Effects of Nitrogen Application on the Abundance and Distribution of Protist Communities in the Rhizosphere of Beta vulgaris

This experiment was carried out in the experimental base of Hulan Campus of Heilongjiang University ( Harbin City, Heilongjiang Province, China, 45 ° 59 ′ 58 ′ ′ N, 126 ° 37 ′ 47 ′ ′ E ) from April 2021 to September 2021. Sugar beet variety H004 was sown on April 26,2021, with nitrogen fertilizer treatment ( N120,120 kg · hm-2 ) and control without nitrogen fertilizer ( N0,0 kg · hm-2 ). Phosphorus and potassium fertilizers were P2O5 ( 90 kg · hm-2 ) and K2O ( 120 kg · hm-2 ), and the fertilizer types were urea, calcium superphosphate and potassium sulfate. Each treatment was repeated 3 times, and each treatment was repeated 4 ridges, a total of 12 ridges, each ridge length 10 m, width 0.65 m, plot area 78 m2. Samples were taken before the sowing period ( May ), seedling period ( June ), leaf rapid growth period ( July ), root expansion period ( August ) and harvest period ( September ). Sugar beet rhizosphere and non-rhizosphere soil samples were collected and tested at − 80 ° C ( mainly for studying rhizosphere data ).Spearman correlation analysis and RDA analysis were performed on the abundance and physicochemical properties of protozoa in the rhizosphere soil of sugar beet.