Synergistic Effects of Silicon and Mycorrhiza on Sorghum Grown under Saline Water Irrigation

Abstract

Salinity stress is a major constraint to crop productivity, affecting physiological processes such as photosynthesis and disrupting osmotic and ionic balance. Exogenous application of silicon has been shown to enhance plant tolerance to salinity by improving photosynthetic efficiency, metabolic activity and molecular responses. Similarly, mycorrhizal fungi help to mitigate salinity-induced stress by enhancing nutrient uptake. To investigate the combined effects of silicon and mycorrhiza on sorghum under saline irrigation, a field experiment was conducted in 2022 at farmer’s field in Kuppuchipalayam village, Karur District, Tamil Nadu. The study included five silicon levels (0, 50, 100, 150, and 200 kg/ha) applied through diatomaceous earth and three mycorrhiza levels (0, 25, and 50 g/plant), under saline water irrigation with an electrical conductivity of 10 dS/m. The experiment was laid out in a factorial randomized block design (FRBD) with two replications, using sorghum var. K12 as the test crop. Results revealed that both silicon and mycorrhiza significantly alleviated the negative effects of salinity, improving plant growth and yield. Plant height, leaf area index (LAI), chlorophyll content (SPAD) and dry matter production (DMP) increased with higher silicon levels, peaking at 200 kg Si/ha, resulting in respective increases of 9.2%, 53.6%, 19.0%, and 25.1% over the control. Yield parameters such as number of ear heads/m², no. of filled grains/ear head, grain yield and stover yield were also maximized at this level, with the highest grain and stover yield reaching 4286.3 kg/ha and 7096.7 kg/ha, showing 25.4% and 21.7% increases over control. Mycorrhiza application at 50 g/plant significantly enhanced all measured parameters over 25 g/plant and control, with grain and stover yields increasing by 10.3% and 10.7%, respectively. The interaction between silicon and mycorrhiza was significant, with the best performance observed at 200 kg Si/ha + 50 g VAM/plant, resulting in yield improvements of 40.5% (grain) and 33.4% (stover) compared to untreated control.