Silicon application improves drought tolerance in peanut (Arachis hypogaea L.) under variable planting densities

Although silicon (Si) fertilization and increased planting density have individually shown promising results in improving crop growth and yield, little is known about their combined effects, particularly under drought conditions. This study evaluated the effects of Si concentrations (0, 50, 100 and 200 ppm) and planting density (5, 10 and 15 plants pot-1) simultaneously on growth responses of peanut (Arachis hypogaea L.) under two water regimes (well-watered: 60% water holding capacity (WHC) and water stress: 20% WHC) in the greenhouse. Si significantly enhanced most shoot parameters across water treatments. Higher planting density (15 plants pot-1) significantly reduced most shoot growth parameters while promoting root attributes regardless of water treatments. Si stimulated proline accumulation by 312.7% under water-stressed conditions compared with 170.0% under well-watered conditions. Proline concentration was positively correlated (r = 0.46, P < 0.01) with peroxidase activity. All these results indicate that Si application combined with appropriate planting density can potentially improve peanut plant performance under drought stress while enhancing land-use efficiency in water-limited and land-scarce agricultural systems. This study also suggests future research to evaluate the combined effects of Si fertilization and planting density on the yield attributes of peanut under field conditions.