Synthetic Nitrogen Fertilizers Research Articles

Annual consumption and types of synthetic nitrogen fertilizers: Ammonia emission indicators for mitigation strategies in the European Union

Anthropogenic ammonia (NH3) emissions are primarily derived from agricultural activities. NH3 emissions from synthetic nitrogen (N) fertilizers are associated with the annual consumption of various N fertilizers. In this study, the annual consumption of different types of synthetic N fertilizers in the EU countries, derived from the database of the International Fertilizer Association, was analyzed, and the implementation of mitigation measures for NH3 emissions at the national level was assessed. NH3 emissions were estimated using the emission factors of different N fertilizers in cool, temperate and hot climates, and low- and high-pH soils, as the European Environment Agency proposed. The results revealed that the annual consumption of various synthetic N fertilizers (average values from 2016 to 2020) varied markedly in different EU countries. France, Germany, Poland, Spain, and the United Kingdom had the largest annual consumption of synthetic N fertilizers. NH3 emissions from urea-based fertilizers are the highest in most EU countries. The annual NH3 emissions were associated with the type of synthetic N fertilizer consumed. For example, although the annual synthetic N fertilizer consumption in Germany was 38% and 41.5% higher than those in Spain and Italy, the annual NH3 emissions in Germany were 63% and 20% lower than those in Spain and Italy, respectively, due to the high proportion of urea-based fertilizers with the highest emission factor among the synthetic N fertilizers in Spain and Italy. Thus, mitigation strategies should be tailored to specific types of N fertilizers with high emission factors and proportions to minimize NH3 emissions. Since the NH3 emissions from urea-based fertilizers are the highest in the EU countries, especially in the top five countries, we recommend the addition of urease inhibitors to urea fertilizers as one important strategy for mitigating NH3 emissions.

Sustainability analysis of irrigated and rainfed wheat production systems under varying levels of nitrogen fertilizer through coupling of emergy accounting and life cycle assessment

Most of the crop production systems have strived for improving crop productivity by increasing various resource inputs; especially water and synthetic nitrogen (N) fertilizer, without considering their environmental consequences. Yet, only few studies have evaluated the sustainability of cropping systems simultaneously using life cycle assessment (LCA) and emergy accounting (EMA) techniques. The former highlights pollutant emissions and environmental impacts, while the latter emphasizes resource consumption and system efficiency. In this three-year field study, the environmental impacts and sustainability of farming systems were estimated under rainfed and irrigated patterns at four N application rates in the Northwest China. Our result indicated that the irrigated pattern enhanced grain yield by 9%, while simultaneously increasing 8% of environmental impact and 12% of emergy input based on per hectare of wheat production. Almost similar results of environmental impact per kg basis of grain production and emergy sustainability index revealed that irrigation practice did not decrease the overall sustainability of a cropping system. Conversely, the higher N levels of 240 and 360 kg N ha−1 did not provide a proportionate yield return and were accompanied by increased environmental impacts of 20% and 69%, respectively on per kg grain production basis, when compared to an N dose of 120 kg N ha−1. Meanwhile, the gross unit emergy value revealed that the production efficiency under 120 kg N ha−1 was enhanced, in comparison with other N levels. Therefore, a moderate N dose of 120 kg N ha−1 under both irrigated and rainfed patterns is highly recommended for adoption due to its overall advantage in terms of yield returns, environmental impact and production efficiency.

Ammonia Retention in Biowaste via Low-Temperature-Plasma-Synthesized Nitrogen Oxyacids: Toward Sustainable Upcycling of Animal Waste.

Sustainable fertilizer production is a pressing challenge due to a growing human population. The manufacture of synthetic nitrogen fertilizer involves intensive emissions of greenhouse gases. The synthetic nitrogen that ends up in biowaste such as animal waste perturbs the nitrogen cycle through significant nitrogen losses in the form of ammonia volatilization, a major human health and environmental hazard. Low-temperature air-plasma treatment of animal waste holds promise for sustainable fertilizer production on farmlands by enabling nitrogen fixation via ionization, forming nitrogen oxyacids. Although the formation of nitrogen oxyacids in plasma treatment of water is well-established, the extent of nitrogen oxyanion enrichment in animal waste and its downstream effects on acidifying the waste remain elusive because many compounds found in complex biowaste media may interfere with absorbed NOx species. This work aims to establish that plasma treatment of dairy manure can suppress ammonia loss by volatilization via acidification of animal waste while enriching the waste in total nitrogen due to nitrogen retained in ammonia as well as adding nitrogen oxyacids by reacting NOx with the aqueous slurry. To this end, air-plasma effluent containing NOx is bubbled through dairy manure, which is then analyzed for changes in the nitrogen oxyanion content and pH. Increasing the plasma treatment time results in more acidic manure, reduced ammonium content in the downstream acid trap, and increased nitrogen oxyanion content, where the yield of nitrogen oxyanion from absorbed NOx species is approximately 100%. Increased plasma treatment also led to an increase in the total Kjeldahl nitrogen and the total nitrogen. These results indicate that plasma treatment of animal waste can significantly suppress ammonia pollution from animal husbandry facilities such as dairy farms while upcycling animal waste as a rich organic source of nitrogen.

