Application Of Livestock Manure Research Articles

Effects of phosphate fertilization and sulfadiazine on plant growth, root morphology, nitrogen and phosphorus uptake of soybean and maize

Low soil phosphorus (P) availability is a limiting factor for crop production. Application of livestock manure as organic fertilizer can increase soil P availability, but may cause soil contamination with antibiotics such as sulfadiazine (SD), thus adversely affecting plant growth and nutrient uptake. The effects of P (0 and 50 mg kg−1) and SD (0, 1, 10, and 100 mg kg−1) levels on plant growth, root development, and nitrogen (N) and P uptake of maize and soybean were examined in a pot experiment using a loess soil as the test soil. High levels of SD considerably inhibited plant growth of both crops. Both P fertilization and SD negatively affected root development of both crops, especially at higher SD levels. For both crops, the average root diameter and the proportion of thick roots increased with increasing soil SD level. When soil SD level was ≤10 mg kg−1, the effects of P fertilization and SD on plant N and P concentrations, and N:P, N- and P-utilization efficiency were not significant in most cases. The effects of SD on plant N and P nutrition could not be of a great concern when soil SD level was ≤10 mg kg−1. Overall, soil SD pollution could reduce plant biomass and inhibit root development of soybean and maize, with a stronger effect on root development than on plant biomass at a high soil SD level (≥10 mg kg−1). In agricultural production, attention should be paid to soil SD pollution via manure application.

Assessing the risk of E. coli contamination from manure application in Chinese farmland by integrating machine learning and Phydrus

This study aims to present a comprehensive study on the risks associated with the residual presence and transport of Escherichia coli (E. coli) in soil following the application of livestock manure in Chinese farmlands by integrating machine learning algorithms with mechanism-based models (Phydrus). We initially review 28 published papers to gather data on E. coli's die-off and attachment characteristics in soil. Machine learning models, including deep learning and gradient boosting machine, are employed to predict key parameters such as the die-off rate of E. coli and first-order attachment coefficient in soil. Then, Phydrus was used to simulate E. coli transport and survival in 23692 subregions in China. The model considered regional differences in E. coli residual risk and transport, influenced by soil properties, soil depths, precipitation, seasonal variations, and regional disparities. The findings indicate higher residual risks in regions such as the Northeast China, Eastern Qinghai-Tibet Plateau, and pronounced transport risks in the fringe of the Sichuan Basin fringe, the Loess Plateau, the North China Plain, the Northeast Plain, the Shigatse Basin, and the Shangri-La region. The study also demonstrates a significant reduction in both residual and transport risks one month after manure application, highlighting the importance of timing manure application and implementing region-specific standards. This research contributes to the broader understanding of pathogen behavior in agricultural soils and offers practical guidelines for managing the risks associated with manure use. This study's comprehensive method offers a potentially valuable tool for evaluating microbial contaminants in agricultural soils across the globe.

Effects of the combined application of livestock manure and plant residues on soil organic carbon sequestration in the southern Loess Plateau of China

Increasing soil organic carbon (SOC) sequestration enhances the stability and productivity of agricultural ecosystems. Organic material application is a direct and effective way to maintain and improve SOC sequestration. However, currently, there is little knowledge on efficient practices for combined organic material application to improve SOC sequestration. In this study, we evaluated the effect of three organic materials alone or in combination on SOC sequestration in a 4-year field experiment. Eight treatments were included: control (CK, conventional chemical fertilizer), green manure (G), straw (S), decomposed sheep manure (M), green manure plus straw (GS), green manure plus sheep manure (GM), straw plus sheep manure (SM), green manure, and straw plus sheep manure (GSM). In 2020, decomposed sheep manure application (M, SM, GM and GSM) resulted in the greatest cumulative SOC sequestration (9.5–10.8 Mg C ha−1), followed by those in treatments S (6.1 Mg C ha−1) and GS (6.9 Mg C ha−1). The SOC sequestration efficiency in the M treatment (44.8 %) was greater than that in the others (15.2–34.8 %). A random forest model revealed that organic material quantity and quality, enzyme activity, and microbial community composition were the primary factors determining SOC sequestration. Sheep manure application increased SOC sequestration by increasing lignin quantity and proportion. Incorporating green manure and straw return enhanced SOC sequestration by promoting microbial growth and increasing soil C-acquiring enzyme activity. However, interactions between sheep manure and plant residues resulted in decreases in SOC sequestration efficiency compared with sheep manure application alone. This is because combined fertilization stimulated microbial growth and enzyme activity, causing changes in microbial community structure and accelerating organic material and SOC decomposition. Thus, we do not recommend combining livestock manure with straw or green manure to improve SOC sequestration and soil quality in the southern Loess Plateau.

