Long term impact of different tillage systems on carbon pools and stocks, soil bulk density, aggregation and nutrients: A field meta-analysis

doi:10.1016/j.catena.2020.105102

CATENA

Volume 199, April 2021, 105102

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Highlights

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A field meta-analysis to assess soil quality under conservation tillage.
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Conservation tillage associated with increases in SOC, N, P and K stocks and aggregate stability.
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Slow wetting and room storage of conservative tillage soil favored aggregate stability.
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Increased bulk density under conventional tillage persists non injurious for crop progress.
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The response of soil properties vary with the management practices.

Abstract

Intensive tillage frequently has adverse impact on soil physical quality and soil organic carbon stocks in temperate regions. A consequence of this has been a reduction in crop production over the years demonstrating the necessity of effective and sustainable agriculture. This study aimed to evaluate soil organic carbon (SOC) storage and pools, soil bulk density, aggregation and nutrient availability under different tillage systems (no-tillage, chisel and conventional tillage), based on a long field experiment. After 10 years of crop rotation, in 0–30 cm soil depth, no-tillage system had higher total organic carbon over conventional tillage treatment. Plots under no-till and chisel treatments in 0–10 cm depth, had 7–13%, 34–35% and 9–15% higher non-labile fraction (Cfrac₄), very-labile fraction (Cfrac₁) and total organic carbon (TOC), respectively compared to that of conventional ones. Also, no-till system had higher passive carbon pool and carbon management index than conventional system. In addition, the conservative tillage, reduced soil bulk density compared with conventional tillage in the surface layer. The stability of slow-wetting and room storage aggregates from conservative tillage were significantly higher (p < 0.05) than conventional tillage. Overall, stability of soil aggregates is improved under conservative tillage. Tillage system, crop rotation and residues, increased soil available nutrients N, P and K in the 0–10 cm depth, with the highest values in no-tillage system. Therefore, conservation tillage could be recommended as a tillage practices that improve fertility soil characteristics and production sustainability.

Introduction

Conservation tillage systems, here outlined as no-tillage (or zero tillage) with residue retention, has been accepted as a promising strategy (and a key management system) that preserve and restore soil physical and soil organic pools and dynamics (Vazquez et al., 2019). Due to their convenience in minimizing input costs, improving water storage and preserving soil carbon (C), conservation tillage is recognized as a long-term sustainable practice for agricultural ecosystems (Li et al., 2019). As in most parts of Europe, the application of conservation tillage in Romania is limited but the interest is growing continuously.

In the context of conservation agriculture practices, no-tillage system can also enhance soil quality by improving soil structure, intensifying soil biological activity, improving the nutrient cycle, increasing the soil water holding capacity and the water infiltration characteristics (Hellner et al., 2018, Borges et al., 2018) and also plays a crucial role in sustaining agricultural productivity and preserving environmental quality (Raus et al., 2016, Amezketa, 1999). Lampurlanes et al., 2016, Jat et al., 2019, Zuber and Villamil, 2016, Li et al., 2018 found that conservative tillage showed promising trends in improving soil enzyme and microbial activity and enhance soil structure and crop yields. An issue based on long-term tillage in North America showed that the larger SOC content in the 21–35 cm soil under CT did not completely equilibrate the gain in the 0–20 cm soil under NT (Angers and Eriksen-Hamel, 2008). The main challenges with the adoption of NT include soil compaction, weed management, and stratification of organic matter and nutrients. Therefore, further research is still needed to evaluate the effects and mechanisms of conservation tillage practices on changes in soil quality along the soil profile (Angers and Eriksen-Hamel, 2008).

Soil physical property dynamics within different tillage system are well documented but a systematic synthesis is needed to enhance how these practices affect soil physical properties on a global scale and how these changes in soil physical properties are linked to multiple ecological components at cropping system level (Li et al., 2019).

Soil structure, the spatial arrangement of primary soil particles and aggregates with associated pore networks, is a key parameter for soil sustainability management; it provides vital functions and acts as an optimum medium for plant growth (Lehmann et al., 2017). Soil aggregation plays an important role in soil structure and organic matter stabilization, which furthermore supports soil fertility through minimizing soil erosion, mediating air permeability, infiltration and nutrient cycling (Zhang et al., 2018). In addition, soil aggregate stability can defend soil organic carbon from mineralization because it physically reduces the accessibility of organic compounds for microorganism, enzymes and oxygen. The process of soil carbon associated aggregate destabilization vary with macro and microaggregates. The degree of mineralization can be intensified by macroaggregate conversion to dimension of microaggregates (Jat et al., 2019). The soil organic matter associated with macroaggregates was more labile and less processed than that associated with the microaggregates. Organic matter is also an important agent responsible for binding soil mineral particles together (Jat et al., 2019).

