Crop Rotation Changes Research Articles

Composition of the weed flora in sugar beet cultivation in Germany – nationwide trials 1995–2022

Long-term data from 449 herbicide trials across Germany from 1995–2022 were used to characterise the weed composition in sugar beet cultivation. The assessments of 1782 untreated control plots showed local weed species composition and weed pressure. The most common weeds were Chenopodium album (82.3% of all plots), Polygonum convolvulus (52.2%) and Galium aparine (25%). The average number of weed species in the field trials decreased from 4.9 in 1995 to 2.6 in 2022, significantly influenced by trial location and year. The occurrence of the most frequent weeds has also changed. C. album and P. convolvulus increased while G. aparine and Matricaria chamomilla decreased. Possible reasons for these changes are different tillage systems and intensities as well as changes in crop rotation with decreased crop diversity. Herbicide treatments and different active ingredients also affect the occurrence and proportion of weeds. The trial sites were assigned to clusters accounting for climate attributes and soil properties to identify regional differences in weed infestation. Regions with low soil quality, high temperatures and low precipitation had higher weed diversity, presumably due to low crop cover and, thus, lower weed suppression. The proportion of C. album was very high in all regions because it can grow under a wide range of environmental conditions. For P. convolvulus, significant regional differences existed in its proportion of total weed infestation. Its importance was lower in regions with poorer soils.

Effect of no-till followed by crop diversification on the soil microbiome in a boreal short cereal rotation

Diversification of agricultural practices, including changes in crop rotation, intercropping or cover cropping, influence the soil microbiome. Here the impact of tillage and crop diversification on the soil microbiome is reported, being one of the few boreal studies. The field experiment consisted of four treatments with four replications all having a short cereal rotation practice namely an oat (Avena sativa) – spring barley (Hordeum vulgare) – wheat (Triticum aestivum) rotation for the past 10 years until spring 2018. During that period two of the treatments were conventionally tilled with moldboard ploughing whereas the other two were no-tillage treatments. From the growing season 2018 until fall 2020 the main crop in all treatments was spring barley. The first conventional tillage treatment was diversified with English ryegrass (Lolium perenne) as an undersown cover crop for the next three growing seasons. The first no-tillage treatment continued with spring barley only. The second conventional tillage and no-tillage treatment had winter rapeseed in rotation in 2019. Bulk soils were sampled in May 2018 before diversification and then in October 2018, 2019, and 2020. The results showed a clear effect of tillage on the beta-diversity of the soil microbiome and an increase in fungal richness. Barley monoculture interrupted with winter rapeseed resulted in a minor change of the fungal and bacterial community composition. Other fungal and bacterial alpha diversity measures did not react to tillage or diversification nor did the gene copy abundances involved in the N cycle. In conclusion tillage had a profound effect on the soil microbiome hindering impact of the diversification.

Diversification of crop rotations and soil carbon balance: impact assessment based on national-scale monitoring data

A successful crop rotation choice is key to the profitability and sustainability of farm management and may simultaneously have an impact on soil organic carbon (SOC) content. In this study, we estimated how changes in crop rotations affected SOC balance in Finland between 2009 and 2018, using geospatial data and Bayesian modeling. The area designated for perennial-dominated and diverse cereal rotations increased over the study period. Perennial grassland rotation was found to have a positive impact on SOC balance, while rotations dominated by annual crops did not differ in their impacts on SOC content. At the national scale, changes in Finnish crop rotations resulted in an estimated annual mitigation of the loss of SOC content by 1336 Mg C year−1 in mineral soils and reduced the carbon dioxide emissions of organic soils by 10,475 Mg C year−1. The combined effect of these two contributions is 11,811 Mg C year−1, with an 80% probability interval of (−6600; 30,300) Mg C year−1. While the overall impact of changes in crop rotations on SOC is relatively small, a continued change to more diverse and perennial-dominated crop rotations may have other agronomic and environmental benefits, e.g. on resilience and biodiversity.

