Reducing Tillage Intensity Research Articles

Soil Nitrate Nitrogen Content and Grain Yields of Organically Grown Cereals as Affected by a Strip Tillage and Forage Legume Intercropping.

Reducing tillage intensity and increasing crop diversity by including perennial legumes is an agrotechnical practice that strongly affects the soil environment. Strip tillage may be beneficial in the forage legume–cereals intercropping system due to more efficient utilization of biological nitrogen. Field experiments were conducted on a clay loam Cambisol to determine the effect of forage legume–winter wheat strip tillage intercropping on soil nitrate nitrogen (N-NO3) content and cereal productivity in various sequences of rotation in organic production systems. Forage legumes (Medicago lupulina L., Trifolium repens L., T. alexandrinum L.) grown in pure and forage legume–winter wheat (Triticum aestivum L.) strip tillage intercrops were studied. Conventional deep inversion tillage was compared to strip tillage. Nitrogen supply to winter wheat was assessed by the change in soil nitrate nitrogen content (N-NO3) and total N accumulation in yield (grain and straw). Conventional tillage was found to significantly increase N-NO3 content while cultivating winter wheat after forage legumes in late autumn (0–30 cm layer), after growth resumption in spring (30–60 cm), and in autumn after harvesting (30–60 cm). Soil N-NO3 content did not differ significantly between winter wheat strip sown in perennial legumes or oat stubble. Winter wheat grain yields increased with increasing N-NO3 content in soil. The grain yield was not significantly different when comparing winter wheat–forage legume strip intercropping (without mulching) to strip sowing in oat stubble. In forage legume–winter wheat strip intercropping, N release from legumes was weak and did not meet wheat nitrogen requirements.

Changes in degree of phosphorus saturation and risk of P loss upon twelve years of manuring and reduced tillage

Adoption of minimum tillage and application of fertilizer integrated with farmyard manure in the long-term has been envisaged to sustain rice-based cropping systems in the Indo-Gangetic plains of India. However, substitution of mineral fertilizer based on crop N requirement results not only in increase of the total P load but also in the distribution of P fractions and soil properties that influence P adsorption. A twelve year old experiment consisting of two tillage (conventional, CT and minimum, MT tillage) and three fertilization treatments (100% inorganic fertilization, IF, 100 and 50% organic fertilization, OF) was examined to unravel the relationship between tillage and manuring effects on distribution of soil P forms vis-à-vis soil test P and how it relates to degree of P saturation (DPS). Reduced tillage intensity and organic fertilization resulted in increase of all P fractions and soluble P. Olsen-P varied from 3.4 to 59.4 mg kg−1 and was exponentially (NH4F-P/NaOH-P) or linearly (Occ-P/H2SO4-P) related to P fractions by direct or indirect effects. Increase in pH and total organic carbon coupled with increase in P load especially in OF and MT treatments resulted in decrease in the P maximum adsorption capacity (PMAC) and P bonding energy of the soil. Consequently, the degree of phosphorus saturation increased with decrease in PMAC and a change point was noted at 13.62% DPS above which soluble P increased more rapidly. Olsen P, which is used as an index of P availability, increased with reduction of tillage and organic manure addition and was closely associated with all the P fractions and DPS. The Olsen P at the change point DPS was 50.4 mg kg−1 which indicated risk of P losses and hence could be used as an index for risk assessment and identify soils that need to be managed agronomically and environmentally to avoid P losses to the environment.

Economic analysis of organic cropping systems under different tillage intensities and crop rotations

AbstractCosts of production and organic price premiums are defining factors influencing the economic viability of organic crop production systems. Different agronomic practices, such as crop rotation and tillage intensity, are known to affect the economic performance of the production systems. The aim of this study was to compare the impact of two crop rotation sequences (simplified and diversified) and two levels of tillage intensity (high and low) on the cost of production, gross return and gross margin of crops when grown under organic management in the semi-arid Brown soil zone of the Canadian Prairies. The 2-year simplified rotation sequence consisted of forage pea (Pisum sativum L.) grown as a green manure followed by hard red spring wheat (HRSW) (Triticum aestivum L.), while the 4-year diversified rotation sequence was forage pea green manure followed by flax (Linum usitatissimum L.) or yellow mustard (Sinapis alba L.), field pea or lentil (Lens culinaris L.) and HRSW. Our hypothesis that a more diversified crop rotation would increase profitability over a traditional simplified crop rotation was supported by the findings. However, the findings did not support our hypothesis that reducing tillage intensity, and the combination of tillage reduction and diversified crop rotation through a synergetic response, would further enhance profitability. Analysis of the breakeven prices and breakeven yields for crops indicated the importance of adopting diversified crop rotations and choosing crops with high organic price premiums as means to maximize the long-term profitability of organic cropping systems.

