Forms of application of silicon in quinoa and mechanisms involved in the association between productivity with grain biofortification

Abstract Multiple aspects of the physiological and nutritional mechanisms involved with silicon (Si) absorption by quinoa plants remain poorly investigated, as well as the best way of supplying this element to crops. Thus, this study aimed at evaluating whether the application of Si increases its uptake by quinoa plants and consequently the use efficiency of N and P, as well as the levels of phenolic compounds in the shoots, crop productivity and the biofortification of grains. For this purpose, the concentration of 3 mmol L-1 of Si was tested, according to the following procedures: foliar application (F), root application in the nutrient solution (R), combined Si application via nutrient solution and foliar spraying (F+R), and no Si application (0). The provision of Si through the leaves and roots promoted the highest uptake of the element by the plant, which resulted in an increased use efficiency of N and P. Consequently, such a higher uptake favored the productivity of grains. The optimal adoption of the application of Si through leaves and roots promoted the highest Si concentration and ascorbic acid (AsA) content in quinoa grains. Combining root and leaf application of Si was the best way to supply this nutrient, as it increased the use efficiency of N and P, and favored both the productivity and biofortification of quinoa grains with Si and AsA.