Does livestock-Manure-Derived Biochar Suitable for the Stabilization of Cadmium and Zinc in Contaminated Soil?

Both livestock-manure and livestock-manure-derived biochar have been used to remediate heavy metal-contaminated soil. However, direct comparisons of the heavy metal stabilization efficiency of livestock-manure and EQC-manure-biochar (derived from an equal quantity of corresponding livestock-manure) are limited. In the present study, the effect of livestock-manures and EQC-manure-biochars on soil properties and heavy metal bioavailability and leachability were compared using two contrasting soils (Ferralsols and Fluvisols). The results showed that both the livestock-manures and EQC-manure-biochars significantly changed soil pH, available phosphorus, available potassium, alkaline nitrogen and organic matter content (p < 0.05), but the trends were variable. In Ferralsols, the DTPA-extractable Cd and Zn decreased by -0.38%~5.70% and - 3.79%~9.98% with livestock-manure application and by -7.99%~7.23% and - 5.67%~7.17% with EQC-manure-biochars application. In Fluvisols, the DTPA-extractable Cd and Zn decreased by 13.39%~17.41% and - 45.26%~14.24% with livestock-manure application and by 10.76%~16.90% and - 36.38%~16.37% with EQC-manure-biochar application. Furthermore, the change in TCLP-extractable Cd and Zn in both soils was similar to that of DTPA-extractable Cd and Zn. Notably, the Cd and Zn stabilization efficiency of the EQC-manure-biochars was no better than that of the corresponding livestock-manures. These results suggest that the use of livestock-manure-derived biochar is not cost-effective for the remediation of heavy metal-contaminated soil.

Mitigating Greenhouse Gas Emissions from Crop Production and Management Practices, and Livestock: A Review

Agriculture is the second most important greenhouse gas (GHG: methane (CH4) and nitrous oxide (N2O) emissions)-emitting sector after the energy sector. Agriculture is also recognized as the source and sink of GHGs. The share of agriculture to the global GHG emission records has been widely investigated, but the impact on our food production systems has been overlooked for decades until the recent climate crisis. Livestock production and feed, nitrogen-rich fertilizers and livestock manure application, crop residue burning, as well as water management in flood-prone cultivation areas are components of agriculture that produce and emit most GHGs. Although agriculture produces 72–89% less GHGs than other sectors, it is believed that reducing GHG emissions in agriculture would considerably lower its share of the global GHG emission records, which may lead to enormous benefits for the environment and food production systems. However, several diverging and controversial views questioning the actual role of plants in the current global GHG budget continue to nourish the debate globally. We must acknowledge that considering the beneficial roles of major GHGs to plants at a certain level of accumulation, implementing GHG mitigation measures from agriculture is indeed a complex task. This work provides a comprehensive review of agriculture-related GHG production and emission mechanisms, as well as GHG mitigation measures regarded as potential solutions available in the literature. This review also discusses in depth the significance and the dynamics of mitigation measures regarded as game changers with a high potential to enhance, in a sustainable manner, the resilience of agricultural systems. Some of the old but essential agricultural practices and livestock feed techniques are revived and discussed. Agricultural GHG mitigation approaches discussed in this work can serve as game changers in the attempt to reduce GHG emissions and alleviate the impact of climate change through sustainable agriculture and informed decision-making.

Separated two-stage hydrothermal liquefaction of livestock manure for high-quality bio-oil with low-nitrogen content: Insights on nitrogen migration and evolution

