Organic Carbon Balance Research Articles

Effect of Different Irrigated Crop Successions on Soil Carbon and Nitrogen–Phosphorus–Potassium Budget Under Mediterranean Conditions

Sustainability in agroecosystems relies on the optimized use of resources to achieve consistent yields while maintaining or improving soil health. The monitoring of soil quality is crucial when changes from rainfall-fed to irrigated crop systems occur. The objective of this study was to assess the impact of different crop successions in the Mediterranean area under irrigation and different technical practices. The soil nitrogen–phosphorous–potassium (NPK) and soil organic carbon (SOC) balances were observed in four fields with irrigated annual crops in a two-year succession timeframe, namely, sunflower–maize (P1), sunflower–clover (P2), maize–sunflower (P3), and alfalfa–alfalfa (P4). The SOC and nutrient balance, integrating the total irrigation, mineral fertilizers, and exported yield, was calculated for each farm. Except for maize–sunflower succession (P3), all fields presented a negative SOC balance at the end of the two-year crop succession, indicating losses from 2.84 to 4.91 Mg SOC ha−1 y−1. While in N-fixing plants the soil N decreased, in the remaining crops a surplus was observed, possibly leading to future N losses. The continuous depletion of soil P revealed a potential underestimation of this nutrient. Soil K appears to be related to specific crop management practices, namely, crop residue incorporation after harvest. In annual irrigated crops under Mediterranean conditions, crop succession can induce soil fertility degradation if conservation practices are absent.

Priming and balance of soil organic carbon differ with additive C:N ratios and long-term green manuring

The input of organic C strongly alters the magnitude and direction of the microbial mineralization of soil organic matter (SOM), a phenomenon known as the “priming effect” (PE). The C:N ratios of additives are expected to affect the intensity of PE as it balances the C and N requirements of microbial growth. Growing of green manure (GM) crops in agricultural system strongly regulates PE intensity as it enhances the level and stability of SOM. However, the driving factors of additive C:N ratios and long-term GM crops on PE remain unclear. We addressed this knowledge gap by performing a 92-day incubation of 10-year summer fallow-wheat and GM-wheat soils by adding mixtures of 13C-labelled glucose and ammonium sulfate differing in the C:N ratio (15 vs. 50). The PE was increased by 148–288 % due to the high C:N ratio of the added mixtures, indicating that the quality of input exerted effects on the PE across the two soils. The PE of green manured (GMd) soil was increased by 23 % (p < 0.05) compared with that of summer fallow soil, as microorganisms produce extracellular enzymes such as β-glucosidase and leucine aminopeptidase to co-metabolize SOM. Nevertheless, compared with the summer fallow soil, 26 % more glucose-C was sequestered in GMd soil to compensate for C loss. We propose a conceptual model of “N mining” and “co-metabolism” to explain the effect of additive C:N ratio on PE in the soils under different GM practices. The “N mining” is the main cause of PE when the additive C:N ratio is high, and the “co-metabolism” becomes the dominant factor in long-term GMd soil with high SOM content and stability. Our findings demonstrate the importance of long-term incorporation of GM-driven changes in organic C inputs and SOM content and stability in regulating PE and soil C dynamics. Understanding the C dynamics under long-term GM practices contributes to formulate optimized agricultural strategies for promoting C sequestration and accurately predict soil C dynamics in the future.

Contrasted effects of shade tree legumes on soil organic carbon stock and carbon balance in 20-year cacao agroforestry, Ivory Coast

