夏播玉米根系分布与含氮量对氮肥类型与施氮量的响应

连续两年施用不同氮肥和用量，考察了夏玉米（郑单958）根系在不同土层的分布与含氮量，分析其与产量、地上部氮素累积量的相关性。结果表明:1）施氮抑制夏玉米生育前期根系生长与下扎，抑制作用表现为:复合肥＞包膜尿素＞尿素；施氮使吐丝期0—25与50—80 cm土层根量增大，25—50 cm土层根量减少；总根量表现出:尿素＞复合肥＞包膜尿素，且差异显著。2）施氮显著提高夏玉米9叶展开期0—25 cm土层与吐丝期25—80 cm土层根系含氮量；氮肥类型影响根系含氮量，且差异显著。3）吐丝期25—80 cm土层根系含氮量与产量呈显著正相关（P＜0.05)，与地上部氮素累积量呈极显著正相关（P＜0.01﹚；在25—50 cm，根系鲜重密度、体积密度和干重密度与产量及氮素累积量表现为负相关，在其他土层表现为正相关。其中，0—80 cm土层根系干重密度与产量呈显著正相关（P＜0.05)，0—25 cm土层根系鲜重密度与产量、0—80 cm土层根系鲜重密度与氮素累积量呈明显正相关（P＜0.1）。可见，玉米根系分布与含氮量明显受到氮肥类型与施氮量的影响，施氮主要通过提高表土层根系鲜重、根系总鲜重与总干重及中下层根系含氮量实现夏玉米增产增效目的。

Responses of roots distribution and nitrogen content of summer maize to nitrogen fertilization types and amounts

A fertilization experiment on different types and rates of N fertilizers was conducted in successive two years, the distribution of roots and N content of summer maize (Zea mays L., cultivar: Zhengdan958) were investigated and their correlations to yield and shoot N accumulation were analyzed. The main results show that:1）growth and downward extending of roots before the 9-leaf stage of summer maize are restrained by N application, and the restraining effect indicates a trend of compound fertilizer＞coated urea＞urea. Amounts of roots are increased in 0–25 cm and 50–80 cm soil layers, while decreased in 25–50 cm soil layer by N application at the silking stage. Total amount of roots indicates a trend of urea＞compound fertilizer＞coated urea, and significant differences among three types of N fertilizers are observed. 2）N contents in roots are improved significantly by N fertilization in 0–25 cm soil layer at the 9-leaf stage and 25–80 cm soil layer at silking stage. N content of roots is affected by type of N fertilizer, and significant differences among N fertilizers are observed. 3）Positive correlation at 0.05 and 0.01 probability level exist between yield, N accumulation amount of shoot and N content of roots in 25–80 cm soil layer at the silking stage, respectively. Correlations of roots density of fresh weight, volume and dry weight to yield and N accumulation amount of shoot are negative in 25–50 cm soil layer respectively, while they are positive in other soil layers, there into positive correlation at 0.05 probability level between yield and roots density of dry weight in 0–80 cm soil layer, and positive correlation at 0.10 probability level between yield and roots density of fresh weigh in 0–25 cm soil layer, and between N accumulation amount of shoot and roots density of fresh weigh in 0–80 cm soil layer are observed. These results show that root distribution and N content of summer maize are obviously affected by types and rates of N fertilization. The effects of N application on increasing of yield and N efficiency of summer maize are achieved mainly by improving fresh weight of roots in topsoil, total fresh weight and dry weight of roots and N content of roots in middle and lower soil layers.