Continuous Application Of Manure Research Articles

Low Carbon Loss from Long-Term Manure-Applied Soil during Abrupt Warming Is Realized through Soil and Microbiome Interplay.

Manure application is a global approach for enhancing soil organic carbon (SOC) sequestration. However, the response of SOC decomposition in manure-applied soil to abrupt warming, often occurring during diurnal temperature fluctuations, remains poorly understood. We examined the effects of long-term (23 years) continuous application of manure on SOC chemical composition, soil respiration, and microbial communities under temperature shifts (15 vs 25 °C) in the presence of plant residues. Compared to soil without fertilizer, manure application reduced SOC recalcitrance indexes (i.e., aliphaticity and aromaticity) by 17.45 and 21.77%, and also reduced temperature sensitivity (Q10) of native SOC decomposition, plant residue decomposition, and priming effect by 12.98, 15.98, and 52.83%, respectively. The relative abundances of warm-stimulated chemoheterotrophic bacteria and fungi were lower in the manure-applied soil, whereas those of chemoautotrophic Thaumarchaeota were higher. In addition, the microbial network of the manure-applied soil was more interconnected, with more negative connections with the warm-stimulated taxa than soils without fertilizer or with chemical fertilizer applied. In conclusion, our study demonstrated that the reduced loss of SOC to abrupt warming by manure application arises from C chemistry modification, less warm-stimulated microorganisms, a more complex microbial community, and the higher CO2 intercepting capability by Thaumarchaeota.

Effects of Different Conditioners on Soil Microbial Community and Labile Organic Carbon Fractions under the Combined Application of Swine Manure and Straw in Black Soil

The return of straw and manure to agricultural fields can impact soil organic carbon (SOC) and biological properties. However, there is a lack of research on how to use swine manure, maize straw, and various conditioners together affects soil bacterial and fungal populations. This study aimed to investigate six treatments, namely, only maize straw (S00), maize straw combined with swine manure (S0Z), maize straw combined with biochar and swine manure (SCZ), maize straw combined with boron slag and swine manure (SBZ), maize straw combined with biological agent and swine manure (SJZ), and maize straw combined with bio-organic fertilizer and swine manure (SFZ). The results showed that after the two-year return, all treatments increased the SOC content in 2023, which was 12.55–26.89% higher than S00. And the SCZ treatment significantly increased the soil organic carbon (SOC), dissolved organic carbon (DOC), easily oxidizable carbon (EOC), particulate organic carbon (POC), and microbial biomass carbon (MBC) content by 26.89%, 25.44%, 56.88%, 16.08%, and 43.54%, compared to S00. A redundancy analysis (RDA) showed that the continuous application of manure, maize straw, and conditioners has a positive impact on the diversity and abundance of soil microbial communities, enhancing the accumulation of soil carbon. Furthermore, our research revealed that soil fungi exhibited higher sensitivity in soil carbon composition following the addition of manure, straw, and conditioners to agricultural fields than bacteria. In conclusion, the addition of different conditioners to the fields is beneficial to biodiversity conservation from the perspective of achieving soil carbon storage and soil protection. Our findings suggested that the combination of maize straw, biochar, and swine manure was been proven to be the most effective treatment for increasing labile organic carbon fractions and enhancing the microbial community.

Changes in soil profile organic carbon and hydro‐physical properties as impacted by long‐term manure and inorganic fertilizer rates under a corn–soybean rotation system

AbstractUsing manure appropriately may enhance organic carbon and hydro‐physical properties while avoiding the negative impact on the environment. However, how manure impacts soils, especially at lower depths, is still not well studied. Therefore, the objective of this study was to assess the impact of different manure and inorganic fertilizer application rates on soil profile organic carbon and hydro‐physical properties under corn (Zea mays L.)–soybean (Glycine max L.)–spring wheat (Triticum aestivum L.) rotation at Beresford (established in 2003) and Brookings (established in 2008) sites in South Dakota. The treatments included low manure (LM), medium manure (MM), high manure (HM), medium fertilizer (MF), high fertilizer (HF), and control (CK). Four replicated intact soil cores were collected from all the treatments at 0‐ to 10‐cm, 10‐ to 20‐cm, 20‐ to 30‐cm, and 30‐ to 40‐cm depths. Considering treatments by depth interactions, the LM and MM decreased bulk density (ρb) by 6.9%–22.1%, as compared to the CK at 0–30 cm for either site. The HM decreased ρb by 16.4%–24.7%, as compared to the HF at 30–40 cm for either site. On observing treatment as the main effect, the MM and HM increased the soil water retention (SWR) at 0 and −5 kPa compared to MF, HF, and CK in Brookings, and the MM increased the SWR at −30 kPa as compared to the MF in Beresford at 0‐ to 40‐cm depths. The data suggest that continuous manure application may enhance organic carbon and hydro‐physical properties at lower depths. Therefore, this study concluded that long‐term manure application showed greater improvements when compared to long‐term application of inorganic fertilizer alone. It can improve hydro‐physical properties, thereby stabilizing the soil structure and improving water retention at lower depths.

