Abstract:

【Background】 Planting of alfalfa in degraded meadow in cold mollisol area of Northeast China is an effective method for rapid vegetation restoration.Reasonable fertilization is an effective measure to improve the yield and quality of alfalfa. In order to reduce the rolling damage of soil and alfalfa plants by machinery in the process of fertilizing. It is generally advisable to fertilize the soil at one time before and after alfalfa plants have returned to green in spring. The turning green period of alfalfa in the mollisol area of Northeast China is from late April to early May, and in this time, fertilizer is often applied. However, there has been few studies on the effect of fertilizer on alfalfa at different time of early spring. 【Objective】 The purpose of this experiment was to study the effects of fertilizer application in different periods of early spring on the performance and nutritional quality of alfalfa, and to determine the best fertilizing period for alfalfa in early spring. In order to provide technical guidance for the restoration of degraded meadow by planting alfalfa in the mollisol area of cold region. 【Method】 Alfalfa in its second years after was used as the experimental material, and the type of fertilizer was self-developed special fertilizer for alfalfa (patent number: 201810193040.0). And the contents of N, P, K is 14.20%, 10.86%, 10.47%. A period of fertilizer was set up every 5 days from April 20 to May 15, and the amount of fertilizer was fixed at 525 mm. The alfalfa was mowed three times every year. The effects of fertilizer on the production performance and nutritional quality of alfalfa in different periods of early spring were investigated. 【Result】 Fertilizer as all time could significantly promote the growth at all cuts, among which earlier fertilizer trend to increase the plant height of the first cut and the average plant height over the whole year, and the late fertilizer trended to increase the plant height of the second and third cut, but the difference was not significant. Early fertilizer could significantly increase the hay yield of each cut, and the early application trend of increase the hay yield of the first cut while decrease the hay yield of the second and third cuts. The effect of different fertilizing time on the average hay yield in the whole year was not significant. The average crude protein content of each harvest and that of the whole year was significantly increased by fertilizer. But the effect of different fertilizing time periods on the annual average crude protein content was not significant. Compared with no fertilizer, the contents of NDF and ADF in all treatments were significantly decreased. Fertilizing early could reduce the contents of NDF and ADF significantly, in the first crop of alfalfa , and the decrease of the contents of NDF and ADF in the second crop was more obvious in the early spring than in the early spring. The difference between the contents of NDF and ADF in the third harvest was not significant. In the whole year, the contents of fiber in April 20 treatment was the lowest. The treatment of April 25 had little difference with the treatment of April 20. And difference between two treatments of April 20 and April 25 and treatments of others is significant. 【Conclusion】 Through the comprehensive analysis, in the mollisol area, the alfalfa which has been planted 2 years fertilizer near April 25 has great nutrition quality and annual output, when fertilizer was carried out once a year.

Key words: alfalfa, fertilizing time, production performance, nutritional quality