Primary Study On The Nitrogen Utilization Efficiency Of Nitrogen Fertilizer Postphone And Nitrate Absorption Approaches In Rice

Rice is the main grain crop in China.The application of nitrogen fertilizer was an important measure to ensure the high and stable yield of rice.A large number of studies at home or in the field determined the base,topdressing fertilizer for increasing rice yield.Several fertilization strategies had ever been summarized such as one-time and split-times fertilization technique,which played very important roles for maintaining high grain yield.Too much fertilization at the early growing stage of rice is not consistent with the law of nutrient demand at different growth stage,resulting in low fertilizer utilization efficiency,high nutrient loss and non-point pollution.Therefore,reasonable fertilizer input and management are beneficial to rice growth and yield formation,which will increase fertilizer utilization efficiency,and realize the"high quality,high yield,high efficiency,ecological safety"goals.In this paper,fertilization doses were recommended based on the soil nutrient contents and the actual nitrogen needs of rice at different growth stages.The percentage of nitrogen applied at base,tillering and panicle growing stages were also determined according to the rice needs.The effects of water channel inhibitor and anion channel inhibitor on nitrogen uptake in rice were also studied.The main results are listed as follows:1.At tillering stage,the highest plant height,tiller numbers and SPAD were 59.47?cm?,9.70?10⁴/667m²?and 39.76 in the conventional treatments?CG?.At tillering stage,compared with CG treatments,plant height increased by 3.00%,4.53%and 6.60%,tiller numbers increased by 10.67%,15.84%,16.92%,and SPARD increased by 0.46%,5.25%and 5.50%in PF1,PF2 and TZ,respectively.In the mature stage,the plant height of rice in PF1,PF2 and TZ was 1.54%,3.59%and 4.07%higher than that in conventional fertilization?CG?,respectively.At the heading and maturing stages,the rice height in PF2was 2.27%and 2.09%higher than that in PF1,the tiller number in PF2 were 5.78%and1.67%higher than that in PF1,and the SPAD in PF2 were also 4.82%and 1.56%higher than that in PF1.2.At the tillering stage,the nitrogen content of rice leaves ranged from 29.33g/kg to40.98g/kg,and the maximium nitrogen content?40.98g/kg?was found in the CG.At the jointing stage,the nitrogen content of rice leaves ranged from 29.33g/kg to 40.98g/kg,the highest N contents?23.35g/kg?was detected in the PF1 treatments.At the heading stage,the nitrogen content of rice leaves was between 14.74g/kg and 21.11g/kg,the highest N contents?20.27g/kg?was detected in the TZ treatments.At the mature stage,the nitrogen content of rice leaves ranged from 12.58g/kg to 20.47g/kg,the higher N contents was found in the PF2?20.40g/kg?and TZ?20.47g/kg?treatments.3.With the rice growth,the total and net nitrogen accumulatedin rice gradually increased from tillering to mature stage At the tillering stage,the total nitrogen accumulated in rice ranged from 0.079g/plant to 0.16g/plant,the highest total and net nitrogen accumulation in rice were detected in CG treatments which were 0.155g/plant and 0.155g/plant,respectively.At the jointing stage,the total and net nitrogen accumulated in rice were ranged from 0.12g/plant to 0.30g/plant,and from 0.03g/plant to 0.19 g/plant,respectively,andthe highest total and net nitrogen accumulation in rice were detected in PF1 treatments,which were 0.304g/plant and 0.186g/plant,respectively.At the heading stage,the total and net nitrogen accumulated in rice ranged from 0.16g/plant-0.41g/plant,and from 0.04g/plant-0.17g/plant,respectively,and the highest total and net nitrogen accumulation in rice were detected in TZ treatments,which were 0.408g/plant and0.167g/plant,respectively.In the mature stage,the total nitrogen accumulated in rice ranged from 0.71g/plant to 1.37g/plant.The total nitrogen accumulated in rice in PF1,PF2and TZ 9.4%were 28.3%and 29.2%higher than that in CG,respectively.The net nitrogen accumulated in PF1,PF2 and TZ were 8.6%,33.8%and 35.2%,higher than that in CG,respectively.4.Rice yield followed the rule of:TZ>PF2>PF1>CG.TZ.Compared with CG,total heading numbers increased by 18.60%?11.42%and 15.29%,grain numbers per ear increased by 16.75%?9.82%and 15.08%,seed setting rates increased by 7.97%?3.65%and 5.71%,thousand kernel weigh increased by 11.36%?1.70%and 6.50%,rice yield increased by 2.78%?1.15%and 1.52%,in TZ?PF1 and PF2 treatments,respectively.From the economic view,the output to input ratios in TZ,PF1 and PF2 were 3.8%,0.10%and0.73%higher than that in CG,and the nitrogen utilization efficiency increased by 18.61%?10.12%and 17.18%in TZ,PF1 and PF2 than that in CG,respectively.The output to input ratios and nitrogen utilization efficiency in PF2 were 0.64%and 7.1%higher than that in PF1,respectively.5.With the increase of nitrogen concentrations from 0 to 32mmol/L,the nitrogen content and accumulation in rice expressed the rule of the firstly increased and then slowly decreased.When the nitrogen concentration increased to 4mmol/L,the contents of nitrogen in rice stem and root were 38.71g/kg and 20.07g/kg,which were 38.5%and 40.0%higher than that in the control,and nitrogen accumulated in rice stem and root were 26.3 mg/plant and 4.7 mg/plant,which were 40.7%and 23.4%higher than that in the control,respectively.6.When the nitrogen concentration was 4 mmol/L,the nitrogen content of rice increased from 0 to7d and then reduced from 7 to14d,respectively The highest nitrogen contents in rice stem and roots were 33.52g/kg and 20.07g/kg,the highest nitrogen accumulation anounts in rice stem and roots were 33.7mg/plant and 8.8mg/plant,respectively at the 7^thh incubation period.7.There were significant differences in nitrogen contents in rice stem and root at different concentrations of water channel inhibitor HgCl₂.When the concentration of HgCl₂ was0.5mg/L,the nitrogen contents in rice stem and root decreased by 11.7%and 12.5%,respectively,which are significant difference from the control without HgCl₂ addition?p<0.05?.8.Nitrogen content and accumulation in rice were significant differences after incubation6h with 10,20 and 100?mol/L of DIDS.Nitrogen content and accumulation in rice stem and root decreased by 18.4%,14.9%and 5.4%,29.2%when incubation with with addition of 10?mol/L of DIDS,which were significant differences from the control without DIDS addition.9.Nitrogen content and accumulation in rice were significant differences after incubation12h with with addition of 10,20 and 100?mol/L of DIDS.Nitrogen content and accumulation in rice stem decreased by 31.0%and 6.1%when incubation with 20?mol/L of DIDS,which were significant differences from the control without DIDS addition?P<0.05?.10.Nitrogen content and accumulation in rice were significant differences after incubation24h with with addition of 10,20 and 100?mol/L of DIDS.Nitrogen content and accumulation in rice roots decreased by 25.6%and 25.0%when incubation with 100?mol/L of DIDS,which were significant differences from the control without DIDS addition?P<0.05?.11.Nitrogen content and accumulation in rice were inhibated after incubation 48h with addition of 10,20 and 100?mol/L of DIDS,wherereas no significant differences were detectd int eh treatments with and without addition of DIDS?P>0.05?.