Effects of Nitrogen Treatments on Dry Matter Production and Photosynthetic Characteristics of Summer Maize( Zea mays L. ) under Super-high Yield Conditions

Nitrogen treatment is an important prerequisite to achieve high grain yield of summer maize. The objective of this study was to reveal the effects of nitrogen treatments on yield, dry matter production and photosynthetic characteristics of summer maize under super- high yield( ≥15 000kg·hm- 2) conditions. An split plot design field experiment was conducted using three maize hybrids‘Suyu30',‘Suyu20',‘Suyu29'as materials. Six nitrogen levels which were 0,360,405,450,495,540kg·ha- 1respectively were designed in this study of four years. Meanwhile,the key quality of dry matter production simulated with Richards equation and photosynthetic of five different stages were analyzed. Results showed the yields of three maize hybrids reached the peak at 450kg·ha- 1nitrogen level,which were 13798kg· ha- 1,15455kg · ha- 1,16787kg · ha- 1,respectively. According to the regression equations between nitrogen application rate and yield of three hybrids,we could know that the optimal nitrogen applications of three maize hybrids were 461. 3kg·ha- 1、463. 8kg·ha- 1、452. 8kg·ha- 1,respectively. The yields would decrease when nitrogen application level was too high or too low.( 2) 450kg·ha- 1nitrogen level increased the photosynthetic rate at anthesis stage,decreased magnitude of its decline during filling stage. And the maize population had a higher accumulation rate and a bigger amount of dry materials at 450kg·ha- 1nitrogen level. The results analyzed by Richards model showed that the maximal accumulation rate of dry materials of three maize hybrids appeared at the first 10 days after anthesis stage and the later the higher yield; ‘Suyu29'among three maize hybrids which had the longest active growth period( up to 25 days after anthesis stage nearly) and the maximal accumulation of practical and theoretical dry materials had the highest yield. After comparing the maximal accumulation of practical and theoretical dry materials,we could know that ‘Suyu20'and‘Suyu29'still had the great yield potential. Based on these characteristics,the key points to build the super high- yield maize populations were as followed: increasing the photosynthetic rate during filling stage with nitrogen treatment,delaying the date of the maximal accumulation rate of dry materials,increasing accumulation rate and amount of dry materials in early filling stage using nitrogen application.