Oh! I guess BHP doesn't to long-range economic analysis and planning, just plays the spot potash market. Get a grip and read the announcement (part below). By the time this plant is up and running, demand will also be up and running for a long time. BHP shares are a long-range investment. Note that this mine will have a fifty year life. It takes time (an a lot of money) to get a profitable, long-term asset like this on line. A company wouldn't do it it it didn't have the numbers to justify it.
"BHP Billiton is investing US$2.6 billion to finish the excavation and lining of the Jansen Potash project production and service shafts, and to continue the installation of essential surface infrastructure and utilities. This investment will be spread over a number of years, with completion of both shafts expected during the 2016 calendar year, while the associated works program will extend into the 2017 calendar year.
The longer term outlook for potash, a fertiliser that improves the yield and quality of agricultural production, is strong. As the world’s population grows and incomes in emerging economies improve, agricultural demand is expected to rise. This will increase the need for potash and require the construction of new mines. Our projections assume a shift away from the current marketing dynamic and we believe the potash price will ultimately reflect the cost of adding new supply.
"Jansen is the world’s best undeveloped potash resource and is capable of supporting a mine with annual capacity of ten million tonnes for more than 50 years. With economies of scale and the use of modern mining techniques, Jansen is likely to be one of the lowest cost sources of supply once fully developed. The successful excavation and lining of both shafts will substantially reduce development risk and allow the company to time first production to meet growth in market demand."