Conventional tillage usually involves heavy tillage practices down to 20–25 cm soil depths (Pittelkow et al., 2015); this reliable management practice has resulted in reduced soil bulk density, increased porosity, and improved weed control (Pagliai et al., 2004). Conventional tillage can also adversely affect soil structure, when the process of aggregate formation is disturbed due to destruction of aggregates (Six et al., 2002). Soil aggregates are directly affected through physical disturbance of the macroaggregates and indirectly by alteration of biological and chemical factors (Gupta Choudhury et al., 2014, Li et al., 2019, Bronick and Lal, 2005).

Poor aggregate structure and stability can decrease water infiltration and reduce soil carbon and nutrients in macro and microaggregates. Higher soil aggregation can be achieved by decreasing tillage and increasing residue retention through conservation tillage. Gupta Choudhury et al. (2014) found that the applications of the organics in the form of residues combined with conventional or conservative tillage improved the percent of macroaggregates compared to microaggregates. A positive correlation was reported between aggregate size and soil organic carbon content, so the larger aggregate with higher soil organic carbon minimized the intensity of disintegration of aggregate exposed to water (Blevins et al., 1998).

Soil physical quality has been widely approached by bulk density, to evaluate various soil processes or to estimate soil carbon reserves (Vereecken et al., 2016). Generally, bulk density might be considered an important parameter that reflect soil structure, being an indicator of soil compaction related to total soil and pore space volume (Hernanz et al., 2000).

In addition to environmental services, soil organic carbon is a valuable indicator which maintain soil fertility, soil sustainability, crop yield, and contributes to mitigate climate warming and ensure food safety. Conservation agriculture has proved to be an excellent alternative to conventional agriculture in the long term of sustainable crop production and SOC sequestration. No-tillage/ reduced tillage decreases the carbon oxidation process and soil disturbance with the loss of soil organic carbon and nutrient availability (Kan et al., 2020, Modak et al., 2019). Crop residues behave as a barrier between soil and environment which may have a great role in soil erosion reduction and soil quality indicators (Jat et al., 2019). Maintained good physical, chemical and biological properties particularly those related to soil carbon sequestration are necessary for production sustainability (Martin et al., 2019).

The general objective of this study was the assessment of soil quality-based management practices and parameter identification that are sensitive to soil disturbance. The specific objectives were to investigate the impact of long-term tillage systems on soil aggregate stability, nutrient availability and soil carbon storage pools and dynamics. We hypothesized that the conservation tillage improves soil physical properties and organic carbon stocks.

Section snippets

Study site description

This study was part of a long field experiment conducted during 2009–2019, at the Research Farm of the Agricultural University Iasi - Romania (47°07′ N latitude, 27°30′ E longitude). The climate in the experimental area is a temperate-continental type; the mean values precipitation of the last 20 years at this site reaches 517.8 mm with an average air temperature of 9.4 °C. Significant deviations from the long-term average and temperature have been observed in the last 10 years. The

Carbon fraction and C-stabilization

Tillage and cropping system significantly influenced TOC content and C-fractions, C-pools and C-management indices in the 0–10 cm depth soil layer (Table 3 and Fig. 2). The concentration of TOC (p < 0.05) in the surface soil 0–10 cm was maximum (37.0 g kg⁻¹) in no-tillage variant with similar values at the sub-surface depth 10–20 cm (31.4–31.6 g kg⁻¹) in both the conservative treatments. The increase of TOC under reduced tillage was more in surface soil 0–10 cm than of 10–20 cm and 20–30 cm

Conclusions

The results obtained maintain the assumption that conservation tillage can improve soil physico-chemical properties, especially by reducing bulk density and increasing stability of aggregates and soil total organic carbon. The addition of crop residues in chisel and no-tillage treatments, increased non labile C fraction Cfrac4 in 0–20 cm depth. The effect of tillage practices on total organic carbon and soil available nutrients was notable after ten-year rotation. The effect was intense for

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

Authors acknowledge the logistic support from Competitiveness Operational Programme (COP) 2014 – 2020, under the project number 4/AXA1/1.2.3. G/05.06.2018, SMIS2014+ code 119611, with the title “Establishing and implementing knowledge transfer partnerships between the Institute of Research for Agriculture and Environment - IAȘI and agricultural economic environment”.

