Sources Of Nitrogen Fertilizer And Nitrogen Ratio Of Base And Topdressing On Nitrogen Use Of Direct Seeding Rice

Rice is one of the main food crops in China,and it is also the crop with the largest consumption of chemical fertilizer in China.Jianghan Plain is the main area of rice cultivation in China,which is faced with the problems of excessive application of chemical fertilizer and large loss of nutrients in rice fields.Therefore,according to the research area of rainfall characteristics and live on rice growth characteristics of different fertilizer source live on rice and nitrogen under different than field trials,aims to reveal the different nitrogen fertilizer source and base after comparing different live on rice growth and nitrogen runoff,erosion,ammonia volatilization losses and the influence of nitrogen fertilizer utilization,in order to live on rice scientific fertilizing and will provide a scientific basis for effectively reduce rice nitrogen loss.In this study,direct seeding rice was as the research object,a nitrogen use efficiency experiment was carried out in the scientific research base of Yangtze University from 2019 to 2020 under different nitrogen fertilizers and their base-to-topdressing ratio,where the total amount of N（180 kg/hm²）,P₂O₅（75 kg/hm²）and K₂O（105 kg/hm²）was same for each treatment.No N application was used as the auxiliary treatment（N0）to calculate N use efficiency.According to different N source and base-to-topdressing ratio,three treatments were set in 2019:1)the nitrogen from the common compound fertilizer（CF）,and the nitrogen ratio of base and topdressing was 4:6,which was used as the control（CK）;2)nitrogen from control-release fertilizer and urea,the nitrogen ratio of base and topdressing was 7:3（CRBF+U）;3)nitrogen from seaweed polysaccharide urea,nitrogen ratio of base and topdressing 4:6（HTN-WR）.based upon experiments in 2019,3 experiments were increased in 2020that are:control-release fertilizer used only and no topdressing of nitrogen（CRBF）;nitrogen from common compound fertilizer,nitrogen ratio of base and topdressing was6:4（CF-MR）;nitrogen from seaweed polysaccharide urea,nitrogen ratio of base and topdressing 6:4（HTN-MR）.The growth and nitrogen loss of rice under different treatments were observed,and the nitrogen use efficiency was analyzed.The results showed that:In the 2-year experiment,the runoff loss of nitrogen in CRBF+U was the lowest,which was 20.54-23.29 kg N/hm²,followed by 20.28-22.73 kg N/hm².The runoff loss was mainly caused by drainage before sowing,which accounted for more than 65%～96%of the total.After the application of basic fertilizer,ammonia volatilization in the rice field increased rapidly and reached the peak value at 3 days after the application of basic fertilizer.The order of the peak value was CF-MR>HTN-MR>CRBF>CK>HTN-WR>CRBF+U,and it decreased to no significant difference about 10 days after the application of basic fertilizer.After applying tillering fertilizer,the ammonia volatilization flux reached the peak value 2 days after topdressing,and the order of the peak value was CK>HTN-WR>CF-MR>HTN-MR>CRBF+U>CRBF,which decreased to no significant difference about the 10th day after applying tillering fertilizer.The total ammonia volatilization loss of CRBF+U,HTN-WR,CRBF and HTN-MR was 37.12%-42.84%,9.73%-21.66%,42.46%and 14.03%lower than that of CK in the whole growth period,respectively,and the total ammonia volatilization loss of CF-MR was 8.57%higher than that of CK.Both CRBF+U and HTN-WR could significantly reduce ammonia volatilization loss in paddy fields.The nitrogen accumulation of all treatments at tillering stage was as follows:CRBF+U>CRBF>CK>HTN-WR>HTN-MR>CF-MR;the total nitrogen accumulation of each treatment from jointing stage to maturity stage accounted for51.29%～59.54%of the total nitrogen accumulation,and the specific expression was Cr BF+U>HTN-WR>CK,CRBF+U,HTN-WR,CRBF,HTN-MR treatments increased nitrogen apparent use efficiency and nitrogen agronomic use efficiency by17.39%～32.92%,18.85%～34.57%,39.25%,4.43%and 9.25%～14.18%,8.74%～13.33%,11.95%,respectively.3.33%,the nitrogen apparent use efficiency and agronomic use efficiency of CF-MR decreased by 9.56%and 13.07%,respectively.The results indicated that CRBF+U treatment improved the nitrogen transfer of stem,sheath and leaf from jointing to maturity,and improved the nitrogen use efficiency of direct seeding rice.The