The practical utilization of hydrothermal liquefaction (HTL)-derived bio-oil encounters limitations due to its high nitrogen (N) content, specifically when derived from protein-rich feedstock such as algae and livestock manure. In this study, a separated two-stage HTL (ST-HTL) was developed for producing bio-oil with high yield and low N-content. The main objective of this study was to reveal the N migration and evolution during the HTL process for a better understanding of the detailed mechanism. The separated two-stage HTL yielded the highest bio-oil, 32.90 wt%, with a maximum energy recovery of 68.47 %. In conventional HTL-derived bio-oil (280 °C), 38.85 % of N and 56.22 % of C (carbon) was transferred to the bio-oil, while 26.04 % of N and 61.34 % of C (carbon) in swine manure was transferred into the ST-HTL-derived bio-oil, which indicated a 32.83 % reduction in N-transfers and 8.35 % increase in C-transfers. GC–MS analysis revealed that the bio-oil from ST-HTL contained a higher proportion of fatty acids and a lower proportion of nitrogenous compounds compared to conventional HTL (280 °C). In addition, FT-ICR MS revealed that the ST-HTL-derived-bio-oil was more saturated than conventional HTL-derived bio-oil (280 °C). The underlying mechanism behind the increased bio-oil yield and reduced N content attained through ST-HTL are discussed in detail, thereby revealing its intrinsic merits. Thus, it is the first study to propose the N migration and evolution pathways during ST-HTL through detailed characterizations, thus, demonstrating its potential for improving the feasibility of processing high-protein livestock manure and promising practical applications.

Impact of residual antibiotics on microbial decomposition of livestock manures in Eutric Regosol: Implications for sustainable nutrient recycling and soil carbon sequestration

The land application of livestock manure has been widely acknowledged as a beneficial approach for nutrient recycling and environmental protection. However, the impact of residual antibiotics, a common contaminant of manure, on the degradation of organic compounds and nutrient release in Eutric Regosol is not well understood. Here, we studied, how oxytetracycline (OTC) and ciprofloxacin (CIP) affect the decomposition, microbial community structure, extracellular enzyme activities and nutrient release from cattle and pig manure using litterbag incubation experiments. Results showed that OTC and CIP greatly inhibited livestock manure decomposition, causing a decreased rate of carbon (28%–87%), nitrogen (15%–44%) and phosphorus (26%–43%) release. The relative abundance of gram-negative (G-) bacteria was reduced by 4.0%–13% while fungi increased by 7.0%–71% during a 28-day incubation period. Co-occurrence network analysis showed that antibiotic exposure disrupted microbial interactions, particularly among G- bacteria, G+ bacteria, and actinomycetes. These changes in microbial community structure and function resulted in decreased activity of urease, β-1,4-N-acetyl-glucosaminidase, alkaline protease, chitinase, and catalase, causing reduced decomposition and nutrient release in cattle and pig manures. These findings advance our understanding of decomposition and nutrient recycling from manure-contaminated antibiotics, which will help facilitate sustainable agricultural production and soil carbon sequestration.

Response of soil antibiotic resistance genes and bacterial communities to fresh cattle manure and organic fertilizer application

Livestock manure use in agriculture contributes to pollutants like antibiotic resistance genes (ARGs) and resistant bacteria. This practice could potentially facilitate ARGs development in soil ecosystems. Our study aimed to explore ARGs and bacterial communities in cattle manure from Ningxia beef cattle farms with varying breeding periods. We also assessed the impact of different application rates of cattle manure compost, created by mixing manure with different growing periods, on soil's physicochemical and heavy metal properties. High-throughput PCR and sequencing were used to analyze ARGs and bacterial communities. We aimed to understand ARGs dynamics in cattle manure during breeding stages and the impact of different fertilizer application rates on soil bacteria and resistance genes. We found 212 ARGs from cattle manure, spanning tetracycline, aminoglycoside, multidrug, and MLSB categories. Relative ARGs abundance was presented across breeding stages: lactation (C1), breeding (C3), pre-fattening (C4), calving (C2), and late fattening (C5). pH, total nitrogen (TN), electrical conductivity (EC), arsenic (As) and cadmium (Cd) presence significantly impacted ARGs quantity and microbial community structure in manure. Mobile genetic elements (MGEs) were the primary factor altering ARGs in manure (65.56%). Heavy metals contributed to 18.60% of ARGs changes. Manure application changed soil ARGs abundance, notably in soils with high application rates, primarily associated with aminoglycoside, multidrug and sulfonamide resistance. Soils with higher manure rates had elevated MGEs, positively correlated with most ARGs, suggesting MGEs' role in ARGs dissemination. Soil microbial community structure was influenced by fertilization, particularly with the highest application rate. Heavy metals (specifically Cd, contributing to 23.12%), microbial community changes (17.42%), and MGEs (17.38%) were the main factors affecting soil antibiotic resistance. Our study establishes a framework for understanding ARGs emergence in manure and treated soils. This informs strategies to mitigate environmental ARGs transmission and guides diverse livestock manure application and management.