Cacao–based agroforestry systems are promoted as adaptation and mitigation solutions for cacao production and carbon sequestration. Based on a 20-year experiment, we assessed the impact of associated shade tree legume (ATL), Albizia lebbeck and Acacia mangium on the total carbon stock (in soil at 60 cm depth + tree biomass + litter) of cacao stands. This study included cacao systems shaded with either A. lebbeck (Cacao-Alb) or A. mangium (Cacao-Aca) and full-sun cacao stands (Control). Soil organic carbon (SOC) contents (up to 60 cm deep) were estimated by a calibrated near-infrared spectroscopy model. Total tree biomasses were estimated using allometric equations. Leaf litter was sampled from 1-m2 quadrats. Compared to Control, Cacao-Aca had a significant negative impact on the carbon stock in the cacao biomass (−47%) as well and in the soil at depths of 10 cm (−23%), 30 cm (−21%) and 60 cm (−12%). In contrast, Cacao-Alb had a nonsignificant effect on carbon storage in the cacao biomass, whereas it generally had a positive influence on the SOC stock regardless of depth, i.e., +6% at the 0–10 cm depth, +7% at 0–30 cm, +20% at 30–60 cm and + 11% at 0–60 cm. Cacao-Aca had a significant positive impact (+71%) on the total carbon stock per hectare. The increase in Cacao-Alb relative to that in the Control reached +38%, but the difference was not significant. These contrasting results between the two tree legume species could be explained by the high-quality litter, reflected by the lower C/N and C/P ratios produced by A. lebbeck, and the greater negative impact of A. mangium on cacao biomass. The main finding of this study is that the impact of intercropping cacao with shade tree legumes on the stand-level total carbon stock depends on the ATL species.

Climate-regulation of organic carbon export in erosive mountain settings: A case study from Taiwan since the last glacial maximum

The balance between the burial of biospheric organic carbon (OCbio) in the ocean and the oxidation of rock-derived organic carbon across landscapes (OCpetro) helps to regulate atmospheric CO2 and O2 over geological time. However, we lack reconstructions of these processes over the timescales necessary to properly understand the drivers and feedbacks operating. Here we use a sediment core from the Zhuoshui River delta in Taiwan, which receives sediments from a rapidly uplifting and eroding catchment, to reconstruct the variations in OC content and radiocarbon composition since the Last Glacial Maximum (LGM). We find that the export of OCbio and the oxidation of OCpetro are both modulated by climate-driven changes in physical erosion and temperature. During cold and dry periods, such as the LGM and the Younger Dryas (YD), shallow erosion and low temperature enhanced the preservation of OCbio in the biosphere in catchment, while deep erosion and high temperature during warm and wet periods, such as the Holocene, favored the dilution and degradation of OCbio. The weathering intensity of OCpetro (ω) was inversely related to physical erosion, suggesting a lower intensity of oxidation during the Holocene period while the overall oxidation flux was enhanced. This suggests that the degree of weathering was primarily controlled by physical erosion. We propose a proxy to estimate the ratio of fluxes of OCbio export and OCpetro oxidation, and show that the net balance between these two processes shifted from a carbon sink during the late deglacial period to a carbon source during the mid-late Holocene. Our study reveals that with CO2 rise, a warmer and wetter climate would promote the exposure and oxidation of OCpetro by erosion in this mountain range, leading the organic carbon balance towards a CO2 source to the atmosphere.

Fractions of Organic Matter and Soil Carbon Balance in Different Phases of an Agroforestry System in the Cerrado: A Ten-Year Field Assessment

Integrated production systems composed of trees, crops and pastures have shown good results in improving soil quality and the capacity to store carbon in the soil, being efficient in mitigating greenhouse gas emissions. Despite this, changes in carbon stocks and soil organic matter fractions in the initial stages of implementing an agroforestry system remain unclear. This study evaluated the carbon balance and the dynamics of soil organic matter fractions in an agroforestry system conducted over a decade. Total carbon, labile carbon, carbon from particulate organic matter, organic carbon associated with minerals and inert carbon were determined at depths 0–10 cm, 10–20 cm and 20–40 cm. Soil carbon stocks were also estimated for the 0–40 cm depth. Total carbon increased in the agroforestry system compared with a low-productivity pasture. The total carbon stock in the last growing season (68.57 Mg ha−1) was close to the original soil stocks under native Cerrado vegetation (76.5 Mg ha−1). After 10 years, there was a positive balance in the soil carbon stock of both the total carbon and the soil organic matter fractions. The successional agroforestry system is a good alternative to increasing soil total carbon stocks and labile and non-labile fractions of soil organic matter.

