Effects of Foliar Application of Potassium Silicate and Nanoparticles (silicon + zinc) in Different Stages of Growth and Development on Quantitative Yield and Grain Enrichment of Rice (Oryza sativa L.)

Rice (Oryza sativa L.) is one of the three major food crops worldwide. Approximately 50% of the world’s population uses rice as a staple food. Silica and zinc among nutrients play a key role in improving plant nutrition and increasing rice growth, so that a lack of these elements reduces growth and consequently reduces yield. Also fortifying rice with silicon and zinc can correct deficiencies of these elements in humans who consume rice.

This experiment was conducted as factorial based on a randomized complete block design with three replications at the private farm located in Babol (North of Iran) during the years 2017-18 and 2018-19. Measured values of electrical conductivity, soil acidity, organic carbon, total nitrogen, available phosphorus, available potassium, zinc content and soil texture for the first and second years were 2.33 dS m -1 and 1.27 dS m -1 , 7.48 and 7.26, 3.27 % and 2.16 %, 0.32 % and 0.21 %, 11 mg kg-1 and 6 mg kg-1 , 320 mg kg-1 and 238 mg kg-1 , 0.96 mg kg-1 and 0.89 mg kg-1 , Clay and Clay, respectively. The treatment included three levels of foliar application (Potassium silicate, Silicon nanoxide, and Zinc nanoxide) as the first factor and five levels of developmental stages (T1: beginning of tillering + middle of tillering + late of tillering + end of panicle emergence, T2: middle of tillering + late of tillering + end of panicle emergence, T3: late of tillering + end of panicle emergence, T4: late of tillering and T5: end of panicle emergence) as the second factor.

The results showed that none of the studied traits were affected by the year. Maximum grain yield was obtained by foliar application silicon nanoxide (7733 kg ha-1 ) and zinc nanoxide (7498 kg ha-1 ), which was, respectively, due to increasing the total number of spikelets and the percentage of filled spikelets (1420.0 spikelets and 95.53%, respectively) and increasing the total number of tillers and 1000- grain weight (19.73 tillers and 26.80 g, respectively). The highest grain yield (7716, 7700 and 7492 kg.ha-1 ) and the percentage of filled spikelets (94.83, 94.72 and 93.89%) were obtained under T1, T2 and T3 treatments, respectively. By foliar application of silicon nanoxide and zinc nanoxide, the highest biological yield (19213 and 18986 kg ha-1 , respectively) and, the highest grain silica concentration (3.13%) and grain zinc concentration (15.97 mg kg-1 ) were recorded. The minimum 1000-grain weight (24.11 and 24.00 g), the maximum total number of spikelets per panicle (143.1 and 143.2 spikelets) and the highest concentration of grain silica (3.00 and 2.97%) were obtained under T1 and T2 treatments, respectively. However, the highest total number of tillers per hill and the highest number of grain were obtained under T1 and T2 treatments, respectively. The interaction between treatments showed that the maximum total number of spikelets per panicle was obtained by foliar application of potassium silicate under T1 treatment (151.5 spikelets) and foliar application of silicon nanoxide under T2 treatment (153.3 spikelets). Also, the highest concentrations of silica and zinc in grain were obtained by foliar application of silicon nanoxide under T1 treatment (3.97%) and zinc nanoxide under T2 treatment (21.67 mg kg-1 ), respectively.

According to the results of this study, we found that grain yield increases with the application of nanoparticles as well as foliar application during crop growth and development. In order to enrich rice grains, foliar application of nanoparticles in the middle of tillering, late of tillering and end of panicle emergence is also necessary