The Grain Production Efficiency Of Maize Hybrids Released In Different Years

This study is to analyze the changes of The grain production efficiency in different years,which are the main varieties in China since the 1970s,including xidan1,danyu13,yedan13,zhengdan 958,and a new variety yudan 606.and the experiment of density and fertilization was carried out in 2014-2016.The result showed that:1.The growth period and grain filling duration of maize varieties in different years continued to be prolonged with the age,but the growth period was maintained at 110 days after the 1990s and the duration of grain filling was maintained at 65 days,and the proportion of modern varieties was increased.The effects of low nitrogen stress on the growth period and the duration of grain filling were not significant.The effects of low nitrogen stress on the growth period and grain filling duration of maize were studied.Under low nitrogen stress,the growth period and grain filling duration Shortened 5-7 days,modern varieties did not reduce is not obvious.With the advance of the year,the growth period and the duration of grain filling in different age maize varieties were prolonged,and the grain length was long.2.With the advance of the times,The results showed that the LAI,spikelet leaf SPAD,dry matter weight per plant,dry matter mass,grain weight and harvest index of maize varieties increased in different ages,and the rate of plant stalk and lodging rate decreased significantly.The LAI of the maize varieties increased,the LAI of the maize varieties,the LAI of the cultivars,and the percentage of the dry matter in the modern varieties was much higher than that of the past varieties,and the LAI of the past varieties decreased rapidly at the high density of late grain filling stage.The dry matter weight per plant,the grain weight,the harvest index,the empty stalk rate and the lodging rate were reduced,and the decrease of the modern varieties was less than that of the past.Low nitrogen stress had a certain inhibitory effect on LAI,spikelet SPAR,total dry matter weight,grain weight,harvest index and grain filling characteristics of LAI and panicle leaves in different age.The late SPAD was significantly lower than that of modern Species,so that the early varieties of early grain filling early failure serious,resulting in reduced grain yield.With the increase of density,the resistance of modern varieties,resistance to low nitrogen increased,plant traits and yield traits were optimized,conducive to high yield.3.With the advance of the times,the accumulation of dry matter increased,and the proportion of dry matter to stem was increased and decreased.Under the condition of low nitrogen,the dry matter of the stem(sheath)leaves of the old cultivars was more than the modern varieties,and the senescence of the old varieties was accelerated.The follow-up ability of the leaves was significantly decreased.The modern varieties ZD958,XY335 and YD606 reached the maximum grain(Wmax),grain filling active period(P)and average grain filling rate(Gave)were higher than those of the old cultivars XD1,ZD2,DY13,YD 13(Gmax),the maximum grain filling rate(Tmax),the maximum grain filling rate(Gmax)High.The results showed that,with the advance of the year,the leaf function of different maize was stronger and the grain filling intensity was enhanced.Under the nitrogen stress,the new varieties could still maintain the higher leaf size and improve the grain production efficiency.