Changes in organic carbon content and its physical and chemical distribution in paddy soils cultivated under different fertilisation practices

摘要

Purpose Chemical protection facilitates soil organic carbon (SOC) sequestration and stabilisation due to a strong chemical binding with mineral surfaces and metal ions (e.g. iron [Fe], aluminium [Al] and calcium [Ca]). However, there is not much information regarding the role of chemical protection in SOC stabilisation in paddy soils, particularly in terms of the specific forms of organo-mineral complexes such as Fe-, Al- and Ca-bonded OC. Materials and methods We sampled paddy soils at the 0-20 cm soil layer from a long-term field experiment (initiated in 1981) conducted under humid subtropical conditions in China, which has five fertilisation treatments (i.e. control treatment without fertiliser [CK], chemical fertiliser only [CF], green manure [GM], Straw and Manure) with equivalent nutrient inputs (i.e. N, P2O5 and K2O at the rates of 135-67.5-135 kg ha(-1), respectively, for both early and late rice) except CK. We determined the chemical binding forms of SOC and the associated soil properties in the particulate fraction (PF, > 53 mu m) and the mineral-associated fraction (MAF, < 53 mu m), which were obtained using a low-energy ultrasonic dispersion procedure, of a paddy soil in the long-term fertilisation experiment.