Role of Lakes, Flood, and Low Flow Events in Modifying Catchment‐Scale DOC:TN:TP Stoichiometry and Export

AbstractThe balance of organic carbon (OC), nitrogen (N) and phosphorus (P) plays a crucial role in determining the processing, retention, and movement of these solutes across the aquatic continuum. Floods and droughts can significantly alter the quantity and ratios of OC:N:P export within inland waters, but how these ratios change, and are coupled within watersheds that integrate rivers and lakes, is not well known. We investigated the stoichiometry and export of dissolved organic carbon (DOC), total N (TN) and total P (TP) in two lake watersheds (10 inflows, 2 outflows) in the southern Boreal Shield over a 37‐year period. Although DOC, TN, and TP concentration behaved similarly, DOC:TN:TP ratios varied seasonally, strongly modulated by stream discharge. DOC:TN, DOC:TP and TN:TP export initially increased rapidly with increasing discharge, peaking at 10%–20% exceedance of the annual discharge for DOC:TP and TN:TP ratios, indicating a rapid depletion of catchment OC sources. Both flood and low flow events resulted in lower DOC:TN and lower DOC:TP export—thereby increasing the relative contributions of stream TN and TP. Consequently, elevated annual discharge coupled with infrequent but high floods and periods of low flow events increased the contributions of TN and TP relative to DOC. Overall, the lakes retained DOC, while increasing TN relative to TP. Nonetheless, the flow regime played a role in modulating nutrient retention in the lakes, likely due to changes in residence time, and the interplay of physical, photochemical, and biological degradation processes.

Fast Transit of Carbon Inputs in Global Soil Profiles Regardless of Entering Depth

AbstractClimate and land management changes are altering carbon inputs to soil. The consequence of such input changes on long‐term soil organic carbon (SOC) balance depends on the transit behavior of carbon inputs. Using observational carbon input and radiocarbon data in global soil profiles, we reveal that on average nearly 25% of new entering carbon leave soil in 1 year irrespective of entering depth, and the remained fraction after 30 years is only ∼13%. Nevertheless, the majority of SOC is older than 30 years in all soil depths. Together, these results demonstrate low transfer efficiency of carbon inputs to aged SOC which is the meaningful carbon component for long‐term SOC sequestration. Additionally, we reveal that SOC aging and carbon input transiting are two distinct processes, which should be simultaneously, but mechanistical‐separately, considered to predict and manage SOC dynamics in response to carbon input changes under climate and land management changes.

Wetland soil organic carbon balance is reversed by old carbon and iron oxide additions.

Iron (Fe) oxides can stabilize organic carbon (OC) through adsorption and co-precipitation, while microbial Fe reduction can disrupt Fe-bound OC (Fe-OC) and further increase OC mineralization. The net effects of OC preservation and mineralization mediated by Fe oxides are still unclear, especially for old carbon (formed from plant litters over millions of years) and crystalline Fe oxides. Accelerating the recovery of wetland carbon sinks is critical for mitigating climate change and achieving carbon neutrality. Quantifying the net effect of Fe-mediated OC mineralization and preservation is vital for understanding the role of crystalline Fe oxides in carbon cycling and promoting the recovery of soil carbon sinks. Here, we explored the OC balances mediated by hematite (Hem) and lignite addition (Lig) to freshwater wetland (FW, rich in C and Fe) and saline-alkaline wetland (SW, poor in C and Fe) soil slurries, incubated under anaerobic conditions. Results showed that Lig caused net OC accumulation (FW: 5.9 ± 3.6 mg g-1; SW: 8.3 ± 3.2 mg g-1), while Hem caused dramatic OC loss, particularly in the FW soils. Hem inhibited microbial Fe(III) reduction by decreasing the relative abundance of Fe respiration reducers, while substantially enhancing OC mineralization through the shift in the microbial community structure of FW soils. Lig resulted in carbon emission, but its contribution to preservation by the formation of Fe-OC was far higher than that which caused OC loss. We concluded that crystalline Fe oxide addition solely favored the increase of OC mineralization by adjusting the microbial community structure, while old carbon enriched with an aromatic and alkyl promoted Fe-OC formation and further increased OC persistence. Our findings could be employed for wetland restoration, particularly for the recovery of soil carbon sinks.