Balancing Non‐CO2 GHG Emissions and Soil Carbon Change in U.S. Rice Paddies: A Retrospective Meta‐Analysis and Agricultural Modeling Study

AbstractU.S. rice paddies, critical for food security, are increasingly contributing to non‐CO2 greenhouse gas (GHG) emissions like methane (CH4) and nitrous oxide (N2O). Yet, the full assessment of GHG balance, considering trade‐offs between soil organic carbon (SOC) change and non‐CO2 GHG emissions, is lacking. Integrating an improved agroecosystem model with a meta‐analysis of multiple field studies, we found that U.S. rice paddies were the rapidly growing net GHG emission sources, increased 138% from 3.7 ± 1.2 Tg CO2eq yr−1 in the 1960s to 8.9 ± 2.7 Tg CO2eq yr−1 in the 2010s. CH4, as the primary contributor, accounted for 10.1 ± 2.3 Tg CO2eq yr−1 in the 2010s, alongside a notable rise in N2O emissions by 0.21 ± 0.03 Tg CO2eq yr−1. SOC change could offset 14.0% (1.45 ± 0.46 Tg CO2eq yr−1) of the climate‐warming effects of soil non‐CO2 GHG emissions in the 2010s. This escalation in net GHG emissions is linked to intensified land use, increased atmospheric CO2, higher synthetic nitrogen fertilizer and manure application, and climate change. However, no/reduced tillage and non‐continuous irrigation could reduce net soil GHG emissions by approximately 10% and non‐CO2 GHG emissions by about 39%, respectively. Despite the rise in net GHG emissions, the cost of achieving higher rice yields has decreased over time, with an average of 0.84 ± 0.18 kg CO2eq ha−1 emitted per kilogram of rice produced in the 2010s. The study suggests the potential for significant GHG emission reductions to achieve climate‐friendly rice production in the U.S. through optimizing the ratio of synthetic N to manure fertilizer, reducing tillage, and implementing intermittent irrigation.

Introduction of soybean into maize field reduces N2O emission intensity via optimizing nitrogen source utilization

The application of synthetic nitrogen (N) fertilizer has increased anthropogenic N2O emission in global croplands. Due to the advantage of biological nitrogen fixation (BNF), the introduction of legume may lessen N2O emission intensity (emission/yield) in cereal field. Yet, this speculation lacks strong evidences and the relevant mechanistic explanations. A two-year field study was conducted using static chamber method (15N isotope labeling in fertilizer) in the mono- and inter-cropping fields with soybean introduced in maize field in semiarid rainfed Loess Plateau. The results indicated that maize-soybean intercropping showed 13 % lower N2O emission intensity than monocropping, attributed to 14 % and 20 % lower annually N2O emissions in intercropped zone than that of sole maize and soybean zones respectively. Also, a 15 % higher grain yield was observed in intercropped maize relative to that in sole maize. Particularly, during the peak time of emission following N fertilization and BNF within growing season, soybean introduction reduced 25 % and 24 % of N2O emissions in intercropped zone than sole maize and soybean zone respectively. It also favored maize plant with an additional 17 % more fertilizer-derived N, 21 % less soil-derived N and 30 kg N ha−1 soybean transferred-N from BNF. The contributions of N fertilization, BNF and soil initial organic N to N2O production were lessened in intercropping. In this case, the capacity of substrates N transformation into N2O emissions was lowered. Critically, soybean introduction reduced soil ammonia oxidation (as evidenced from amoA AOA and AOB gene abundance) in intercrops’ rhizosphere, and increased soil nitrite reduction (nirS and nirK gene abundance) in maize rhizosphere, and improved soil N2O reduction to N2 (nosZ gene abundance) in soybean rhizosphere. Therefore, soybean introduction optimized N source use for lower N2O emission intensity, via reducing the transformation of substrate N into N2O, and modifying the expression of nitrification and denitrification functional genes.