yield of direct seeding rice under each treatment was 7683.33-9633.25 kg/hm²,CRBF+U,HTN-WR,CRBF and HTN-MR increased production by 9.25%-10.24%,4.91%-4.76%,6.49%and 1.81%,respectively.However,the yield of CF-MR decreased by 7.09%,which was due to the significant increase of grain number per panicle and seed setting rate,indicating that appropriate nitrogen fertilizer deferment was conducive to the formation of direct seeding rice yield.The CRBF+U and HTN-WR treatments reduced the nitrogen runoff loss and ammonia volatilization loss,increased the nitrogen transfer of stem,sheath and leaf from full heading stage to maturity stage,and increased the nitrogen use efficiency and yield of direct seeding rice.In 2020,the experiment was carried out in the scientific research base of Yangtze University in order to reduce the loss of nitrogen and phosphorus and improve the use efficiency of nitrogen by adjusting the base topdressing ratio of nitrogen fertilizer.Taking the customary nitrogen application ratio（basal fertilizer:tillering fertilizer:panicle fertilizer=6:4:0）as control（CK）,eight basal/topdressing ratios（T1 to T7）were set according to the reduced ratio of basal fertilizer nitrogen use.The ratios of basal fertilizer,tillering fertilizer and panicle fertilizer were 4:6:0（T1）,4:4:2（T2）,4:2:4（T3）,2:6:2（T4）,2:4:4（T5）,0:8:2（T6）and 0:6:4（T7）,respectively.To calculate N use efficiency（NUE）,no fertilization was used as blank control（CK0）.The growth and development of rice and nitrogen loss in paddy field under different treatments were observed,and the nitrogen use efficiency was analyzed.The results showed that:The runoff loss of nitrogen in the experiment was 8.58～28.99 kg N/hm².The runoff loss was mainly caused by drainage before sowing,which accounted for19.50%-73.26%of total runoff loss.After the application of basal fertilizer,ammonia volatilization in the rice field increased rapidly,and reached the peak value at 3 days after the application of basal fertilizer,and the order of the peak value was CK>,T2>,T3>,T1>,T5>,T4>,T7>and T6,and decreased to no significant difference about10 days after the application of basal fertilizer.After applying tiller fertilizer,the ammonia volatilization flux reached the peak value at 2 d after topdressing,and the order of the peak value was T6>T7>T1>T4>CK>T2>T5>T3.After applying tiller fertilizer,the peak value decreased to no significant difference at about 10 d.After applying panicular fertilizer,it was T5>T3>T7>T6>T4>T2>CK>T1.Compared with CK,the total ammonia volatilization loss of direct sowing rice under 40%basal（T1-T3）,20%basal（T4-T5）and no basal fertilizer（T6-T7）decreased by 7.78%-31.96%,11.49%-24.93%,6.86%and 19.44%,respectively.The ammonia volatilization loss of paddy field was significantly reduced by applying 40%N at base fertilizer.The nitrogen accumulation of each treatment at tiller stage was T1>T2>CK>T4>T5>T3>T7>T6;The total nitrogen accumulation of each treatment from jointing stage to maturity stage accounted for 60.27%-67.93%of total nitrogen accumulation,respectively.The apparent and agronomic utilization rates of T1-T3treatments were 3.64%-10.57%and 1.29%-15.04%higher than those of CK,respectively,but the apparent and agronomic utilization rates of CK treatments were4.42-19.34%and 4.03%-50.97%higher than those of T4-T7 treatments.The results indicated that the application of 40%base fertilizer could improve the nitrogen transfer of stem,sheath and leaf from jointing stage to maturity stage and improve the nitrogen use efficiency of direct seeding rice.The yield of direct seeded rice under each treatment was 6366.67-8270.00 kg/hm²,and the yield of direct seeded rice under 20%（T4-T5）and no（T6-T7）basal fertilizer was 1.95%-3.47%and 15.40%-17.14%less than that under CK,respectively.Compared with CK,40%（T1-T3）increased yield by 0.65%-7.64%,respectively.The increase was due to the significant increase in grain number per panicle and seed setting rate,which indicated that appropriate deferment of nitrogen fertilizer could contribute to the yield formation of direct seeding rice.The ratio of basal fertilizer:tillering fertilizer:panicle fertilizer:4:4:2 reduced the amount of nitrogen runoff loss and ammonia volatilization loss,increased the amount of nitrogen transfer from stem,sheath and leaf from jointing stage to maturity stage,and increased the nitrogen use efficiency and yield of direct seeding rice.