Impact of reduced tillage on soil organic carbon and nutrient budgets under organic farming

Abstract

No-tillage (NT) and reduced tillage (RT) systems are well-known management tools for reducing soil erosion and improving soil fertility. NT and RT may improve the environmental and economic performance of organic farming, but they are still not common practice among organic farmers. This paper presents the effects of tillage [RT versus conventional tillage (CT)], fertilization (slurry versus manure compost) and biodynamic preparations (with versus without) on soil fertility indicators such as soil organic carbon (C org ), microbial biomass and microbial activity, soil nutrients and nutrient budgets in an organic farming system during the first six-year crop rotation period of a long-term experiment on a clayey soil in a temperate climate. RT caused stratification of soil organic carbon (C org ), microbial properties and soil nutrients in the soil profile. Under RT, C org in the 0-10 cm soil layer increased from 2.19 to 2.61% (w/w) from 2002 to 2008, whereas it remained constant under CT. In both tillage treatments, C org remained constant in the 10-20 cm soil depth. Microbial biomass C increased by 37% under RT in the 0-10 cm soil depth and microbial activity [dehydrogenase activity (DHA)] was enhanced by 57%. Soil microbial biomass C and DHA in the 10-20 cm soil depth were also higher under RT (+ 10 and + 17%, respectively). Soluble soil P and K were 72 and 40%, respectively, higher in 0-10 cm soil depth under RT when compared with CT. Fertilization showed no effects on the measured soil properties. Biodynamic preparations increased solely the C mic -to-N mic (soil microbial biomass C to soil microbial biomass N) ratio by 7% in the 0-10 cm soil depth. Nutrient budgets for P were balanced in all treatments, but N and K exports were higher under RT compared to CT. We conclude that RT is a suitable method for increasing indicators of soil fertility in organic farming systems. The combined effects of RT and an organic farming system with a diverse, ley-based crop rotation and organic fertilization merit further promotion and it may be considered for supporting actions by the agricultural policy schemes.

Overview of Organic Cover Crop-Based No-Tillage Technique in Europe: Farmers’ Practices and Research Challenges

“…In Europe, published papers dealing with tillage issues in OF are focused on RT, and it is difficult to discern from this knowledge about NT [13,15,17,20,44,[47][48][49]. While there are some references referring to organic MBNT in arable crops, data analysis on this technique is often presented in the context of a comparison with traditional ploughing and RT [15,20,[50][51][52].…”

“…Green manure, also called cover crop, is referred to as any crops implemented with the aim of soil fertility preservation and improvement. While certain aspects of these surveys' data have been published elsewhere, we will employ a unique approach focusing solely on the farmer-reported practices and perceptions regarding NT and cover crop management, and place the survey information against the backdrop of the European literature on conservation agricultural practices in both organic and conventional systems, creating a framework upon which to overview knowledge and challenges specific to the organic MBNT in Europe [13,17,18,54,55]. In particular, review papers focused on the implementation of NT practices within the European biological, physical, and chemical contexts are used to describe the pedo-climatic effects on MBNT implementation in Europe [3,8,46,56].…”

“…In reality, however, without use of synthetic herbicides, farmers often depend on intensive tillage to manage weeds [15,16]. This can result in soil degradation: decreases in biological activity and biodiversity, increases in soil erosion, losses in organic matter content, and destruction of soil physical structure due to frequent machine traffic and tillage activities on the field [17,18]. Organic NT represents an opportunity to mitigate these drawbacks, improve soil The specific integration of cover crops into NT practices is an innovative alternative recently developed to mitigate environmental pollution, such as nitrate leaching, reduce inputs (fertilization, herbicides), and suppress weeds via cover crop competition for nutrient and water resources [9,10] ( Figure 1).…”

“…In reality, however, without use of synthetic herbicides, farmers often depend on intensive tillage to manage weeds [15,16]. This can result in soil degradation: decreases in biological activity and biodiversity, increases in soil erosion, losses in organic matter content, and destruction of soil physical structure due to frequent machine traffic and tillage activities on the field [17,18]. Organic NT represents an opportunity to mitigate these drawbacks, improve soil fertility components, and provide further benefits regarding European farmers' working conditions (labor savings, energy consumption reduction, etc.)…”

Reduced Tillage and No-Till in Organic Farming Systems, Germany—Status Quo, Potentials and Challenges

“…Wilhelm [31] also analyzed the relation between production system and the adoption of RT and NT and found that 39% of the farmers who used RT primarily or exclusively grew forages, mainly with on-farm use, compared with 26% of farmers who grew food crops [31]. As RT in organic farming typically results in yield reductions for cereals but not legume leys and maize (Zea mays L.) [18], forage farmers probably are more willing to convert to RT. Cash-crop oriented, stockless arable organic farms in Germany are larger in size than mixed farms and the reduction of labor and fuel costs may be a strong driver for RT.…”