A modelled quantification of reduced nitrogen fertiliser requirement and associated trade-offs from inclusion of legumes and fallows in wheat-based crop sequences

ContextGlobally there is a need to increase crop production and maintain soil fertility while reducing environmental impact. Intensive wheat production is dependent on synthetic nitrogen (N) fertilisers which represent ∼38% of total on-farm greenhouse gas emissions in Australia and contribute to N pollution. There are four major sources of N available for crop production 1) N mineralised from native soil organic matter (SOM) 2) N derived from biological fixation by legume-associated rhizobial bacteria 3) synthetic N fertiliser 4) N-rich manures, composts, biosolids and other organic wastes. Farmers can emphasise use of these different sources through their management. ObjectivesIn this study we use crop simulation to predict the minimum amount of N fertiliser required for semi-arid wheat crops to achieve economic yield (EY – defined as 80% of water limited potential yield, PYw) when grown in long-term (1991–2020) sequences and at different rotational intensities with either; grain legumes (GL, source 2), legume winter cover crops (CC, source 2) and winter fallow (WF, source 1) compared to continuous wheat (CW, source 3). Results and conclusionsLegume and fallow phases at 25–67% intensity (e.g. one out of four to two out of three crops) reduced the long-term mean fertiliser N application required to achieve EY. For every % area increase of GL and CC, the mean N applied to achieve EY was reduced by 1.3 kg N kg ha-1 (0.43–1.9 N kg ha-1). For every % area increase of WF the mean N applied to achieve EY was reduced by 1.1 kg N kg ha-1 (0.4–1.6 N kg ha-1). Global warming potential emissions from soil (CO2 and N2O) increased compared to CW when legume intensity increased in high rainfall environments with high SOM but decreased at increasing intensity in low rainfall environments with low SOM. Food energy production (kJ ha-1yr-1) was reduced relative to CW by inclusion of CC and WF and to a lesser extent GL in sequences due to reduced total grain production over the study period. However, protein yield increased as GL intensity increased relative to CW. The most profitable sequences over a 30-year period were CW, or GL at different intensities depending on environment. ImplicationsDiversification of wheat-based cropping systems with legumes reduces N fertiliser requirement, but depending on farming system context this benefit can trade off against production, profitability and environmental outcomes. Evaluation and exploitation of appropriate farming system contexts to achieve mutually beneficial outcomes is required to allow farmers and policy makers to make informed decisions on how to increase food production whilst minimising environmental impacts.

Costs and benefits of synthetic nitrogen for global cereal production in 2015 and in 2050 under contrasting scenarios

Cereals are the most important global staple crop and use more than half of global cropland and synthetic nitrogen (N) fertilizer. While this synthetic N may feed half of the current global population, it has led to a massive increase in reactive N loss to the environment, causing a suite of impacts, offsetting the benefits of N fertilizers for food security and agricultural economy. To address these complex issues, the NBCalCer model was developed to quantify the global effects of N input on crop yields, N budgets and environmental impacts and to assess the associated social benefits and costs. Three Shared Socioeconomic Pathway scenarios (SSPs) were considered with decreasing N agri-environmental ambitions, through contrasting climate and N policy ambitions: sustainability (SSP1H), middle-of-the-road (SSP2M) and fossil-fueled development (SSP5L). In the base year the contribution of synthetic N fertilizer to global cereal production was 44 %. Global modelled grain yield was projected to increase under all scenarios while the use of synthetic N fertilizer decreases under all scenarios except SSP5L. The total N surplus was projected to be reduced up to 20 % under SSP1H but to increase under SSP5L. The Benefit-Cost-Ratio (BCR) was calculated as the ratio between the market benefit of increased grain production by synthetic N and the summed cost of fertilizer purchase and the external cost of the N losses. In base year the BCR was well above one in all regions, but in 2050 under SSP1H and SSP5L decreased to below one in most regions. Given the concerns about food security, environmental quality and its interaction with biodiversity loss, human health and climate change, the new paradigm for global cereal production is producing sufficient food with minimum N pollution. Our results indicate that achieving this goal would require a massive change in global volume and distribution of synthetic N.