Mitigation effects and microbial mechanism of two ecological earthworms on the uptake of chlortetracycline and antibiotic resistance genes in lettuce

The contamination of greenhouse vegetable soils with antibiotics and antibiotic resistance genes (ARGs), caused by the application of livestock and poultry manure, is a prominent environmental problem. In this study, the effects of two ecological earthworms (endogeic Metaphire guillelmi and epigeic Eisenia fetida) on the accumulation and transfer of chlortetracycline (CTC) and ARGs in a soil–lettuce system were studied via pot experiments. The results revealed that earthworm application accelerated the removal of the CTC from the soil and lettuce roots and leaves, with the CTC content reducing by 11.7–22.8 %, 15.7–36.1 %, and 8.93–19.6 % compared with that of the control, respectively. Both earthworms significantly reduced the CTC uptake by lettuce roots from the soil (P < 0.05) but did not change the CTC transfer efficiency from the roots to leaves. The high-throughput quantitative PCR results showed that the relative abundance of ARGs in the soil and lettuce roots and leaves decreased by 22.4–27.0 %, 25.1–44.1 %, and 24.4–25.4 %, respectively, with the application of earthworms. Earthworm addition decreased the interspecific bacterial interactions and the relative abundance of mobile genetic elements (MGEs), which helped reduce the dissemination of ARGs. Furthermore, some indigenous soil antibiotic degraders (Pseudomonas, Flavobacterium, Sphingobium, and Microbacterium) were stimulated by the earthworms. The results of redundancy analysis indicated that the bacterial community composition, CTC residues, and MGEs were the main parameters affecting the distribution of ARGs, accounting for 91.1 % of the total distribution. In addition, the bacterial function prediction results showed that the addition of earthworms reduced the abundance of some pathogenic bacteria in the system. Overall, our findings imply that earthworm application can substantially reduce the accumulation and transmission risk of antibiotics and ARGs in soil–lettuce systems, providing a cost-effective soil bioremediation practice for addressing antibiotic and ARGs contamination to guarantee the safety of vegetables and human health.

Dynamic Changes in Antibiotic Resistance Genes During Biological Fermentation of Chicken Manure and Pig Manure

Livestock manure is a major carrier that stores and transmits antibiotic resistance genes (ARGs). The aim of this study was to identify the crucial environmental factors that result in the change in relative abundance of ARGs and MGEs to explore effective methods to reduce the occurrence of ARGs. The abundance of ten ARGs and five MGEs were measured using real-time quantitative PCR with 0, 3, 7, 10, 14, 21, 28, 45, 60, and 75 d in CM and PM aerobic composting. The succession law of the bacterial community was analyzed using 16S rRNA high-throughput sequencing. Furthermore, the abundance of ARGs and MGEs was correlated with the properties (temperature, moisture content, pH, and DOC) of composting piles to identify the crucial factors affecting the variation in ARGs and MGEs. The results showed that the abundance of ARGs and MGEs in PM was higher than that in CM. Composting significantly reduced the relative abundance of nine ARGs and five MGEs. The removal ratios of three ARGs (tetM, tetT, and aacA) and four MGEs (ISEcp1, IS1216, IS613, and tnp614) in CM reached 99%. The removal ratios of nine ARGs[tetB(P), tetL, tetM, tetO, tetT, aacA, aadD,aphA3, and sat4] and four MGEs (ISEcp1, IS26, IS1216, and tnp614) reached 99% in PM. However, the abundance of the genes tetG, intI1, and IS6100 increased. Firmicutes and Actinobacteria were dominant in CM and PM during composting. Actinobacteria and Proteobacteria may have been the major host bacteria of tetG and intI1. The redundancy analysis showed that moisture and pH were the crucial factors that could influence the differences in the abundance of ARGs and MGEs. The composition and abundance of ARGs were driven by physicochemical properties, bacterial community, and MGEs. Composting could significantly reduce the abundance of ARGs in CM and PM, thus reducing the risk of ARGs being distributed via livestock manure application. However, some ARGs and MGEs remained in high abundance. Therefore, it is necessary to further optimize the composting process, improve the harmless treatment effect of livestock manure, and promote the safe agricultural use of organic fertilizers.