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In agricultural ecosystems, soil organic carbon (SOC) which is affected by management practices, is important for soil health, food security, and climate change mitigation. However, accurately assessing the influence of agricultural management practices on SOC storage is a challenge, due in part to the uncertainty of calculation approaches used to estimate SOC stocks. Although equivalent soil mass (ESM) is widely recommended over the fixed depth (FD) approach, few field studies directly compare FD with different ESM approaches. Hence, the magnitude of potential difference in estimated SOC stocks among different approaches is not well known. Here, we collected soil cores (0–60 cm depth) from a 24-yr experiment (Ridgetown, Ontario, Canada) to investigate (1) the effect of two tillage systems (conventional tillage: CT, moldboard plowing to ∼20 cm deep; no-tillage with zone tillage: NT/ZT) on different SOC estimates (n=448), including concentration and stocks estimated by FD and ESM (cubic spline interpolation model: ESM_cubic__spline, linear interpolation model: ESM_linear, and non-modeling fit: ESM_{non_model}); and (2) the relative difference of SOC stocks estimated by FD and ESM under NT/ZT system. The tillage effect on SOC stock was more pronounced than SOC concentration (P<0.05; except for 0–5 cm depth), indicating that using SOC concentration alone appears to be unreliable for evaluating tillage system effects on carbon sequestration. Furthermore, FD overestimated SOC stocks under NT/ZT (P<0.05), mainly due to greater soil bulk density than CT (P<0.05). Specifically, in the 0–60 cm depth, FD overestimated about 15% (or 30.6 Mg ha⁻¹) of cumulative SOC stocks than ESM_cubic__spline. However, the differences in SOC stocks estimated among three ESM approaches (ESM_cubic__spline, ESM_linear, and ESM_{non_model}) were negligible (P>0.05; Cohen’s d<0.2), suggesting that these approaches may work equally well when soil depth increment is small (< 10 cm). Overall, we recommend using the ESM approach to calculate SOC stock, especially when comparing treatments where soil bulk density varies. Our findings may help to guide policy decision-making towards more accurately quantifying SOC stock when considering climate change mitigation practices.
Soil bulk density assessment in Europe
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The topsoil Land Use and Cover Area frame Statistical survey (LUCAS) aims at collecting harmonised data about the state of soil health over the extent of European Union (EU). In the LUCAS 2018 survey, bulk density has been analysed for three depths, i.e., 0–10 cm = 6140 sites; 10–20 cm = 5684 sites and 20–30 cm =139 sites. The laboratory analysis and the assessment of the results conclude that the bulk density at 10–20 cm is 5–10% higher compared to 0–10 cm for all land uses except woodlands (20%). In the 0–20 cm depth, croplands have 1.5 times higher bulk density (mean: 1.26 g cm⁻³) compared to woodlands (mean: 0.83 g cm⁻³). The main driver for bulk density variation is the land use which implies that many existing pedotransfer rules have to be developed based on land use. This study applied a methodological framework using an advanced Cubist rule-based regression model to optimize the spatial prediction of bulk density in Europe. We spatialised the circa 6000 LUCAS samples and developed the high-resolution map (100 m) of bulk density for the 0–20 cm depth and the maps at 0–10 and 10–20 cm depth. The modelling results showed a very good prediction (R²: 0.66) of bulk density for the 0–20 cm depth which outperforms previous assessments. The bulk density maps can be used to estimate packing density which is a proxy to estimate soil compaction. Therefore, this work contributes to monitoring soil health and refine estimates on carbon and nutrients stocks in the EU topsoil.
X-ray computed tomography – Measured pore characteristics and hydro-physical properties of soil profile as influenced by long-term tillage and rotation systems
