Mechanism Of Nitrogen Efficiency Differences In Spring Maize Varieties And Response Of Subsoiling With Reducing Nitrogen

The problem of resource waste and environmental pollution caused by excessive application of nitrogen fertilizer is becoming more and more serious.The rational use of nitrogen fertilizer has become a hot topic.Due to the irrational tillage mode of the main maize production areas,the shallowness of the tilth layer,the solid plow bottom,the increase of the bulk density,the poor capacity of the soil storage and fertilizer,the increase of the resistance to the root ligation,the absorption and utilization of the deep nutrients of corn,the reduction of the nitrogen use efficiency and the increase of maize yield was limited.In this experiment,four different nitrogen efficiency varieties were selected as experimental materials.Under the conditions of deep loosening 40cm and rotary tillage15cm,3 nitrogen application levels of 300kg/hm~2,150kg/hm~2 and 0kg/hm~2 were applied.Based on the soil root structure canopy physiological yield,the difference of nitrogen efficiency and the mechanism of response to subsoiling and nitrogen reduction were systematically studied.The results provide a theoretical basis for the utilization of suitable nitrogen efficiency varieties in Inner Mongolia plain irrigation area and deep tillage and nitrogen reduction measures to achieve high yield and efficiency of spring maize.The results of the study show that:(1)The cluster analysis of 30 maize varieties showed that the varieties with high absorption efficiency and high efficiency(double high type)?the high and low absorption efficiency high efficiency varieties(high low type)?the varieties with low efficiency of absorption efficiency(low high type)and low efficiency of absorption efficiency(double low type).(2)The difference in nitrogen efficiency of different nitrogen efficiency types mainly lies in root dry weight,root length,root surface area,SPAD value,leaf area,dry matter accumulation,dry matter transport,dry matter accumulation,grain contribution rate,nitrogen accumulation,and nitrogen transport after flower,grain nitrogen.The amount of element accumulation and its contribution to grain,GS activity,yield and yield components were double high varieties>high low varieties>low high varieties>double low varieties,while the decrease of leaf area after silk spit was a double high varieties<low high varieties<low high varieties<double low varieties;lower GS activity of 30d and 20d after silk spit.The two high varieties and low varieties were significantly smaller than those of high and low varieties and two low varieties,and the nitrogen absorption efficiency showed high and low varieties>double high varieties>double low varieties>low high varieties,and the nitrogen use efficiency showed low high varieties>double high varieties>double low varieties>high and low varieties.(3)Subsoiling alleviated the effect of nitrogen reduction on root,canopy and yield.The root dry weight,root length and root surface area of the root system of different nitrogen efficiency types were reduced,and the area of top leaf and the decrease of SPAD after nitrogen reduction were reduced;and the dry matter accumulation,the decrease in the accumulation of grain in the mature period and the increase in the amount of dry matter transport increased.Nitrogen accumulation,nitrogen transport,grainnitrogen accumulation and GS activity decreased at the silk stage and maturity stage.Moreover,the alleviating effect on double high varieties and high and low varieties is greater than that of low and high varieties and double low varieties.(4)Deep pine increased nitrogen absorption efficiency and nitrogen use efficiency after nitrogen reduction,increased nitrogen efficiency by 16.43%,19.75%,27.18%and11.34%,and reduced the yield by 51.27%,42.55%,33.52%and 3.41%respectively.If the yield 800kg/666.7m~2 above was maintained under the condition of 150kg/hm~2 nitrogen amount,to achieve the best effect of high yield and efficiency,double high varieties should be selected.