施氮对不同种植密度下夏玉米产量及子粒灌浆的影响

以夏玉米杂交种郑单958为材料,在不同种植密度(52500、67500、82500株/hm2)及不同供氮水平(0、120、240、360kg/hm2)下对玉米子粒产量、产量构成、植株地上部干物质积累、子粒灌浆动态及灌浆过程中的物质代谢状况进行了研究。结果表明,不同施氮水平及种植密度下子粒产量的差异主要是由穗粒数所决定。产量及穗粒数的形成与植株地上部干物质积累密切相关,施氮可明显促进植株地上部干物质积累量的增加。穗顶部与中下部子粒的灌浆动态及物质代谢具有明显的不同,授粉后5～20d,顶部子粒灌浆体积、干重、灌浆速率、总可溶性糖、蔗糖、淀粉含量均明显低于中下部子粒;同化物供应的差异是导致顶部与中下部子粒发育差异的一个重要原因。顶部子粒灌浆体积、干重、总糖、淀粉含量施氮处理高于不施氮处理;施氮可明显促进同化物的积累及向顶部子粒的供应,促进顶部子粒灌浆,减少败育,增加有效粒数,提高产量。

Effect of nitrogen supply on yield and grain filling in summer maize with different crop density

Maize grain yield was closely associated with kernel number at maturity, and kernel number was affected by apical kernel abortion mainly occurred at early grain filling stage. The objectives of this work were (i) to evaluate the (effect) of N on grain yield and its components, and to determine the relationship between grain yield and above-ground (dry) matter accumulation; (ii) to analyze the difference of kernel development between apical and mid-basal kernels at grain filling stage, and explore the possible reasons affecting kernel development. The field experiment with summer maize (Zea mays L.) hybrid Zhengdan 958 were carried out at Wuqiao experiment station of China Agricultural University in 2003. The treatments consisted of different crop densities( 52500 plant/ha, 67500 plant/ha, 82500 plant/ha) and nitrogen supply rates (0 kg/ha, 120 kg/ha, 240 kg/ha, 360 kg/ha). Grain yield and its components, above-ground dry matter accumulation, grain filling and content of soluble carbohydrates in summer maize were studied. The results showed that the grain yield per plant was mainly depended on the number of kernels per ear at maturity while the kernel weight was relatively constant. The grain yield and kernel number were closely associated with above-ground dry matter accumulation apparently improved by nitrogen supply. Grain filling and metabolism of soluble carbohydrates in apical and mid-basal kernels were apparently different. In 5—20 day after pollination(DAP), the size of fresh grain, grain dry weight, grain filling rate, total content of soluble sugar, content of sucrose and starch in apical kernels were lower than these in the mid-basal kernels, while in apical kernels these were higher in nitrogen supply treatments than in treatments without nitrogen supply. The grain filling rate in apical kernels began to (decrease) in 15—20 DAP while kernel abortion usually occurred. The results suggested that one of the main reasons affecting development of apical and mid-basal kernels was assimilate supply. Assimilate supply in apical kernels could be improved by nitrogen supply and kernel abortion were inhibited.