Different organic farming systems under greenhouse do not improve soil C storage but affect microbial functions across soil aggregates

AbstractVegetable crops production is usually based on organic fertilizers purchased off‐farm while the care of soil fertility based on the maintenance of adequate level of soil organic matter receives few attentions. Organic production in plastic tunnel‐greenhouses represents the most intensified organic production system. Therefore, we compared four alternative organic production systems mainly characterized by the combination of fertilizer application practices based on compost, cover crops and commercial organic fertilizers. The systems were: input substitution organic method (BAU), biodynamic method (BIODYN), organic‐agroecological (AGROEC) and a not fertilized but organically managed control (CNT). The objective of this study was to explore in a 3‐year long trial, the effects of different organic systems on soil organic carbon (SOC) balance and the possible effects on soil chemical–physical characteristics, enzymatic activities involved in the C, N and P cycling, total bacterial biomass (16S rRNA), and the microbial functional genes cbbL and amoA in bulk soil and in three aggregate size fractions (macroaggregates &gt;250 μm, free microaggregates 250–53 μm and free silt plus clay (free‐SC) &lt; 53 μm). The conducive microclimatic conditions for soil microbial activities under the greenhouse, together with the transition toward a more intensive rotation and tillage, determined a decrease of the SOC stock (from 5.9 Mg C ha−1 in BIODYN to 10.8 in CNT) that was only partially balanced by C input distributed to soil (from 4.6 Mg C ha−1 in CNT to 31.6 in AGROEC). The different organic systems did not seem to directly affect chemical and microbial properties in the bulk soils. The higher SOC decline in CNT, however, resulted in the degradation of soil structure but at same time led to the increase of the FDAse in the bulk soil. At aggregate level, instead, more evident effects of organic systems were observed on both chemical–physical and microbial properties. The impact of organic systems on enzymatic activities differed in the different aggregate size classes while the effect on bacterial biomass and functional genes was the same in all aggregate size classes. Interestingly, the cbbL gene abundance in soil aggregates, especially in macroaggregates, was correlated positively to OC inputs (r = .82; p &lt; .001). The amoA gene and bacterial biomass, instead, put in evidence for BIODYN, a significant decrease in soil aggregates that seemed to be related, particularly in macro and free microaggregates, to the low amount of total N content. In soil aggregates, only AGROEC compared with CNT, determined the increment of the phosphatase in macroaggregates, while BIODYN and BAU highlighted even lower values of β‐d‐glucosidase, β‐d‐glucosaminidase and phosphatase in free‐SC. In conclusion in high‐input organic systems under tunnels, the misleading notion that a high supply of OC and TN through green manuring, compost amendment etc., improves per se soil health is challenged.

The soil microbial necromass carbon and the carbon pool stability drive a stronge priming effect following vegetation restoration

The priming effect stands as a critical factor influencing the balance of soil organic carbon (SOC). Following vegetation restoration, the carbon (C) pool stability in Platycladus orientalis forests (PO) varies, and the priming effect resulting from exogenous C addition also differs significantly. Here, we selected PO with restoration ages of 10, 15, and 30 years in the rocky mountainous area in northern China and conducted measurements of soil properties, microbial communities, microbial necromass C (MNC), SOC fractions, and the priming effect characteristics to explore the main influencing factors of the priming effect, especially the microbiological mechanisms. Our results showed that the ratio of mineral-associated organic C to particulate organic C increased. The characteristics of the priming effect showed the same pattern, and there was a significant positive correlation between the C pool stability and the priming effect. The diversity of the fungal communities increased with increasing vegetation restoration age, and the content and proportion of fungal necromass C (FNC) also increased synchronously, reaching the maximum value in the soil of PO that had been restored for 30 years. In addition, the soil water content and total nitrogen indirectly affected the priming effect by influencing the microbial communities. In summary, the results suggested that vegetation restoration can enhance the C pool stability by promoting an increase in soil FNC, thereby producing a positive priming effect. This can help deepen our understanding of the SOC mineralization changes induced by fresh C input following vegetation restoration and provides a theoretical basis for better explaining the C cycle between soil and atmosphere under the vegetation restoration models in the future.