Effects of Combined Pollution of Tetracycline and Sulfamethazine on Tomato Growth and Antibiotic Absorption

Antibiotics are widely used in livestock and poultry farming for disease prevention and animal growth promotion. Due to the low absorption rate of antibiotics by animals, antibiotics can remain in livestock and poultry manure as parent or metabolites and enter the farm environment with the application of livestock and poultry manure, which has potential effects on crop growth. This study assessed the effects of single and combined contamination of antibiotics in soil on tomato plants. The accumulation of antibiotics in tomato plants and the impacts on crop growth were investigated. A pot experiment with sandy soil was conducted in a greenhouse, and a 100-day tomato growth experiment was conducted by adding different doses of tetracycline and sulfadiazine (0, 25, and 50 mg/kg). The antibiotic contents in various tissues and organs of the tomato were examined, and the changes in photosynthetic intensity and biomass of the tomato were observed to simulate the effects of exogenous antibiotic addition on the growth and quality of the tomato. The results indicated that tomato plants simultaneously absorbed tetracycline and sulfamethazine from soil. Antibiotics were primarily absorbed by tomato roots and were further delivered to plant leaves, stems, and fruits. Antibiotics exhibited the highest concentration in roots, followed by leaves, stems, and fruits. The contents of tetracycline and sulfamethazine in plant tissues elevated with the increase in soil antibiotics, which were higher in the vegetative growth stage than those in the late growth stage. At concentrations of 25 and 50 mg/kg, tetracycline and sulfamethazine combined pollution significantly reduced leaf photosynthetic rates and plant biomass. Notably, high levels of antibiotics led to decreases in tomato yield and quality. Additionally, high concentrations of antibiotic contamination elevated leaf nitrogen, phosphorus, and potassium, but reduced the leaf carbon/nitrogen ratio, as well as reduced the vitamin C content in the fruits. Overall, since antibiotics can accumulate in vegetables and enter the food chain, the findings are crucial for evaluating the impacts of soil antibiotic contamination on the production and food safety of tomato products, and will also add to our knowledge of antibiotic migration into the food chain.

Exploring the interaction between agronomic practices and soil characteristics on the presence of antibiotic resistance genes in soil

In this study, field-scale experiments were carried out to analyze the coupling effects of typical agronomic measures and soil types on soil antibiotic resistance genes (ARGs) using high-throughput fluorescence quantitative PCR. The results indicated that agronomic measures enhanced ARG abundance in different soil types. For the same soil type, the enhancement of ARG abundance in response to agronomic measures could be ordered as follows: livestock manure application (257.6–131.7 %) > sewage irrigation (57.6–35.0 %) > plastic film mulching (21.2–5.0 %). Under the same agronomic measures, enhancement of ARG abundance according to soil type was: clay (257.6–21.2 %) > loam (147.8–15.9 %) > sandy (131.7–5.0 %). Furthermore, the contributions of environmental factors in determining ARG abundance in different soil types differed in response to the application of different agronomic measures. Phthalates had the most and least pronounced effects on ARG abundance in sandy and loam soils, respectively. Effects of moisture on ARG abundance were minor in loam soil, but greater in clay and sandy soils. These findings provide new insights into the dissemination of soil ARGs promoted by the adoption of agronomic measures.

Global agricultural ammonia emissions simulated with the ORCHIDEE land surface model

Abstract. Ammonia (NH3) is an important atmospheric constituent. It plays a role in air quality and climate through the formation of ammonium sulfate and ammonium nitrate particles. It has also an impact on ecosystems through deposition processes. About 85 % of NH3 global anthropogenic emissions are related to food and feed production and, in particular, to the use of mineral fertilizers and manure management. Most global chemistry transport models (CTMs) rely on bottom-up emission inventories, which are subject to significant uncertainties. In this study, we estimate emissions from livestock by developing a new module to calculate ammonia emissions from the whole agricultural sector (from housing and storage to grazing and fertilizer application) within the ORCHIDEE (Organising Carbon and Hydrology In Dynamic Ecosystems) global land surface model. We detail the approach used for quantifying livestock feed management, manure application, and indoor and soil emissions and subsequently evaluate the model performance. Our results reflect China, India, Africa, Latin America, the USA, and Europe as the main contributors to global NH3 emissions, accounting for 80 % of the total budget. The global calculated emissions reach 44 Tg N yr−1 over the 2005–2015 period, which is within the range estimated by previous work. Key parameters (e.g., the pH of the manure, timing of N application, and atmospheric NH3 surface concentration) that drive the soil emissions have also been tested in order to assess the sensitivity of our model. Manure pH is the parameter to which modeled emissions are the most sensitive, with a 10 % change in emissions per percent change in pH. Even though we found an underestimation in our emissions over Europe (−26 %) and an overestimation in the USA (+56 %) compared with previous work, other hot spot regions are consistent. The calculated emission seasonality is in very good agreement with satellite-based emissions. These encouraging results prove the potential of coupling ORCHIDEE land-based emissions to CTMs, which are currently forced by bottom-up anthropogenic-centered inventories such as the CEDS (Community Emissions Data System).

