Although stubble burning is an effective way to deal with crop residue in the short term, the practice is pretty bad for the soil.
For one, you lose the nitrogen in the residue to the air through burning. With all the cattle in India, I would think you could just feed the residue to them, and this says it could make up about 50% of their diet. And you might be able to grab some human edible calories first through the leaf protein concentrate process. There is also cellulosic ethanol or cellulosic sugar, though those are likely not economical now.
Thanks for the suggestions! Anyone who works on this topic in the future should probably investigate them further. My current rough impression is that, even if there were a market for the stubble, the process of baling the stubble for transport and sale would either be time-and-labor intensive or require equipment that the average farmer in the region can’t afford. Because of the nature of the crop cycle, farmers are under intense pressure to clear the stubble quickly, hence the appeal of stubble burning.