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Soil hydro-physical properties and pore characteristics are crucial for crop production as they determine water, air, and nutrients transfer. Long-term tillage and crop rotation studies provide valuable insights into the effects of management practices on various soil properties. Because of the inherent differences between the surface and sub-surface soils, the impact of management systems can be pronounced differently at different soil depths. Though many studies have reported the tillage and rotation effects on soil hydro-physical properties, their vertical impacts to a depth of 40 cm were less explored. This study aims to assess the impact of long-term tillage and crop rotations on soil hydro-physical properties and pore characteristics to a depth of 40 cm utilizing the X-ray Computed Tomography (XCT) technique. Intact soil cores of 7.6 cm height × 7.6 cm ∅ were collected from tillage [no-till (NT); reduced-till (RT); conventional-till (CT)] and crop rotation [continuous corn (CC) – Zea mays L. and corn-soybean (CS) – Glycine max [Merr.] L.] plots of 0–40 cm depth (each sample for 10 cm increment). The XCT scanning allowed us to investigate the soil pore size distribution, porosity, number of branches, and average branch length. Measured hydro-physical properties in the study include bulk density (ρ_b), plant available water content (PAW), saturated hydraulic conductivity (K_sat), and water retention. XCT image analysis revealed that NT with CC/CS rotation increased the number of macropores at surface and sub-surface depths. However, the number of mesopores was higher with NT × CS. In addition, NT lowered the ρ_b by 9.6 % and increased the PAW by 28 % compared to the CT. K_sat was higher under NT × CS at 0–10 cm and had a strong positive correlation with the XCT-measured number of macropores. Therefore, we conclude that NT with CS rotation can potentially improve soil pore characteristics and hydro-physical properties, leading to enhanced soil function.
Conservation tillage in temperate rice cropping systems: Crop production and soil fertility
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Conventional tillage (i.e. ploughing) that is applied in Italian rice fields ensures high grain yields, but may result in negative effects on physical and chemical fertility of soil. Conservation tillage can be a viable alternative to conventional allowing to reduce the environmental and economic impact of rice cultivation. However, there is limited knowledge on the effects of these alternative tillage systems on rice yield and paddy soil fertility in temperate climates.
The aim of this study was to evaluate the effects on yield and soil fertility of conservation tillage in the medium term in temperate rice continuous monoculture system.
A six-years monocrop rice experiment (2014–2019) was carried out in North-West Italy, comparing three tillage methods: conventional tillage (ploughing – CT), minimum tillage (MT), and no tillage (NT) combined with three N fertilization rates (N0, N − 120 kg N ha⁻¹ year⁻¹, and N + − 160 kg N ha⁻¹ year⁻¹). The study evaluated yield, yield components, plant N uptake, apparent N recovery (ANR), soil bulk density, total soil organic carbon (SOC) stock and C and N distribution between different soil organic matter (SOM) fractions.
MT showed a similar grain yield to CT, while a 15 % reduction was recorded with NT, which was penalized by low plant density and high soil compaction in the surface layer. Although NT exhibited higher panicle density, spikelets per panicle, and 1000-grain weight than CT and MT, these factors were not sufficient to compensate for the grain yield gap. NT resulted in decreased plant N uptake and ANR, making increasing N fertilization in NT ineffective for recovering the yield gap with CT. After six years, no significant difference was found in SOC stock among the tillage treatments. However, conservation tillage influenced the vertical distribution of SOC, resulting in higher concentration in the superficial soil layer (0–15 cm) compared to CT. MT led to the highest amounts of labile and physically protected SOM in the 0–15 cm layer compared to NT, where lower crop residue input due to lower straw production limited the accumulation of these types of SOM fractions.
MT use production resources more efficiently compared to CT and sustains soil fertility by promoting organic matter and nitrogen inputs, facilitating soil aggregation and preventing soil compaction. Yield reductions and excessive soil compaction are the main obstacles to the wide adoption of NT.
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Degradation of agricultural waste is dependent on chemical fertilizers in long-term paddy-dry rotation field
