Study On Yield And In Vitro Digestibility Of Italian Ryegrass Affected By Fertilization And Mowing In South Of Guizhou

By use of winter fallow field, there are more than 10 million hm² planting area of annual ryegrass in Guizhou Province, which produced great ecological, social and economic benefits, however, there are more than 50 million hm² idle winter fallow field in Guizhou Province. So its necessary to carry out studying on rice-annual ryegrass crop rotation system. In this study, annual Ryegrass named diamond T was selected and a series of research including fertilization and cutting were carried out. Effects of N, P, K fertilizer ratio and different cutting treatments on yield, nutritional components and in vitro digestion of annual ryegrass were quantitative analyzed, aiming to provide practical operational guidance for production. The main results showed as follows:1. Effects of N, P, K fertilizer ratio on yield of annual ryegrass under paddy crop rotation systemThe result of fertilizer application study on ryegrass showed that the optimum fertilizer composition out of 16 different combinations was 1300kg/hm² of N, 650kg/hm² of P and 650kg/hm² of K. With the optimum fertilizer composition, the annual ryegrass displayed the stronggest regeneration ability, higest fresh yield of 105750kg/hm² and hay yield of 28900kg/hm². According to the equation of linear regression Y=5440.59 +52.35X₁ +4.19X₂-5.657X₃, R²=0.706, when the fertilizer compositon as 130g/m² of N, 120g/m²of P, and 0g/m² of K, the annual ryegrass could reach the highest fresh yield of 12.75kg/m²2. Effects of mowing on the yield of annual ryegrassThe result of mowing test shows: All of the 16 mowing treatments, the cutting height was better to be about 30-40cm. and the stubble height should be 6-8cm, or the cutting height was 40-50cm and stubble height was 4-6cm. Their corresponding fresh yield and hay yield were 81225kg/hm² and 74525kg/hm²,18325kg/hm²and 17075kg/hm² respectively. So lower height and higher stubble is helpful to yield increase of annual ryegrass.3. Effects of mowing on the nutritional components of annual ryegrassAccording to the experimental results, when the mowing height was 30-40 cm, and the stubble height was 6-8cm, the annual ryegrass possessed higer crude protein content and lower crude fiber content than the other 15 treatments. The crude protein ranged from 10.35% to 17.92% with an average of 15.83%, and the crude fiber content was 19.72%-38.86%,with an average of 27.88%.4. Effects of mowing on in vitro digestibility of annual ryegrassIn all of the 16 experimental plots, the No.1 plots showed the highest in vitro digestibility of 73.68%, this means that as for in vitro digestibility of annual ryegrass, the best mowing way was 30-40 cm mowing height and 0-2cm stubble height. The No. 2 plot also had relatively high in vitro digestibility of 73.26%, and its mowing height was 30-40 cm, stubble height was 2-4cm. Based on the equation of linear regression, lower stubble height of annual ryegrass corresponding to higher in vitro digestibility.5. Effects of mowing on in vitro digestion amount of annual ryegrassAs for the in vitro digestion amount, the better mowing way were 30-40cm mowing height and 6-8cm stubble height with a in vitro digestion amount of 10829.94kg/hm², and mowing height was 40-50 cm, stubble height was 4-6cm with a in vitro digestion amount of 11276.02kg/hm². From the in vitro digestion amount and yield linear equations y=467.66+0.097x₁+6.77x₂, R²=0.775, we could draw a conclusion that in vitro digestion was concupositive correlation with yield.6. The best cultivation and management model for rice-annual ryegrass rotation systemCompared by tests of fertilization and mowing, we summarized a set of best cultivation and management model for rice-annual ryegrass rotation system in Southern Guizhou. The optimum fertilizer composition for high yield of annual ryegrass was 130g/m² of N, 120g/m² of P, and 0g/m² of K; The best mowing way as following: the cutting height was better to be about 30-40 cm, and the stubble height should be 6-8cm. According to the above mowing treatment, the annual ryegrass showed the higher in vitro digestion amount and crude protein content, but lower crude fiber content than the other treatment.