Phosphorus Fertigation Conferred Lodging Tolerance and Improved Grain Quality in Chenopodium quinoavia Enhanced Root Proliferation and Stalk Strength

Root architectural traits are most affected by phosphorus (P), one of the most limiting primary macro-nutrients in the soil. In a 2-year field experiment, variations in P-dependent root proliferation and their impact on stalk strength, lodging resistance, and grain quality traits of quinoa (Chenopodium quinoaWilld.) were studied. Basal P fertilizer applications (control, 50, 100, and 150 kg ha−1of superphosphate) were applied, and lodging rate and related traits were investigated. The quinoa grown without P-inputs exhibited 15% less root surface area and 17–19% less root diameter than 100 kg P ha−1. The application of 150 kg P ha−1increased total root length by 17 and 8% in the 2 years. Control plants exhibited higher total soluble sugar fraction and malondialdehyde (MDA) contents, while this pattern was notably reverted after 100 kg P ha−1application. Furthermore, the total free protein, lipid, and starch content of quinoa grains were enhanced by P application which exhibited 8, 5–12, and 10% increase at 100 kg P ha−1, respectively. This primarily suggested amelioration of oxidative stress by P-application linked with high superoxide dismutase activity and inhibition of lipid peroxidation in quinoa roots. Therefore, we singled out 100 kg P ha−1as the optimal level, promoting stalk strength and reducing the risk of lodging through enhancements in root diameter and stalk strength, leading to increased quinoa yield and grain quality traits.