Carbon Farming: A Promising Approach to Climate Mitigation and Adaptation in India

This article addresses India's role in the reduction of GHG emissions, the impact of renewable energy and the application of solar energy. In response to the climatic challenges, India is meticulously stepping towards offsetting or the onset of carbon farming such as organic cultivation and solar energy interventions. Offset carbon farming area of 5. 387 Mha organic farming could sequester carbon annually of 6.567 mt, simultaneously; it has the advantage of reducing synthetic nitrogen fertilizer application doses ranging from a minimum of 0.27 mt and a maximum of 1.08 mt per hectare. Furthermore, solar energy can indirectly be used as SWH suitable for average family households contributing carbon credits of 771 kg-824 kg in addition to saving an annual electricity burden of around 1365 kWh to 1459 kWh and directly utilized for solar PV electricity generation of 1 MW will offset approximately 730 tons of CO2 emissions, which is equivalent to 33, 183 carbon-absorbing trees (22 kg of CO2 absorbed/ tree/year). Carbon farming has challenges encompassing economic, technological, policy, and knowledge-based barriers that require innovative solutions and concerted stakeholder efforts.

Long‐term fertilization regulates dissimilatory nitrate reduction processes by altering paddy soil organic carbon components

AbstractTo enhance rice yields, synthetic nitrogen (N) fertilizers are often applied in rice paddy fields. Under waterlogged conditions, denitrification, anaerobic ammonium oxidation (anammox) and dissimilatory nitrate reduction to ammonium (DNRA) are the main N transformation processes. However, the effects of long‐term fertilization on the dissimilatory nitrate reduction processes remain largely unclear. Here, we investigated rates of denitrification, anammox and DNRA and the abundance of bacterial and nitrate reduction‐related genes (16S rRNA, narG, nirK, nirS, nosZ and hzsB) in rice paddy fields under different fertilization regimes [i.e., non‐fertilization (CK), NPK fertilization (NPK) and NPK fertilization plus straw returning (NPKS)]. The rates of denitrification, anammox and DNRA in the CK treatment were 46.18, 0.35 and 1.29 nmoL N g−1 h−1, respectively, which were significantly (p < .05) increased by 7.32%–27.78%, 2.45–4.12 folds and 1.01–13.23 folds by NPK and NPKS treatments. This was largely consistent with the increased bacterial and nitrate reduction‐related gene abundances in the NPK and NPKS treatments. In addition, NPKS also significantly increased the relative contribution of DNRA to the total nitrate reduction relative to NPK and CK treatments, indicating that NPKS was more beneficial to N retention in the paddy field. Changes in rates of dissimilatory nitrate reduction processes in response to NPK and NPKS treatments were correlated to variations of soil total N, ammonium contents, pH, soil organic carbon (SOC) contents and nitrate reduction‐related genes, among which SOC contents had the highest explanation. Specifically, fulvic‐like compounds, alkyl C and methoxyl and nitrogen‐alkyl C were the key components determining denitrification, anammox and DNRA rates, respectively. Overall, our study suggests that long‐term NPK and NPKS fertilization stimulate rates of dissimilatory nitrate reduction processes mainly by altering soil C components and NPKS is more effective in maintaining soil fertility in the paddy field.

Optimizing Renewable Ammonia Production for a Sustainable Fertilizer Supply Chain Transition.

Local renewable ammonia production using electrolytic hydrogen is an emerging approach to alleviate emissions attributed to synthetic nitrogen fertilizer production while also insulating against fluctuations in fertilizer prices and mitigating transportation costs and emissions. However, replacing ammonia currently produced using fossil fuels will not be immediate. To this end, we develop a supply chain transition model, which first optimizes the design and hourly operation of new renewable ammonia facilities to minimize production costs and then optimizes the annual installation timing, production scale, and location of these new renewable facilities along with ammonia transportation to meet county resolution demands. The objective is to augment and eventually replace conventional ammonia market imports in an economically competitive manner. We performed a case study for Minnesota's ammonia supply chain and found that a full transition to in-state renewable production by 2032 is optimal. This is incentivized by the U.S. federal government's clean hydrogen production credits. This transition results in 99 % reduction in carbon intensity along with stable supply costs below $475 per metric tonne. New renewable production facilities are an order of magnitude smaller than existing conventional plants. They use both wind and solar resources and operate dynamically to minimize expensive battery and hydrogen storage capacities.

