| Long-term shortage of livestock land and forage supplies restricted the development of our animal husbandry to some extent, and the shortage of forage became particularly serious in the winter season, so, taking full advantage of winter fallow fields to plant forage crops appeared to be more and more important. Studies on forage rape were conducted in the northwest of China far more than the south of China. The research on forage rape germplasm screening and appropriate cultivation techniques opened a precedent of making use of forage rape in Chongqing.At first, basing on the intake rate of adult rabbit, biological yield and nutritional value, three rape materials with forage promotional value were selected from200rape cultivars which contain low mustard acid and low sulfoglucoside. And then, further cultivation experiments including these three materials were conducted in Chongqing winter fallow fields. In this study, firstly, we discussed growth dynamic of nine traits which were closely related to biological yield, including plant height, number of total leaves, number of effective leaves, stem diameter, fresh matter weight per plant, dry matter weight per plant, leaf area per plant, leaf area index and stem/leaf ratio. Then, the growth dynamic of seven traits related to forage quality of the plant, including crude protein(CP), ether extract(EE), crude ash(Ash), calcium(Ca), total phosphorus(TP), neutral detergent fiber(NDF) and acid detergent fiber(ADF). At last, the effect on biological yield and plant nutrient composition content at both floral initiation/bolting and early flowering stages in different cultivation methods. Our results were as follows:1. In this study,20materials with high intake rate were selected from200rape cultivars. Further analysis on feeding experiment, biological yield and nutrient composition of these20materials showed that:there was no significant difference of intake rate in20materials, however, significant difference was found in both biological yield and nutrient composition content, and the overall nutrient composition content were high. Three forage rape materials with high GE were selected from these20materials, they were Zhongshuang12,20R and Xishuang1respectively.2. Plant density had no evident effect on growth stages of forage rape. Different sowing date had great effect on the seedling and floral initiation/bolting stage of forage rape, however, much less effect on the flowering stage was found. With the sowing time delayed, the time of seedling, floral initiation/bolting and flowering stage were prolonged, shortened and almost unchanged respectively. In addition, the time of floral initiation/bolting and flowering stage were respectively nearly the same in three different materials, Xishuang1had less5days in seedling stage than the other two materials.3. The change trend of plant traits in different sowing date, materials and plant density in the whole growth stages were basically the same respectively. With the sowing time delayed, the measured value of all plant traits were reduced, different sowing date had no significant effect on the plant height and stem diameter, but extremely significant or significant effect was found on the other traits, with maximum effect in the floral initiation/bolting stage. Xishuang1had slightly higher measured value of total leaves, number of effective leaves, fresh matter weight per plant and dry matter weight per plant than both Zhongshuang12and20R in the whole growth stages, the measured values of these traits between Zhongshuang12and20R were respectively nearly the same. Measured values of the other traits showed no evident difference between different materials. Different plant density had evident effect on the number of effective leaves, stem diameter, fresh matter weight per plant, dry matter weight per plant and leaf area per plant, but less effect on the other traits. With the plant density increased, the measured values of all traits were reduced.4. Correlation and path analysis of plant traits on both floral initiation/bolting and early flowering stages showed:the leaf area per plant and stem diameter had larger effect on the fresh matter weight per plant, if other conditions were fixed, increasing these two indicators were the direct and important measure to increase the biological yield of forage rape.5. Sowing at17/9and before could extremely significantly improve fresh matter yield of forage rape at both floral initiation/bolting and early flowering stages, there was not significant difference of fresh matter yield between different materials and plant density respectively, and once harvest could extremely significantly improve fresh matter yield of forage rape than stubble harvest at early flowering stage.6. The change trend of nutrient composition content in different sowing dates and materials were basically the same respectively in the whole growth stages. With the advance of growth process, the content of CP, EE, Ash, Ca and TP were decreased, while the content of NDF and ADF showed an upward trend. Firstly, at floral initiation/bolting stage of forage rape, significance differences were found in both CP and EE content between different sowing dates, and also in CP, EE, NDF and ADF content between different materials, there were no significance differences in these nutrient composition content between different planting densities. The forage quality of20R was both higher than that of Zhongshuang12and Xishuang1. Then, at early flowering stage of forage rape, extremely significance differences were found in both CP, NDF and ADF content between different sowing dates, there were no significance differences in these nutrient composition content between different materials, and the same to different planting density. Sowing early appropriately could significantly improve the forage quality of forage rape at early flowering stage. The EE content of20R was significantly higher than that of Zhongshuang12and Xishuang1. No significant differences were found in EE content between different sowing dates, also different planting densities. Comprehensive analysis of nutrient composition and fresh matter yield showed:The highest GE in different materials and sowing dates were20R and first sowing date (5/9) respectively. |
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