Field-level land-use data reveal heterogeneous crop sequences with distinct regional differences in Germany

Crop cultivation intensifies globally, which can jeopardize biodiversity and the resilience of cropping systems. We investigate changes in crop rotations as one intensification metric for half of the croplands in Germany with annual field-level land-use data from 2005 to 2018. We proxy crop rotations with crop sequences and compare how these sequences changed among three seven-year periods. The results reveal an overall high diversity of crop sequences in Germany. Half of the cropland has crop sequences with four or more crops within a seven-year period, while continuous cultivation of the same crop is present on only 2% of the cropland. Larger farms tend to have more diverse crop sequences and organic farms have lower shares of cereal crops. In three federal states, crop rotations became less structurally diverse over time, i.e. the number of crops and the number of changes between crops decreased. In one state, structural diversity increased and the proportion of monocropping decreased. The functional diversity of the crop sequences, which measures the share of winter and spring crops as well as the share of leaf and cereal crops per sequence, remained largely stable. Trends towards cereal- or leaf-crop dominated sequences varied between the states, and no clear overall dynamic could be observed. However, the share of winter crops per sequence decreased in all four federal states. Quantifying the dynamics of crop sequences at the field level is an important metric of land-use intensity and can reveal the patterns of land-use intensification.

ИССЛЕДОВАНИЕ ЗНАЧИМОСТИ ПОСТРОЕНИЯ ВЕРШИН ГРАФА ПОСЕВНЫХ ПОЛЕЙ ДЛЯ ПЛАНИРОВАНИЯ РАБОТЫ АВТОМОБИЛЬНОГО ТРАНСПОРТА НА МИКРОУРОВНЕ

Analyzes the position of the Volgograd region among the agrarian regions of the Russian Federation on the study of acreage. In the Volgograd region, the largest share is occupied by the production of high-quality winter wheat. The different categories of the agro-industrial complex of the Volgograd region that ensure sustainable grain production are analyzed. The technological scheme of winter wheat cultivation with the allocation of boundary deadlines for operations and the determination of the volume of transport work is investigated. It is established that the greatest costs in the cultivation of winter wheat fall on the period of harvesting and transportation of the crop. It is proposed to plan the operation of motor transport and combine harvesters in the cultivation of winter wheat using graph theory. The authors for the first time introduce the concept of «transport capacity of the graph of sowing fields». The question of constructing the structure and the influence of various factors on the formation of the vertices of the graph of winter wheat sowing fields is investigated. The basic requirements for the fields of cultivated crops included in the top have been developed. It is established that the modification of the graph by years is associated with changes in crop rotation and demand for export grain.

A Novel Unsupervised Object-Level Crop Rotation Detection With Time-Series Dual-Polarimetric SAR Data

Crop rotation is subsidized by the government because of its many advantages. Monitoring whether crop rotation is beneficial for agricultural management, and can also provide a reference for government subsidy policies for crop rotation. In this paper, we propose an unsupervised object-oriented crop rotation detection method using time-series polarimetric SAR (PolSAR) data. On the one hand, we construct the change detection matrix based on the likelihood ratio test (LRT) distance to perform temporal filtering. Then, the pixel-level temporal change image is generated using Shannon entropy and maximum between-class variance (OTSU). On the other hand, we perform temporal segmentation on time-series PolSAR images to obtain superpixel results. Finally, the object-level crop rotation results are obtained with the probabilistic label relaxation (PLR) model. 42 Sentinel-1 dual-polarization SAR datasets during 2018 and 2019 are selected for detecting crop rotation changes on farms within Jinchang, China. Experimental results show that the crop rotation detection accuracy and <i>Kappa</i> coefficients of this method can reach 96.21% and 0.8989, respectively.

DK-RIM: Assisting Integrated Management of Lolium multiflorum, Italian Ryegrass

Lolium multiflorum (annual Italian ryegrass) and other grass weeds are an increasing problem in cereal cropping systems in Denmark. Grass weeds are highly competitive and an increasing number of species develop resistance against the most commonly used herbicide modes of action. A diverse management strategy provides a better overall control of grass weeds and decreases the reliance on herbicides. The bio-economic decision support system, DK-RIM (Denmark-Ryegrass Integrated Management), was developed to assist integrated management of L. multiflorum in Danish cropping systems, based on the Australian RIM model. DK-RIM provides long-term estimations (10-year period) and visual outputs of L. multiflorum population development, depending on management strategies. The dynamics of L. multiflorum plants within the season and of the soil seed bank across seasons are simulated. The user can combine cultural weed control practices with chemical control options. Cultural practices include crop rotation changes, seeding density, sowing time, soil tillage system, and cover crops. Scenarios with increasing crop rotation diversity or different tillage strategies were evaluated. DK-RIM aims at being an actual support system, aiding the farmer’s decisions and encouraging discussions among stakeholders on alternative management strategies.

