Improving of Quinoa Nitrogen Metabolism Enzyme Activity, Nitrogen Uptake and Assessing Quinoa Yield of Different Fertilizers

[Purpose] Nitrogen is the most crucial nutrient for achieving optimal yields. Recognizing the potential for improved nitrogen acquisition and utilization through appropriate fertilizer types, we conducted a 2-year field experiment. Variations in nitrogen metabolism enzyme activity and their impact on nitrogen uptake, as well as the yield and economic benefits of quinoa (Chenopodium quinoa Willd.), were studied across different fertilizer types. [Method] Five different fertilizer treatments were administered, including composite fertilizer, organic fertilizer, bio-microbial fertilizer, slow-release fertilizer, and controlled-release fertilizer, each supplying 120 kg ha-1 of nitrogen. Additionally, a control group received no fertilizer. [Results] The results revealed a substantial uptick in the activity levels of Glutamine synthetase (GS) and nitrate reductase (NR) within quinoa leaves when bio-microbial and slow-release fertilizers were applied, GS activity increased by 4.1-25.6%, while NR activity increased by an impressive 21.6-69%. Furthermore, the application of slow-release fertilizers significantly increased the dry matter and nitrogen accumulation in quinoa, with the highest proportion of nitrogen being allocated to the grains. Notably, slow-release fertilizer yielded the highest quinoa output, averaging 4525.8 kg ha-1, and secured the greatest economic returns. In contrast to other treatments, slow-release fertilizer demonstrated remarkable enhancements, with nitrogen fertilizer utilization efficiency, nitrogen absorption efficiency, and harvest index improving by 8.5-67.2%, 11.1-42.9%, and 4.4-4.6%, respectively. [Conclusion] Therefore, slow-release fertilizer was selected as the optimal fertilizer type, enhancing nitrogen metabolism enzyme activity through improving nitrogen uptake and utilization, which subsequently boosted quinoa yields and economic efficiency.