Temporal Soil Bacterial Community Responses to Cropping Systems and Crop Identity in Dryland Agroecosystems of the Northern Great Plains

Industrialized agriculture results in simplified landscapes where many of the regulatory ecosystem functions driven by soil biological and physicochemical characteristics have been hampered or replaced with intensive, synthetic inputs. To restore long-term agricultural sustainability and soil health, soil should function as both a resource and a complex ecosystem. In this study, we examined how cropping systems impact soil bacterial community diversity and composition, important indicators of soil ecosystem health. Soils from a representative cropping system in the semi-arid Northern Great Plains were collected in June and August of 2017 from the final phase of a 5-year crop rotation managed either with chemical inputs and no-tillage, as a USDA-certified organic tillage system, or as a USDA-certified organic sheep grazing system with reduced tillage intensity. DNA was extracted and sequenced for bacteria community analysis via 16S rRNA gene sequencing. Bacterial richness and diversity decreased in all farming systems from June to August and was lowest in the chemical no-tillage system, while evenness increased over the sampling period. Crop species identity did not affect bacterial richness, diversity, or evenness. Conventional no-till, organic tilled, and organic grazed management systems resulted in dissimilar microbial communities. Overall, cropping systems and seasonal changes had a greater effect on microbial community structure and diversity than crop identity. Future research should assess how the rhizobiome responds to the specific phases of a crop rotation, as differences in bulk soil microbial communities by crop identity were not detectable.

Short-term impacts of different tillage practices and plant residue retention on soil physical properties and greenhouse gas emissions

Reducing tillage intensity and plant residue retention have the potential to mitigate climate change by reducing soil greenhouse gas emissions. Few comparative studies have explored the effects of different tillage practices and plant residue retention on the net balance of GHG emissions in the short term (1–2 years). We hypothesised that reducing tillage and plant residue retention decreases GHG emissions compared to conventional ploughing and residue removal. We estimated the effects of different tillage practices; no-tillage, minimum-tillage and traditional ploughing as well as plant residue retention on; 1) bare-soil GHG emissions, 2) the net ecosystem exchange (NEE), and ultimately, 3) the potential for climate change mitigation, CO2 equivalent. GHG fluxes were measured using the static chamber method and soil physical properties were assessed using X-ray Computed Tomography (CT) and a range of traditional methods. No-tillage increased bulk density and shear strength compared to minimum-tillage and ploughed soil. Soil moisture content and organic matter content at 0−5 cm depth were higher in no-tillage and minimum-tillage compared to ploughed soil. No-tillage increased soil−CO2 emissions and CH4 uptake but reduced NEE−CO2 emissions and increased NEE−CH4 uptake. No and minimum-tillage resulted in 56 % and 40 % reduction in CO2 equivalent emissions respectively compared to ploughing for the combined crop-soil measurements. Changes in the CH4 and CO2 were interlinked to changes in soil pore architecture and physical properties. Taken together our data demonstrate that no-tillage and minimum-tillage have potential to contribute to climate change mitigation through reducing GHG emissions.

