To mitigate soil salinity resulting from irrigation with well water containing high salt content, which negatively impacts the growth and productivity of soybean crops, a field experiment was conducted at the Soil and Water Resources Research Station of the College of Agriculture, Tikrit University, during 2025 growing season as a factorial experiment with a split-plot arrangement randomized complete block design with three replications. Two types of irrigation water were used: river water (Tigris River) and well water, which represented the first factor (main plots), while the second factor (sub plots) represented melatonin combinations (soaking + spraying). Traits of relative growth rate (RGR), crop growth rate (CGR), net assimilation rate (NAR), leaf chlorophyll content, protein content, and grain yield were studied. The results showed that all studied traits were affected by the irrigation water type. Plants irrigated with well water were more affected by the salinity and exhibited lower values ​​than plants irrigated with river water. Melatonin stimulates plants to tolerate the accumulated salinity in the soil due to irrigation with saline water and mitigates its effects on soybean plants. Treatment of melatonin T8 [100 (soaking) + 200 (spraying) µmol] irrigated with river water was the superior treatment in all studied traits and showed the highest values, reaching 0.1027, 0.0736, and 0.0450 g g^-1 day^-1 of RGR, 0.00182, 0.00315, and 0.00643 g cm^-2 day^-1 of CGR, and 0.00677, 0.00621, and 0.00395 g cm^-2 day^-1 of NAR, for measurement periods of 30-60, 60-90, and 90-120 days after planting, respectively. Chlorophyll content, protein content, and grain yield gave the values of 39.522 SPAD,37.826%, and 20.0867 tons ha⁻¹, respectively. Melatonin plays a key role in promoting the growth and productivity of soybean crops, as well as mitigating the effects of salinity on soybean yield.

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