The Relationship Between Organic Carbon and Ca in the Profile of Luvisols: A Case Study of a Long-Term Experiment in Pulawy, Poland

The aim of this study was to determine the impact of multi-year variations in nitrogen fertilisation (N) and farmyard manure application (FYM) in two 4-year crop rotations, A and B—which differed primarily in terms of their organic matter management systems (A: poor vs. B: enrichment)—on changes in the content of calcium and soil organic carbon at three soil horizons of Luvisols, and on the dynamics of these changes over the past 40 years. Mineral N fertilisation was found to affect the movement of Ca in the profiles of both rotations. Most Ca accumulated in the soil layer at >55 cm in the profiles of both rotations. The total Ca content was similar in both rotations; however, a correlation analysis revealed a stronger relationship between organic carbon and Ca in the enriched-cropping system (rotation B) compared to the poor-organic-matter system (rotation A). In the 0–30 cm soil layer, the correlation coefficient between organic carbon and Ca was r = 0.52 in rotation B, while in rotation A, it was lower at r = 0.23. In deeper layers, this relationship weakened or became non-significant. Under the climatic and soil conditions of Poland, where the phenomenon of nutrient leaching into the soil profile is prevalent, it is extremely important to manage these nutrients in a sustainable way in order to limit their loss. The predominantly sandy texture of the topsoil horizons (0–30 cm) of the Luvisols prevents any significant enrichment of these horizons in Corg, even over a very long period of time, i.e., more than 40 years.