A SMAF assessment of U.S. tillage and crop management strategies

The Soil Management Assessment Framework (SMAF) was developed to collectively assess biological, chemical, and physical soil health changes due to management practices. SMAF scoring curves were designed to be site-specific but were never validated at national scale. Our goal was to verify the national effectiveness of SMAF for detecting changes induced by conservation practices. Data from 456 articles representing the U.S. was compiled as input for a SMAF analysis. Soil organic-C (SOC), microbial biomass-C (MBC), β-glucosidase activity (BG), macroaggregate stability (AS), bulk density (BD), pH, soil-test P and K indices and an overall soil quality index (SQI) were computed. Measured, scored, and SQI values were used to evaluate tillage intensity [conventional (CT), reduced tillage (RT), no-till (NT), and zero disturbance (perennial systems; PER)] and soil cover [annual cropping systems without cover crops (ANCC), annual cropping systems with cover crops (ACC), and year-round soil cover (perennial systems; PER)]. Reducing tillage intensity and increasing soil cover increased topsoil SOC, MBC, BG, and AS values (measured and scored). SMAF scoring curves were sensitive to agronomic practice effects on soil function. The highest SQI values were associated with perennial systems (zero soil disturbance) and year-round living roots. Within annual cropping systems, cover cropping, and NT demonstrated better soil biological and physical functioning. However, SMAF scores underestimated the effects for SOC and BG and overestimated the effects for AS, suggesting the algorithms for those indicators should be reevaluated and improved. Overall, this national assessment confirmed the utility of SMAF and highlighted benefits of conservation practices. • Sensitivity of SMAF scoring functions to land use was assessed on a national scale. • Current SMAF algorithms generally detected soil health changes due to management practices. • Some SMAF scoring curves (SOC, aggregate stability, and β-glucosidase) need to be improved. • All soil health indicators used in SMAF react to conservation practices on a national scale.

Biological soil health indicators respond to tillage intensity: A US meta-analysis

Tillage intensity affects soil microbiological activity in many ways, often driven by changes in soil organic C (SOC) content. The magnitude and direction of those changes, however, depends on inherent (e.g., soil type and texture), experimental (e.g., study duration and sampling depth) and agronomic factors (e.g., cropping system and crop residue management). This nationwide meta-analysis examines published effects of chisel plowing (CP), no-tillage (NT), and perennial cropping systems (PER) relative to moldboard plow (MP) on seven soil health indicators: SOC, microbial biomass C (MBC), microbial biomass N (MBN), soil respiration (Resp), active-C (AC), beta-glucosidase activity (BG) and soil protein (Prot) within four soil depth increments in 302 studies from throughout the United States (U.S.). Overall, converting from MP to CP primarily affected topsoil (0 to ≤ 15 cm) SOC, MBC, and Resp, whereas converting from MP to NT significantly increased all seven soil health indicators in the topsoil. Below the topsoil, NT had greater MBC, MBN, Resp, and BG relative to MP (i.e., 15 to 25-cm). The impact of NT was affected by latitude, soil order, time under NT, and cropping system. Among soil orders, management practices had the largest positive effects in Ultisols, Inceptisols, Alfisols, and Mollisols. Those effects were most noticeable at lower latitudes, in systems that included cover crops or residue retention, and in experiments conducted for at least three years. Perennial systems had a positive effect on all soil health indicators at all soil depths (0 to >40-cm). The positive response of PER systems compared to MP was enhanced at lower latitudes and in Alfisols, Inceptisols, Entisols, and Mollisols. Based on this meta-analysis, reducing tillage intensity, planting cover crop and/or minimizing crop residue removal within annual cropping systems can significantly improve soil biological health in the U.S. Finally, we demonstrate that SOC and many other biological indicators are sensitive to management practices, confirming their utility in soil health assessment.

Tillage Intensity Effects on Soil Structure Indicators—A US Meta-Analysis

Tillage intensity affects soil structure in many ways but the magnitude and type (+/−) of change depends on site-specific (e.g., soil type) and experimental details (crop rotation, study length, sampling depth, etc.). This meta-analysis examines published effects of chisel plowing (CP), no-tillage (NT) and perennial cropping systems (PER) relative to moldboard plowing (MP) on three soil structure indicators: wet aggregate stability (AS), bulk density (BD) and soil penetration resistance (PR). The data represents four depth increments (from 0 to >40-cm) in 295 studies from throughout the continental U.S. Overall, converting from MP to CP did not affect those soil structure indicators but reducing tillage intensity from MP to NT increased AS in the surface (<15-cm) and slightly decreased BD and PR below 25-cm. The largest positive effect of NT on AS was observed within Inceptisols and Entisols after a minimum of three years. Compared to MP, NT had a minimal effect on soil compaction indicators (BD and PR) but as expected, converting from MP to PER systems improved soil structure at all soil depths (0 to >40-cm). Among those three soil structure indicators, AS was the most sensitive to management practices; thus, it should be used as a physical indicator for overall soil health assessment. In addition, based on this national meta-analysis, we conclude that reducing tillage intensity improves soil structure, thus offering producers assurance those practices are feasible for crop production and that they will also help sustain soil resources.

