Evidence-Based Review on Soil Properties Limiting Crop Yields in Sweden – A Study using Soil Inventory Data and Long-Term Soil Fertility Experiments

Soil inventory data and yield statistics representing ninety national yield survey districts, and experimental data from ten Swedish long-term soil fertility experiments, were evaluated with the aim of identifying the most yield-limiting soil properties. The same soil variables influencing crop yields were identified in the national and experimental datasets, where it was significantly affected by ammonium-acetate extractable plant-available soil phosphorus, soil organic matter (SOM) and soil pH. Concentrations of plant-available potassium and magnesium in soil had no significant impact on yield, except in potatoes. Soil pH was found to have the greatest potential to affect crop yields, even at values higher than 6.5 (pH(H₂O)) for most crops. Surprisingly, increasing SOM content reduced yields, probably due to lower pH in soils that are richer in SOM.

In order to fully exploit the known benefits of SOM, liming requires more attention. The demand for plant-available soil P by high-yielding crops has increased since the 1990s, now ranging from 60-100 mg kg^-1 soil. Furthermore, yields increased significantly with a pH of up to 7.0. Consequently, current Swedish recommendations require updating, with new target values for both plant-available soil P and soil pH.