Evaluation of Nitrogen Release Characteristics and Enhanced Efficiency of a Novel Synthetic Slow-Release Nitrogen Fertilizer

Evaluation of Nitrogen Release Characteristics and Enhanced Efficiency of a Novel Synthetic Slow-Release Nitrogen Fertilizer

Environmental effect of improved forage fertilization practices in the beef production chain

Feeding is one of the most important factors influencing production efficiency and the environmental impact of livestock production. This study evaluates the possibility of reducing the impact of beef cattle production by optimizing the fertilization management of home-grown forage on the same farms. To this end, two scenarios were compared on two beef cattle farms in northern Italy, a baseline scenario (BS) and a scenario with optimized management (OMS) in terms of nitrogen fertilizer use. The cradle-to-gate LCA (Life Cycle Assessment) approach was used to compare the environmental performances in the different scenarios. Two different functional units (1 t dry matter of forage self-produced and 1 kg live weight of beef cattle produced) were used to express the results in relation to different stages of the supply chain. Inventory data were translated into indicators to reflect environmental pressures as well as resource scarcity by means of the ReCiPe 2016 Midpoint (H) method.The reduction of synthetic nitrogen fertilization, particularly during top fertilization, maintain yields at satisfactory levels while substantially reducing most of the evaluated impacts (e.g., Climate change from 17 % to 23 %). On the other hand, trade-offs among the different impact categories can be identified (e.g., terrestrial acidification grows up to 52 % for wheat silage).The optimization of the fertilization also involves a reduction in the impact of the feed as a whole and then of the beef cattle produced, even though the increasing number of external inputs, not affected by best fertilization practices, for each of these two phases leads to increasingly smaller reductions in impact. Ultimately, the optimization of internal crop production practices is important from an environmental point of view for farms but represents only one of the possible mitigation interventions necessary to mitigate the entire agricultural supply chain.

Exploring the short-term in-field performance of Recovered Nitrogen from Manure (RENURE) materials to substitute synthetic nitrogen fertilisers

Exploring the short-term in-field performance of Recovered Nitrogen from Manure (RENURE) materials to substitute synthetic nitrogen fertilisers

Dynamics of soil nitrogen and N-cycling-related genes following the application of biobased fertilizers

Biobased fertilizers recovered from animal manure are sustainable substitutes for synthetic mineral nitrogen (N) fertilizers, showing high potential to minimize environmental pollution while maintaining nutrient supply. This study investigated the response of maize (Zea mays L.) and soil microbes to the application of biobased fertilizers, i.e., pig manure (PM), the liquid fraction of digestate (LFD), and evaporator concentrate (EVA) in replacement of calcium ammonium nitrate (CAN) in a 56-day pot experiment. Apart from maize plant growth and soil chemical properties, the abundance of N-cycling-related genes was determined by destructive sampling on days 8, 16, and 56 after fertilization. The detected gene copies of bacterial and archaeal amoA in the soil were significantly increased by N fertilization. Relatively high NH4+-N concentrations (37.5–62.5 mg kg−1 soil dry weight) applied in this experiment may have promoted gaseous N losses via nitrifier nitrification and nitrifier denitrification shortly (8–16 days) after fertilization. Consequently, net N loss was observed in all the fertilized treatments, however, biobased fertilizers resulted in lower N loss as compared to CAN. The presence of maize plants also reduced the N loss, probably driven by the continuous NO3−-N uptake which reduced the N source for denitrification. Overall, the application of PM and LFD revealed no significant difference with CAN regarding either plant growth or soil biochemical properties. Whereas the EVA application resulted in lower biomass and nutrient uptake in the young maize plant compared to other treatments, probably attributed to salt stress due to the imbalanced ratio of N and Na in this product.

Marsh archive reveals human population history and future implications for estuarine health in Long Island Sound

Coastal marshes are efficient ecosystems providing a multitude of benefits for invertebrates, birds, fish and humans alike. Yet despite these benefits, wetlands are threatened by anthropogenic inputs such as human wastewater which contain high levels of nitrogen (N). Increased nitrogen loads cause eutrophication and hypoxia in estuaries leading to further degradation of these valuable ecosystems that are already stressed by sea level rise and climate change. Policies to protect wetlands via wastewater treatments are reactive rather than proactive and a growing body of research shows that characteristics associated with population health and economic activity can be identified in wastewater. Analysis of a 2-m salt marsh sediment core reveals δN15 signatures indicative of human population rise and connects human impact to ecosystem health. Using key X-ray fluorescence (XRF), pollen, sediment and nitrogen signatures along the core, a robust chronology was produced dating back to 1700. This result was coupled with population data to observe the relationship between δN15 levels and population over three centuries. There is a statistically significant positive correlation between δN15 and population. Other external factors such as federal government policies (regulating clean water) show a clear reduction in this association but the use of synthetic nitrogen fertilizer masks the strength of this relationship. Further research to refine the relationship between population and δN15 could be beneficial in predicting nitrogen loads as human population grows, which in turn would create a proactive system to protect our coastal ecosystems.