Energy partitioning and evapotranspiration over a rotated paddy field in Southern China

There have been recent significant changes in crop rotation and irrigation methods in paddy fields in southern China. Examining the dynamics of energy exchange and evapotranspiration (ET) in rotated paddy fields is important for better understanding of land surface processes affected by human activities. In the present study, energy fluxes, including net radiation (Rn), latent heat flux (LE), sensible heat flux (H) and soil heat flux (G) were investigated using two years (2016–2017) eddy covariance measurements from a rotated paddy field in southern China. The results showed that LE was the main consumer of Rn. Seasonal LE/Rn varied from 0.77 to 0.86 for the rice seasons, and from 0.48 to 0.51 for the milk vetch and fallow seasons. H showed an opposite seasonal trend with LE. G was higher during the milk vetch and fallow seasons because of the greater coverage of exposed soil. The high Priestley-Taylor coefficient (α, 1.11 ± 0.16) and decoupling factor (Ω, 0.71 ± 0.15) corroborated the energy-limited conditions for the rotated paddy field, indicating that Rn was the main meteorological factor governing ET. Canopy conductance (Gc) was closely related to α, suggesting that daily ET was significantly affected by Gc. Vapor pressure deficit (VPD), photosynthetically active radiation (PAR) and leaf area index (LAI) played secondary roles in daily ET through their effects on Gc. ET was also affected by the wet and dry conditions of the paddy field. ET was slightly enhanced under dry conditions when LAI was low, while it decreased when LAI was large.

Changes in crop rotations would impact food production in an organically farmed world

The debate about organic farming productivity has often focused on its relative crop yields compared with conventional farming. However, conversion to organic farming not only results in changes in crop yields, but also in changes in the types of crops grown. To date, the effects of such changes on global crop production have never been systematically investigated. Here, we provide a novel, spatially explicit estimation of the distribution of crop types grown, as well as crop production, under a scenario of 100% conversion of current cropland to organic farming. Our analysis shows a decrease of −31% harvested area, with primary cereals (wheat, rice and maize) compensated by an increase in the harvested areas with temporary fodders (+63%), secondary cereals (+27%) and pulses (+26%) compared with the conventional situation. These changes, paired with organic-to-conventional yield gaps, lead to a −27% gap in energy production from croplands compared with current production. We found that ~1/3 of this gap is explained by changes in the types of crops grown (a contribution rising to 50% when focusing on food crops only), and that such changes strongly affect the repartition of total production among different crop types. Feeding the world organically would thus require profound adaptations of human diets and animal husbandry. ‘Eating organic’ requires farming differently. Organic agriculture manages crop varieties and rotations to manage pests and nutrients. This study analyses different scenarios of organic conversion, finding that a smaller area worldwide planted with wheat, rice and maize must be offset by more nitrogen-fixing crops, such as beans, alfalfa and clover. Even then, caloric energy would fall by about 27% from current production.

A long-term precision agriculture system sustains grain profitability

After two decades of availability of grain yield-mapping technology, long-term trends in field-scale profitability for precision agriculture (PA) systems and conservation practices can now be assessed. Field-scale profitability of a conventional or ‘business-as-usual’ system with an annual corn (Zea mays L.)-soybean (Glycine max [L.]) rotation and annual tillage was assessed for 11 years on a 36 ha field in central Missouri during 1993 to 2003. Following this, a ‘precision agriculture system’ (PAS) with conservation practices was implemented for the next 11 years to address production, profit and environmental concerns. The PAS was multifaceted and temporally dynamic. It included no-till, cover crops, crop rotation changes, site-specific N and variable-rate or zonal P, K and lime. Following a recent evaluation of differences in yield and yield variability, this research compared profitability of the two systems. Results indicated that PAS sustained profits in the majority (97%) of the field without subsidies for cover crops or payments for enhanced environmental protection. Profit was only lower with PAS in a drainage channel where no-till sometimes hindered soybean stands and wet soils caused wheat (Triticum aestivum L.) disease. Although profit gains were not realized after 11 years of PA and conservation practices, this system sustained profits. These results should help growers gain confidence that PA and conservation practices will be successful.

