Effect of Foliar and Soil Application of Chelated Zinc, Humic Acid, and Tryptophan Amino Acid Spray on the Growth and Yield of Maize (Zea mays L.) under Salt-Stressed Soil Conditions

• MUNTAHA MAHMOUD JAWAD Hussein Aziz Mohammed 2

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A field experiment was conducted at the Research Station of the Department of Soil Sciences and Water Resources, College of Agriculture, University of Diyala, during the autumn season of 2025. The study aimed to evaluate the effects of chelating zinc application, humic acid, and foliar spraying of the amino acid tryptophan on the growth and yield of yellow corn (Zea mays L., cv. Drachma) grown in salt-affected soil. The study was laid out in a Randomized Complete Block Design (RCBD) using a factorial arrangement with three replications, comprising 36 experimental units. The experiment involved three factors: chelating zinc applied at three levels (0, 5, and 10 g plant⁻¹), humic acid at two levels (0 and 5 g plant⁻¹), and foliar application of tryptophan at two concentrations (0 and 100 mg L⁻¹). The recorded data were statistically analyzed using the SAS software, and the Least Significant Difference (LSD) test was adopted to compare treatment means at a probability level of 0.05%. The results are summarized as follows:

The addition of zinc at the third level (10 g plant⁻¹) decreased electrical conductivity (EC) values, increased soil organic matter percentage, increased available zinc concentration in the soil and in plant grains, and increased total grain yield, with statistically significant percentage increases/changes of (62.67%, 25.74%, 75.67%, 86.43%, and 21.31%, respectively).

Meanwhile, the application of humic acid at the second level (5 g plant⁻¹) led to a reduction in electrical conductivity values and an increase in soil organic matter percentage, available zinc concentration in the soil, grain zinc concentration, and total grain yield, with statistically significant increases of (19.72%, 29.41%, 91.17%, 29.23%, and 12.60%, respectively).

Furthermore, foliar spraying of amino acid at the second level (100 mg L⁻¹) significantly increased grain zinc content and total grain yield, with significant increases of (7.67% and 17.21%, respectively).

Scientific Keywords: Electrical Conductivity (EC), Soil Organic Matter (SOM), Available Zinc in Soil, Total Yield.

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