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The intensification of livestock production, to accommodate rising human population, has led to a higher emission of ammonia into the environment. For the reduction of ammonia emissions, different management steps have been reported in most EU countries. Some authors, however, have criticized such individual measures, because attempts to abate the emission of ammonia may lead to significant increases in either methane, nitrous oxide, or carbon dioxide. In this study, we carried out a meta-analysis of experimental European data published in peer-reviewed journals to evaluate the impact of major agricultural management practices on ammonia emissions, including the pollution swapping effect. The result of our meta-analysis showed that for the treatment, storage, and application stages, only slurry acidification was effective for the reduction of ammonia emissions (−69%), and had no pollution swapping effect with other greenhouse gases, like nitrous oxide (−21%), methane (−86%), and carbon dioxide (−15%). All other management strategies, like biological treatment, separation strategies, different storage types, the concealing of the liquid slurry with different materials, and variable field applications were effective to varying degrees for the abatement of ammonia emission, but also resulted in the increased emission of at least one other greenhouse gas. The strategies focusing on the decrease of ammonia emissions neglected the consequences of the emissions of other greenhouse gases. We recommend a combination of treatment technologies, like acidification and soil incorporation, and/or embracing emerging technologies, such as microbial inhibitors and slow release fertilizers.

Gaseous emissions are the main loss pathways of nutrients during dairy slurry storage. In this study, we compiled published data on cumulative ammonia (NH3), nitrous oxide (N2O) and methane (CH4) emissions from dairy slurry storage and evaluated the integrated effects of slurry pH, total solids (TS), ambient temperature (T) and length of storage (LOS) on emissions using linear mixed effects models. Results showed that the average nitrogen (N) loss by NH3 volatilization from slurry storage was 12.5% of total nitrogen (TN), while the loss by N2O emissions only accounted for 0.05–0.39% of slurry TN. The NH3–N losses were highly related to slurry pH, lowering slurry pH leading to significant decrease of emissions. Temperature also affected NH3–N losses, with higher losses from slurry storage under warm conditions than cold conditions. No significant relationship was observed between NH3–N losses and slurry TS contents within a range from 21–169 g kg−1. The losses of N2O–N from dairy slurry storage were less affected by slurry pH, TS contents and temperature. The carbon (C) loss as CH4 emissions varied from 0.01–17.2% of total carbon (TC). Emissions of CH4–C presented a significant positive relationship with temperature, a negative relationship with slurry TS contents and no significant relationship with slurry pH ranging from 6.6–8.6. Length of storage (more than 30 days) had no significant influence on cumulative gas emissions from slurry storage. This study provides new emission factors of NH3, N2O and CH4 in the percentage of TN or TC from dairy slurry storage. Our results indicate the potential interactive effects of slurry characteristics and storage conditions on gaseous emissions from slurry storage. Farm-scale measurements are needed to accurately estimate nutrient losses from liquid manure storage.

Low-disturbance liquid manure injection is increasingly important for sustainable soil management because it reduces residue burial, minimizes surface disruption, and lowers energy demand during application. However, the performance of low-disturbance shanks has not been systematically optimized, and their interaction with soil remains poorly quantified. This study developed an integrated discrete element method (DEM)–experimental framework to evaluate and optimize the performance of a purpose-built injector shank featuring a 45° rake angle, 25 mm thickness, and 110 mm width. The framework aimed to identify operating conditions that balance soil disturbance and energy efficiency. A DEM soil model was constructed using mechanical properties obtained from laboratory characterization tests and validated against soil bin experiments measuring draft force and soil rupture area across five working depths (100–250 mm) and three travel speeds (350–450 mm/s). The calibrated model showed strong agreement with experimental observations, yielding mean absolute relative errors of 1.7% for draft force and 6.2% for rupture area. Following validation, a multi-objective optimization was performed to minimize draft force while maximizing soil rupture, two key indicators of energy demand and injection effectiveness. Optimization results identified the most favorable operating parameters at a forward speed of 450 mm/s and an injection depth of 150 mm, achieving a desirability score of 0.884. The integrated DEM–experimental framework demonstrated reliable predictive capability and enables virtual testing of soil–tool interactions prior to field implementation. This study provides a scientifically grounded approach for improving injector shank operation and supports sustainable manure management by identifying settings that achieve adequate soil disruption while reducing energy consumption.