Contribution of climate and land cover changes to reduction in soil erosion rates within small cultivated catchments in the eastern part of the Russian Plain during the last 60 years

The eastern part of the Russian Plain is an important agricultural region of European Russia with high proportion of cultivated lands in the steppe, forest-steppe and forest (southern part) landscape zones. Soil erosion is the main process of land degradation and surface water contamination there. Climate and land cover changes have been observed in this region during the last 30 years. However, field quantitative assessments of soil erosion rates are not available for the eastern part of European Russia due to the lack of monitoring data as well as the evaluation of erosion/deposition processes in cultivated catchments using other field methods. Three representative small cultivated catchments with high (> 80%) proportion of cultivated lands were selected in the forest (southern part), forest-steppe and steppe zones of the study region to evaluate sedimentation rates in dry valley bottoms of the catchments for two-time intervals (1963–1986 and 1987–2016) based on the application of the bomb-derived and Chernobyl-derived 137Cs isotope for sediment dating. The 3–4 depth 137Cs profiles were used to assess the sedimentation rates within the each investigated catchment. It was established that the sedimentation rates have considerably decreased (at least 2–3 times) over the last 30 years compared to 1963–1986 in all the investigated catchments. This is in agreement with results of erosion rate calculations using erosion models for the forest zone, however not consistent with erosion rates assessments for the forest-steppe and steppe zones. According to the model calculations, erosion rates show a slight decrease in the forest-steppe zone and increase in the steppe zone. The reduction in surface runoff during snowmelt period is one of the reasons for decrease in erosion rates within cultivated slopes for all the investigated catchments. The increase in proportion of perennial grasses in the regional crop rotation is another important reason for the decrease in erosion rates for the catchment located in the south of the forest zone. The importance of land cover changes in a major decrease of soil losses from the cultivated fields of the investigated catchments located in the forest-steppe and steppe zones cannot be identified due to the lack detailed information about crop rotation for those particular sites. However, available regional information about crop rotation changes for the two-time intervals (1960–1980 and 1996–2012) do not explain very high reduction in sedimentation rates in the dry valley bottoms after 1986.

Impacts of climate change adaptation options on soil functions: A review of European case-studies.

Soils are vital for supporting food security and other ecosystem services. Climate change can affect soil functions both directly and indirectly. Direct effects include temperature, precipitation, and moisture regime changes. Indirect effects include those that are induced by adaptations such as irrigation, crop rotation changes, and tillage practices. Although extensive knowledge is available on the direct effects, an understanding of the indirect effects of agricultural adaptation options is less complete. A review of 20 agricultural adaptation case‐studies across Europe was conducted to assess implications to soil threats and soil functions and the link to the Sustainable Development Goals (SDGs). The major findings are as follows: (a) adaptation options reflect local conditions; (b) reduced soil erosion threats and increased soil organic carbon are expected, although compaction may increase in some areas; (c) most adaptation options are anticipated to improve the soil functions of food and biomass production, soil organic carbon storage, and storing, filtering, transforming, and recycling capacities, whereas possible implications for soil biodiversity are largely unknown; and (d) the linkage between soil functions and the SDGs implies improvements to SDG 2 (achieving food security and promoting sustainable agriculture) and SDG 13 (taking action on climate change), whereas the relationship to SDG 15 (using terrestrial ecosystems sustainably) is largely unknown. The conclusion is drawn that agricultural adaptation options, even when focused on increasing yields, have the potential to outweigh the negative direct effects of climate change on soil degradation in many European regions.

Potential benefits of farm scale measures versus landscape measures for reducing nitrate loads in a Danish catchment

To comply with the EU Water Framework Directive, Denmark must further reduce the nitrate (N)-load to marine ecosystems from agricultural areas. Under the anticipated future spatially targeted regulation, the required N-load reductions will differ between catchments, and these are expected to be mitigated by a combination of land and water management measures. Here, we explored how the expected N-load reduction target of 38% for a Danish catchment (River Odense) could be achieved through a combination of farm and landscape measures. These include: (a) N-leaching reduction through changing the crop rotation and applying cover crops, (b) enhancing N-reduction through (re)establishment of wetlands, and (c) reducing N-leaching through spatially targeting of set-aside to high N-load areas. Changes in crop rotations were effective in reducing N-leaching by growing crops with a longer growing season and by allowing a higher use of cover crops. A combination of wetlands and changes in crop rotations were needed for reaching the N-load reduction target without use of set-aside. However, not all combinations of wetlands and crop rotation changes achieved the required N-load reduction, resulting in a need for targeted set-aside, implying a need for balancing measures at farm and landscape scale to maximize N load reduction while minimizing loss of productive land. The effectiveness of farm scale measures is affected by farm and soil types as well as by N-reduction in groundwater, while the possibilities for using wetlands for decreasing the N-load depends on landscape features, allowing the establishment of wetlands connected to streams and rivers.

