关键词: Spring maize, Nitrogen efficiency, Subsoiling, Nitrogen reduction, Morphological character, Yield

Abstract: In this experiment,4 spring maize cultivars with different nitrogen fertilizer absorption and utilization rates were tested.Two tillage methods of deep pine （40 cm） and rotary tillage （15 cm） were used,with 2 nitrogen application rates 300 and 150 kg/hm².The indexes of root structure-canopy physiology-yield of each variety were analyzed and compared.The results showed that deep pine reduced the dry weight,the length and the surface area of the root for each variety,and decreased their leaf area and chlorophyll relative content （SPAD） after the nitrogen reduction.In addition,the remission effect of the double and high varieties was shown to be greater than that of the low height and the double low variety.The nitrogen absorption and utilization efficiency after the nitrogen reduction in various varieties improved by 16.44%,29.52%,27.36%,and 12.69%,respectively,and the decrease of yield was reduced by 51.27%,42.55%,33.52%,and 3.41%,respectively.The double and high variety should be selected if the yield of 12 000 kg/hm² above is maintained under the condition of deep pine nitrogen application 150 kg/hm².

Key words: Spring maize, Nitrogen efficiency, Subsoiling, Nitrogen reduction, Morphological character, Yield