Liquid manure is a significant source of methane (CH4), a greenhouse gas. Many livestock farms use manure additives for practical and agronomic purposes, but the effect on CH4 emissions is unknown. To address this gap, two lab studies were conducted, evaluating the CH4 produced from liquid dairy manure with Penergetic-g® (12 mg/L, 42 mg/L, and 420 mg/L) or AgrimestMix® (30.3 mL/L). In the first study, cellulose produced 378 mL CH4/g volatile solids (VS) at 38 °C and there was no significant difference with Penergetic-g® at 12 mg/L or 42 mg/L. At the same temperature, dairy manure produced 254 mL CH4/g VS and was not significantly different from 42 mg/L Penergetic-g®. In the second lab study, the dairy manure control produced 187 mL CH4/g VS at 37 °C and 164 mL CH4/g VS at 20 °C, and there was no significant difference with AgrimestMix (30.3 mL/L) or Penergetic-g® (420 mg/L) at either temperature. Comparisons of manure composition before and after incubation indicated that the additives had no effect on pH or VS, and small and inconsistent effects on other constituents. Overall, neither additive affected CH4 production in the lab. The results suggest that farms using these additives are likely to have normal CH4 emissions from stored manure.

The growth of field crops needs appropriate soil nutrients. As a basic fertilizer, liquid manure provides biological nutrients for crop growth and increases the content of organic matter in crops. However, improper spraying not only reduces soil fertility but also destroys soil structure. Therefore, the precise control of the amount of liquid manure is of great significance for agricultural production and weight loss. In this study, we first built the model of spraying control, then optimized the BP neural network algorithm through a genetic algorithm. The stability and efficiency of the optimized controller were compared with PID, fuzzy PID and BPNN-PID control. The simulation results show that the optimized algorithm has the shortest response time and lowest relative error. Finally, platform experiments were designed to verify the four control algorithms at four different vehicle speeds. The results show that, compared with other control algorithms, the control algorithm described here has good stability, short response time, small overshoot, and can achieve an accurate fertilizer application effect, providing an optimization scheme for research on the precise application of liquid manure.

Liquid manure storage contributes substantially to environmental emissions within manure management systems. This study evaluated Yucca schidigera extract (YE) as a sustainable microbial modulator for mitigating ammonia (NH 3 ) and greenhouse gas emissions during 60-day storage of liquid chicken manure. Three treatments were established: no additive (control, CK), 0.1% biological deodorant (positive control, BF), and 0.5% YE. The results demonstrated that both YE and BF significantly reduced electrical conductivity (EC) (YE: 38.35%; BF: 34.51%) and ammonium nitrogen (NH 4 ⁺-N) content (YE: 14.15%; BF: 20.21%) relative to CK, while elevating the C/N ratio by 9.97% (YE) and 18.63% (BF). Total nitrogen decreased by 23.88% (YE) and 26.34% (BF) from initial levels. In addition, the cumulative NH 3 emissions of YE and BF decreased significantly by 20.18% and 20.12% compared to CK. However, YE increased CH₄ emissions by 17.43%, elevating global warming potential, whereas BF exhibited no significant effect on CH 4 . Neither additive influenced CO 2 or N 2 O emissions. Microbial analysis revealed YE enriched Firmicutes (e.g., Fermentimonas ), while BF enhanced Actinobacteriota (e.g., Corynebacterium ) and Proteobacteria . Both additives suppressed ammonia-producing bacteria (e.g., Proteiniphilum ). Mantel tests analysis indicated NH 3 emissions correlated positively with EC and NH 4 ⁺-N ( P  < 0.01), while CH 4 emissions correlated with organic matter (OM) content ( P  < 0.05). These findings elucidate the microbial mechanisms of YE in mitigating the NH 3 emission during liquid manure storage, whereas YE may induce trade-offs in CH 4 emission. In the future, the formulation of compound plant-derived additives will be necessary for the synergetic abatement of carbon and nitrogen gases. Graphical Abstract

Land application of animal manure has been accepted as an effective method and disposal option, which has economic, environmental and social benefits, while also sometimes exists questions about its impact on soil and water quality and crop yields. This paper presents a field-scale study in Chongming Island, Shanghai, China, where land application of digested swine liquid manure with chemical fertilizer supplement in paddy field (SMC field) was conducted to study the short-term effect on soil quality in different depth, pollutant losses by surface runoff, pollutant concentrations in groundwater and crop yields, compared to conventional paddy field with land application of pure chemical fertilizer (CKC field). The results indicated that: (1) in groundwater, the concentrations of chemical oxygen demand (COD), nitrate nitrogen (Nitrate-N), total phosphorus (TP) and dissolved phosphorus (DP) were significantly increased by 24.69, 17.04, 11.76 and 21.05%, respectively, in the SMC field; (2) in surface runoff, the loss loading of COD, TP and DP was significantly increased by 32.18, 15.46 and 28.13%, respectively, while the ammonia nitrogen (Ammonia-N) was significantly decreased by 31.81%, in the SMC field; (3) in the different depth of soil, the contents of total nitrogen presented a greater decrease in the SMC field, while the contents of TP presented a greater decrease in the CKC field, compared to the properties of original soil; (4) for the crop yields, there was no significant difference between the SMC and CKC field. These practices had proved the feasibility for land application of swine liquid manure in the paddy field, and this approach could be extended after being rate modified to concern the nutrient utilization and pollution risk to water environment.

