A study which looked at how farm practices affect nitrous oxide levels has found it depends on the crops. Nitrous oxide is a potent greenhouse gas.

Expressing emissions per unit of crop yield rather than on a more conventional per area basis produced very different results, says the study’s leader.

When the study looked at how much was gas emitted compared to yield of grain, it found not tilling the field reduced emissions. Tilling or not tilling didn’t make much difference when the study looked at emissions per area of field.