The presented study sought to determine the foliar application of potassium nitrate effects and addition of black tea leaf wastage to soil on the biochemical qualities (zinc, protein, oil percentage, and carbohydrate) of wheat (Triticum aestivum L.) and the content of NH₄N, Na, Mg, Ca, Cl, and pH of the soil. The pot experiment commenced in the spring of 2022 in a randomized complete block design (RCBD) with a factorial arrangement having two factors and four replications in Al-Hindia city, Kerbala, Iraq. The first factor was a potassium nitrate compound comprising three levels (control, 1000, and 3000 g 1000 l^-1), and the second factor was black tea leaf waste mixed with soil in four doses (control, 25, 45, and 55 g 1000 l^-1). The results showed the impact of black tea wastes mixed with the soil of higher significance, increasing the NH₄N, Na, Mg, Ca, and Cl to 29.28 mg kg^-1, 3.75, 3.88, 5.88, and 6.79 mm l^-1, respectively, and higher impact in reducing the soil pH (7.54) at a concentration of 55 g 1000 l^-1). The black tea leaf waste (55 g 1000 l^-1) helped raise the treated wheat’s zinc, protein, oil, and carbohydrate percentages. The foliar application of potassium nitrate compound (3000 g 1000 l^-1) considerably affected increasing the proportion of zinc, protein, and oil in wheat grains.

Keywords: Triticum aestivum L., potassium nitrate, black tea leaf waste, zinc, protein, oil percentage, carbohydrates

Key findings: Black tea wastes mixed with high-quality soil increased the NH₄N, Na, Mg, Ca, and Cl of the soil to 29.28 mg kg^-1, 3.75, 3.88, 5.88, and 6.79 mm l^-1, respectively, and highly impacted reducing the soil pH (7.54) at a concentration of 55 g 1000 l^-1). Black tea leaf waste (55 g 1000 l^-1) also boosted the wheat’s zinc, protein, oil, and carbohydrate content. The potassium nitrate compound (3000 g 1000 l^-1) foliar application increased wheat grain’s zinc, protein, and oil concentrations.