Impacts of tillage practices on soil carbon stocks in the US corn-soybean cropping system during 1998 to 2016

Tillage alters the thermal and wetness conditions in soil, which facilitates soil organic matter oxidation and water transportation, leading to rapid depletion of soil carbon (C). Little is known about tillage intensity change (TIC) and its impacts in the US corn-soybean rotation system over the past two decades. Using time-series tillage maps developed from a private survey and a process-based land ecosystem model, here we examined how tillage intensity has changed across the nation and affected soil organic carbon (SOC) storage from 1998 to 2016. Results derived from the combination of tillage survey data and cropland distribution maps show that total corn-soybean area consistently increased from 62.3 Mha in 1998 to 66.8 Mha in 2008 and to 73.1 Mha in 2016, among which the acreage under no-till system increased from 16.9 Mha in 1998 to 28.9 Mha in 2008, while conservation and conventional tillage decreased by 3.8 and 3.9 Mha, respectively. The extent of no-till practice in corn-soybean lands shrank by 2.6 Mha from 2008 to 2016, while conservation and conventional tillage increased by 2.8 and 6.1 Mha in the same period. Modeling simulations reveal that historical tillage practices led to a soil C loss of 10.3 (spring till only) to 15.2 (tilled in both spring and fall) Tg C yr−1 in the study area from 1998 to 2016. In addition, reduced tillage intensity in corn-soybean cropland contributed to SOC accumulation at 1.0 Tg C yr−1 (1.6 g C m−2 yr−1) from 1998 to 2008, but the SOC gain was offset by SOC reduction at 2.4 Tg C yr−1 (3.4 g C m−2 yr−1) from increased tillage intensity during the period 2008–2016. For both periods, TIC-induced hydrological C loss accounted for 15% of the SOC change, while the rest was attributed to gaseous-C loss.

Soil N2O emissions in Mediterranean arable crops as affected by reduced tillage and N rate

Nitrous oxide (N2O) is emitted from agricultural soils as a product of biotic pathways of the nitrogen (N) cycle. Agricultural practices may affect soil water content, temperature and N availability, and consequently N2O emissions. Thus, it is necessary to identify strategies to mitigate N2O emissions while maintaining crop yields. This two-year study on durum wheat and sunflower in a Mediterranean environment evaluated the influence of tillage intensity (plowing vs. minimum tillage) and N fertilizer rate (N0, N1 and N2: 0, 110 and 170 kg N ha−1, respectively, for wheat, and 0, 80 and 140 kg N ha−1, respectively, for sunflower) on crop yields and N2O emissions. Reducing the N fertilizer rate by ca. 40% resulted in an average mitigation of ca. 35% of cumulative N2O emissions during the growing season of both crops. From N1 to N2, the grain yield of sunflower did not increase, but that of wheat did so by ca. 25%. Indeed, yield-scaled N2O emissions of N0, were the highest in wheat (259 ± 45 g N2O–N Mg−1 dry grain, 12.2 ± 2.0 g N2O–N kg−1 N uptake) and the lowest in sunflower (62 ± 7 g N2O–N Mg−1 dry grain, 2.0 ± 0.2 g N2O–N kg−1 N uptake). Reducing tillage intensity decreased cumulative N2O emissions significantly only for sunflower during the second year (by 35%), but not for any other treatment. The effect of the reduced tillage depth on grain yield varied between the 2 years, being negative only under wetter growing seasons (− 12% in wheat and − 9% in sunflower).

Correction to: Undersown cover crops have limited weed suppression potential when reducing tillage intensity in organically grown cereals

The original version of this article unfortunately contained layout errors in Figure 5. The correct figure is shown below. The original article has been corrected.

