Fig. 2. Soil surface CO2 flux measured in continuous maize for the P2 (86400–98800 plants ha–1) plant population at the two fertility treatments (M1 = recommended best management; M2 = intensive) and in the unfertilized control at the P3 (108700–116100 plants ha–1) plant population during the 27-mo study. Also shown is soil temperature at the 0.1-m depth and water-filled pore space in the top 0.1 m of soil.