Carbon dioxide from wheat crops

Despite the absorption of carbon dioxide into vegetation by photosynthesis during crop growth, a surprising quantity of carbon dioxide is actually liberated into the atmosphere by a wheat crop (1). The net annual emission may be of the order of 2 tonnes/hectare. It comes chiefly from the reduction of carbon in the soil, respiration of crop residues, tractor fuel, and perhaps burning of the stubble. (The burning of stubble helps control disease.) Another greenhouse gas, nitrogen oxide (N₂O) is released by any applied fertilizer.

(1) Howden, S.M. and G.J. O’Leary, 1997. Evaluating options to reduce greenhouse gas emissions from an Australian temperate wheat cropping system. Environ. Modelling & Software, 12, 169-76.