Comparison of NPs Foliar Application of Silicon and Zink with Soil Application on Agronomic and Physiological Traits of Rice (Oryza sativa L.)

Among the nutrients, silicon (Si) and zinc (Zn) play a key role in improving plant nutrition and increasing rice (Oryza sativa L.) growth, because their deficiency reduces growth and yield. Si, as one of the most abundant soil elements, helps to increase the amount of photosynthesis, improve performance, prevent lodging, and reduce pests and diseases. Zn is one of the most important micronutrients involved in protein synthesis and carbohydrate metabolism. One of the most important uses of nanotechnology in various aspects of agriculture in the water and soil section is the application of nano-fertilizers for plant nutrition. Nano-fertilizers can increase the nutrients use efficiency, improve plant growth and reduce environmental impacts compared to traditional methods. The purpose of this research was to evaluate the effect of Si and Zn by two forms of nanoparticles (NPs) foliar application and soil application in order to increasing the nutrient uptake efficiency and improving the rice grain yield.
  This experiment was conducted as a randomized complete block design (RCBD) with 16 treatments and three replications in two locations of Mazandaran province (Amol and Nour) in 2016. The treatments included two forms of Si and Zn application: foliar application (nanoparticles source) and soil application (common source) as individually or mixtures treatments. For soil application, Si fertilizer was applied at the rate of 400 kg Ca2SiO4 ha-1 and Zn fertilizer at the rate of 40 kg ZnSO4 ha-1 as basal in experimental plots. Foliar application of nano-SiO2 and nano-ZnO in the concentration of 50 mg L-1 was applied at four plant growth stages (early tillering, middle tillering, panicle initiation and full heading stage) in plots. At the end of season, some yield components, grain yield as well as the concentrations and uptake of Si and Zn in grain were determined. The combined analysis of experimental data were done by using MSTAT-C software. The means were compared using the LSD test at 5% of probability level.
  The results revealed that yield components, yield and concentration and uptake of experimental elements in rice grain were significantly increased by Si and Zn application in both methods of NPs foliar application and soil application compared to the control. In the case of soil application of the elements, combined use of Si and Zn was never statistically superior to use of only Zn in terms of yield, concentrations and uptake of test elements, but there was a significant difference in the sole application of Si in terms of panicle length and Zn concentration and uptake in rice grain. The combined application of Si and Zn as soil was statistically superior to the separate application of both elements in terms of fertile tillers per hill at Amol and filled grains per panicle at Nour site. In the case of NPs foliar application, combined use of Si and Zn was not statistically superior to use of only Zn in terms of yield and all other studied parameters, but superior to the separately use of Si for fertile tillers number in both experimental sites and Zn concentration and uptake in rice grains.
  The Zn application had a better effect on Zn concentration and uptake in grain compared with Si, but there was no significant difference between Si and Zn application in terms of grain yield. There was no significant difference between the methods used in this experiment in terms of grain yield and concentration and uptake of Si and Zn in grain. Therefore, according to the results of this research, NPs foliar spray and soil application of Si and Zn is effective way for increasing concentration and uptake of test elements and as well as improving rice grain yield in soils having low-availability of these two nutrients.