title: Characterisation of soils under long-term crop cultivation without fertilisers: a case study in Japan.
abstract: Certain farms in Japan, namely unfertilised farms (UFs), have been able to maintain high productivity for over 40 years without applying fertilisers or composts. This study aimed to characterise the physicochemical, biological and micromorphological properties of soil in UFs compared with control farms in Eniwa and Nariita and to identify characteristics that are associated with crop productivity. In UFs, no plough pan was observed. The thickness of the effective soil depth (ESD) of UFs was greater than that of CFs. The concentrations of soil organic carbon, total nitrogen and nitrate-nitrogen in ESD of UFs were higher than those in ESD of CFs. Soil microstructure observations indicated the strong development of a granular microstructure with large amounts of void space and a high fractal dimension in both surface and subsoil horizons of UFs. Dry yield had a strong correlation with ESD thickness and fractal dimension of voids. Thus, the management of unfertilised cultivation promoted the development of soil aggregation in both A and B horizons. The increase in ESD, soil pore spaces and complexity with the development of subsoil structure improved the productivity of unfertilised cultivation.
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan.
authors.forename: Hiroko
authors.identifier: 0000-0001-6990-5658
authors.initials: H
authors.lastname: Nakatsuka
authors.affiliation: Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Tamura
keywords: Andosols; Fractal dimension; Micromorphology; Organic farming; Physicochemical properties; Soil; Unfertilised farming system