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The practice of returning straw to agricultural fields is a globally employed technique. Such agricultural fields also receive a significant amount of nitrogen (N) and phosphorus (P) fertilizers, because these two macronutrients are essential for plant growth and development. However, the consequences of such macronutrients input on straw decomposition, soil dissolved organic matter (DOM), key microbes, and lignocellulolytic enzymes are still unclear. In a similar aim, we designed a long-term straw returning study without and with different N and P nutrient supplementation: CK (N₀P₀), T1 (N₁₂₀P₀), T2 (N₁₂₀P₆₀), T3 (N₁₂₀P₉₀), T4 (N₁₂₀P₁₂₀), T5 (N₀P₉₀), T6 (N₆₀P₉₀), and T7 (N₁₈₀P₉₀), and evaluated their impact on rice and oilseed rape yield, soil DOM, enzymes, lignocellulose content, microbial diversity, and composition. We found straw returning improved overall yield in all treatments and T7 showed the highest yield for oilseed rape (30.31–38.87 g/plant) and rice (9.14–9.91 t/ha) during five-years of study. The fertilizer application showed a significant impact on soil physicochemical properties, such as water holding capacity and soil porosity decreased, and bulk density increased in fertilized treatments, as compared to CK. Similarly, significantly low OM, cellulose, hemicellulose, and lignin content were found in T7, T4, T3, and T2, while high values were found in CK and T5, respectively. The fluorescence excitation-emission matrix spectra of DOM of different treatments revealed that T3, T7, T4, and T6 showed high peak M (microbial by-products), peak A and peak C (humic acid-like) as compared to others. The microbial composition was also distinctive in each treatment and a high relative abundance of Chloroflexi, Actinobacteriota, Ascomycota, and Basidiomycota were found in T2 and T3 treatments, respectively. These findings indicate that the decomposition of straw in the agricultural field was dependent on nutrients input, which facilitated key microbial growth and impacted positively on lignocellulolytic enzymes, which further aided the breakdown of all components of straw in the field efficiently. On the other hand, high input of chemical based fertilizers to soil can lead to several environmental issues, such as nutrient imbalance, nutrient runoff, soil pH change and changes in microbial activities. Keeping that in consideration, we recommend moderate fertilizer dosage (N₁₂₀P₉₀) in such fields to achieve higher decomposition of crop straw with a small yield compromise.
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Amid rising energy crises and greenhouse gas (GHG) emissions, designing energy efficient, GHG mitigation and profitable conservation farming strategies are pertinent for global food security. Therefore, we tested a hypothesis that no-till with residue retaining could improve energy productivity (EP) and energy use efficiency (EUE) while mitigating the carbon footprint (CF), water footprint (WF) and GHG emissions in rice-wheat double cropping system. We studied two tillage viz., conventional and conservation, with/without residue retaining, resulting as CT0 (puddled-transplanted rice, conventional wheat -residue), CTR (puddled-transplanted rice, conventional wheat + residue), NT0 (direct seeded rice, zero-till wheat -residue), and NTR (direct seeded rice, zero-till wheat + residue). The overall results showed that the NTR/NT0 had 34% less energy consumption and 1.2-time higher EP as compared to CTR/CT0. In addition, NTR increased 19.8% EUE than that of CT0. The grain yield ranged from 8.7 to 9.3 and 7.8–8.5 Mg ha⁻¹ under CT and NT system, respectively. In NTR, CF and WF were 56.6% and 17.9% lower than that of CT0, respectively. The net GHG emissions were the highest (7261.4 kg CO₂ ha⁻¹ yr⁻¹) under CT0 and lowest (4580.9 kg CO₂ ha⁻¹ yr⁻¹) under NTR. Notably, the carbon sequestration under NTR could mitigate half of the system's CO₂-eq emissions. The study results suggest that NTR could be a viable option to offset carbon emissions and water footprint by promoting soil organic carbon sequestration, and enhancing energy productivity and energy use efficiency in the South Asian Indo-Gangetic Plains.

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Long term impact of different tillage systems on carbon pools and stocks, soil bulk density, aggregation and nutrients: A field meta-analysis

Highlights

Abstract

Introduction

Section snippets

Study site description

Carbon fraction and C-stabilization

Conclusions

Declaration of Competing Interest

Acknowledgements

Soil Tillage Res.

Geoderma

Soil Tillage Res.

Geoderma

Soil Tillage Res.

Catena

Soil Till. Res.

J. Terramechanics

Field Crop Res.

Catena

Soil Biol. Biochem.

Soil Tillage Res.

Soil Tillage Res.

Agri. Eco. Environ.

Soil Till. Res.

Geoderma

Soil Till. Res

Soil Tillage Res.

Soil Tillage Res.

Catena

Agric. Ecosyst. Environ.

Eur. J. Soil Biol.

Sci. Total. Environ.

Eur. J. Soil Biol.

Ecol. Indic.

Soil Biol. Biochem.

Soil aggregate stability: a review

J. Sustain. Agric.