Grain size and yield of quinoa with the application of organic matter and biological and mineral fertilizers

The search for alternative crop nutrition practices is essential to reduce dependence on synthetic chemical fertilizers and contribute to sustainability. This study aimed to evaluate the integrated effect of biological fertilizers (3.7 L ha⁻¹), soil mineral fertilizer (90-60-52 kg ha⁻¹ of NPK), foliar mineral fertilizer (1.5 L ha⁻¹), and organic matter (1 t ha⁻¹ of compost) on quinoa growth, yield, and grain size distribution. Seven treatments were evaluated: T1 (control), T2 (soil mineral), T3 (soil mineral + foliar), T4 (biological), T5 (biological + organic), T6 (biological + soil mineral), and T7 (biological + soil mineral + organic). The experiment followed a randomized complete block design with four replicates, and the data were analyzed using ANOVA (p < 0.05). The results indicated that quinoa has high nutritional demands, as the absence of any type of fertilizer resulted in the lowest yield and grain size. While biological fertilizers significantly improved agronomic variables, the integrated fertilization strategy (T7) produced the highest yield (1.89 t ha⁻¹) and the largest proportion of large grains (57%), representing increases of 4.2 and 3.6 times, respectively, compared to the control. Mineral fertilizers alone (T2) resulted in the most homogeneous size distribution, a desirable characteristic for the industry. We concluded that integrated fertilization is a effective strategy for quinoa cultivation, offering a viable pathway to reduce the exclusive use of chemical fertilizers.