Dynamic changes of different soluble humus zinc in chicken manure

Chicken manures added with Cu and Zn were used for composting experiment to study the changes of humus complexed zinc（humus-zinc）extracted by H2O, NaOH and NaOH-Na4P2O7 mixture (expressed as H2O-Zn，NaOH-Zn and NaOH-Na4P2O7-Zn), respectively. The effect of copper in compost on humus-zinc and the relationship between humus-zinc and available Zn were also revealed. H2O-Zn of raw manure accounted for 0.74% of total Zinc of the compost, and decreased with the manure composting. With the increase of adding zinc (Cu/Zn was 1: 1, 1: 2 and 1: 3), H2O-Zn increased correspondingly, and decreased with the process of decomposition. The average percentages of H2O-Zn to total Zinc of the treatment of 1: 1, 1: 2 and 1: 3 were lower than that of the control (raw materials). H2O-Zn was increased with the increase of copper content. NaOH-Zn accounted for 62.41% of total Zn of the raw manure and decreased dramatically with the compost proceeding. With the increase of adding Zn, NaOH-Zn increased, but decreased with decomposing process. During decomposition, the added copper increased the content of NaOH-Zn. NaOH-Na4P2O7-Zn accounted for 13.59% of total copper of the raw manure, which increased with time of composting. With the added Zn content increasing in compost manure, the percentage of NaOH-Na4P2O7-Zn to total Zn changed slightly. The added copper had no significant effect on NaOH-Na4P2O7-Zn. Before composting, of all humus–zinc extracted by H2O, NaOH and NaOH-Na4P2O7 , respectively, 50%–85% of extracted humus–Zn was present in NaOH fraction, 10%–50% in NaOH-Na4P2O7 fraction, and 0–5% in H2O fraction. After composting, 6%–41% of extracted humus–zinc was present in NaOH fraction, 58%–92% in NaOH-Na4P2O7 fraction, and 0–2% in H2O fraction. With the added zinc contents increasing, the distribution percent of NaOH-Na4P2O7-Zn (Pressed as percent of extracted Zn) decreased. H2O-Zn，NaOH-Zn, and DTPA-Zn were positively correlated to each other and all were negatively correlated to NaOH-Na4P2O7-Zn. (P≤0.01).