Weed community dynamics under repeated fertilization with different nutrient sources over 5 years

Soil fertility management through the application of synthetic fertilizer or livestock manures is crucial to maintaining the productivity and profitability of cropping systems. Little, however, is known about the response of weed communities to different livestock manure nutrient sources. As weed communities with increased diversity are considered part of more sustainable agroecosystems, it is necessary to find management practices that result in diverse weed communities of acceptable densities without negative impacts on crop productivity. Here, we monitored the effect of five nutrient sources, with similar goals for nitrogen (N) management, including synthetic fertilizer, liquid pig manure, two types of solid pig manure, and solid dairy manure on the weed community in a five-year (2008-2012) study. The abundance, species richness, Simpson’s diversity, Simpson’s evenness, and species turnover in weed communities were assessed over time. Crop biomass, mid-season plant-accessible soil nitrate-N, and pre-season soil phosphorus were determined. The application of liquid pig manure or synthetic fertilizer enhanced crop biomass likely through increased crop accessibility to N. The continued use of these sources of nutrients over time, contributed to low density, low species richness, and low diversity weed communities, particularly through the decline of broadleaf weed species. Liquid pig manure and synthetic fertilizer treatments were lower in weed density and diversity than solid manures. Solid manure treatments were associated with increased weed densities and reduced crop biomass; however, these nutrient source treatments resulted in more diverse weed communities. Regardless of the nutrient treatments, we observed drastic declines in weed community abundance, species richness, and diversity in drier years. Our study suggests that a management practice that increases the accessibility of N to the crop, possibly through a mixture of solid manures and synthetic fertilizers or liquid pig manure, may be ideal for promoting a profitable cropping system with decreased densities and improved diversity in weed communities. Technological advances that provide more precise placement of solid manures to increase the accessibility of N to the crop, may further contribute to achieving such profitable and multifunctional agroecosystems.

Effects of Oxytetracycline/Lead Pollution Alone and in the Combined Form on Antibiotic Resistance Genes, Mobile Genetic Elements, and Microbial Communities in the Soil.

The application of livestock manure is the leading cause of antibiotic and heavy metal pollution in agricultural soil. However, the effects of oxytetracycline (OTC) and lead (Pb) pollution in the single or combined form on antibiotic resistance genes (ARGs) in the soil need to be further studied. This study was planned to investigate the effects of OTC and Pb application on ARGs, mobile genetic elements (MGEs), and bacterial abundance in the soil. The relative abundance of ARGs and MGEs increased by 0.31-fold and 0.03-fold after the addition of 80 mg kg-1 Pb to the soil, and by 0.49-fold and 0.03-fold after the addition of 160 mg kg-1 Pb. In addition, under the premise of the existence of OTC, the inhibitory effect of a low concentration of Pb on ARG is stronger than that of a high concentration of Pb, resulting in a lower abundance of ARGs. The abundance of ARGs and MGEs increased by 0.11-fold and 0.17-fold after the addition of OTC (30 mg kg-1) to the soil at a Pb concentration of 80 mg kg-1 and by 0.18-fold and 0.04-fold at a Pb concentration of 160 mg kg-1. The addition of OTC and Pb in the soil also decreased the many bacterial communities such as Bacteroidetes, Proteobacteria, Acidobacteria, and Firmicutes. Redundancy analysis (RDA) showed that organic matter content and pH were positively correlated with the abundance of ARGs and MGEs. At the same time, electrical conductivity (EC) had a negative correlation with the abundance of ARGs and MGEs in the soil. Intl1 was significantly associated with tetB, sul1, tetQ, sul2, and sul3. Network analysis illustrated that Actinobacteria, Bacteroidetes, and Proteobacteria were the main host bacteria causing changes in the abundance of ARGs and MGEs, and they were also predominant phylum in the culture environment. This conclusion can provide a reference for the related research of ARGs in soil.

