Carbon Sequestration Strategies in Response to Fertilizer Application

Carbon (C) sequestration in agricultural soils requires the application of organic matter to maintain crop yields and offset greenhouse gas (GHG) emissions. This chapter reviewed net ecosystem C balance (NECB), net GHG balance (NGB), and the factors controlling GHG in soils. In addition to net primary production (NPP) and microbial decomposition (Rh), NECB is mainly composed of organic matter supply and harvesting as C input and output, respectively. As for NGB, nitrous oxide (N2O) and methane (CH4) emissions are added to NECB. Fertilization increases crop production but also tends to increase Rh and N2O emissions. Soil temperature and soil moisture are significant factors controlling N2O emissions. In order to offset negative NGB, the input of organic matter to the soil is indispensable. This amount was estimated to be 3.5 t C ha−1 y−1 as the amount of C input from manure in Japanese managed grassland. In this case, it corresponds to an increase in soil organic C of 6 to 12 per mille in the top 30 cm soil. N2O emissions are greatly reduced by continuous use of organic fertilizer compared to inorganic fertilizer. It is increasingly important to consider soil management with organic fertilizers that reduce chemical fertilizers without reducing yields.