If your goal is merely to pull CO2 out of the air, that would be the way to go. But that is not their goal; they want to increase agricultural yields to reduce

If your goal is merely to pull CO2 out of the air, that would be the way to go. But that is not their goal; they want to increase agricultural yields to reduce the need for expansion of agricultural land. Pulling CO2 out of the atmosphere is a side-benefit.