The paper presents a model of investment risk associated with projects that promote primary production, such as plantations, forests, aquaculture and agribusiness generally, commonly through managed investment schemes (MISs) set up as businesses. An analysis of business failures leads to a finite probability that the investor will lose money. The attractiveness of the investment is further diminished because of the uncertainty in the downstream return on investment and time of the return. Based on probabilistic arguments, the paper presents a robust model and method on which to make investment decisions. The approach is practical and will be useful to people interested in managed agribusiness investments. The approach is significant in that it quantifies what heretofore was largely undertaken qualitatively.