Nano and micro manure amendments decrease degree of phosphorus saturation and colloidal phosphorus release from...

The manure fertilizer increases the phosphorus (P) saturation of soils and the colloidal P release to water bodies. Manure of different particle-sizes may have different effects on colloidal P release by soil, and to date there is limited knowledge on colloidal P release from soils amended with different size manures. We produced sheep micro- (S_Micro) and nano-manure (S_Nano), and poultry micro- (P_Micro), nano-manure (P_Nano) from bulk samples by wet fractionation method. The fractionation reduced the P contents of micro- and nano-manures, and enriched them in ash and calcium, iron (Fe), magnesium, and aluminum (Al) phosphate minerals compared with the bulk manures. The degree of P saturation (DPS) in Anthorsol and Cambisol was decreased (S_Micro, 17.6 and 17.2 %; S_Nano, 14.5 and 13.3 % and P_Micro, 19.0 and 19.7 mg kg^-1; P_Nano, 17.0 and 14.3 mg kg^-1) and released less colloidal P (S_Micro, 3.12 and 3.78 mg kg^-1; S_Nano, 3.01 and 3.56 mg kg^-1 and P_Micro, 3.34 and 3.92 mg kg^-1; P_Nano, 3.21 and 3.65 mg kg^-1) than the soils receiving the bulk manures. The decrease in colloidal P was correlated with less DPS in both soils amended with micro and nano manures. That is, the only measurable effect of manure particle size on colloidal P release from the amended soils was due to chemical fractionation during separation of the size fractions. It was suggested that nano and micro manures were the effective approach to reduce colloidal P release from manure amended soils.