Hi,
At first, prefer use DNS instead of IP address : that's better :)
You look like to have not configure the agent : if you put the server's address in the configuration file, there is no need to force the inventory by command line. You just need to call ocsinventory-agent and nothing more.
Attention, in the crontab, you have no path : use the full path to call ocsinventory-agent (command whereis to get it).