Preliminary estimating the contemporary sedimentation trend in dry valley bottoms of first-order catchments of different landscape zones of the Russian Plain using the 137Cs as a chronomarker

A general trend of erosion processes over the last 50–60 years can be estimated by dating sediments washed off from arable lands and accumulated in the first-order dry valleys bottoms. Three small (first-order) catchments were chosen as objects of the study. They are located, respectively, in the southern part of the taiga zone, the zone of temperate broad-leaf forests and the forest-steppe zone of the Russian Plain. To date the sediments accumulated in the bottoms the radioactive caesium-137 (137Cs) of global (since 1954) and Chernobyl origin (1986) had been used as a chronomarker. The average (for all the catchments) sedimentation rates during the global 137Cs fallout period (1963(1954)–1986) are at least 0.88–2.71 cm per year.For the period that has passed since the Chernobyl accident (1986–2015(2016)) the average rates were 0.15–1.07 cm per year. The greatest reduction in the sedimentation rates is observed in the subzone of the southern taiga, the lowest one is in the forest-steppe zone of the Russian Plain. The main reason for such significant reduction in the rates of sedimentation of the soil erosion products in the dry valley bottoms was a reduction of surface runoff within the catchments during a snowmelt period, as well as crop-rotation changes there.

Integrating Historic Agronomic and Policy Lessons with New Technologies to Drive Farmer Decisions for Farm and Climate: The Case of Inland Pacific Northwestern U.S.

Climate-friendly best management practices for mitigating and adapting to climate change (cfBMPs) include changes in crop rotation, soil management and resource use. Determined largely by precipitation gradients, specific agroecological systems in the inland Pacific Northwestern U.S. (iPNW) feature different practices across the region. Historically, these farming systems have been economically productive, but at the cost of high soil erosion rates and organic matter depletion, making them win-lose situations. Agronomic, sociological, political and economic drivers all influence cropping system innovations. Integrated, holistic conservation systems also need to be identified to address climate change by integrating cfBMPs that provide win-win benefits for farmer and environment. We conclude that systems featuring short-term improvements in farm economics, market diversification, resource efficiency and soil health will be most readily adopted by farmers, thereby simultaneously addressing longer term challenges including climate change. Specific ‘win-win scenarios’ are designed for different iPNW production zones delineated by water availability. The cfBMPs include reduced tillage and residue management, organic carbon (C) recycling, precision nitrogen (N) management and crop rotation diversification and intensification. Current plant breeding technologies have provided new cultivars of canola and pea that can diversify system agronomics and markets. These agronomic improvements require associated shifts in prescriptive, precision N and weed management. The integrated cfBMP systems we describe have the potential for reducing system-wide greenhouse gas (GHG) emissions by increasing soil C storage, N use efficiency (NUE) and by production of biofuels. Novel systems, even if they are economically competitive, can come with increased financial risk to producers, necessitating government support (e.g., subsidized crop insurance) to promote adoption. Other conservation- and climate change-targeted farm policies can also improve adoption. Ultimately, farmers must meet their economic and legacy goals to assure longer-term adoption of mature cfBMP for iPNW production systems.

Climate change impacts on the ecology ofFusarium graminearum species complex and susceptibility of wheat toFusarium head blight: a review

Fusariumhead blight (FHB) of wheat, caused mainly by a few members of theFusarium graminearumspecies complex (FGSC), is a major threat to agricultural grain production, food safety, and animal health. The severity of disease epidemics and accumulation of associated trichothecene mycotoxins in wheat kernels is strongly driven by meteorological factors. The potential impacts of change in climate are reviewed from the perspective of the FGSC life cycle and host resistance mechanisms influenced by abiotic pressures at the ecological, physiological and molecular level. Alterations in climate patterns and cropping systems may affect the distribution, composition and load of FGSC inoculum, but quantitative information is lacking regarding the differential responses among FGSC members. In general, the coincidence of wet and warm environment during flowering enhances the risk of FHB epidemics, but the magnitude and direction of the change in FHB and mycotoxin risk will be a consequence of a multitude of effects on key processes affecting inoculum dynamics and host susceptibility. Rates of residue decomposition, inoculum production and dispersal may be significantly altered by changes in crop rotations, atmospheric carbon dioxide concentration ([CO2]), temperature and precipitation patterns, but the impact may be much greater for regions where inoculum is more limited, such as temperate climates. In regions of non-limiting inoculum, climate change effects will likely be greater on the pathogenic rather than on the saprophytic phase. Although the mechanisms by which abiotic stress influences wheat defences againstFusariumspecies are unknown, available data would suggest that wheat may be more susceptible toFusariuminfection under future climate conditions. Additional research in this area should be a priority so that breeding efforts and climate resilient management strategies can be developed.

