I think the water allocation is the key . It's not necessarily bound to a particular location . A lot of that had been bought up even before the Chinese got interested .
Otherwise , buying agricultural land is pretty speculative imo. Also , well out of reach of the smaller property investor.
The returns are ordinary at best so you are purely punting on capital growth .
You are right about land shortage though and that is the underlying fundamental of property investment . Supply vs demand .
The irony is that we are building houses around Australia on some of our most productive agricultural land .