Effects Of Nitrogen Levels On Nitrogen Uptake And Utilization, And Yield Formation Of Different Nitrogen Efficiency Maize Cultivars

The high N efficiency maize cultivar Zhenghong 311 and low N efficiency maize cultivar Xianyu 508 grown under different nitrogen levels, was used to clarify the effects of nitrogen on dry matter production, nitrogen absorption and accumulation, chlorophyll content and key enzyme activity involved in nitrogen metabolism in leaf, yield and its components of different nitrogen efficiency maize cultivars, in 2012 and 2013. The results showed as follows:1. The plant height and leaf area of high N efficiency cultivar Zhenghong 311 were significantly high than low N efficiency cultivar Xianyu 508. Plant hight and leaf area could be improved to some extent. The plant height and leaf area of high N efficiency cultivar Zhenghong 311 have higher increase amplitude in low-middle nitrogen levels, while the low N efficiency cultivar Xianyu 508 have higher increase amplitude in high nitrogen level.2. Nitrogen fertilizer levels have significant effects on dry matter accumulation of maize, while the impact degree in there exist certain differences in the two kinds of cultivars. Dry matter accumulation of the high N efficiency maize cultivar Zhenghong 311 is higher than the low N efficiency maize cultivar Xianyu 508, but with the increase of nitrogen fertilizer levels the difference showed a trend of shrinking. Compared with Xianyu 508, Zhenghong 311 showed higher proportion of leaf and stem sheath dry matter distribution that maintain the lager vegetation, which is the basis of its high yield.3. Nitrogen content of plant was increased significantly by nitrogen fertilization, and increase amplitude was reduced in the late growth stage, but the effect degree of nitrogen content of plant by nitrogen fertilizer levels in two kinds of cultivars have some differences. The promotion of nitrogen fertilization on nitrogen content of plant of the high N efficiency maize cultivar Zhenghong 311 are significantly higher than the low N efficiency maize cultivar Xianyu 508. Nitrogen fertilization made nitrogen accumulation increased of the high N efficiency maize cultivar Zhenghong 311 in the whole growth period, while the nitrogen accumulation of low N efficiency maize cultivar Xianyu 508 just increased in sowing-jointing stage and jointing-silking stage. So the difference of the two kinds of cultivar on nitrogen accumulation was not significant before the jointing stage, but the nitrogen accumulation of high N efficiency maize cultivar was significantly higher than the low N efficiency maize cultivar after the jointing stage.4. Increased nitrogen fertilizer reduced nitrogen absorption efficiency of the two cultivars, and reduced the nitrogen use efficiency and production efficiency. Compared with the low N efficiency maize cultivar Xianyu 508, the high N efficiency maize cultivar Zhenghong 311 has stronger ability of nitrogen absorption and accumulation, that is to say the nitrogen absorption of Zhenghong 311 is higher, and the nitrogen physiological efficiency of Zhenghong 311 also is higher under the low nitrogen fertilizer levels. So relative to Xianyu 508, Zhenghong 311 not only is the type of high nitrogen absorption efficiency, but also is the type of high N use efficiency under the low nitrogen fertilizer levels.5. The yield of high N efficiency maize cultivar Zhenghong 311 was first increased and then decreased with the increased of nitrogen fertilizer levels, while the yield of low N efficiency maize cultivar Xianyu 508 was increased with the increased of nitrogen fertilizer levels in the range of the experiment, and the increase amplitude of yield was gradually narrowed. So between yield and nitrogen fertilizer levels Zhenghong 311 and Xianyu 508 both all are characterized by quadratic convex function relationship, but the gap of nitrogen fertilizer level at the highest yield is larger. The optimal N application of Zhenghong 311 and Xianyu 508 were 277.1 kg/ha and 445.5 kg/ha, and the optimal N application of Zhenghong 311 was far lower than Xianyu 508. The advantage of Zhenghong 311 on yield was more obvious under low nitrogen fertizer levels, and the advantage was lost under high nitrogen fertizer levels, indicated that Zhenghong 311 is relatively resistant to desert, while Xianyu 508 is relatively resistant to fertilizer.6. The chlorophyll content(SPAD) of two cultivars was significantly increased by increased nitrogen fertilizer, but the increase amplitude have differences between cultivars. the increase amplitude of low N efficiency maize cultivar Xianyu 508 was larger in the earlier growing stage, while the increase amplitude of high N efficiency maize cultivar Zhenghong 311 was larger in middle and later stage. This difference was mainly manifested on the middle and lower leaves, indicated that reasonable application of nitrogen fertilizer is more beneficial to prevent the premature senility of middle and lower leaves of Zhenghong 311 in the later stage. The activity of NR, GS and GDH in the ear leaf of high N efficiency maize cultivar Zhenghong 311 after silking were higher than the low N efficiency maize cultivar Xianyu 508, especially in the check treatment. Increased nitrogen fertilizer increased the activity of NR, GS and GDH in the ear leaf of two cultivars, but the increase amplitude of Zhenghong 311 was less than the Xianyu 508. The optimal N application to maintain higher GS and GDH activity of Zhenghong 311 was lower than Xianyu 508, indicated that the high N efficiency maize cultivar Zhenghong 311 has stronger ability of nitrogen absorption and assimilation, this could be one of the important physiological mechanism of the high N efficiency maize cultivar Zhenghong 311 resistance to desert.