The Role of Soil Organic Matter for Maintaining Crop Yields: Evidence for a Renewed Conceptual Basis

Soil organic matter content and crop yield

“…Bauer and Black (1992) attributed the decline in productivity of degraded soils to decline in nutrients. Schjønning et al (2018) reported a positive effect of SOM on reduction of mineral N needed to obtain the potential crop yield and concluded that SOM does add to crop production other than what can be attributed to nutrient supply capacity.…”

“…Thus, a critical threshold can be highly soil/site specific and depends on a range of inherent and managerial factors. Sustainable management of SOM content also has benefits toward saving/replacement of N and other fertilizers (Schjønning et al 2018;Hijbeek et al 2018), along with saving of some irrigation water (Williams et al 2016;Ankenbauer and Loheide II 2017).…”

Crop yield after 5 decades of contrasting residue management

“…For example, the recent meta-analysis by Hijbeek et al (2017) highlighted and ordered the positive effects of organic input on crop yields as supplying nutrients to cereals first, and beyond that to some root and tuber crops second. Even though positive results are more frequently reported for cereals (maize or wheat) (Monreal et al 1997;Wei et al 2016;Hijbeek et al 2017;Schjønning et al 2018) than for root or tuber crops (potato or sugar beet) (Hijbeek et al 2017), Schjønning et al (2018) did report a negative, nonnutritional effect from organic input in wheat.…”

“…Long-term soil management with different organic inputs (e.g., crop residues and poultry manure) was shown to increase crop yields beyond the background variation caused by crop type and seasonal climate conditions. Despite the widely-held view that organic inputs enhance crop yields (e.g., Monreal et al 1997;Pituello et al 2016;Wei et al 2016;Hijbeek et al 2017;Schjønning et al 2018), the nature of their mutually beneficial relationship is still a matter for debate. Indeed, it is difficult to assert that yields rise due to improved soil conditions or vice versa.…”

Rights-of-Soil

“…Among a wide range of soil properties (i.e., physical, chemical, biological, and ecological; figure 2), protecting, restoring, and sustaining SOC stock is critical because of its numerous ecosystem services (Schjønning et al 2018). It is essential that soil's selfregulating capacity or resiliency is protected and enhanced to strengthen the provisioning of goods and services (figure 3).…”