| Silage corn (Zea mays L.) was the indispensable foundational feed of livestock husbandry. With the development of dairy husbandry, the planting scale of silage corn expanded. Northern region of Heilongjiang Province, the important base of breeding cows, had great demand for silage corn. However, in this region where the annual average accumulated temperature of≥10℃only was about 2000℃, most special silage corn varieties had bad growth such as bad mature of kernel(or no grain) and high water content seriously affecting the quality of silage fermentation and the healthy development of dairy husbandry. The research based on the situation of the northern region designed monocropping and mixed planting experiments in order to obtain high yield and quality corn silage. In monocropping experiment, 7 silage corn varieties and 13 common corn varieties were used as research object and the phenophase, main agronomic traits, fresh yield, dry matter yield and nutrient composition were determined, besides, the grey relevancy theory was used to comprehensive evaluation. The purpose of monocropping experiment was to select suitable silage corn in northern region. In mixed planting experiment, 3 corn varieties of different growth duration were planted by two ways (intercropping and mixed planting), and in three mixed societies; the phenophase, main agronomic traits, fresh yield, dry matter yield and nutrient composition were determined and compared with those monocropping corn; the effects of mixed planting on the growth, production and nutrient content of the corn were discussed; finally, the comprehensive appraisal of treatments was taken by Milk 2006 index. The purpose of mixed planting was to find out the suitable silage societies of corn mixed and corresponding planting model. The main conclusions of experiments were as following:1. Under monocropping model, the phenophase of 20 corn varieties was different in harvest time; KD reached ripening stage; H7, H6 and DN9 reached soft dough stage; H4, H9, LD, DN8, H8, DN2, YG, ZY, F167, H5, DN0 and PZ reached the milk stage; GY6, DQ, GY5 and ZB reached grain filling stage.2. Under monocropping model, in harvest time, among tha all 20 tested corn varieties, the tallest was ZB, average 376.33 cm, and the shortest was KD, average 222.00 cm; the ear hight of ZB was 198.64 cm which was the tallest, and the ear hight of KD was 79.33cm which was the lowest; ZB had the most green leaves, average 15.67 pcs, and KD had the least green leaves, average 8 pcs; the H6 had the biggest basilar stem diameter, average 2.97cm, and YG had the least basilar stem diameter, average 2.20cm.3. Under monocropping model, in 20 tested corn varieties, the highest fresh whole-plant corn yield was DQ, and the lowest was KD; the highest dry matter yield was H4, and the lowest was GY5.4. Under monocropping model, in 20 tested corn varieties, LD had the highest CP content and GY6's CP content was the lowest; ZB had highest NDF content and DN9's NDF content was lowest; H6 had the highest ADF content and DN9's ADF content was lowest; DN9 had the highest EE content and ZB's EE content was lowest; PZ had the highest starch content and ZB's starch content was the lowest.5. Grey correlation method was used to evaluate 20 tested corn varieties, the best comprehensive appraisal score was ZY, and then DN0; the lowest comprehensive appraisal score was KD.6. Compared with monocroping model, mixed planting had no significant effect on phenophase and main agronomic traits including plant hight, ear hight basilar stem diameter and the quantity of green leaves at harvest time.7. The fresh whole-plant corn yield of mixed planting treatments was lower than that of monocroping treatments; on the other hand, the dry matter yield of mixed planting treatments was higher than that of monocroping treatments.8. Compared with monocroping treatments, mixed planting increased the CP yield, EE yield and starch yield and decreased the NDF and ADF content of society.9. The comprehensive appraisal of each treatments was taken by Milk 2000 index, the result showed that J1 had higher class score than other treatments and was suitable to plant in the northern region of Heilongjiang province where the annual average accumulated temperature was about 2000℃.
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