The Effects Of Nitrogen Levels On Characteristics Of Root And Nutrient Uptake Of Hybrid Rice Under Different Planting Methods

The study were conducted to explore the effect of nitrogen?N?levels on the yield and its components,root traits and nutrient uptake of hybrid indica rice under different planting methods in 2016-2017.Two-factor-split design was used in this study,with the F-you 498?medium-late ripe indica hybrid rice?as material.The main area was set as planting methods:mechanical transplanting?T1?,precision hill direct seeding?T2?and artificial transplanting?T3?.N levels was set up as the sub-area,include 0 kg/hm²,90 kg/hm²,135kg/hm²,180 kg/hm²,respectively.¹⁵N micro-region experiment which based on 2016experiment was added in 2017 experiment.32 hills of rice,which were evenly distributed in each plot,were selected as the micro-region under N fertilization.8 hills of rice were applied to the ¹⁵N basal fertilizer,¹⁵N tiller fertilizer,panicle fertilizer and ¹⁵N full amount fertilizer,respectively.And the uptake and utilization of N fertilizer of indica hybrid rice s were studied with N levels treatments under different planting methods.The main findings are as follows:1.Effects of planting methods and N levels on yield and its components of indica hybrid riceYield of T3 was not significantly different from that of T1,and which both were higher than that of the T2,by 9.92%¹3.80%and 8.09%¹5.00%,respectively.With the increase of N level,rice yield increased significantly,and yield was the highest yield with N3 treatment.The effective panicle of T1 and T2 was significantly higher than that of T3,but the spikeletes per panicle was opposite.Compared with T1 and T3,the seed setting rate of T2 was significantly lower than that of T1 and T3.The relationship between N levels and yield and its component was also different under different planting methods.And the increase yield of T1 and T2 was mainly dependent on the increase of effective panicle.With the increase of N level,effective panicle increased significantly.Under N0 treatment,the 1000-grain weight and seed setting rate were higher than the other N treatment,and the difference between N treatments was not significant.2.Effects of planting methods and N levels on nutrient uptake and accumulation of indica hybrid riceThe planting methods and N levels had a significant effect on the uptake and accumulation of nitrogen?N?,phosphorus?P?and potassium?K?nutrients in rice.The results are as follows:?1?The plant N accumulation in heading stage and maturity showed T3>T1>T2.And the plant N accumulation of T1 and T3 were lower than T2 by 0.73%².39%and4.22%⁸.22%in maturity,respectively.While at jointing-heading stage and heading-mature stage,the N accumulation rate of T3 was higher than that of T1 and T2.The plant N accumulation in different growth periods increased significantly with the increase of N application rate.N agronomic efficiency and N harvesting index?NHI?of T3 were higher than that of T1 and T2.And N grain production efficiency of T1was better than that of T2and T3.The N grain production efficiency and NHI decreased with the increase of N rate,and N grain production efficiency was significantly higher than that of N fertilizer treatment.?2?The maximum amount of P accumulation appears at the maturity.And the jointing-heading stage is the rapid accumulation of phosphorus.The P accumulation of T3was higher than that of T1 and T2 before heading stage.With the increase of N level,the P accumulation of plant increased,which showed the synergistic absorption between N and P.Compared with N0 treatment,the P accumulation of N treatments was higher 6.76%³4.12%under T1,16.72%³0.26%higher under T2,7.79%⁴3.35%higher under T3.The P accumulation rate of T2 was 54.42%⁵4.65%and 19.42%⁵0.59%higher than that of T1and T3.At before jointing and jointing-heading stage,the P accumulation rate increased with the increase of N level.However,the low N treatment was propitious to the P accumulation at maturity,rapidly.?3?The K accumulation was the highest at jointing-heading stag,followed by before jointing stage,with least accumulation at heading-maturity.The K accumulation amount of T1 and T3 in the maturity was higher than that of T2 by 3.87%⁴.06%and 2.80%⁶.70%,respectively.With the increase of N level,rice K accumulation increased significantly.Jointing-heading stage was the fastest K accumulation period in whole growth stages of rice.And the K accumulation rate of T2 was significantly higher than that of T1 and T3.The K accumulation rate increased with the increase of N level before jointing stage and jointing-heading stage.?4?F-you 498's N contents was fertilizer-N which is 19.54%³1.28%,and the soil-N which is 68.72%⁸0.46%.In the maturity,rice plant N from basal fertilizer was the2.47%⁵.38%,the tiller fertilizer was the 3.61%⁷.56%,and form the panicle fertilizer was the 12.23%¹8.41%,respectively.At the maturity ¹⁵N of basal,tiller and panicle fertilizer were eventually transferred to the panicle.Under ¹⁵N basal,tiller and panicle fertilizer treatments,¹⁵N panicle accumulation of T3 was higher than that of T1 and T2.The proportion of the ¹⁵N composition of the stem sheath,leaf and spike of the T1 and T3was the same as that of panicle fertilizer>tiller fertilizer>basal fertilizer.However,the proportion of basal and tiller fertilizer accounted for total N accumulation in all organs of T2 was similar.Under different planting methods treatments,¹⁵NUE and ¹⁵N recovery rate of panicle fertilizer>tiller fertilizer>basal fertilizer.¹⁵NUE of T3 is higher than that of T1and T2.Under basal fertilizer,¹⁵NUEof T1 and T2 are lower than T3 by 13.96%and14.26%,respectively.Under tiller fertilizer,¹⁵NUE of T1 and T2 are lower than T3 by 2.39%and 19.25%,respectively.Under panicle fertilizer,¹⁵NUE of T1 and T2 are lower than T3by 7.24%and 22.72%,respectively.3.Effects of different cropping patterns and nitrogen levels on root characteristics of indica hybrid riceThe N level had significant or very significant effect on the root characteristics of rice under different planting methods.Before jointing and jointing-heading stage were two peaks of root growth,and the roots gradually died out after heading stage.Compared with N0 treatment,N fertilizer treatment significantly increased root dry weight,per stem and population root length,per stem and population root volume,per stem root and population root number and root bleeding intensity of per stem root and population.Compared with the T1 and T3,the root length of T2 was the longest in the whole growth period,but the root dry weight was lower,the root diameter was smallest,and the bleeding intensity of per stem was lower after heading.Compared with T3,the root diameter of T1 was smaller,the number of per stem root was small,the root dry weight of per stem was lower after heading,and the per stem root length decreased quickly,but the bleeding intensity of per stem was small,but the intensity of population was great.With N rate increase,population root number increase,but per stem root length decrease.All the above,in this study,while the soil fertility is higher,the most suitable N level of T1 is 135 kg/hm²,N level of T2 and T3 is 90kg/hm².While the soil fertility is lower,the optimum nitrogen level of T1,T2 and T3 is 135 kg/hm²,but also ensure the reasonable growth of root system to maintain high NUE.