Study On The Relationship Between Root Growth And Flower Pod Formation Of Spring Soybean Based On The Different Nitrogen Application Rates

As the basis for the formation of the soybean yield,the flower pods are synchronized with the establishment of the root system.However,the relationship between the growth of soybean roots and the formation of flower pods is not yet clear.Therefore,under the conditions of field drip irrigation（0,75,150,225 kg/hm²）,the growth,the photosynthetic characteristics,the dry matter accumulation,the transport characteristics,and the formation of flower pods of Xin da dou 27 hao law are researched.The results are obtained as follows:（1）The total dry weight of root system,the length of lateral root and the surface area of lateral root present the trend of decreasing after increasing with the adding of the nitrogen application,when they were dug from the soil of 0-80 cm.And they were the best under the condition of N_150.They increased by 27.3%,49.46%and 38.14%,compared with N₀during R5.The soil layer increased by 27.0%,29.02%and 34.24%,compared with N₀,when they were dug from the soil of 0-20 cm.The wound flow of each plant increased by176.0%during R5.The nodule number and mass per unit area reduced by 8.74%,34.6%,when compared N₁₅₀ with N₀ during R5.The activity of soil root system increased by 44.3%,25.1%,when compared N₁₅₀with N₀ during R2.Nitrogen application inhibits the growth of root nodules,but a reasonable application of the nitrogen could promote the root growth in 0-20 cm soil layers and increase 0-40 cm soil layers root system activity.（2）Leaf area index can be increased by the increasing of the nitrogen application,which is mainly caused by the increase of the leaf area of the main stem 7-19.Nitrogen application can improved the chlorophyll content of the leaves of the different canopies,which can delay the leaves senescence of the top and middle leaves of the soybean in late.Meanwhile,nitrogen application can improve the net photosynthesis rate（Pn）and the transpiration rate（Tr）of the leaves of the different canopies in different growth period,by which the decline of net photosynthesis rate and the transpiration rate of the different canopies can be delayed in middle and late growth period.The dry matter production can be increased by nitrogen application,which is mainly caused by the increase of the dry matter production of the top and middle stems.The soybean yields can be improved by the increase of the dry matter production,the translocation and the grain yield,which can reach the highest when processed by N₁₅₀,was 4889.62 kg/hm²,in which the largest dry matter production,the dry matter production of the stems,the translocation and the grain yield were 16133.8 kg/hm²,5364.7kg/hm²,1830.5kg/hm2,34.12%respectively.（3）The flowering period can be prolonged for 1-2 days and the total opening flowers of per unit yield can be significantly increased by nitrogen application,in which the increase of the flowers is mainly caused by the flowers of the 13-18 nodes.The beginning of flower pods can be delayed,the budding stages can be prolonged,the number of the flower pods,the total cavity number and the seed setting rate can be increased obviously by nitrogen application,in which the increase of the number of the flower pods is mainly caused by the flowers pods of the 13-18 nodes.（4）Nitrogen fertilizer significantly increased the flowering and pod period,the total dry weight of root system,the length of lateral root and the surface area of lateral root present the trend of increasing with the adding of the nitrogen application,when they were dug from the soil of 0-80 cm,and they were the best under the condition of 150 kg·hm^-2.The increasing of the total dry weight of root system,the length of lateral root and the surface area of lateral root were positively correlated with the number of the flowers during flowering stage,The correlation coefficient were 0.998^**,0.912 and 0.870;The increasing of the total dry weight of root system,the length of lateral root and the surface area of lateral root were positively correlated with the number of the pods during podding period,the correlation coefficients were 0.856,0.963^*and 0.968^*.There was a significant positive correlation between the increases of the root morphology and the formation of the flowers number and the flower pods number in the flower pods period of soybean.（5）A reasonable amount of the nitrogen application can promote the growth of 0-20 cm soil system roots,increased the activity of 0-40 cm system roots,increased the area of middle and top leaves,increased the photosynthetic rate of different canopies,and increased the dry matter production and transshipment in the top and middle of the plant,increase the number of flowers and flower pods,improved the total cavity number and the seed setting rate,which can increase the production of the soybean.