Undersown cover crops have limited weed suppression potential when reducing tillage intensity in organically grown cereals

Adoption of reduced tillage in organic cropping has been slow, partly due to concerns about increasing weed infestation. Undersown cover crops (CCs) are considered to be a feasible option for weed management but their potential for weed suppression is insufficiently investigated in low-till organic cropping. The possibilities to reduce primary tillage by introducing CCs to maintain weed infestation at a level that does not substantially jeopardize crop yield were studied in a field experiment in southern Finland during 2015–2017. Eight different CC mixtures were undersown in cereals and the response in weed occurrence was consecutively assessed in spring barley, winter wheat, and finally, as a subsequent effect, in spring wheat. Growth of CCs was too slow to prevent the flush of early emerging weeds in spring barley whereas in winter wheat, CCs succeeded in hindering the growth of weeds. However, CCs could not prevent the increase of perennial weeds in a reduced tillage system in which the early growth of spring wheat was retarded in cool 2017. Consequently, after 2 years of reduced tillage, weed biomass was about 2.6 times higher and spring wheat yield was 30% lower than in plowed plots, respectively. No major differences in weed control efficacy among CC treatments were evident. A grain yield benefit was recorded after repeated use of leguminous CCs. The need for long-term field studies remains of particular interest regarding post-harvest performance and influence of CCs on perennial weeds before the inversion tillage.

Soil Fertility and Quality Response to Reduced Tillage and Diversified Cropping under Organic Management

Core Ideas A 6‐year organic field trial evaluated two tillage intensities (high and low) and two rotation sequences, simplified (wheat‐green manure) and diversified (wheat‐oilseed‐pulse‐green manure). Soil moisture and NO3‐N content were highest in the simplified rotation under high tillage. There were few soil P differences, although levels were higher for the low than high tillage in the simplified rotation. Reduced tillage intensity tended to increase soil organic C and decreased the percentage of erodible soil particles. Soil NO3‐N and PO4‐P content were also analyzed within the soil profile, down to 120 cm. During the past few decades, organic crop production in Canada and beyond has become increasingly widespread. In the Canadian Prairies, organic agriculture has traditionally relied on summer fallow and mechanical tillage for nutrient and pest management. More recently, there has been a substantial increase in the use of legume green manure, diversified crop rotations, and reduced tillage. Our objective was to determine if organic wheat (Triticum aestivum L.) production using diversified crop rotations and reduced tillage could optimize production while minimizing its environmental impact within the Brown soil zone of Western Canada. A 6‐yr (2010 to 2015) field study evaluated two tillage intensities (high and low), and two rotation sequences, simplified (wheat–green manure) and diversified (wheat–oilseed–pulse–green manure). Precipitation throughout the study period was substantially greater than the long‐term mean. Spring soil NO3−N and P content were highest in the first years of this trial. Soil moisture and NO3−N content were highest in the simplified rotation under high tillage. There were few soil P differences, although levels were higher for the low than high tillage in the simplified rotation. Reduced tillage intensity tended to increase soil organic C and decreased the percentage of erodible soil particles. These soil quality changes would result in an increase in the soil’s resistance to wind and water erosion, thus promoting environmental sustainability.

Potential for no-tillage and clipped-weed mulching to improve soil quality and yield in organic eggplant production

ABSTRACTDeep-inversion tillage for weed control and residue incorporation can have a detrimental effect on agroecosystems. Despite the potential for no-tillage (NT) organic farming to improve soil quality, the yield response of NT can vary. This study compared the effects of NT and conventional rotary tillage (CT), leafmould application (LM+) and no leafmould (LM–), clipped-weed mulch application (CM+) and no weed mulch (CM–) on eggplant yield and crop residue (Solanum melongena L.) and on soil chemical and physical properties under standard organic farming conditions. In both years, NT CM+ resulted in higher yield and crop residue than in NT CM–. Soil bulk density was 34 and 32% lower in 2014 and 2015, respectively, in NT compared with CT. In both years, CM+ had a significant impact on the water content in the surface-layer in both tillage systems. Soil organic carbon and active carbon concentrations, at 0–2.5 cm depth, were 85 and 20% higher in NT than in CT. In October, NO3-N, exchangeable Mg2+, Ca2+ (in 0–2.5 cm only) and available P (in 0–2.5 cm only) were higher in NT than in CT in soil layers 0–2.5 cm and 2.5–7.5 cm. CM+ resulted in increased soil inorganic nitrogen in NT plots during the growing season. The results suggested that NT with CM+ application can be a valuable conservation practice for increasing yield and soil carbon in organic farming by reducing tillage intensity.

