Rice straw is the main source of organic C inputs in the paddy
fields and is often attributed to the increase in SOC concentration
after returning to paddyfields (Pan et al., 2004; Ji et al., 2012; Liu
et al., 2012). Rice straw is often incorporated to different soil depth
by using different powered machines (Liu et al., 2012), resulting in
a larger amount of rice straw incorporated to the shallow plough
layer.