A field experiment was conducted with two soybean varieties (MAUS-2 and KBS-23) and seven treatments in a randomized complete block design with three replications to investigate the effect of foliar application of silicic acid on soybean yield and seed quality under field condition. Significant increase in haulm, pod and seed yield was observed with the foliar application of silicic acid at 2 mL L⁻¹ for three times and 4 mL L_-1 for two times in MAUS-2 and KBS-23 variety, respectively. Foliar applied silicic acid significantly improved protein yield of KBS-23 variety and oil yield of MAUS-2 variety. Greater variation in silicon (Si) content among the various plant parts of soybean were recorded with the application of silicic acid and boric acid. The highest silicon content was in haulm followed by husk and seed. Among the two varieties, KBS-23 responded better for foliar application of silicic acid than MAUS-2 variety. Application of boric acid also enhanced the growth and yield of soybean over control. Foliar application of silicic acid at two different doses (2 and 4 mL L⁻¹) for two or three times significantly enhanced the yield, quality and Si content of soybean. Application of silicic acid at 2 mL L⁻¹ thrice and 4 mL L⁻¹ twice along with recommended dose of fertilizer was effective in MAUS-2 and KBS-23 variety, respectively.

The foliar nutrition of silicic acid is considered to be a novel approach in enhancing the performance of many crops worldwide. The present study aimed to assess if the foliar application of silicon (Si) could influence the performance of soybean varieties with distinct crop duration, MAUS-2 (long duration) and KBS-23 (short duration). Field experiments were conducted in two consecutive years (2016 and 2017) of varied rainfall with foliar application of silicic acid @ 2 and 4 mL L⁻¹ for three and two sprays each. The results showed significant enhancement in the yield, seed quality (protein and oil content), and uptake of nutrients (N, P, K, Ca, Mg, S, and Si) by various parts viz., seed, husk, and haulm of both varieties with foliar nutrition of silicic acid. However, the short duration variety, KBS-23, responded well under low rainfall conditions (2016) with two sprays of foliar silicic acid @ 4 mL L⁻¹ and MAUS-2 variety in the second season under higher rainfall (2017) with three sprays of foliar silicic acid @ 2 mL L⁻¹, along with the recommended dose of fertilizer. This research revealed that the effectiveness of foliar silicic acid nutrition differs with the duration of the varieties, number of sprays given, and water availability in the soil during the cropping period.