Using pig slurry as starter fertilizer for maize ( Zea mays L.), injected below the row prior to planting is a reasonable way to omit application of additional mineral fertilizer in areas with intensive animal farming. However, delayed early growth and a lack of knowledge on nutrient availability limit the interest of farmers. To extenuate farmers concerns a field trial was conducted in 2014 and 2015 to get detailed information on nitrogen (N) uptake, the subsequent influences on crop growth at different vegetative growth stages and final yield of silage maize. Besides an unfertilized control, two liquid manure injection treatments (without and with nitrification inhibitor [NI]) were compared to slurry broadcast application + mineral N and phosphorus (P) starter fertilizer at planting (MSF). In 2014, NI treatment yields increased (+16.5%) and N uptake increased (+9.6%) compared to broadcast treatment. In 2015, cold and dry conditions during early growth limited P plant availability and reduced crop growth in treatments without MSF. However, when a NI was added to the slurry prior to application, plants showed less P deficiency symptoms and better growth. At harvest no differences between the fertilized treatments were observed. In both years apparent N recovery was increased when manure was injected (48% without, and 56% with NI, respectively) compared to broadcast application of manure (43%) indicating that N losses were lower. However, further knowledge on soil N transformation and N loss pathways in systems with slurry injection is needed.

Treatment of liquid swine manure (LSM) is an option to improve nutrient management. Mineral fertilizer, raw LSM, and LSM treated by anaerobic digestion, flocculation, filtration, or natural decantation were sidedressed (100 kg N ha-1) to grain corn (Zea mays L.) on a clay and a loam soil. Over 3 yr, corn grain yield (6 to 11 Mg ha-1), N export (83 to 176 kg ha-1), and P export (19 to 40 kg ha-1) were similar among LSM types and between LSMs and mineral fertilizer. This was attributed to the immediate incorporation of LSM to minimize N volatilization. Treated LSMs reduced P input to soil by 3 to 24 kg ha-1, compared with raw LSM. This reduced corn P export by 2 to 4 kg ha-1 on the clay soil, but had no effect on the loam soil. Soil NO3 content after harvest was higher with the mineral fertilizer (19-31 kg NO3-N ha-1) than with LSMs (13-20 kg NO3-N ha-1) in the clay soil, but was similar for all treatments in the loam soil. We conclude that when sidedressed to corn and immediately incorporated, raw and treated LSMs have a fertilizer value similar to the mineral fertilizer. Moreover, the risk of postharvest NO3 accumulation with the raw and treated LSMs was similar to mineral fertilizer on the loam and lower on the clay.

Dairy rotations rely on corn silage, which is estimated to have significant nitrous oxide (N 2 O) emissions. This study examined whether including legumes within rotations can reduce N 2 O emissions from the soil surface and dissolved in tile-drainage water. Emissions of N 2 O were measured from the soil surface and in tile drainage. Cropping systems were: corn–corn (CC), corn + cover crop-corn (C + cc), soybean–corn (SC) and alfalfa–alfalfa (AA) on a clay soil. Liquid dairy manure provided 2-year total N inversely related to legume cropping: 310 (CC), 280 (C + cc), 110 (SC), 50 kg N ha −1 (AA). Losses of N 2 O via tile drainage were 0.1–0.3% of total emissions. Ratios of N 2 O-N to NO 3 − -N in drainage were at least 63% lower than the IPCC default value (0.0075). Reductions of N 2 O emissions were only observed from established alfalfa in year 2. Compared to the SC treatment, which had the highest emissions in year 2, the AA treatment had 62% lower surface N 2 O and 88% lower dissolved N 2 O flux. Alfalfa had low yield in the first year, which led to high yield-scaled N 2 O emissions; thus, alfalfa may need to be grown 4 years to achieve a similar average yield scaled emission factor as CC. Silage corn had consistently high yield, averaging 317 kg ha −1  yr −1 for N yield, which was 36% higher than AA. As a result, CC had the lowest N 2 O emissions scaled by N-yield over the 2 years, averaging 2.6% of N-yield, which was 59% lower than AA on average.