It is the rate of producing organic matter (food) by producers.
It is the process of breaking down of complex organic matter or biomass
from the body of dead plants and animals with the help of decomposers
into organic raw material such as CO2,
and other nutrients.
It depends on the photosynthetic capacity of the producers.
It occurs with the help of decomposers.
Sunlight is required by plants for primary production.
Sunlight is not required for decomposition by decomposers