Grazing exclusion is more beneficial for restoring soil organic carbon and nutrient balance than afforestation on degraded sandy land.

Vegetation restoration is an effective measure to improve the ecosystem service of degraded sandy land ecosystem. However, it is unclear how vegetation restoration on severely desertified land affect soil organic carbon (SOC) sequestration and nutrients balance. Therefore, this study was designed to clarify the response of SOC, total nitrogen (TN), total phosphorus (TP), and the resulting stoichiometric ratios (C:N:P) to afforestation and grazing exclusion, and to quantify their dynamics over time. We conducted vegetation community investigation and soil sampling in natural sparse-forest grassland (the climax community stage), afforestation (Pinus sylvestris var. mongolica (40-year, 48-year), Caragana microphylla (20-year, 40-year)), and grazing exclusion (20-year, 40-year) in China's Horqin Sandy Land. Soil C:N:P stoichiometry and its driving factors under different restoration measures were then studied. Afforestation and grazing exclusion significantly (p < 0.05) increased SOC, TN, and TP concentrations. Vegetation restoration significantly increased C:N, C:P, and N:P ratios, indicating that nutrient limitations may occur in the later stages of restoration. The C:N, C:P, and N:P ratios after a 40-year grazing exclusion were closest to those of natural sparse-forest grassland. The N:P under grazing exclusion increased from 3.1 to 4.1 with increasing restoration age (from 20 to 40 years), which was close to the national mean values (4.2). Moreover, afforestation may lead to water deficit in the surface soil. Vegetation restoration is the main factor leading to changes in soil C:N:P stoichiometry, and indirectly affects soil C:N:P stoichiometry by altering soil structure and chemical properties. In terms of ecological stoichiometry, grazing exclusion was more conducive to restore SOC and nutrient balance than afforestation on severely desertified land. Due to the poor soil nutrients, attentions should be paid to the soil nutrients and water conditions in the later stages of vegetation restoration. Those findings can provide valuable information for the restoration of degraded sandy land in semi-arid areas.

ОЦЕНКА ЗАПАСОВ УГЛЕРОДА И КОМПОНЕНТОВ УГЛЕРОДНОГО СЛЕДА БАЛАНСОВЫМ МЕТОДОМ НА ПАХОТНЫХ ЗЕМЛЯХ РЕГИОНОВ РОССИИ

The paper analyzes the problems of carbon stocks variation in the pool of cropland mineral soils at the regional scale of the Russian Federation. The carbon stock balance of cropland soils was evaluated by estimating carbon gains and losses, and then the components of the carbon footprint were measured as a ratio of soil organic carbon balance to crop production quantity in terms of grain equivalent (t C/t grain eq.). The estimates for the period 2011-2020 have revealed that there is generally a small net gain of carbon on cropland in Russia, mainly due to the intake of carbon from plant residues. Most of the steppe region of Russia suffers from net losses of carbon at levels from -0.15 t C/t grain eq. up to -0.69 t C/t grain eq. In other regions, such as the Central Chernozem and Black Sea Coast regions, net carbon gain is observed in the range of 0.1-0.3 t C/t grain eq. due to the intake of significant biomass of crop and root residues as a consequence of intensive crop production.

Soil organic carbon balance across contrasting plant cover ecosystems in the Peruvian Amazon

Soil organic carbon balance across contrasting plant cover ecosystems in the Peruvian Amazon

Microbial-driven carbon fixation in natural wetland.