Vertical distribution and composition of weed seeds within the plough layer after eleven years of contrasting crop rotation and tillage schemes

Tillage methods and crop rotation are probably the two most important cropping factors affecting weed communities, particularly when herbicide use is restricted. This study examined weed dynamics following eleven years of different tillage and crop rotation treatments. The aboveground grass weed flora was recorded each year and the content and vertical location of individual weed seeds within the plough layer (0–20cm) were determined after 11 years of continuous mouldboard ploughing (P), pre-sowing tine cultivation to 8–10cm soil depth (H8-10) and direct drilling (D). The content of weed seeds, especially grass weeds, was determined for three distinct soil layers (0–5, 5–10 and 10–20cm), reflecting the cultivation depths of the tillage treatments. The annual grass weeds, Apera spica-venti and Vulpia myuros, were promoted by non-inversion tillage and in the case of V. myuros also by frequent cropping of winter cereals. The two non-inversion tillage treatments caused a strong stratification of weed seeds within the plough layer, with the majority of the seeds being accumulated in the upper soil layers, at 0–5 and 5–10cm, and markedly less so in the 10–20cm layer. Ploughing resulted in a more even distribution between the three layers. It is suggested that in cases where severe grass weed problems have built up in a non-inversion tillage system and where changes in crop rotation are ineffective or undesirable, inversion of the upper soil layer with the lower one could be considered a management option.

ATRIBUTOS FÍSICOS DE UM LATOSSOLO VERMELHO CULTIVADO COM PLANTAS DE COBERTURA, EM SEMEADURA DIRETA

A utilização do sistema de semeadura direta associado ao uso de plantas de cobertura e à rotação de culturas altera alguns atributos físicos do solo e pode indicar mudança em sua qualidade. Este estudo objetivou utilizar o índice de estabilidade de agregados (IEA) e o índice de sensibilidade (IS) para avaliar alterações nos atributos físicos do solo com o uso de diferentes plantas de cobertura após 12 anos de semeadura direta. Com delineamento de blocos ao acaso, utilizaram-se as coberturas: crotalária, milheto, sorgo, braquiária, pousio (vegetação espontânea), amostradas no ano de 2012, mais uma testemunha sem cobertura (semeadura convencional) desde o ano de 2000, em que foram coletadas três amostras por parcela, perfazendo um total de 12 amostras por tratamento, com quatro repetições. Foram avaliadas a densidade do solo (Ds), macroporosidade (Ma), microporosidade (Mi), porosidade total (PT), estabilidade dos agregados (EA), diâmetro médio geométrico (DMG) e ponderado (DMP), índice de sensibilidade (Is) e índice da porcentagem de agregados com diâmetro superior a 2 mm (AGRI). A utilização das diferentes coberturas e a introdução do sistema de semeadura direta após 12 anos causaram alterações positivas nos atributos físicos na camada superficial do solo. As correlações positivas e negativas significativas entre densidade do solo e os outros atributos físicos avaliados evidenciaram a sua importância como bom indicador da qualidade do solo. Por meio do índice de sensibilidade, constatou-se que microporosidade aumentou mais do que os outros atributos físicos após a implantação do sistema de semeadura direta na área.

