Study On Nitrogen Efficiency And Physiological Characteristics Of Maize

Since 1930's, the maize hybrids have been breeded, the maize yield constantly increases. A main aspect bringing on yield rising is plentiful nitrogen(N) fertilizer input. However, the range of yield increasing is lower than that of N fertilizer input rising, which results in obvious drop of N use efficiency(NUE). Moreover, excessive N fertilizer can not only bring economical loss, but also lead to the pollution of groundwater of farmland, lake and river. Therefore, it is imperative to improve NUE. The most effective and basic channel is the development of high N-efficiency(NE) cultivars. So, considering the continuable agricultural progress, it is significative to seek high NE maize variety resource and further research and reveal hereditary discrepancy and physiological and biochemical mechanisms on N absorption, tranportation and utilization etc, which can provide main basis and some reference information for the directional breeding of high NE maize hybrids.Adopting solution cultures at four nitrate levels(0.04,0.4,2,4mmol/L), five main maize cultivars (Denghai1, Xidan2, Chengdanl4, Nongdal08 and Yayu2) from Chongqing city were screened to study NE, their difference and physiological and biochemical basis of N absorption and utilization. The results shows that:1 There is significant difference between five cultivars. In the same N level, there is significant difference in the way of morphologic, physiological and biochemical characteristics. The difference in NE is mainly determined by N absorption efficiency(NAE) under low N and by both NAE and NUE together under high N. For Yayu2, its growth rate ,matter accumulation and photosynthetic activity is not the highest, but compared with the suitable N supply, the range of decrease is little under lower N, and its NUE under two levels is higher, and NAE is high under lower N level and is in the middle under suitable N; For Chengdan14, its growth potential is very strong, but the scope of decrease is the greatest under lower N level among five hybrids, and the NUE is lower under all four N levels. The amount of growth and matter accumulation of Xidan2 is great, but the scope of decrease is also greater; All parameter values of Denghail is in the middle; The scope of decrease...