How to plant napier grass effectively, especially on clay soil? How many kg we can get from 1 m2 napier grass?

Question

I already planted napier grass in 2000 m2 area. Quantity is not even sufficient for 5 no. cattles in a month rotation.

Answer 1

To start with, the amount of moisture available and the soil quality will so greatly influence yield that nobody can answer yield expectations without them. In general this will be true of any plant species.

Most grass species will produce more when interplanted with an appropriate  legume that has been inoculated so that it produces its own nitrogen fertilizer.

Answer 2

How long has it been since you planted it? Napier grass spreads rapidly through rhizomes. Given enough time you should get good coverage, even in a clay soil, unless it is very dry.