Nitrogen and Phosphorus Replacement Value of Three Representative Livestock Manures Applied to Summer Maize in the North China Plain

Land application of livestock manure may reduce the use of mineral fertilizers and alleviate the environmental degradation associated with mineral fertilizers application. However, how to optimize utilization of livestock manure value is not well understood and documentation regarding the nitrogen (N) and phosphorus (P) fertilizer replacement values (NFRV and PFRV, respectively) needs further scrutiny. Therefore, three representative livestock manures, i.e., pig, chicken, and cattle manure, were applied at different usages to assess their N and P availability in comparison to reference mineral fertilizers over summer maize growing seasons. The results show that the average NFRVs of pig, chicken, and cattle manures were 41.7–58.4%, 27.5–44.4%, and −3.6–36.1%, respectively, when based on different references (grain yield, total dry matter yield, grain N uptake, total N uptake), at different N application levels. The NFRV increased with the elevated N application rate for cattle manure treatment. In the P trials, livestock manure had a higher PFRV at a low P application level, and the average PFRVs of pig, chicken, and cattle manures were 80.3–164.8%, 77.9–143.7%, and 94.1–168.0%, respectively, at different P application levels. We conclude that livestock manure produced the lowest NFRV and highest PFRV at a low fertilizer application rate; pig manure had the highest N availability; and cattle manure had the highest P availability.

PSVIII-8 Impacts of Phosphorus Intake on Beef Heifer Growth Performance and Conception Rates

Abstract The objective of this experiment was to further investigate the effects of phosphorus intake on beef heifer growth performance and conception rates. An increase in phosphorus soil concentrations from use of livestock manure as fertilizer in Northwest Arkansas has led to greater phosphorus concentrations available in forages. This study was designed to determine if phosphorus supplementation is warranted when adequate phosphorus soil concentrations exist. This experiment was conducted over 2 years using two separate groups of weaned crossbred Angus heifers (n=72/year). Approximately 30 d after weaning, heifers were stratified by body weight (average initial weight 262kg) and allocated randomly to 14 groups (8 in Year 1, 6 in Year 2). Groups were assigned randomly to 1 of 2 treatments: 1) a free-choice-mineral mix that contained no supplemental phosphorus (CON), or 2) a free-choice-mineral mix with 4% supplemental phosphorus and identical concentrations of other supplemental minerals (4PMIN). Heifers grazed 2.24 ha mixed grass pastures with a history of livestock manure application and were supplemented with soy hulls (0.5% of body weight) daily. On d 112, heifers &amp;gt; 273 kg body weight had an ultrasound evaluation of reproductive tracts (1= infantile, 5= cyclic). Heifers were determined pregnant or open via rectal ultrasonography. Data were analyzed using the MIXED or GLIMMIX procedures of SAS 9.4 with group within year as the experimental unit. There were no differences in gain for either treatments for the 224-day period (P ≥ 0.14). Reproductive tract scores did not differ (P = 0.95). There were no differences for conception rates (AI or natural bred) (P ≥ 0.55). Overall pregnancy was 79% for CON and 83% for 4PMIN. Heifers grazing pastures with a history of livestock manure application did not benefit from adding supplemental phosphorus in the free choice mineral offered.

ARGs distribution and high-risk ARGs identification based on continuous application of manure in purple soil

