Effect of organic farming on a Stagnic Luvisol soil physical quality

Abstract The organic farming system is reported as having an influence on soil chemical, biological and physical features. The objectives of this study were to examine the physical quality of Stagnic Luvisol soil subject to organic and conventional farming with crop rotations that included root crops and legumes. The experiment was established in 2008 as a split-plot randomised block design to examine the effects of these farming systems, i.e. conventional (CFS) and organic (OFS), and the sub-plot treatment of the crop species in the following crop rotation: potatoes, winter wheat, oats/common vetch mixture and winter spelt wheat. Undisturbed soil samples were collected in 2014 to determine the water retention parameters and morphometric characterization of soil pores. The soil moisture characteristic curve was determined in pressure chambers with ceramic plates. The macropore system for the investigated soil was characterised using image analysis on sections of soil samples hardened with polyester resin. With OFS treatment, significantly higher values for the soil bulk density were recorded than with CFS. The bulk density was also affected by crop species. Higher values were characterised for winter wheat and oat/vetch mixture than for potatoes and spelt. The highest porosities in terms of transmission pores and fissures were noted for potatoes cultivated in the CFS system, whereas with CFS the soil under winter wheat was characterised by the lowest contribution of large pores. The highest water retention in terms of PWC (productive water retention) and AWC (available water retention) was obtained for the CFS system. Organic farming resulted in lower macroporosity, 0.65% on average, whereas with conventional farming this was 0.82%. These differences were more pronounced in terms of small pores with diameters 50–100 μm. For different crops, the level of macroporosity significantly changed. Soil housing potatoes and spelt was characterised by a higher macropore volume, in the diameter ranges 50–1000 μm. The farming systems applied significantly changed all tested plant biomass production. The highest grain and potato tuber yields were characterised for CFS. However, the highest root biomass crop species produced in the OFS treatment than in the CFS.