Since cotton was a major crop on farm land, if the price of cotton increased, the price of farm land would also increase. This would increase the demand for farm land and shift it to the right. Would the supply curve of farm land also increase because more individuals would want to sell their land? Or would just the demand of farm land would shift to the right?
This is more an economics question than a history one. The supply curve represents the relationship between supply and price, not the absolute value of supply.
If more people sell their land because of the increased price, it doesn't mean that the relationship change. But if more people want to sell their land with the same price (e.g. when people become afraid that price will crash in the future), then you can say that the supply curve "shifts to the right".
Illustration: see the curve below. There is more supply at B than A, but B and A are within the same curve.
Yes cotton demand did make some farmland more valuable, but not all farmland.
In 1781 cotton spun amounted to 5.1 million pounds, which increased to 56 million pounds by 1800. In 1800 less than 0.1% of world cotton cloth was produced on machinery invented in Britain. In 1788 there were 50,000 spindles in Britain, rising to 7 million over the next 30 years.
The price of cotton did increase during the industrial revolution. Demand dramatically increased and this fueled the dramatic increase in cotton as a cash crop. It wasn't just farm land which would be necessary to supply the ever increasing demands of the automated looms of the early industrial revolution. It was farmlands with proximity to ports and roads so the cotton could be transported. This meant that centralized production had a huge advantages over smaller farmers. It was the large farms which mass produced farm goods which filled most of the demand for cotton. Those institutions which massed produced farm goods at the dawn of the industrial revolution were known as Plantations.
Prominent plantation crops included rubber, sugar cane, tobacco, figs, rice, kapok, sisal, and Indigofera, used to produce indigo dye. The demand for cotton would become one of the plantations greatest cash crops.
Yes cotton demand did make some farmland more valuable, but not all farmland. Just the large aristocratic farmers who were in a position to export cotton on the large scale that was required to meet demand.