The Yield And Quality Effect And The Mechanism Of Fertilization To Two Rotation Pasture

Pasture is the feed of livestock and the foundation of the livestock farming. Ryegrass (Gramineae Lolium) and Sudangrass(Gramineae Sorghum) are two broadly cultivated pasture. Former report has studied the nutrient requirement characteristics of the two grasses and the proper fertilization dosage with detailed information of NPK proportion.In this thesis, using rotation G. Lolium and G. Sorghum as a model system, several different ratios of organic fertilizer to normal NPK fertilizer and different dosage have been tried to improve the yield and quality of the two grasses. The thesis also elucidated the function of N, P, K respectively in the yield and quality improving progress. The main results of the thesis:1. The yield and quality of the G. Lolium and G. Sorghum could be improved if the fertilizer is properly applied. In the experimental controlled field, the limiting factor is N rather than P, K. The fresh grass production is boosted along with the N increasing. In the control without N, the growth of the grasses is severely restricted. Applying P in the NK base fertilizer and applying K in the NP base fertilizer could also improve the yield somehow but not as sharp as N. The applying of N could raise the crude protein of the grasses, which is demonstrated in two periods of crop-rotation.2. The mixture use of NPK fertilizer could promote the growth and nutrition absorption of the grasses tested. The use of N increased the N absorption and the plant height of the two grasses. The P have similar but compromised effect as P. K has nearly no effect on the plant height and nutrition absorption.3. Applying N could raise the amount of chlorophyll in the ryegrass leaves and then the net photosynthetic rate, resulting in the higher resistance to cold pressure in winter.4. After 3 year observation, no matter whether the plants are fertilized, the soil pH has the tendency of decreasing, while the fertilized soil would decrease more slowly. As to the soil organic matter, in all the treatments, including fertilized and non-fertilized soil, the soil organic matter raises after the grasses planted , but more rapidly in fertilized soil.5. The growth and nutrition dynamic change of Sudangrass: the Sudangrass has the highest growth and accumulation rate during June to mid July and mid August to the beginning of September. During July to mid August, the Sudangrass grows slowly because of the higher temperature and less rain. After the beginning September, as the weather condition changed, the Sudangrass enters the end of growth season and would grow slowly. So it's of no necessity for top dressing, there are no significant differences between the after and non top dressing treatments at that time.