The Dependence of Cereal Yields on Soil Organic Carbon in Concert With Other Soil Properties and Management

ABSTRACT Maintaining or even enhancing the productivity of arable soils is essential for ensuring food security, in addition to meeting feed and fibre needs. Relationships between yield, soil properties and management are complex and vary between environments; therefore, site‐specific knowledge of yield‐governing factors is needed to close any potential yield gaps. Soil organic carbon content (SOC) is a potential key factor in soil fertility management due to its manifold influence on soil functions. This study assessed the association of spring cereal yield with SOC and other soil properties as well as management practices in boreal mineral soils. Linear mixed‐effects models were applied on a data set collected from 43 field sites in Finland varying in production potential with special interest in yield response to soil C content. Soil data comprised soil texture and total C content, plant‐available nutrient concentrations, pH and cation exchange capacity. Management data consisted of information on the use of fertilisers and liming, crop rotation, method of tillage, plant protection measures and water regime. Many of the soil properties were intercorrelated, and the most appropriate model variables were selected after tentative examinations. The resulting model showed a significant positive yield response of 342 ± 100 kg ha −1 per 1 percentage point increase in SOC. Soil clay content had a negative effect on yield, with a decrease of 33.9 ± 15.7 kg ha −1 per percentage point increment when the proportion of clay exceeded 40%. In addition, nitrogen (N) fertiliser rate, which showed a positive connection with other management efforts, significantly affected cereal yields (56.6 ± 9.7 kg ha −1 yield increase per kilogram of N applied) for spring varieties of barley, oats and wheat. Liming and use of fungicides also had a clear positive effect on yields. The results indicate that even in boreal mineral soils with a relatively large range of SOC content (range 1.3%–9.1% in present study), high SOC has a positive effect on yield. Furthermore, SOC is especially beneficial in soils with > 40% clay content where it can alleviate the negative yield effects of high clay content. The results underline that sustaining SOC reserves in the northern soils is vital for maintaining soil productivity apart from its importance for mitigating climate change.