Effects Of Topdressed N-Fertilizer On Translocation And Distribution In Soybean Plants

A pot experiment was conducted to study the effects of topdressed N-fertilizer on N distribution and translocation in soybean using the 15N tracer technique, supposing N 60 kg/hm2 basal of N rate and on the base of N 30 kg/hm2 , topdressed fertilizer- 15N 30 kg/hm2 at the R1, R2, R3, R4 stages, sampling at the R1, R3, R4, R5, R6 and R8 stages to test N content, the dry matter weight and the 15N atom percent, calculated each index of correlation, the results are as follows:Topdressing N at different stages could influence 15N accumulation of soybean plants. For different N topdressing, the best effect was N30+30R2, and the second was N30+30R4.The most notable effects of N topdressed at different stages on 15N distribution in soybean was at the R5, the distribution ration was 34.28%. The results showed that N topdressing at R2 could obviously keep the soybean having high N level in soybean plants and increase soybean yield.The largest 15N transfer amount translocation in soybean leaves and soybean stems was in N30+30R2,add to 3.40 2.51mg/pot and 66.7% 90.01%, compared with N30+30R1and N30+30R3, significant at 5%. Topdressing N at R2 could promot the translocation in organs, and play a very important part in promoting N accumulation in soybean seeds.For different N topdressing, the highest fertilizer-N use efficiency in soybean was N30+30R2, reached by 56.75%. Topdressing N at R2 could enhance the fertilizer-N use efficiency in soybean stages, but the absorption mechanism also need further study.The different N topdressing could influence N accumulation of soybean plants. The most significant effects of N topdressing on soybean's N accumulation is to the R5, the R8 by the N30+30R2, compared with N60, enhanced 22.73% and 15.56% respectively, significant at 5%. Topdressing N at R2 could obviously enhance the soybean N accumulation in R5, extend R5, so played an very important part in promoting the soybean yield.The most notable effects of N topdressed at different stages on N distribution in soybean leaves was at the R5, compared with N60, the N30+30R2 treatment enhanced 5.98%. Topdressing N at R2 might maintain high N level in soybean leaves, delay the soybean leaves senility after blossomed, enhance the soybean leaves biological activity, coordinate nitrogen assignment proportion with various organs better, optimize the soybean N nutrition to assign certain function. The highest soybean yield was N30+R2, compared with N60, enhanced by 11.85%, significant at 5%,other topdressing treatments were N30+30R4ï¹¥N30+30R3ï¹¥N30+30R1, compared with N60, enhanced 8.49%, 6.80% and 1.26% respectively. Topdressing N could be able to raise the soybean yield, but the best effect was the N30+30R2.