Effects of tillage and winter cover cropping on microbial substrate-induced respiration and soil aggregation in two Japanese fields

Abstract

We hypothesized that cover cropping could increase soil microbial activities under various tillage systems and that increased microbial activities would improve soil properties. Soil sampling was conducted at two fields in Japan in 2009. At the Ibaraki field (Andosol, clay loam), three tillage practices (no-tillage, plowing to 30 cm, and rotary tillage to 15 cm) and three types of winter cover cropping [bare fallow as control, hairy vetch (Vicia villosa Roth), and rye (Secale cereale L.)] were conducted from 2003 to 2009. At the Hokkaido field (Fluvisol, light clay), two tillage practices (autumn tillage and rotary tillage with a rotary tiller to a depth of 15 cm once in autumn and twice in a year, respectively), and four types of winter cover cropping (bare fallow, hairy vetch, bristle oat (Avena strigosa L.), and a mixture of hairy vetch and bristle oat) were conducted from 2006 to 2009. Soil microbial activities and the fungal-to-bacterial activity ratio (F/B ratio) were estimated by the substrate-induced respiration (SIR) method with the use of selective antibiotics. At the Ibaraki field, rye cover cropping showed higher microbial SIR than bare fallow at depths of 0-30 cm and rotary tillage maintained higher microbial SIR than no-tillage or plowing at depths of 7.5-15 cm. There was no meaningful interaction effect between cover cropping and tillage on microbial SIR. At the Hokkaido field, cover cropping and tillage had only limited effects on microbial SIR. High F/B ratios (indicating fungal dominance) were recorded with the use of cover crops in both fields. Fungal SIR, estimated from the microbial SIR and F/B ratio, was closely related to the content of total soil organic carbon (SOC) and the mean weight diameter (MWD) of water-stable aggregates. Based on SOC, fungal SIR was significantly higher under rye cover cropping. The relationship between fungal SIR and MWD was affected by tillage. We conclude that rye cover cropping and rotary tillage were very effective in increasing fungal SIR, SOC, and MWD in the Ibaraki soil. Field practices that enhance fungal activities might be effective in improving certain types of arable soil.

Responses of soil nematode community structure to soil carbon changes due to different tillage and cover crop management practices over a nine-year period in Kanto, Japan

“…Christensen et al (2012) compared fungal biomass and fungivorous nematodes between conventional and organic fields in Denmark and reported that higher inputs of crop residue enhanced fungal biomass and fungivorous nematodes abundance. Nakamoto et al (2012) also reported that both rye and hairy vetch cover crops increased microbial activities and improved soil aggregate stability with increasing SOC. Zhaorigetu et al (2008) also reported that the use of a rye cover crop increased fungal biomass near the soil surface.…”

“…Crop residue quality and incorporation of residues in the soil also affects the decomposition process. Nakamoto et al (2012) determined the fungal-to-bacterial biomass ratio by a substrate-induced respiration-inhibition approach, suggesting that for a cover crop with a higher C:N ratio, such as rye, incorporation increased fungal biomass more than for a cover crop with a lower C:N, such as hairy vetch, and that crop residue cover on soil surfaces by NT also enhances fungal biomass more than does the incorporation of residue by tillage inversion. The relative abundance of fungivorous and bacterivorous nematodes theoretically provides information about fungal and bacterial contributions to decomposition of soil organic matter (Ferris et al, 2001;Vestergård, 2004).…”

“…Continued NT system; however, reduces soil hardness and BD with increased soil organic matter and the introduction of cover crops (Logsdon and Karlen, 2004;Raper et al, 2000). NT or conservation tillage and cover crop management increase soil organic matter content after long-term management, and this increase brings about soil structure changes, such as in BD and soil aggregate stability (Higashi et al, 2014;Nakamoto et al, 2012).…”

Response of Soil Surface Greenhouse Gas Fluxes to Crop Residue Removal and Cover Crops under a Corn–Soybean Rotation

“…Crop residue returned to the soil is an important management practice in mitigating GHG emissions, as its decomposition can generate fluxes of GHGs. Much research has been focused on the implications of crop residue on soil biological activities (Blanco‐Canqui and Lal, 2009; Butterbach‐Bahl et al, 2013; Lehman et al, 2014; Lehman et al, 2015), indicating that an increase in crop residue accumulation on the soil surface increases microbial activity (Karlen et al, 1994; Nakamoto et al, 2012; Wienhold et al, 2013). Jin et al (2014) hypothesized that removing plant residue from the soil surface may decrease GHG fluxes by reducing the microbial substrate.…”

The Role of Organic Fertilizers in Transition to Sustainable Agriculture in the MENA Region

“…While grains and vegetables require bacterial dominance or a balance between fungi and bacteria, orchard trees need a dominance of fungi, which are more effective at immobilizing nutrients, Organic Fertilizers preventing leaching. For grasslands, higher F/B ratios are an indication of more sustainable systems, with less environmental impacts [92]. It should be noted that biomass in itself is not a complete indicator for fungal and microbial activity [92] and that the distribution across various depths is also important for fertility and GHG flux dynamics.…”