Study On Canopy Structure Charactistics And Light,Nitrogen Utilization Traits Of Different Maize Hybrids Under High Plant Density

Understanding the relationship between dry matter productivity and nitrogen utilization of maize hybrids and grain yield under high plant density, we conducted a field experiment in 2014 and 2015, using two maize hybrids(XY335, and ZD958) and five rates of N application(N0, N1, N2, N3, and N4)(and through shading at filling stage) to compare the difference of dry matter productivity, nitrogen utilization and remobilization and the contribution to grain yield under high plant density(90000 plant ha-1).(1) The main results showed that the angle between leaf and stem, leaf orientation value and LAI were higher under N rate, the upper leaf orientation value(LOV) of XY335 was higher than ZD958 by 18.42%, the lower and middle LOV was lower than ZD958 by 16.43% and 27.11%, the LAI attenuation in advance at N3 treatment, especially the part of lower leaf. Canopy light interception rate increase with the increase of n application rate and highest in the 300 kg ha-1, mian is to increase the interception of upper leaves, XY335 under the N rate of 200 kg ha-1 light energy utilization efficiency reach highest was 1.08g·MJ-1, ZD958 reach highest was 1.08g·MJ-1 at the N rate of 300 kg ha-1, but the ZD958 have higher light utilization efficiency than XY335。Leaf nitrogen content increased with the increase of N application rate, the nitrogen content of XY335 showed a trend of slow at the beginning and quickly to reduce some times later, and ZD958 decreased slower gradually after silking; 200 kg ha-1 level of each layer of leaf photosynthetic nitrogen use efficiency was highest, upper XY335 PNUE average is 12.52% higher than ZD958, ZD958 low in the middle is 3.61% and 31.79% at lower of ZD958.Filling stage of PAR interception rate, light utilization rate and photosynthetic nitrogen use efficiency were significantly positive correlation and with yield.(2) The average maximum grain yield in two years was higher in XY335, however, the optimum N application rate was approximately 4.8-10.6% lower than ZD958. In nitrogen treatments XY335 had higher total dry matter accumulation, dry matter accumulation after flowering, and the dry matter translocation efficiency than that of ZD958, however, it was contrary in treatments without nitrogen application. At the same time, the magnitude of gradual increases in dry matter accumulation, as well as dry matter translocation efficiency, with increased N application was better in XY335 especially under high density plantation. N concentrations in leaf and stem were different at silking and harvesting stage i.e. higher in XY335 at silking(p<0.05) and lower at harvest. This could be explained due to better translocation efficiency in XY335 than ZD958 after silking. The grain N content had small difference between cultivars at high plant density, however, it was significantly increased in XY335 at lower plant density(p<0.05). In nitrogen treatments, XY335 had higher N accumulation at pre-silking and post-silking and the contribution of the leaf N translocation to grain was significantly higher(p<0.05) than ZD958. At optimal nitrogen application rate, N use efficiency(NUE) and N recovery efficiency(NRE) was significantly higher(p<0.05) in XY335 under both planting densities, while agronomic nitrogen efficiency(ANUE) and partial factor productivity from applied N(PFPN)was not significantly different between them. In XY335, NUE was significantly higher under high planting density, as indicated in results, due to higher dry matter production and better translocation efficiency during filling stage.(3) Under the condition of lower nitrogen stress, in shade treatments, the yield and dry matter accumulation enhancement compered with contrast; the normal nitrogen treatment, shade significantly reduced maize yield and dry matter accumulation, high density treatment did fall by increasing yield and the accumulation of dry matter, yield and dry matter accumulation XY335 volume fell more than ZD958. LAI reduce after shade, and reduce the attenuation of low nitrogen treatment lower and middle leaf LAI, the decrease of XY335 is more significant;After shade, high nitrogen treatment LAI reduce significantly, accelerated the aging of high density treatment LAI, especially the lower LAI of XY335;Shade improved the low nitrogen treatment of leaf chlorophyll content, lower chlorophyll a/b, and the XY335 photosynthetic rate is higher;And high density after shade treatment chlorophyll content declined, especially XY335 lower leaf chlorophyll content decreased significantly, the rise of the chlorophyll a/b, photosynthetic rate decreased.Showed that weak light stress on shade XY335 photosynthetic performance impact is more significant, become the important factor of high yield limitation.Those suggest that the group has the advantage of hybrid under higher density can improve canopy light interception by canopy structure change, change the regulation of leaf nitrogen distribution by control N application to improve energy utilization efficiency and photosynthetic nitrogen use efficiency, and increase production. XY335 as high nitrogen efficient(HNE) variety, and in northeast China, this type of spring maize varieties are better to obtain high production and efficiency in intensive input crop production.