Enhancing nutritional quality of Amaranthus cruentus (L.) with fertilisers and salicylic acid

Globally, deficiency of essential vitamins and minerals in major staple food crops is a great challenge to human health. The use of fertilisers and elicitors has been suggested as a sustainable approach to enhance food quality. Therefore, this study investigated the effects of compost at 5 and 10 t/ha, poultry manure at 5 and 10 t/ha, and NPK 15:15:15 fertiliser applied at rates of 50 and 100 kg N/ha, Salicylic Acid at 125 and 250 µM/L, and their combinations on the growth and food quality of Amaranthus cruentus, a globally consumed vegetable. The experiment was conducted in a screenhouse and arranged in a completely randomized design with three replicates. Data were collected on marketable yield, dry matter, chlorophyll, folate, zinc, iron, crude fibre, ash, and moisture contents. SA250+NPK50 enhanced the marketable yield by 88.0%, and SA125+NPK100 enhanced dry matter accumulation by 92.6% compared to the control. The combination of SA250+NPK50 also increased chlorophyll content by 67.0% relative to the control. Amaranthus cruentus treated with SA250+NPK50 had higher folate (285.00 µg/100g) and iron (348.00 mg/kg) contents than control (125.00 mg/kg and 138.00 mg/kg, respectively), while zinc (47.00 mg/kg) was highest in Amaranthus cruentus treated with SA250+CP10. In addition, Amaranthus cruentus treated with SA125+PM5 had significantly higher crude fibre (13.10%) and ash (12.35%) contents than the control. The combined application of 250 µM/L salicylic acid and 50 kg N/ha NPK fertiliser improved the yield and quality of Amaranthus cruentus, especially in terms of folate, iron, and zinc, which are important micronutrients for human health.