On the evening of 7 November, a deep fog settled along the stretch of 250 kilometres between Sirsa and Gurgaon in Haryana. By ten in the night, it was thick enough to make travel almost impossible. In places, visibility shrank to not more than five metres. State transport buses cut their trips short. Cars, trucks and buses which kept moving towards Delhi did so cautiously, taking as long as six hours to cover a distance of 150 kilometres.

That night, the consensus among drivers and locals was that the fog was not natural but man-made. Not only does this part of India have several industrial units and power plants, in the months of October and November, farmers in Punjab burn fields to clear the crop stubble left after their kharif harvest. A sudden nip in the air that evening appeared to have trapped the emissions from both industry and burning fields close to the earth.

The fog underscored just how poorly India's pollution problem is understood. While the worsening of Delhi's air during the winter gets some attention, there is barely any acknowledgement that the blanket of chemical soup extends all the way till Punjab, and perhaps to the south of Delhi too.

There is also little understanding of what's needed to tackle the problem.

In the run up to the winter, Delhi chief minister Arvind Kejriwal asked Punjab government to ensure farmers did not burn their fields. A better alternative, he said, would be to plough the stalks back into the earth where they can decompose into humus.

But on the ground, things aren't as simple.

Earlier that afternoon, travelling from Faridkot to Sirsa, I spoke to a farmer setting his fields afire. He knew about the pollution caused by crop burning. He knew Delhi had asked Punjab to stop the practice. But he said he had no option but to burn his crop stubble.

Over the years, the profitability of Punjab agriculture has fallen. The farmer, who did not want to disclose his name, told me he cultivated the fields as a sharecropper. He leased the land annually from a larger farmer for Rs 40,000 per acre. He spent another Rs 15,000 per acre on cultivating the basmati rice crop. However, with basmati prices staying low this year, he made just Rs 30,000 per acre. This leaves him with Rs 25,000 still pending per acre and further investments to be made for planting the wheat crop.

Given the economics, he said he could not spare the Rs 5,000 per acre it would cost to rent a tractor and plough the stubble into the earth. And it wasn't just about the money, he added. "It is not enough to just plough in the stubble. We will have to water the field so that it decomposes. Which means we have to also wait a month before sowing the next crop."

There are other solutions, of course. It is possible to make the crop stubble economically useful as fuel for electricity generation. A few power plants that use the stubble are functioning in Punjab but more are needed.

There is also a need to improve the economics of agriculture and, needless to say, to ensure better compliance from industry as far as its emissions go.

Without a better understanding of why farmers burn their fields, all we will have are meaningless diktats which don't get followed. And a fog that will not go away.