中文摘要：

通过测定粗蛋白、消化率和代谢能三个营养指标研究玉米不同生殖生长期各器官和空间位置的营养成分含量的变化。结果表明：9月24日玉米（Zea Mays L.）籽粒产量达到最大,产量为67 531 kg/hm2,若以收获籽粒为目的,则应在此时期收获。若以收获整株作为饲料为目的,玉米收获最佳期应在9月4日~9月9日之间,9月4日收获整株玉米可消化干物质量为7 802 kg/hm2,代谢能为107 374 MJ/hm2,9月9日收获整株玉米粗蛋白总量为704 kg/hm2;玉米秸秆下部粗蛋白含量低,中上部秸秆营养较好,可以考虑将下部作为燃料,中上部用作家畜的优质粗饲料。

英文摘要：

The changes in nutrients of corn at different growing periods, organs, and spatial locations were examined by determining crude protein, in vitro digestib yield of corn （ Zea Mays L. ） was 67 531 kg/hm2, ility, and metabolic energy. The results showed that the maximum which was observed in September 24. Therefore, this is a preferred time to harvest corn. The most total metabolic energy and total crude protein of whole-crop corn were 107 374 MJ/hm2 and 704 kg/hm2, and they were observed in September 4 and 9, respectively. The most total metabolic energy （107 374 MJ/hm2） of whole-crop corn was also observed from September 4 - 9. So this period should be the optimal time to har- vest whole-crop corn as forage. Furthermore, the lower part of the plant had lower crude protein level, and the upper part of the plant had more nutrient content, so the lower and upper parts of plant should be used as fuel and forage feed, respectively.