With the development of global industrialization, carbon neutrality has become an issue that we must be paid attention to. Microorganisms not only have an important impact on the carbon chemical cycle between the Earth's biosphere and biogeography but also play a key role in maintaining the global organic carbon balance. Wetlands are the main reservoir of organic carbon in the mainland of China, and wetland carbon sinks are indispensable for China to achieve the goal of "dual carbon," and China has taken the consolidation and improvement of wetland carbon sink capacity as an important part of the carbon peaking action plan. As a unique low-latitude, high-altitude seasonal plateau wetland in China, Napahai shows high research value. However, the role of microbes in maintaining dissolved organic carbon balance in this area has not been reported. In the study, six carbon fixation genes, accA, aclB, acsA, acsB, cbbL, and rbcL, were analyzed based on metagenomics to elucidate the rich genetic diversity, uniqueness and differences in the Napahai plateau wetland. It was found that the microbial diversity in the Napahai plateau wetland was different from other habitats. In addition, the aclB gene, a rare taxon with high genetic diversity and rich species in the Napahai plateau wetland, played a key role in the microbial metabolic pathway. Finally, the construction of a metabolic pathway through the Kyoto encyclopedia for genes and genomes revealed the contribution of microbes to carbon fixation and the role of microbes in maintaining the organic carbon balance of the Napahai plateau wetland.

Efficiency of Application of Organic, Organo-Mineral and Mineral Fertilizer Systems on Sod-Podzolic Heavy Loamy Soil in Sis-Urals

In a long-term field experiment, laid down in 1968, an assessment of the effectiveness of the use of organic, mineral and organo-mineral fertilizer systems on sod-podzolic heavy loamy soil was carried out. It was found that in the climatic conditions of the Urals, the organic fertilizer system was inferior to the mineral and organo-mineral fertilizer systems in terms of its effect on crop yields. In some rotations of crop rotations, the organo-mineral fertilizer system was more effective, in others - the mineral fertilizer system. The effectiveness of the use of fertilizers depending on the conditions of humidification of the growing season is considered. The balance of organic carbon and basic nutrients in the soil is calculated. Long-term cultivation of agricultural crops without the use of fertilizers led to the loss of 10 tons of organic carbon, ~2300 kg of nitrogen, 780 kg of phosphorus and 2700 kg of potassium from the soil. High negative balances of basic nutrients in the control variant led to a deterioration in soil fertility indicators. It is shown that the use of all fertilizer systems provided an increase in the content of mobile phosphorus and potassium compounds in the soil relative to the initial level by 1.2-3.0 times. When using organic and organo-mineral fertilizer systems, the maintenance of organic carbon content at the initial level (1.3%) was noted. When using a mineral fertilizer system, the maintenance of the organic carbon content at the initial level was noted only at a higher saturation of the arable land with NPK. The mineral fertilizer system has led to acidification of the soil.

Mixed planting improves soil aggregate stability and aggregate-associated C-N-P accumulation in subtropical China

Research on the variations in soil aggregate stability and ecological stoichiometry at aggregate scales by stand type is of great significance in investigating the distribution, limitation, balance, and cycling of organic carbon, nitrogen, and phosphorus (C-N-P). However, the effect of pure and mixed Chinese fir plantations on soil aggregate stability, organic carbon (OC), total nitrogen (TN), and total phosphorus (TP) stoichiometry characteristics at aggregate scales is still unclear. In this research, we explored the variations in soil aggregate mean weight diameter (MWD) and geometric mean diameter (GMD); soil OC, TN, and TP contents and stocks and the C:N:P ratios as affected by different stand types (mixed stands of Chinese fir and Mytilaria laosensis, mixed stands of Chinese fir and Michelia macclurei, and pure stand of Chinese fir); and aggregate size (&amp;lt;0.25, 0.25–1, 1–2, and &amp;gt;2 mm) at 0–20 and 20–40 cm depths in subtropical China. The soil OC and TN contents, as well as C:N:P ratios declined as aggregate size increased, whereas the C-N-P stocks showed the opposite tendencies, which were more distributed in &amp;gt;2 mm aggregates. Mixed stands of Chinese fir and M. laosensis with Chinese fir and M. macclurei displayed significantly higher soil aggregate stability, aggregate-associated TP content, OC and TN contents and stocks, and C:N and C:P ratios than did pure stands of Chinese fir. Soil aggregate stability was significantly positively correlated with the C-N-P contents and stocks as well as the C:N and C:P ratios, especially the C:N ratio and TN content. Overall, this work offers further information for scientific management and sustainable development of Chinese fir plantations, soil OC and nutrient cycling with ecological stoichiometry in the global terrestrial ecosystem.

