Search

No-till (NT) has repeatedly been reported to result in several environmental advantages, including the reduction of soil erosion, sequestration of carbon from the atmosphere and increase of water retention in soils. However, experimental evidences to date show negative effects of NT on soil physical parameters (i.e., increasing penetration resistance and soil bulk density) and root development of plants, thus reducing crop yield. A three-year field study (2014–2016) was conducted to assess the effects of NT vs conventional tillage (CT) on root growth in maize, soybean, and winter wheat, on a silty clay soil in the Northern Italy. Root length density (RLD), diameter class length (DCL), root dry weight (RDW) and roots composition (C and N) in the top 60 cm of soil were measured. The total amount of root C (TRC) was calculated by multiplying RDW by root C content. Relationships among root traits, soil bulk density (BD) and penetration resistance (PR) were investigated using the non-parametric Spearman rank coefficient. RLD was significantly increased under NT compared to CT in the topsoil (0–5 cm) in maize (6.37 vs. 2.03 mg cm−3) and winter wheat (5.38 vs. 2.90 cm cm−3), while it was lower in NT than in CT in the deeper soil (5–15 cm) only in maize (3.19 vs. 4.53 cm cm−3). RDW was increased under NT compared to CT in the 0–5 cm layer in maize (3.86 vs.0.50 mg cm−3), soybean (4.33 vs. 0.43 mg cm−3), and winter wheat (0.96 vs. 0.38 mg cm−3). NT significantly reduced root C:N ratio of maize (-9%), increased C:N ratio of soybean (+14%), and did not affect C:N ratio of winter wheat. This was mainly related to the effect of NT on coarse roots, which decreased average roots N content. A negative correlation between root traits (RLD, RDW) and soil physical parameters (BD, PR) was found in this study under NT while no correlation occurred for CT. This corroborates the hypothesis that when tillage is abandoned roots are major drivers and detectors of soil physical conditions, which in turn affects roots growth again. Moreover, these results showed that BD did not always represent the main factor affecting root development and the increase of soil strength and particle density under NT did not reduce downwards root growth, which suggests that stability of continuous biopores as induced by NT in well-structured soils is probably much more relevant than the total amount of pores to affect root traits.

Conventional agricultural practices (CAP) highly impacted soil functions involved in the provision of multiple ecosystem services. No-till (NT) has been repeatedly indicated as a key way to enhance soil fertility and biodiversity, while having a positive effect on the environment and climate change. However, experimental evidence to date shows contrasting effects of NT on physical parameters of soil fertility, as well as on soil organic carbon (SOC) storage and soil biodiversity especially if different soil types and cropping systems are considered. The objectives of the present 7-year field study were: (i) to unravel the effect of NT on SOC, soil bulk density, and water stability index (WSI) of soil aggregates across five different soil types (Silty Clay, Silty Clay Loam, Clay Loam, Silt Loam, and Sandy Loam) and cropping systems (silage vs grain production), (ii) to examine how soil fauna (i.e. microarthropods and earthworms) is affected by NT practices under those soil-crop conditions, and (iii) to assess relationships among responses of soil physical indicators (i.e. soil bulk density and WSI), SOC, and soil fauna. Our results showed that soil bulk density was generally not affected by 7-year NT across all soil types. At the same time, NT increased WSI. It follows that NT may increase stable rather than artificial tillage-derived porosity due to reduced soil disturbance, and increased SOC and biological activity. However, reduced importance for boosting aggregates stability should be attributed to NT where initial SOC is high, clay and silt are predominant soil fractions, and the rate of crop residue is low. Our findings suggest that NT may enhance SOC stock (on average 0.66 Mg C ha−1 year−1) in the 0–30 cm soil layer. However, we found (i) a tendency of NT to decrease SOC concentration in the 15–30 cm soil layer (on average −1.18 g C kg−1), and (ii) no SOC increase induced by NT if crop residues were not left onto the soil surface. Nevertheless, NT practices promoted (i) the microarthropods adaptation measured with the QBS-ar index (105.5 vs 64.7), and (ii) the increase of earthworm abundance (412 vs 123 individuals m−2), which are fundamental for enhancing nutrient cycling and soil porosity. Correlations among soil fauna (i.e. QBS-ar and earthworm density), soil physical parameters (i.e. soil bulk density and WSI), and SOC (i.e. concentration and stock) corroborates the hypothesis that soil fauna adaptation and proliferation are main detectors of soil quality and sensitive indicators of changes in soil tillage.