Predicting Soil Organic Carbon in Agroecosystems under Climate Change

Predicting Soil Organic Carbon in Agroecosystems under Climate Change

Weed-Species Abundance and Diversity Indices in Relation to Tillage Systems and Fertilization

Weeds pose a major threat to world agriculture by reducing detrimentally crop yield and quality. However, at the same time, weeds are major interacting components of the agroecosystems. Abundance and diversity of weeds vary significantly among the several communities. In order to evaluate each community’s structure and the interactions among them, several population indices are used as key tools. In parallel, various cultivation and land management strategies, such as tillage and fertilization, are commonly used in terms of integrated weed management. Estimating the response of weed species on those practices is crucial for both biodiversity maintenance and alternative weed control methods. Many experiments have confirmed the fundamental role of tillage intensity and nutrition supply in weed species’ abundance and diversity. For instance, in some studies, the abundance of perennial weeds was doubled under reduced tillage intensity. In addition, higher values of Shannon-Weiner and Pielou indices were reported in the PK fertilization treatment compared to the control and NK fertilization treatments. The objective of this paper is to provide a brief overview of the key results of these experiments and summarize the part of the literature related to the effect of tillage systems and fertilization on weed species abundance and diversity. Such knowledge could contribute to the sound design and implementation of integrated weed management programs which in turn may lead to a decrease in the density of serious and noxious weeds and an increase in the overall balance of agroecosystems.

Crop yield, weed infestation and soil fertility responses to contrasted ploughing intensity and manure additions in a Mediterranean organic crop rotation

Conservation agriculture and organic farming are two alternative strategies that aim to improve soil quality and fertility in arable cropping systems through reducing tillage intensity, maintaining soil cover and increasing nutrient recycling, using farmyard and green manures. However, these practices can increase weed infestation or decrease nutrient availability. The objectives of this study were to evaluate the effects of tillage type (mouldboard vs. chisel ploughing), fertilization and green manure on soil parameters (SOC, N, bulk density, carbon stocks, and soil microbial biomass Cmic and Nmic), weed abundance and crop yields in a four-year rotation of spelt, chickpea, winter wheat and lentil in the Mediterranean region (Catalonia, Spain). Tillage and green manure did not affect crop yields or weed biomass, although during the last year of the experiment, plots with mouldboard ploughing had less weed biomass and higher lentil biomass. Fertilization was the most important factor, increasing the cereal yields, SOC, N and soil microbial biomass (Cmic and Nmic) content of the soil. However, fertilization did not favour chickpea and lentil crops because weed competition limited legume crop growth. Overall, there was a loss of SOC and a reduction of carbon stocks over the four years of the trial in the soil because of the deep soil tillage (25 cm) and low crop productivity irrespective of tillage type. In contrast, N content increased in all of the plots and was enhanced by fertilization. The use of chisel plough stratified the distribution of SOC and N in the surface layers (0–10 cm). Both Cmic and Cmic/SOC ratio increased in fertilized treatments, suggesting an increased lability of SOC. The application of more stabilized organic matter may be a better practice to build up soil organic matter and to maintain crop yields in organic farming systems.

