Effects Of Nitrogen Application On Yield Formation,Quality And Nitrogen Absorption And Utilization Characteristics Of High Quality Double-season Late Rice

A study was conducted in zengjia village,Sixi Town,Shanggao County,Jiangxi Province in 2017 and 2018.Four late rice varieties with high-quality,including Meixiangxinzhan,Taiyou 398,Tianyouhuazhan and Huanghuazhan,were used as experimental materials.and four levels of nitrogen applications including 0 kg hm-2(NO),135 kg hm-2(N1),180 kg hm'2(N2),225 kg hm-2(N3),were set under mechanical application on yield and components,growth of photosynthetic material,nitrogen absorption and utilization,plant type and lodging resistance,rice quality,and starch physicochemical properties were studied and analyzed systematically.which provided theoretical basis and technical support the coordinated of the yield and quality of high-quality late rice varieties in double-cropping area.The main results are as follows:1.With the increase of nitrogen application,the number of panicles increased,the number of spikelets per panicle increased first and then decreased,the seed setting rate and 1000-grain weigh decreased,as a result,the yield increased first and then decreased,with the highest yield under N2 level.It is reasonable to improve the yield of high quality of double season late rice.with proper application of nitrogen fertilizer,with the increase of nitrogen application,the number of tillers in each growth period increased,while the ear rate decreased.Leaf area index of all varieties increased at jointing stage,increased first and then decreased at heading and mature stage,and reached the maximum value at N2 level.The dry matter accumulation from sowing to jointing and from jointing to heading showed N3>N2>N 1>N0 at different nitrogen application levels,while that from heading to maturity showed N2>N3>N1>N0.With the increase of nitrogen level,the photosynthetic potential from sowing to jointing stage,Crop growth rate and from jointing to heading stage all increased,while from jointing to heading stage,from heading to maturity stage,the photosynthetic potential first increased and then decreased,with the highest level of N2.2,With the increase of nitrogen application,the nitrogen content,nitrogen absorption at each stage,total nitrogen accumulation at maturity and nitrogen accumulation from sowing to jointing and from jointing to heading increased,while the nitrogen accumulation from heading to maturity,nitrogen transfer from stem and sheath and leaf,transport rate and contribution rate increased first and then decreased.As nitrogen amount increased,nitrogen absorption and utilization rate and agronomic utilization rate increased before decreased,and the two indexes all peaked under N2.The physiological utilization rate and partial productivity of nitrogen decreased,and the nitrogen absorption rate of 100kg grain under higher nitrogen level,and there were significant or extremely significant differences among the treatments.3.Leaf length,leaf width and drooping angle of the upper three leaves(sword leaf,inverted two leaf and inverted three leaf)showed N3>N2>N1>N0 under different nitrogen application levels,while the group light transmittance showed the opposite trend.With the increase of nitrogen application,the height of stem center of gravity and the length of basal internode increased.In 2018,the relative height of center of gravity of Meixiangxinzhan,Taiyou398,Tianyouhuazhan and Huanghuazhan N3 were 24.3%,18.1%,16.5%and 21.2%higher than that of N0,respectively.Owing to the the increase of nitrogen,the basal internode diameter of each variety increased,and the thickness of stem wall and the quality of dry matter per internode decreased.For different basal internodes,the lodging index showed the trend of 13(the third internode)>12(the second internode)>I1(the first internode),the opposite trend for the bending force and bending moment.With the increase of nitrogen application,the bending resistance decreased,bending moment and lodging index increased,and the root injury intensity also increased.4.Brown rice rate,milled rice rate and head milled rice rate were the highest under N2 Except for head milled rice rate of Huanghuazhan,which peaked under N3.As more nitrogen was gradually applied,there were growing length-width ratio,protein content and gel consistency of double-season high-quality late rice while in contrast reduction in chalky grain percentage,chalkiness degree and amylose content,which also brought about a steady drop in peak viscosity,trough viscosity,breakdown,final viscosity while a rise in setback and pasting temperature.To sum up,the appropriate increase of nitrogen application can improve the processing quality,appearance quality,cooking and nutritional quality while deteriorate the RVA characteristics.5.With the increase of nitrogen amount,it is found that more small starch particles adhering to the large particles,and whose surface were unsmooth.The starch diffraction patterns of all high-quality late rice varieties under different nitrogen level were type A,which illustrated that the amount of nitrogen application did not change the crystallinity type of starch,but more nitrogen increased the relative crystallinity increased.With the increase of nitrogen application,there were dropping infrared ratio of starch decreased at 1045/1022cm-1,order degree of starch,the peak intensity increased,the electronic density between the crystalline and non-crystalline areas increased,the number of total small starch granules increased,and the number of large starch granules decreased.In terms of starch thermodynamic properties,the values of enthalpy,peak temperature,initial temperature,final value temperature,regenerative enthalpy and regenerative value all decreased with the increase of nitrogen application,and the difference between NO and N3 treatments for each rich variety was significant or extremely significant,which indicated that the application of nitrogen fertilizer could improve the starch thermodynamic properties of high quality late rice.