To cut the pollution enveloping Delhi and asphyxiating its 20 million people, India's top court has ordered a complete halt to stubble burning. But farmers, who are struggling to make a living, say they have no alternative.

In recent days pollution levels hit their highest point in years as smoke — from farms around the Indian capital — combined with other pollutants to form a noxious mix.

Hospitals saw a rush of patients, schools were closed, construction activity was halted and the authorities claimed they got 1.5 million cars off the roads with an odd-even vehicle registration scheme.

Delhi's chief minister, Arvind Kejriwal — calling the city a "gas chamber" — said his government had played its part, and blamed farmers for burning agricultural residue.

But Satnam Singh, a poor farmer in northern Punjab state, says that he has to clear his field ready for the next crop.

Burning of rice residues after harvest, to quickly prepare the land for wheat planting, around Sangrur, Punjab. Image credit: Wikipedia

"Without burning the stubble, we just cannot sow the wheat in the field," Singh told AFP as clouds of acrid smoke rose up from fields all around.

And even though burning stubble is illegal, enforcement is lax.

Government schemes — such as improving access to machinery that removes the need to burn crop residue — have had little impact.

"All these machinery that people talk about, a regular farmer cannot get these machines. They are very expensive. Which farmer can afford that?" said Singh.

This was echoed by Kabal Singh, another farmer in the same region.

"The farmer has no other option but to burn the crop to prepare the land," he told AFP.

"Farmers don’t know how to diversify the crops on their own. Government has to advise us. If they say these areas should grow maize or these areas should grow Basmati rice, then we can follow that," he said.