Land management change greatly impacts biofuels’ greenhouse gas emissions

AbstractHarvesting corn stover for biofuel production may decrease soil organic carbon (SOC) and increase greenhouse gas (GHG) emissions. Adding additional organic matter into soil or reducing tillage intensity, however, could potentially offset this SOC loss. Here, using SOC and life cycle analysis (LCA) models, we evaluated the impacts of land management change (LMC), that is, stover removal, organic matter addition, and tillage on spatially explicit SOC level and biofuels’ overall life cycle GHG emissions in US corn–soybean production systems. Results indicate that under conventional tillage (CT), 30% stover removal (dry weight) may reduce baseline SOC by 0.04 t C ha−1 yr−1 over a 30‐year simulation period. Growing a cover crop during the fallow season or applying manure, on the other hand, could add to SOC and further reduce biofuels’ life cycle GHG emissions. With 30% stover removal in a CT system, cover crop and manure application can increase SOC at the national level by about 0.06 and 0.02 t C ha−1 yr−1, respectively, compared to baseline cases without such measures. With contributions from this SOC increase, the life cycle GHG emissions for stover ethanol are more than 80% lower than those of gasoline, exceeding the US Renewable Fuel Standard mandate of 60% emissions reduction in cellulosic biofuels. Reducing tillage intensity while removing stover could also limit SOC loss or lead to SOC gain, which would lower stover ethanol life cycle GHG emissions to near or under the mandated 60% reduction. Without these organic matter inputs or reduced tillage intensity, however, the emissions will not meet this mandate. More efforts are still required to further identify key practical LMCs, improve SOC modeling, and accounting for LMCs in biofuel LCAs that incorporate stover removal.

The role of soil depth in the evaluation of management‐induced effects on soil organic matter

SummaryThe aim of the current survey was to determine the relevance of the subsoil in the assessment of management effects on soil organic matter (SOM) in arable farming. Data in this survey were provided by the organic arable long‐term field experiment Gladbacherhof (OAFEG). Three different ‘farming types’ were compared: mixed (MF), stockless with rotational ley (SFL) and stockless with cash crops (SFC). Each type had four different tillage treatments: full inversion (FIT), two‐layer plough (TLP), reduced inversion (RIT) and non‐inversion (NIT). The different mean masses of soil organic carbon (SOC) and soil total nitrogen (STN) at 0–30‐, 30–60‐, 60–90‐ and 0–90‐cm soil depths after three crop rotation cycles (17‐year observation period) were evaluated and considered as an indicator of SOM. ‘Farming types’ differ in their effect on SOC and STN mass of the topsoil layer (0–30 cm) in the order MF > SFL > SFC (P < 0.01). For the 0–90‐cm soil depth there were no differences between the treatments. Treatments with different tillage intensity did not show any effect on the contents of SOC or STN within the 0–30‐cm soil depth. However, within the 30–60‐cm depth full‐inversion tillage (FIT) was associated with larger amounts of SOC and STN than the reduced tillage intensity treatments TLP, RIT and NIT (P < 0.01). This situation even resulted in significantly larger SOC and STN masses under FIT (P < 0.05) over the whole soil profile under study (0–90 cm). Our results suggest that sampling depth should be extended to include the effects on the upper subsoil in assessment of the effects of arable management on soil organic matter.Highlights Role of subsoil in the assessment of management effects on soil organic matter in arable farming is rarely accounted for. We investigated SOC and STN contents below 0–30‐cm depth in a long‐term field experiment. Consideration of the subsoil had a marked effect on the differentiation of the treatments. Sampling depth should be extended to include effects of management on the upper subsoil in the assessment of soil organic matter.

Reducing tillage intensity affects the cumulative emergence dynamics of annual grass weeds in winter cereals

SummaryAnnual grass weeds such as Apera spica‐venti and Vulpia myuros are promoted in non‐inversion tillage systems and winter cereal‐based crop rotations. Unsatisfactory weed control in these conditions is often associated with a poor understanding of the emergence pattern of these weed species. The aim of this study was to investigate, understand and model the cumulative emergence patterns of A. spica‐venti, V. myuros and Poa annua in winter cereals grown in three primary tillage regimes: (i) mouldboard ploughing, (ii) pre‐sowing tine cultivation to 8–10 cm soil depth and (iii) direct drilling. Direct drilling delayed the cumulative emergence of A. spica‐venti and V. myuros (counted together) in contrast with ploughing, while the emergence pattern of P. annua was unaffected by the type of tillage system. The total density of emerged weed seedlings varied between the tillage systems and years with a higher total emergence seen under direct drilling, followed by pre‐sowing tine cultivation and ploughing. The emergence patterns of all species were differently influenced by the tillage systems, suggesting that under direct drilling, in which these species occur simultaneously, management interventions should first and foremost consider that A. spica‐venti and V. myuros emerge over a longer period to avoid control failures.