Biological CO2 cycle and organic carbon balance in maize (Zea mays) – soybean (Glycine hispida (Moench) Maxim.) agrocenosis in sod-podzolic soil

Topicality. Today, the search for ways to accumulate organic carbon and restore soil fertility, as well as increase crop yield, is a topical issue for the sod-podzolic soils of Western Polissia. Purpose. To determine the intensity of CO2 emission and the organic carbon balance on sod-podzolic soil at different fertilizer rates in the maize-soybean link against the background of chemical amelioration with incorporation of by-products. Methods. We used such methods as a stationary field trial, comparative and calculation method to determine the accumulated and emitted CO2 by plants, analytical and calculation methods to determine the organic carbon balance. Results. The CO2 emissions from organic matter mineralization amounted to 5.01–5.45 t/ha by the recommended fertilizer rate and calculated by the normative method on the background of dolomite and limestone powder, which was 23.4–34.2 % higher than the control (without fertilizers). The CO2 emission into the atmosphere through plant mass mineralization, depending on fertilization and chemical amelioration, was in the range of 18.6–24.7 t/ha and exceeded the control (without fertilizers) and the background of 1.0 Hh (hydrolytic acidity) CaMg(CO3)2 by 1.2–2.0 times, which is associated with improved soil conditions, higher by-products mass and CO2 accumulation by plants. The highest amount of CO2 was accumulated by maize (64.8–65.0 t/ha) and soybean (15.0–15.8 t/ha) at combination of the fertilizer rate calculated by the normative method with microfertilizers on the background of dolomite flour. The application of calculated fertilizer rates on the background of 1.0 Hh CaMg(CO3)2 provided an advantage in the formation of organic carbon in the soil, which formed a positive balance of 0.12 and 0.15 t/ha. In the variant without fertilizers and chemical amelioration, the ratio of total CO2 emissions into the atmosphere per 1 t of grain yield in the maize-soybean link was 4.65 and 4.62 units, while the application of the fertilizer rate calculated by the normative method against the background of 1.0 Hh CaMg(CO3)2 decreased to 3.78 and 3.89 units, respectively. Conclusions. For increasing the maize and soybean productivity on sod-podzolic loamy sandy soil, incorporation of plant mass into the soil with applying the fertiliser rates calculated by the standard method against the background of 1.0 Nh CaMg(CO3)2 is an effective method to control soil degradation that ensures the inclusion of additional organic carbon into the cycle, which is aimed at its fixation by forming a deficit-free balance of 0.12 and 0.15 t/ha. Key words: emission, organic carbon, productivity, fertilization, land amelioration, plant mass

Assessment of the Condition of the Project Environment for the Implementation of Technologically Integrated Projects of the “European Green Deal” Using Maize Waste