Tetracyclines (TCs) are one of the most widely used antibiotics in livestock and poultry industry. Sichuan province and Chongqing city are the provinces and cities with the most concentrated purple soil distribution in China, as well as the largest livestock and poultry breeding scale. Purple soils with low organic carbon content and poor structure, and manure fertilizers were heavily applied to improve soil quality. However, the research on antibiotic resistance genes (ARGs) dispersal in purple soils is limited. Overall, 234 ARGs subtypes belonging to 15 types were detected in all soils. Long-term application of livestock manures significantly changed the characteristics of ARGs, mobile genetic elements (MGEs), pathogen species and bacterial communities in the soil, and increased by 103.2 %, 13.1 %, 188.6 % and 43.7 % in chicken manure treatments compared with the control, respectively. Partial equation PLS-PM analysis further reveals that the main driving factor of ARGs is bacterial abundance, while bacterial diversity has a negative effect on ARGs abundance. Through ANOVA and network analysis, it was found that 30 ARGs were significantly affected by manure, its relative abundance is 0.8–1.4 times that of the control treatment. The qPCR results also proved that the relative abundance of ARGs including sul2, etc. increased with the increase of manure application and these resistance genes in chicken manure treatments were higher than in pig manure treatments. These resistance genes pose a high risk to public health, and chicken manure application posed a higher risk than pig manure. The TC content in the 40–60 cm soil layer was higher in medium- and high-volume pig manure, which was at risk of being transported to groundwater. Our research results deepen the understanding of ARGs transmission in purple soil under agricultural activities and emphasize the species and distribution of antibiotic resistance genes may differ across soil and manure types.

Revisiting sampling duration to estimate N2O emission factors for manure application and cattle excreta deposition for the UK and Ireland

According to the available guidelines, good practices for calculating nitrous oxide (N2O) emission factors (EFs) for livestock excreta and manure application include that sampling duration should be of at least one year after the nitrogen (N) application or deposition. However, the available experimental data suggest that in many cases most emissions are concentrated in the first months following N application. Therefore resources could be better deployed by measuring more intensively during a shorter period. This study aimed to assess the contribution of the N2O flux in the period directly after N application to the annual net emission. We used a database of 100 year-long plot experiments from different excreted-N sources (dung, urine, farmyard manure and slurry) used to derive EFs for the UK and Ireland. We explored different shorter potential measurement periods that could be used as proxies for cumulative annual emissions. The analysis showed that the majority of emissions occur in the first months after application, especially in experiments that i) had urine as the N source, ii) had spring N application, iii) were conducted on fine-textured soils, or iv) showed high annual emissions magnitude. Experiments that showed a smaller percentage of emissions in the first months also had a low magnitude of annual net emissions (below 370 gN2O–N ha−1 year−1), so the impact of measuring during a shorter period would not greatly influence the calculated EF. Accurate EF estimations were obtained by measuring for at least 60 days for urine (underestimation: 7.1%), 120 days for dung and slurry (4.7 and 5.1%) and 180 days for FYM (1.4%). At least in temperate climates, these results are promising in terms of being able to estimate annual N2O fluxes accurately by collecting data for less than 12 months, with significant resource-saving when conducting experiments towards developing country-specific EFs.

Sustainability assessment of topsoil ecology in Chongqing, China based on the application of livestock and poultry manure

China is the world's largest livestock and poultry breeding country. Heavy metal trace element additives are widely used to prevent animal diseases and promote their growth. China produces approximately 3.8 billion tons of livestock and poultry manure annually, and untreated livestock and poultry manure causes a large amount of heavy metal elements to enter the soil environment. Currently, there is limited research on the accumulation of heavy metals in the soil due to the continuous application of livestock and poultry manure, the resulting pollution risk and the negative effects on soil ecology sustainability. This study thoroughly investigated the effects of livestock and poultry manure on the composition and function of soil microbial, and heavy metal resistance genes using 16S and metagene sequencing and 6 years of field experiments. The application of livestock and poultry manure for 6 consecutive years increased the accumulation of zinc (Zn), copper (Cu), mercury (Hg), and chromium (Cr) in the soil at the experimental sites, and cadmium (Cd) and Hg had higher potential risk levels (single potential ecological risk coefficients (Eri) of Hg and Cd were 190.49–336.52 and 385.43–468.52, respectively). Firmicutes and Zoopagomycota were significantly correlated with the soil Zn and Cd contents and pH. After continuous application of manure, the relative abundance of Hg resistance genes (merA) in soil increased by 7.3–8.2 times compared with inorganic feitilizer treatment (IF), and Cu resistance genes (copF and actP) increased by 2.45–5.45 times and 3.8–4.6 times. Phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt2) and metagenomic function prediction indicated that resistance genes, antioxidant response, and metal output played an important role in heavy metal bioresistance and biotransformation. This work presented heavy metal contents, microbial composition and resistance genes in continuous application of livestock and poultry manure in China, and these data will be of great use in the surveillance, maintenance, and biological removal of heavy metals in manure.