The ratio is depends on the soil locally. So it is better for you to take some photo of your soil, and tell us the slope angle, height, soil condition, etc. then we will recommend you a suitable ratio.
For example, in Zhengzhou city. Our slope soil is usually sandy soil, the ratio of water,soil, rice husk is 1:1.5-2.5:1, if soil is clay, it need to reduce the ratio of soil. 6m3 tank need add water-preserving agent and adhesive 0.5-3kg per tank, grass seed will add 20-30kg per tank.