The contribution of various organic matter fractions to soil–water interactions and structural stability of an agriculturally cultivated soil

Abstract

The presence and mutual interactions of soil organic matter (SOM) and clay particles are major factors determining soil structural stability. In the scope of agricultural management and environmental sustainability, it remains unclear how various mineral and organic matter (OM) fractions, OM-clay interactions and swelling processes in the interparticle space determine soil-water interactions and thus soil structural stability. To investigate this issue, we isolated the mineral and OM fractions of an agriculturally cultivated silty loam soil by soil density fractionation and assessed their hydration characteristics and effects on soil structural stability combining 1 H-NMR relaxometry, soil rheology and single wet-sieving of soil aggregates. The results showed that agricultural management practices, in particular compost and ploughing, as well as various OM-clay interactions significantly affected soil-water interactions and soil structural stability. On the one hand, ploughing reduced soil structural stability by promoting clay swelling as a result of disrupted soil structures and reduced SOM content. On the other hand, compost treatment and reduced tillage increased soil structural stability. In all cases, soil density fractionation showed that compost-derived particulate organic matter (POM) and mineral-associated organic matter (MAOM) restricted clay swelling and resulted in a highly porous and mechanically stable soil matrix. In particular, POM increased soil structural stability by acting as nucleus for soil aggregation and by restricting clay swelling via its presence as solid, granular interparticulate material. In contrast, MAOM seemed to restrict clay swelling via clay surface covering and the formation of viscous interparticulate hydrogel structures.

Land Tenure Insecurity Constrains Cropping System Investment in the Jordan Valley of the West Bank

“…Generally speaking, the research literature has found that farming households with more secure land tenure status tend to adopt more soil and water conservation land management techniques [25,29,53,54]. In our case study, however, despite the large role played by organic matter inputs in regulating soil organic carbon (SOC) and the critical role SOC plays in water capture and storage [55,56] and soil biological activity and diversity [57,58], sharecroppers appear to invest proportionately much more in chemical fertilizer inputs than manure inputs. Given the extremely arid ecological context and the much larger irrigation water inputs compared to farming households that rent land, this may indicate important sustainability concerns for sharecropping farms and provides an additional example, where enhanced land tenure status may not always lead to the adoption of more sustainable agricultural practices (such as Varble et al, 2016).…”

Synergy between compost and cover crops leads to increased subsurface soil carbon storage

“…biomass in ORG plots at 60-100 cm, it did increase biomass at 0-15 and 15-60 cm depths, attributed to more favorable nutrient stoichiometry for biomass formation (Kirkby et al, 2011;Richardson et al, 2014). Increased surface microbial biomass is an important potential source of C and other nutrients to subsurface layers through cell lysis from predation and wet-dry cycles (Bonkowski, 2004;Xiang et al, 2008) and is associated with increased stabilized carbon storage through microbial necromass formation (Buchmann and Schaumann, 2018;Jilling et al, 2020), contributing to the SOC increase observed in ORG systems (Figure 2b).…”

Inter‐community and on‐farm asymmetric organic matter allocation patterns drive soil fertility gradients in a rural Andean landscape

“…The management of organic matter (OM) plays an important role in the productivity and sustainability of soils, both in terms of providing nutrients for crops as well as the maintenance of soil physical qualities and essential biological processes (Palm, Gachengo, Delve, Cadisch, & Giller, 2001; Wood & Bradford, 2018). Soil organic matter (SOM) is essential for promoting a range of ecosystem functions such as improved soil physical structure (Jensen et al, 2019; Sarker et al, 2018), water capture and storage (álvarez, Carral, Hernández, & Almendros, 2013; Buchmann & Schaumann, 2018), carbon (C) sequestration (Takimoto, Nair, & Nair, 2008), and the maintenance of soil biodiversity and activity (Walmsley & Cerdà, 2017).…”