施氮水平对超高产夏玉米籽粒及植株形态学特征的影响

氮肥是夏玉米高产的先决条件，为明确不同施氮水平对超高产夏玉米（13500 kg/hm2）籽粒及植株形态学特征的影响，以苏玉30、 苏玉20、 苏玉29三个玉米品种为材料，连续4年、 在6 个施氮水平（0、 360、 405、 450、 495、 540 kg/hm2）上，对成熟期玉米籽粒及植株的形态学特征进行了统计分析。结果表明，密植条件（82500 plant/hm2）下，产量与施氮水平呈抛物线关系， 三个品种均在 450 kg/hm2 施氮水平下产量最高，分别为13798、 14531、 16787 kg/hm2。适宜的施氮水平（450 kg/hm2）可显著增加穗粒重、 粒长、 粒宽及棒三叶叶夹角角度，增大茎秆第一、 二、 三节间长度及茎粗，缩短果穗位三节间（第七、 八、 九节间）的长度。氮肥水平对籽粒厚度影响不显著。产量和茎粗与第一、 二、 三节间长度分别表现为极显著、 显著正相关关系，与第七节间长度分别表现为显著、 极显著负相关关系，而二者与其他节间长度关系不显著。因此， 育种上可选育粒长和粒宽较大的品种作为玉米超高产育种的方向； 生产上可在第一、 二、 三、 七节间伸长的关键时期， 通过氮肥运筹调节其节间长度，达到扩库、 强源、 畅流的目的，最终建立玉米的超高产群体。

Effects of nitrogen levels on the morphology characteristics of grain and plant of summer maize (Zea mays L.) under super-high yield conditions

Nitrogen (N) is an important prerequisite for achieving high grain yield of summer maize. The objective of this study was to reveal the responses of summer maize to N levels in the morphology characteristics of plants and the yield component factors in some super-high yield (≥13500 kg/ha) maize cultivars. A field experiment with a split-plot design was conducted with three local maize hybrids (Suyu30,  Suyu20 and Suyu29) and six N fertilizer application rates (0,  360,  405,  450,  495 and 540 kg/ha). The statistics results show that a parabolic relationship existed between the yields of three maize hybrids and N rates. The maximum yields turned up at the N 450  kg/ha level,  which are 13798,  14531 and 16787 kg/ha,  respectively. The kernel weight per ear,  grain length,  grain width and the length of internode near ear are increased markedly under the N 450  kg/ha,  which are 239 g (take Suyu29 for example),  12.29 mm,  10.83 mm,  20.2°(above),  43.3°(middle) and 26.1°(below),  respectively. The lengths of 1st,  2nd and 3rd  internodes and stem diameter are also increased,  which are 11.1,  11.4,  11.4 and 2.35 cm,  respectively,  while the lengths of internodes near ear (7th, 8th and 9th internodes) are decreased,  which are 14.3, 14.0 and 15.5 cm,  respectively. The N level does not have insignificant effect on the grain thickness. The yield and stem diameter show significant or extreme significant positive correlations with the lengths of 1st,   2nd and 3rd  internodes,  but significant negative with the length of 7th internode,  and not insignificant with the other lengths of internodes. Therefore,  big grain length and width can be used as indicators in breeding super high-yield of maize cultivars. In practical maize production,  proper N application can be used effectively to regulate the lengths of 1st,  2nd,  3rd and 7th internodes,  thus to build up the super high-yield population of maize through enlarged N sink and effective transfer to yield formation.