|Main authors:||Abdallah Alaoui, Ursula Gämperli Krauer, Tatenda Lemann, Vincent Roth, Gudrun Schwilch & iSQAPER Case Study Site teams|
|iSQAPERiS editor:||Jane Brandt|
|Source document:||Alaoui, A., Gämperli Krauer, U., Lemann, T., Roth, V., Schwilch, G. & iSQAPER Case Study Site teams (2018) Soil quality inventory of case study sites. iSQAPER Project Deliverable 5.2, 23 pp|
Agricultural soils are under a wide variety of pressures, including from increasing global demand for food associated with population growth, changing diets, land degradation and associated productivity reductions, potentially exacerbated by climate change impact (Rogger et al., 2017). Restoring the ecological functions and productivity as well as regulation services of a soil, and preventing further degradation can be achieved with appropriate management practices. These practices may reduce the potential negative impacts of extensive monocultures and the use of heavy machinery operations, since they are highly adaptable to the specific conditions where they are applied (e.g., Sarker et al. 2018). Over the last decade, there has been increasing interest on the impact of agricultural management practices on soil organic carbon (SOC), nutrient cycling and storage worldwide (Dalal et al., 2011; Hoyle and Murphy, 2011; Hoyle et al., 2013; Kopittke et al., 2016). The nutrient contents of soil may be maintained or enhanced by appropriate management practices, favoured by additional organic matter inputs or retention into the system. Management practices such as (i) long-term no-till with stubble retention, along with fertilisation in cropping systems, and (ii) mixed crop–pasture and perennial pasture dominated farming systems, are usually recommended to increase or maintain soil organic matter (SOM) and associated nutrients (Dalal et al., 2011; Hoyle et al., 2013). SOM has been considered a ready source of plant available N, P and S, although its mineralization and nutrient release are enhanced by tillage and stubble retention, which varied with soil type (Sarker et al., 2018).
Conservation tillage, including many practices such as tillage with tined tools at depths down to 15–20 cm or direct seeding without prior cultivation, intends to protect the soil surface from crusting and erosion by leaving crop residues and organic matter at the soil surface. Several studies have shown that conservation tillage increases soil carbon stock (Cookson et al., 2008), has positive effects on soil chemical properties in the upper soil layer and contributed to the increase of wheat biomass until tillering stage (Peigné et al., 2018). It enhances the quantity, activity and diversity of soil microorganisms in the upper soil layers (Cookson et al., 2008), as well as earthworm biomass and diversity (Pelosi et al., 2014). It preserves their habitat (burrows), especially anecic burrows, which favour water infiltration and root penetration (Soane et al., 2012). It tends also to increase water-stable aggregates in the uppermost soil layer under conservation tillage compared to ploughing (Holland, 2004; Blanco-Canqui and Lal, 2007). These improvements allow reductions in labour work, energy consumption and machinery costs (Soane et al., 2012).
Maintenance and/or addition of crop residue are also vital to maintain and increase soil C stocks, respectively, and mitigate climate change impacts (Chatterjee, 2013; Dikgwatlhe et al., 2014) through the formation of humus and soil macroaggregates (Alidad et al., 2012; Liu et al., 2014). Regular inputs of crop residues, organic compost or manure can also increase total SOC, based on the balance between C inputs and decomposition processes. This equilibrium level is affected by the types of C inputs to the system and their conversion into stable C in the soil by microbial communities (Kallenbach et al., 2016). Zhao et al. (2018) showed that return of both maize and wheat straw was the best strategy to improve soil structure, SOC and crop yield. But straw return from one crop was sufficient to maintain initial SOC levels, and maybe sufficient for cellulosic feedstocks. However, there are conflicting research on this topic, since some studies have identified negative effects of straw return on soil aggregates (Bossuyt et al., 2001; Soon and Lupwayi, 2012), suggesting that the effect of straw return on soil aggregation in agricultural soils is related to appropriate management practices and climate conditions (Li et al., 2018).
For appropriate management of agricultural soils, decision-makers need science-based, easily applicable, and cost-effective tools to assess soil quality and soil functions. Since practical assessment of soil quality comprises key soil properties and their variations in space and time, providing such tools remains a research challenge.
Soil quality indicators should be selected according to the soil functions of interest and threshold values have to be identified, based on local conditions to generate a meaningful soil quality index. The selection of indicators can be based on experts’ opinion, statistical procedures, or a combination of both, to obtain a minimum data set (MDS) (»Frequently proposed soil quality indicators).
»Visual soil and plant quality assessment (VSA) methodology, based on key indicators and components of soil quality, allows understanding of the impact of agricultural management practices on soil physical, chemical and biological properties. Visual assessment provides an immediate, effective diagnostic tool to assess soil condition, and the results are easy to interpret and understand. It has been used in several countries and explains differences in crop performance and yield resulting from soil type and management (Ball et al., 2013).
In iSQAPER 14 study sites covering the major pedo-climatic zones of Europe and China were selected with the aim to consider a large variety of AMPs, soil types and cropping systems. In this section of iSQAPERiS we
- select promising AMPs improving soil quality, and
- assess their impacts on soil quality at different study sites in Europe and China.
Note: For full references to papers quoted in this article see