Question

why should seed be sown in moist soil

Answer 1

So seeds are sown in soil so that it get sunlight as well as moisture from soil. After germination and after some growth it absorbs nutrients and water from soil and in the presence of sunlight it makes its own food. After many years it becomes a big tree,its roots grow inside soil in the direction of water.

Answer 2

so that it can get air water sunlight in proper amount