Effects Of Different Phosphorus Fertilizers On Wheat Root Growth And Selenium Absorption

[Objective]Selenium is an essential trace element for the human body.Insufficient or excessive intake can cause illness in humans and animals.Although the soil total selenium content is high in many areas of Xinjiang,the effectiveness of soil selenium is low.This study combined pot experiment and field plot experiment to explore the effect of applying four different forms of phosphate fertilizer on soil effective selenium content,wheat root growth and plant selenium absorption,providing a theoretical basis for the production of selenium-rich agricultural products.[Methods]The test includes:?1?Wheat pot experiment:It contains one factors of phosphate fertilizer.There are five treatments for phosphate fertilizer,namely:no phosphate fertilizer?CK?,phosphoric acid?H₃PO₄,AP?,polyphosphoric acid(H₆P₄O₁₃,PPA),monoammonium phosphate?NH₄H₂PO₄,MAP?and diammonium phosphate??NH₄?₂HPO₄,DAP?,the application amount?P₂O₅?is 0.5 g?kg^-1.As the selenium fertilizer,analytically pure sodium selenite?Na₂SeO₃?was used.The application amount was 2 mg·kg^-1.A total of 5 treatments in the experiment,each treatment is repeated 6 times.?2?Wheat field plot test:contains two factors of selenium fertilizer and phosphate fertilizer,and the amount of selenium application?Se?is set at two levels,namely:no selenium fertilizer(0 kg?hm^-2,SE0),selenium fertilizer(7.2 kg?hm^-2,SE),the analytically pure sodium selenite is used as selenium fertilizer.There are 5 phosphate fertilizer treatments under each selenium fertilizer treatment,namely:no phosphate fertilizer?CK?,phosphoric acid,ammonium polyphosphate??NH₄PO₃?_n,APP?,monoammonium phosphate and diammonium phosphate,the application amount?P₂O₅?is 180 kg?hm^-2.A total of 10 treatments in the experiment,each treatment is repeated 3 times.?Main results??1?Phosphorus fertilizer significantly reduces the effective selenium content in the soil,and the water-soluble selenium,exchangeable selenium,iron-manganese oxide-bound selenium and organic selenium are all significantly reduced.In the absence of selenium fertilizer application,the effective selenium content in the soil treated with ammonium polyphosphate decreased by 52.91%compared with the non-phosphorus treatment;in the selenium fertilizer application,the effective selenium content in the soil treated with monoammonium phosphate decreased by 10.86%.?2?Phosphate fertilizer promotes the growth of wheat shoots and roots.Without selenium fertilizer,the total root weight of 0-60 cm soil layer treated with ammonium polyphosphate increased by 81.15%compared with the non-phosphorus fertilizer treatment;The total root weight of 0-60 cm soil layer treated with monoammonium increased by 50.89%compared with the treatment without phosphate fertilizer.Without the application of selenium fertilizer,the total root length,total root surface area and total root volume of the 0-60 cm soil layer treated with ammonium polyphosphate increased by 76.62%,42.35%and107.22%,respectively,without the application of phosphorus fertilizer;under the condition of selenium fertilizer The total root length,total root surface area and total root volume of 0-60 cm soil layer treated with monoammonium phosphate increased by 121.33%,66.36%and 37.83%,respectively,compared with the treatment without phosphate fertilizer.?3?Without the application of selenium fertilizer,different forms of phosphate fertilizer can promote the absorption of selenium in wheat,but the selenium content of wheat grains ranges from 0.001-0.002mg?kg^-1,which does not meet the national standard of selenium-rich rice(0.04-0.30 mg?kg^-1).Under the condition of applying selenium fertilizer,the selenium content of wheat grains increased significantly and reached the level of selenium enrichment,between 0.185-0.311 mg?kg^-1.Among them,the selenium content of wheat grains treated with monoammonium phosphate increased by 68.11%compared with the treatment without phosphorus fertilizer.?4?Phosphate fertilizer significantly increased wheat yield components and yield.Under the condition of selenium fertilizer application,monoammonium phosphate treatment increased the yield by56.70%compared with the non-phosphorus fertilizer treatment.The selenium content,phosphorus use efficiency and yield of wheat plants treated with monoammonium phosphate treatment were higher than other phosphate fertilizer treatments.?Conclusion?The application of phosphorus fertilizer reduces the effective selenium content of the soil,promotes the growth of wheat shoots and roots,and increases the selenium content of the plant.Without selenium fertilizer application,wheat plants treated with ammonium polyphosphate had the highest selenium content and yield,but the grain selenium content did not meet the national standard for selenium-rich rice.Under the condition of applying selenium fertilizer,the selenium content of wheat grains increased significantly and reached the level of selenium enrichment.The wheat plants treated with monoammonium phosphate had higher selenium content,phosphorus use efficiency and yield than other phosphate fertilizer treatments.Therefore,the combined application of selenium fertilizer and monoammonium phosphate can promote the absorption of selenium in wheat,increase the selenium content in grain,and improve the utilization rate and yield of phosphate fertilizer.