Effects of anaerobic digestion on soil carbon and nitrogen turnover, N emissions, and soil biological activity. A review

Sustainability in agriculture means the inclusion of several aspects, as sustainable agriculture systems must not compromise not only their ability to satisfy future needs by undermining soil fertility and the natural resource base but also sustainable agriculture has had to address a range of other issues including energy use, efficient use, and recycling of nutrients, the effects on adjacent ecosystems including the effects on water bodies and climate change. Organic manures are an important factor to keep the soil fertility level of soils. However, their management is often related to large emissions. In this context, anaerobic digestion is—similarly to composting—a treatment option for stabilization of biogenic wastes leading to a residual product called digestates, enabling the sanitation and the recycling and use as fertilizer. It is also a means to obtain energy from wastes as well as from dedicated energy crops. Therefore, anaerobic digestion potentially addresses several aspects of agricultural sustainability. This review discusses the current state of knowledge on the effects of anaerobic digestion on organic compounds in digestates and the most important processes influencing N emissions in the field, as well as the possible long-term effects on soil microbial biomass and soil fertility. The main findings are that (1) the direct effects of anaerobic digestion on long-term sustainability in terms of soil fertility and environmental impact at the field level are of minor relevance. (2) The most relevant effects of anaerobic digestion on soil fertility as well as on N emissions will be expected from indirect effects related to cropping system changes such as changes in crop rotation, crop acreage, cover cropping, and total amounts of organic manures including digestates. Furthermore, (3) the remaining organic fraction after anaerobic digestion is much more recalcitrant than the input feedstocks leading to a stabilization of the organic matter and a lower organic matter degradation rate after field application, enabling a similar reproduction of the soil organic matter as obtained by direct application of the feedstock or by composting of the feedstock. (4) Regarding emissions, the main direct effect of anaerobic digestion on a farm level is the influence on gaseous emissions during manure or digestate treatment and handling, whereas the direct effects of anaerobic digestion on a field level on emissions (NH3 − and N2O− emissions, NO3 - leaching) are negligible or at least ambiguous. (5) The main direct effects of anaerobic digestion on the field level are short-term effects on soil microbial activity and changes in the soil microbial community. Therefore, in terms of the effects on agricultural sustainability, potential cropping system-based changes induced by introduction of biogas plants are probably much more relevant for the overall performance and sustainability of the cropping system than the direct effects triggered by application of digestates in comparison to the undigested feedstocks. Furthermore, to get the full potential advances from implementation of biogas plants in terms of improvement of the nutrient use efficiency and reduction of greenhouse gas emissions, there is the need to introduce more sophisticated techniques to avoid counteracting effects by pollution swapping, e.g., by gas-tight closure of the digestate stores and direct soil incorporation of the field-applied digestates.

Evaluating the nature conservation value of field habitats: A model approach for targeting agri-environmental measures and projecting their effects

Agricultural practice is one of the most important factors leading to biodiversity loss. EU policies addressing this problem involve the provision of incentives for agri-environmental measures (AEM) and setting of targets for AEM on the national scale (e.g. for the amount of organic farming according to the German sustainability strategy), as well as monitoring their success. For AEM to most efficiently target, implement and monitor, they require comparable evaluation of results, describing their quantitative effects on biodiversity and nature conservation. However, there is a dearth of regional data about species and habitats, parts of biodiversity that are relevant for nature conservation. Thus, quantitative analyses are not typically feasible. Furthermore, impacts of agricultural practices on biodiversity cannot be analysed and evaluated merely from individual cases. Comparisons with average or maximum achievements on different spatial scales (benchmarking) are needed. However, meaningful state and pressure indicators are lacking for modelling the nature conservation value of agricultural fields and the consequences of changing pressures from agricultural practice.In this paper we present a model for evaluating the nature conservation value of field habitats based on projected field flora species richness. We propose a combination of an existing evaluation scale for habitat types, as the basis of the model setup, with field flora species richness. These are combined to obtain differentiated conservation values of field habitats as a measure of agricultural effects. We defined the field flora species richness as the total number of species on a homogenously managed field minus the cultivated crop. Indicators of the model are farming practices and site conditions. Based on an extensive literature review, these indicators were analysed regarding their influence on the flora species richness. Influences of the farming practices were reflected by the crop type, which was used as key indicator. As an outcome, the influence of conventional farming, organic farming and nature conservation oriented management on flora species richness was quantified. Additionally, we integrated the diversity of crop types and (semi-) natural habitats of the surrounding landscape into the model, in order to consider potential effects of landscape heterogeneity on field flora species richness.The model was applied in a case study at the NUTS 3-regional level (Nomenclature of territorial units for statistics), using the example of the AEM organic farming. In a scenario, we evaluated the possible effects of a complete conversion to organic farming on the assumed flora species richness. The results reveal that the modelling approach can be used to test for the effects of (i) conversion between organic and conventional farming, (ii) changes in crop rotations, and (iii) targeted positioning of organic farming or botanical management agreements in comparison to the spatially untargeted offering of payments.