Legacy effects of a 100‐year potato monoculture on soil characteristics at the Skierniewice experimental station

Abstract

Long‐term field experiments offer rare opportunities to assess how sustained fertilization strategies influence soil functioning over decades. Long‐term potato (Solanum tuberosum L.) monoculture on sandy soils is an extreme test of soil system resilience to crop and fertilization pressure. In a unique 100‐year field experiment on sandy soil in east‐central Poland, we evaluated the effects of four fertilization systems (limed control [Ca], mineral [CaNPK], organic [Ca+M], and mineral–organic (CaNPK+M) on total organic carbon (TOC) content and stocks, basic physicochemical properties, and nutrient availability. After 100 years, all treatments showed a substantial decline in TOC (from 46% to 63% relative to 1930), with the highest loss rate under mineral fertilization and the lowest in manured soils. Manure reduced carbon losses, increased TOC and total nitrogen, and lowered bulk density as compared to other treatments. Cation exchange capacity (CEC) remained low (<5.67 cmol _c kg ⁻¹ ) but was significantly higher in manured soils. Mineral fertilization decreased CEC and increased the contribution of hydrolytic acidity compared to the control treatment. Phosphorus availability was high in all treatments, especially in manure‐based systems, whereas available potassium content was low. Soil electrical conductivity was also low, with no salinity risk. Long‐term mineral and organic fertilization did not cause exceedances of heavy metal and As levels relative to national permissible limits for agricultural soils. Overall, the results show that on sandy soils, organic and inorganic fertilization cannot compensate for the long‐term degrading impact of potato monoculture on soil organic matter.