But those whose business involves buying or selling physical grains and oilseeds are aware that the cash price in their own local area, or what their supplier quotes for a given commodity, usually differs from the price that is quoted in the futures market.
Basis can be either positive or negative. A negative basis is referred to as being under, in other words, the cash price is under the futures price. A positive basis is referred to as being over, the cash price is over the futures price.
long hedgers benefit from a weakening basis
The farmer is left with basis risk. In the context of commodity futures trading, basis refers to the difference between the spot price of a commodity and the price of a futures contract for that same commodity. Basis risk is usually smaller than outright price risk.
Shorting the differential between the physical and futures price involves betting that the spread (or difference) between the two prices will decrease over time.
Shorting the differential involves selling the higher-priced asset and buying the lower-priced asset, anticipating that the gap between the two prices will narrow over time.
In a contango market (futures price > physical price): You short the futures (sell the futures contract) and buy the physical (buy the commodity now). If the futures price decreases or the physical price increases, the differential narrows, and you profit.
In a backwardation market (futures price < physical price): You buy the futures and short the physical (sell the commodity you already hold or borrow to sell). If the futures price rises or the physical price falls, the differential narrows, and you profit.
* the hedger’s basis is a reflection of his local cash market relative to the global benchmark futures market
https://www.lme.com/Market-data/Accessing-market-data/Historical-data