Contrasting Effects of Biohumus and Urea on Potato Yield, Tuber Quality, Nitrate Concentration, and Profitability under Mountainous Conditions

Abstract

Sustainable nutrient management is essential for maintaining potato productivity and tuber quality while limiting nitrate accumulation in mountainous agroecosystems. A two-year field experiment conducted in Martuni, Armenia, compared Quicelum, humate, biohumus, mineralized manure, and urea in ‘Marfona’ potato using a randomized complete block design with three replicates. Treatment effects were significant for all seven evaluated yield, yield-component, and tuber-quality traits (P < 0.001), and year effects were significant for all traits (P ≤ 0.019). The treatment × year interaction was significant only for protein content (P < 0.001). Descriptive means indicated numerically earlier emergence, flowering, and physiological maturity under biohumus than under urea. Urea produced the highest tuber yield (48.58 t ha⁻¹), significantly exceeding biohumus (47.62 t ha⁻¹), although the difference was only 2.0%. Biohumus produced the highest dry matter (20.2% FW) and starch contents (15.0% FW) and the lowest nitrate concentration (57.4 mg kg⁻¹ FW). Urea produced the highest protein content in both years and the highest nitrate concentration (72.7 mg kg⁻¹ FW). Under a common farm-gate price with no premium for tuber quality or nitrate concentration, urea generated the highest net profit (3,288.4 × 10³ AMD ha⁻¹), benefit–cost ratio (2.60), and profitability (160.0%), whereas biohumus performed best among the alternative treatments. Under the tested conditions and application rates, urea maximized yield and short-term profitability, whereas biohumus combined competitive yield with higher dry matter and starch contents and lower nitrate concentration.