Optimizing the Incorporated Amount of Chinese Milk Vetch (Astragalus sinicus L.) to Improve Rice Productivity without Increasing CH4 and N2O Emissions

Chinese milk vetch (CMV) is a leguminous green manure that is commonly cultivated in paddy fields and can partially substitute synthetic nitrogen fertilizer. However, the impacts of incorporating CMV on CH4 and N2O emissions are still a subject of controversy. Therefore, we conducted a field experiment over three years to investigate emissions under different substitution ratios: urea only (CF); incorporating a traditional amount of CMV (MV); and with incorporation ratios of 1/3 (MV1/3), 2/3 (MV2/3), and 4/3 (MV4/3) of MV for partial urea substitution. Compared with CF, MV2/3, MV, and MV 4/3 resulted in increased yields. MV and MV4/3 reduced N2O emissions but increased CH4 emissions by 28.61% and 85.60% (2019), 32.38% and 103.19% (2020), and 28.86% and 102.98% (2021), respectively, resulting in an overall increase in total global warming potential (except for MV in 2021). MV2/3 exhibited a low greenhouse gas intensity value ranging from 0.46 to 0.47. Partial least-squares-path model results showed that CH4 and N2O emissions were influenced by substitution ratios, which indirectly regulated the gene abundances of mcrA and nosZ. Overall, the impact of CMV on CH4 and N2O emissions was determined by substitution ratios. MV2/3, which involved partial substitution of synthetic N fertilizer with 15.0 t ha−1 of CMV, resulted in improved rice productivity without increasing CH4 and N2O emissions, making it a recommended approach in the study area.

Manure substitution improves maize yield by promoting soil fertility and mediating the microbial community in lime concretion black soil

Synthetic nitrogen (N) fertilizer has made a great contribution to the improvement of soil fertility and productivity, but excessive application of synthetic N fertilizer may cause agroecosystem risks, such as soil acidification, groundwater contamination and biodiversity reduction. Meanwhile, organic substitution has received increasing attention for its ecologically and environmentally friendly and productivity benefits. However, the linkages between manure substitution, crop yield and the underlying microbial mechanisms remain uncertain. To bridge this gap, a three-year field experiment was conducted with five fertilization regimes: i) Control, non-fertilization; CF, conventional synthetic fertilizer application; CF1/2M1/2, 1/2 N input via synthetic fertilizer and 1/2 N input via manure; CF1/4M3/4, 1/4 N input synthetic fertilizer and 3/4 N input via manure; M, manure application. All fertilization treatments were designed to have equal N input. Our results showed that all manure substituted treatments achieved high soil fertility indexes (SFI) and productivities by increasing the soil organic carbon (SOC), total N (TN) and available phosphorus (AP) concentrations, and by altering the bacterial community diversity and composition compared with CF. SOC, AP, and the soil C:N ratio were mainly responsible for microbial community variations. The co-occurrence network revealed that SOC and AP had strong positive associations with Rhodospirillales and Burkholderiales, while TN and C:N ratio had positive and negative associations with Micromonosporaceae, respectively. These specific taxa are implicated in soil macroelement turnover. Random Forest analysis predicted that both biotic (bacterial composition and Micromonosporaceae) and abiotic (AP, SOC, SFI, and TN) factors had significant effects on crop yield. The present work strengthens our understanding of the effects of manure substitution on crop yield and provides theoretical support for optimizing fertilization strategies.

