Normally, futures price tend to quote at a premium to the commodity spot price. In technical parlance that is called the cost of carry. When you buy cotton futures deliverable at a future date, there is additional cost in terms of blocking funds and storage costs that the seller has to incur. That goes into the calculation of the cost of carry. There are also other reasons for the gap. When there is heavy selling in the futures due to speculative reasons, it is likely that the futures price goes below the spot price. Similarly, when there is too much speculative buying interest in the commodity futures, it tends to widen the carry. Normally, when the carry widens, arbitrageurs enter the market and iron out these spreads.