In the research carried out by the authors, an approach to the assessment of the project environment of technologically integrated “European Green Deal” projects using corn waste was developed, which takes into account the changing project environment, which determines the risk of the specific cost of disposal of corn waste. On the basis of the predicted approach and the established trends of changes in the specific volume of corn food products from its yield, as well as the specific cost of disposal of corn waste from its specific volume under the condition of maintaining the balance of organic carbon in the fields, a computer program in the Python 3.9 language was developed. The program makes it possible to speed up calculations and perform a quantitative assessment of the state of the project environment in certain regions of the implementation of projects of the “European Green Deal” (TIP of the EGD) using corn waste. An approach to assessing the state of the project environment of TIP of the EGD using corn waste is proposed. A block diagram of the algorithm for assessing the state of the project environment was created, which involves the implementation of ten stages. It provides for determining the dynamics of inequality of individual regions in terms of resource potential for the production of clean energy from corn waste according to the Gini index. The Gini index was used to assess three indicators that take full account of the unevenness and dispersion of raw materials in a given area for the production of clean energy. This provides a preliminary assessment of the risks to stakeholders for stakeholders in technologically integrated projects of the “European Green Deal” using maize waste. Based on the proposed approach, a computer program in Python 3.9 was developed. It provides an opportunity to speed up the calculations and perform a quantitative assessment, according to these indicators, of the state of the project environment in some regions regarding the TIP of the EGD. The uneven distribution of raw materials in the territory of Ukraine for the production of environmentally friendly energy from corn waste and the risk of value for stakeholders were assessed. It is established that in the territory of Ukraine there are nine regions (Dnipropetrovsk, Donetsk, Zaporizhzhia, Kirovohrad, Luhansk, Mykolaiv, Odesa, Kharkiv, Chernivtsi), which do not ensure the preservation of the balance of organic carbon in the fields during long-term cultivation of corn. In addition, four regions of Ukraine (Vinnytsia, Poltava, Kherson, Zakarpattia) have an unfavorable project environment in terms of risk. In these regions, the Gini index exceeds the critical value of the three studied indicators. The Zakarpattia region is the most unfavorable for the implementation of the TIP of the EGD. It is established that the minimum material risk for the implementation of technologically integrated projects with the use of corn waste is observed in three regions of Ukraine (Sumy, Rivne, Ternopil).

Uncertainty evaluation and performance assessment of water quality model for mariculture management.

Ecosystem based water quality models are important tools for prognostic site assessment and evaluation of ecosystem-performance of marine fish farms. We present the development and application of a comprehensive Fish Culture Zone Water Quality Model using continuous bi-weekly field data over a six-year period (2012-2017). The model simulates five interacting subsystems: phytoplankton, phosphorus and nitrogen cycles, and the dissolved oxygen (DO) and particulate organic carbon balance. The application of the model to two fish culture zones in Hong Kong shows the model captures the trends of nutrient and DO variation and the performance in quantitative prediction of algal biomass is challenging. The effect of errors in the specification of primary model inputs are evaluated using dimensionless sensitivity coefficients based on First Order Variance Analysis reveals the relative importance of fish stock (loading), physical size (volume), tidal flushing rate and boundary conditions in the prediction of key water quality variables.

The evolution of the carbon footprint of Dutch raw milk production between 1990 and 2019

The development of the carbon footprint (CF) of raw cow milk over time has been scarcely researched. The objectives of this study are (1) to determine the annual raw cow milk CF in the Netherlands between 1990 and 2019 and (2) to identify the factors explaining the development of the raw cow milk CF over time. We applied Life Cycle Assessment (cradle to farm gate) to the average Dutch dairy system and used data collected from national statistics and from the farm accountancy data network.The CF of raw cow milk produced in the Netherlands in 2019 was 992 g CO2-eq. per kg Fat and Protein Corrected Milk (FPCM), while in 1990 it was 1522 g CO2-eq. (kg FPCM)−1. This represents a reduction of 35%. The reduction rate of the CF is affected by the scope of the CF study, i.e. reduction rate is smaller if direct land use change (dLUC) (32%) and soil organic carbon (SOC) balance (29%) are included in the total CF. Methodological choices affect the absolute level of the CF by up to 27%, but the impact on the reduction rate over time is negligible. The results show that continuous improvement in agricultural practices (increased milk and roughage yields, improved feed efficiency and decreased nitrogen application) has played an important role in reducing the CF of milk over the years. Along with this process, the Dutch dairy system has evolved into less grazing and less land devoted to permanent grasslands which decreased carbon sequestration. In order to achieve climate targets, the annual reduction rate needs to be increased and additional efforts are required if the Dutch dairy sector is to play its part in limiting global warming to 1.5 °C. Special attention is needed for the reduction of greenhouse gas (GHG) emission from enteric fermentation and manure storage. However, the main challenge for the future is to find a balanced set of measures to integrally reduce all the sources of GHG emission within the carbon footprint of milk.