Silicon reduces nitrogen stress and improves growth and yield of forage grass under excessive fertilization in tropical soils.

Inadequate nitrogen (N) fertilization management in pastures is common and can lead to N deficiency or excess, resulting in physiological imbalances in forage grasses across different regions of the world. Silicon (Si) fertigation is a promising strategy to mitigate these issues due to its anti-stress properties. However, its effects on the morphogenic growth processes of grasses and their influence on forage nutritional value remain unclear. This study investigated the detrimental effects of low, adequate, and excessive N-urea supply on the morphogenesis, production, and chemical-bromatological composition of Zuri grass in two tropical soils (Ferralsol and Arenosol), with a focus on the mitigating role of nanosilica in these parameters. Low N levels inhibited leaf growth and tillering, whereas excessive N led to excessive increases in morphogenic activity, compromising leaf lifespan and dry matter (DM) production. Si fertigation balanced morphogenesis under both low and excessive N conditions, reducing dead material and lignin content in forage grown in Arenosol. Well-nourished plants exhibited higher DM production in both soils when supplemented with Si. Fertigation with silicon is beneficial for the morphogenesis of grass under low or high N, mitigating DM production losses under N excess, but not under N deficiency. Silicon can optimize forage production in adequately fertilized systems without compromising forage digestibility.