“Alperujo” Compost Improves Nodulation and Symbiotic Nitrogen Fixation of Soybean Inoculated with Bradyrhizobium diazoefficiens

The utilization of compost to enhance plant productivity and symbiotic nitrogen fixation (SNF) has been recognized as an effective alternative to synthetic nitrogen fertilizers. This environmentally sustainable method is readily accessible to farmers. This study investigated the effect of olive pomace (“alperujo”, AL) compost on the nodulation and SNF of soybeans (Glycine max L.) and their natural symbiont (Bradyrhizobium diazoefficiens). For that, soybean plants were subjected to several doses of AL compost under controlled greenhouse conditions. At the end of the experiment, the dry weight of plant biomass (aerial part and roots), the number and fresh weight of nodules, and nitrogen and leghaemoglobin contents were analyzed. The application of AL compost significantly improved soybean growth, as demonstrated by an increase in both plant biomass and height. Furthermore, nodular leghaemoglobin content and nitrogen content were found to be enhanced by the addition of AL compost (7 and 40%, respectively), indicating an increase in nodule effectiveness and symbiotic efficiency. Our results provide clear evidence of the synergetic effect of AL compost on the soybean-B. diazoefficiens association, probably due to AL-compost improved soybean roots development, and rhizospheric organic matter and nutrients assimilation by rhizobia.

Effect of replacing synthetic nitrogen fertilizer with animal manure on grain yield and nitrogen use efficiency in China: a meta-analysis.

To reduce reliance on synthetic nitrogen (N) fertilizer and sustain food production, replacing synthetic N fertilizer with animal manure as an effective method is widely used. However, the effects of replacing synthetic N fertilizer with animal manure on crop yield and nitrogen use efficiency (NUE) remain uncertain under varying fertilization management practices, climate conditions, and soil properties. Here, we performed a meta-analysis of wheat (Triticum aestivum L.), maize (Zea mays L.), and rice (Oryza sativa L.) based on 118 published studies conducted in China. Overall, the results indicated that substituting synthetic N fertilizer with manure increased yield by 3.3%-3.9% for the three grain crops and increased NUE by 6.3%-10.0%. Crop yields and NUE did not significantly increase at a low N application rate (≤120 kg ha-1) or high substitution rate (>60%). Yields and NUE values had higher increases for upland crops (wheat and maize) in temperate monsoon climate/temperate continental climate regions with less average annual rainfall (AAR) and lower mean annual temperature (MAT), while rice had higher increases in subtropical monsoon climate regions with more AAR and higher MAT. The effect of manure substitution was better in soil with low organic matter and available phosphorus. Our study shows that the optimal substitution rate was 44% and the total N fertilizer input cannot be less than 161kg ha-1 when substituting synthetic N fertilizer with manure. Moreover, site-specific conditions should also be considered.

110 Improving Southern Bermudagrass Pastures with Alfalfa: An Evaluation of the Impacts of Alfalfa Establishment Timing and Crabgrass Competition

Abstract Inclusion of alfalfa (Medicago sativa) in bermudagrass (Cynodon dactylon) pastures improves nutritive value, increases grazing days, and reduces the need for synthetic nitrogen fertilizer. Crabgrass (Digitaria sanguinalis) is a very palatable warm-season annual grass with high nutritive value, prolific reseeding ability, and proclivity to volunteer in many southeastern pastures. Crabgrass is a common pest that requires pre-emergent herbicide technologies to control in alfalfa hayfields used to produce stored forage. However, in a grazing system, crabgrass could serve as a key component to a mixture aimed at increasing nutritive value and filling gaps in the grazing season. The purpose of this study is to evaluate the impact of alfalfa establishment timing (fall vs. spring) in bermudagrass pastures in the Coastal Plains, and the resultant impact of crabgrass inclusion rather than removal in alfalfa bermudagrass mixed pastures on nutritive value, botanical composition, forage accumulation, alfalfa stand density and persistence. This on-going two-year study is being conducted in Tifton, GA using a randomized complete block design with 4 replications of the following 6 treatments: Fall Alfalfa + Summer Crabgrass, Fall Alfalfa, Spring Alfalfa + Summer Crabgrass, Spring Alfalfa, Bermudagrass + Synthetic Nitrogen, and Untreated Bermudagrass Control. Data were collected from plots on a 28 to 35-day interval to determine botanical composition, forage availability, and nutritive value. The projected impact of this research is three-fold; first, to identify how differing management strategies for restoring bermudagrass pastures are improved with inclusion of alfalfa. Second, it aims to quantify and support a recommended timing for planting alfalfa in the coastal plains, and third to estimate the impact of crabgrass inclusion in alfalfa bermudagrass systems. Data evaluation and statistical analysis is ongoing for this research and will be finalized in winter 2022.