Effects of foliar spraying different selenium sources at filling stage on main traits， selenium content and rhizosphere soil physicochemical properties of rice

【Objective】To explore the effects of foliar spraying different selenium sources during filling period on rice growth， quality， selenium content and physicochemical properties of rhizosphere soil， so as to provide reference for the selection of exogenous selenium fertilizer and the safe production of selenium-rich rice.【Method】The rice variety Ezhong 5 was as the material， five selenium content gradients（15.0， 22.5， 30.0， 37.5 and 45.0 g/ha， calculated by selenium） were set， the corresponding biological nano selenium［3.0 L/ha（N1）， 4.5 L/ha（N2）， 6.0 L/ha（N3）， 7.5 L/ha（N4）and 9.0 L/ha（N5）］and sodium selenite［32.61 g/ha（Y1）， 48.91 g/ha（Y2）， 65.22 g/ha（Y3）， 81.52 g/ha（Y4）and 97.83 g/ha （Y5）］were sprayed on the leaf surface of rice during filling stage， and equal amount of water spraying as control（CK）. In this research， the agronomic traits， economic traits， quality traits， selenium content of rice and physicochemical properties of rhizosphere soil were investigated respectively.【Result】The results showed that the biological nano selenium spraying improved the grains per panicle， filled grains per panicle， seed setting rate and the 1000-grain weight compared with CK， while these indexes decreased in sodium selenite spraying treatment. In terms of appearance quality， grain length， grain width， grain shape and transparency were not significantly（P＞0.05， the same below）different from CK by two different selenium sources， but they significantly（P＜0.05， the same below）reduced the chalkiness and chalky grain rate， with the maximum decline of 23.13%（N2 treatment）and 39.6%（N5 treatment）respectively. N2 treatment significantly improved the milling quality of the rice， increasing the milled rice rate and head rice rate by 3.07% and 5.89% respectively. In terms of cooking quality， all treatments except Y2 treatment reduced the content of rice amylose content， with the largest decrease in Y5 treatment（12.56%）， at the same time， selenium application had no significant effect on the glue consistency and alkali elimination value. Selenium application increased the protein content of rice（4.76%-30.98%）， and the largest increase was observed in Y3 treatment. The organic matter content of rhizosphere soil was no significantly affected by the application of selenium， but the contents of alkali-hydrolyzed nitrogen， available phosphorus and available potassium were increased by 3.86%（N1 treatment）， 18.86%（Y5 treatment）and 5.57%（N4 treatment）respectively. Meanwhile， the pH of rhizosphere soil was significantly decreased after spraying with sodium selenite. Selenium application could improve the selenium content of rice， but the organic selenium content of rice after biological nano selenium spraying was more than 95.00%， while organic selenium contents of rice in all treatments of sodium selenite were less than 85.00%. 【Conclusion】Different amounts of biological nano selenium and sodium selenite affect the 1000-grain weight，head rice rate，chalky grain rate，chalkiness，amylose content，protein content and selenium content of rice. According to comprehensive analysis， the application of 22.5 or 30.0 g/ha biological nano selenium in the stage of rice grain filling is suitable for the production of organic selenium-rich rice that meets the national standard and local food safety standard of Hubei Province.