What is the distribution of global photosynthesis?
You are perhaps looking for primary production.

That is a measure for the total amount of biomass produced. Primary production is measured in two different ways, gross primary production, that is simply everything produced by the photosynthesis, and net primary production, that is the same, except for that the amount consumed by the plants is subtracted.

The estimates are about 115 gigatons of carbon per year of net production on land, and 55 gigatons of carbon per year for the ocean.


Roughly $\frac{2}{3}$ on land and $\frac{1}{3}$ in the ocean.

Cultivated land contributes to about 9% of the net production on land.
Read more about that here.

Below is the annual average of the net productivity of vegetation on land and in the ocean during 2002 (from http://science.nasa.gov/earth-science/oceanography/living-ocean/remote-sensing/ )