Rice (Oryza sativa L.) is a key food grain crop in Acid Soil Regions of the world. Soil acidity related constraints in rice production are well known. A sustainable and economical method for nutrient combinations and application methods should be developed in order to overcome the constraints and shrinkage in available nutrients associated with rice production (Mohanty and Yamano, 2017). Though the benefits of silicon application in rice plants are well established, the recommendation on soil application of silicon is not adopted by rice growers due to its larger quantity of requirement. So, the development of efficient application method of suitable source of silicon is the need of hour for harnessing the benefits of Si in rice. The seedling root-dipping in Si amended slurry or foliar application of Si at vegetative and reproductive stages of rice plant are reported to be the effective Si application method as alternative to soil application in rice plant (Devi, 2018). However, the information on suitable source of silicon in relation to application method is missing in the literatures. In order to address this research gap, the objectives of the present study were: (1) To compare the effectiveness of Si sources on growth and yield performance of transplanted rice, (2) To find out the effective combination of application method and source of Si and (3) To access the effect of Si fertilization on soil fertility status.
Three sources of silicon were silicic acid hydrate, (C1) SAH, calcium silicate, (C2) CS and sodium meta silicate, (C3) SMS. Each of 3 silicon sources were tested in 5 different application methods: (1) M1, seedling root-dipping (SRD) in soil: water slurry (applied @ 225 mg kg-1 soil for HYV rice, Devi, 2018), (2) M2, foliar spray (1% Si) at the vegetative stage (FSV) , (3) M3, foliar spray (1% Si) at the reproductive stage (FSR), (4) M4, FSV+FSR, and (5) M5, SRD+FSR. Altogether, 96 pots (30 cm diameter, contained 10 kg sandy clay loam soil) were arranged ((3 sources x 5 treatments x 6 replications) + 6 pots as control (no Si application = 96 pots)) and three rice hills (variety: CAU-R1) were maintained. Three replicate pots were harvested at 45 days after transplanting (DAT) and other 3 replicate pots were harvested at maturity.
The concentration of Si was not only the highest (0.045%) in SRD-SAH method (C1M1), but also showed the positive effect in terms of the significant higher plant growth parameters at 45 DAT and root morphological parameters. Application of SAH as SRD (C1M1) or FSV (C1M2) at initial crop growth stages or as a combination of SRD+FSR (C1M5) showed the highest values of yield attributes. Application of CS as SRD (C2M1) supported the significant higher total root length (cm) and root volume (cm3). Application of FSV+FSR (C2M4) produced significant higher total root length (cm) and plant biomass (g) at 45 DAT. Application of CS as FSV (C2M2) produced significant higher plant growth parameters at 45DAT and plant height (cm) at harvesting stage and highest biological yield (g hill-1), straw yield (g hill-1) and least number of chaffed grains. Application of CS as FSR (C2M3) produced significant higher plant growth parameters at the harvesting stage, whereas CS as FSV+FSR (C2M4) supported significant highest plant height (cm) and highest number of filled grains. Application of SMS as FSV+FSR (C3M4) produced significant higher root growth parameters and shoot dry weight (g) during 45 DAT and similarly had significant higher plant growth parameters, highest grain yield (g hill-1), test weight, number of filled grains and biological yield (g hill-1) at harvesting stage.
Interaction effect indicated that the plant height 45 DAT is the highest in C2 (CS), C3 (SMS) and M1 (SRD), root estimated volume(cm3) was significantly higher in C1M1 (SRD-SAH) including yield parameters like grain yield was the highest in C1M1(SRD-SAH) followed by C3M4 (FSVR-SMS) and the straw yield was the highest in C2M1 (SRD-CS).
In conclusion, Silicic Acid Hydrate as seedling root dip method with 225 mg Si kg-1 soil (SRD-SAH) and Sodium Meta silicate foliar spray at vegetative stage and reproductive stage (FSV+FSR-SMS) with 1% Si was found to be the best performing.