Effects of Continuous Manure Application on the Microbial Community and Labile Organic Carbon Fractions

The application of organic materials contributes to the sustainable development of agriculture. Increased manure inputs have a fundamental effect on the composition and dynamics of soil organic carbon (SOC). In this study, we conducted a 10-year field experiment in Changchun, Jilin, Northeast China, to investigate the effects of manure addition on soil organic carbon components and soil microorganisms. Specifically, we established four treatments: (i) chemical fertilizer or no addition of manure (CK), (ii) pig manure with chemical fertilizer (ZF), (iii) cow manure with chemical fertilizer (NF), and (iv) chicken manure with chemical fertilizer (JF). The results showed that the JF treatment significantly increased the soil organic carbon (SOC), dissolved organic carbon (DOC), and readily oxidized organic carbon (ROC) content by 20.36%, 105.9%, and 61.32%, respectively, relative to CK. The microbial biomass carbon (MBC) content in JF, ZF, and NF treatments were significantly higher than that of CK, which increased by 107.24%, 116.45%, and 96.71%, respectively. The particulate organic carbon (POC) content in NF and JF treatments differed significantly, increasing by 25.61% and 19.01%, respectively, relative to CK. Redundancy analysis showed that continuous manure application had a positive effect on soil microbial community diversity and abundance, which was favorable for the accumulation of soil carbon. We also found that soil fungi were more sensitive than bacteria to changes in soil carbon composition following manure application. In conclusion, adding different organic materials can better support biodiversity conservation and realize ecosystem services of surface carbon storage and soil conservation. Our results reveal the importance of microbial fixation in soil carbon dynamics according to the different distribution of active organic carbon pools, which will help enhance our understanding of the carbon cycle.

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.

Continuous manure application strengthens the associations between soil microbial function and crop production: Evidence from a 7-year multisite field experiment on the Guanzhong Plain

A 7-year multisite field experiment was performed to assess the relative importance of climate, soil, and microbial properties of crop production in a wheat cropping system under contrasting fertilization management (i.e., continuous organic vs. chemical fertilization). The results showed that continuous organic application increased the annual grain yield and soil organic carbon by an average of 13.2% and 38.0%, respectively, compared to chemical fertilization. Continuous organic application increased the soil pH, which led to a significant increase in bacterial richness (i.e., Chao1) and diversity (i.e., Shannon index). Notably, organic application favored the growth of Proteobacteria and Actinobacteria but reduced the abundances of Bacteroides, Verrucomicrobia, and Acidobacteria, which ultimately led to a more complicated bacterial co-occurrence network. Importantly, organic application increased the abundances of functional genes involved in C fixation (e.g., sdhD, ACO, and acsB), C degradation (e.g., pulA, celC, and CBH2), N fixation (e.g., anfG and amoC) and nitrification (e.g., nifK), as well as P transporters (e.g., ugpQ and phnC). The structural equation modeling (SEM) results indicated that the annual air temperature and soil pH under chemical fertilizer treatment and the bacterial community structure and functional gene abundance under treatment with organic application were the primary drivers of the yield performance. Variance partitioning analysis further revealed that under chemical fertilization, climate, soil, the bacterial community, and potential function explained 32.0%, 26.7%, 19.9% and 21.4%, respectively, of the overall variance in crop productivity; however, these values shifted to 16.6%, 8.3%, 34.5% and 40.6%, respectively, when organic fertilizer was applied. These findings suggest that continuous organic application reduces the contribution of climate and edaphic conditions to crop yield compared to chemical fertilization but strengthens the associations between soil microbial function and crop production. Overall, this work provides new insights into the complexity of fertilization-induced climate-plant-microbial interactions and highlights the importance of intensified biological interactions for the sustainability of cropping ecosystems.

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.

Agri-environmental implications of N- and P-based manure application to perennial and annual cropping systems

Continuous manure application based on crop nitrogen (N) requirements could substantially increase field nutrient losses from croplands. Although phosphorus-based (P) manure application is an alternative, crops may suffer from potential microbial P immobilization and fixation of P in soil. A three-year study (2012–2014) was carried out in Manitoba, Canada, to evaluate the agronomic and environmental benefits and tradeoffs between N- and P-based liquid and solid swine manure applications on previously established (2009) annual (ACS) and perennial (PCS) cropping systems. The N-based solid manure produced greater aboveground biomass and grain yields of barley than the unfertilized control in the ACS. The N-based liquid manure produced greater biomass than the control in the PCS. Phosphorus-based treatments produced statistically similar canola oilseed grains as the N-based treatments. Seeding the PCS to canola in 2013 produced greater aboveground biomass yields than the ACS; however, the canola oilseed yields were not significantly different between the two systems. The N-based solid manure application increased Olsen P by approximately 30 mg kg−1 in both cropping systems during the three-year study period. Both N- and P-based liquid manure treatments and the N-based solid manure treatment lost significantly greater nitrate through leaching than the control in 2013, when most leaching losses occurred. Our study also showed that some of the environmental benefits of the perennial cropping system, such as reduced nitrate leaching, could be lost when converted to an annual cropping system.

Continuous Manure Application Strengthens the Associations between Soil Microbial Function and Crop Production: Evidence from a 7-Year Multisite Field Experiment in the Guanzhong Plain

Continuous Manure Application Strengthens the Associations between Soil Microbial Function and Crop Production: Evidence from a 7-Year Multisite Field Experiment in the Guanzhong Plain

English

A detailed study on soil resources characterization based on the understanding of the soil system is not available at Dugda district. With the cognizance of this fact, the present study was conducted to characterize the morphological and physicochemical properties of soils, classify the soils according to World Reference Base for Soil Resources (WRB) of Argo-Gedilala Subwatershed in Dugda District of Oromia Regional State, Central Rift Valley of Ethiopia. Four slope classes were considered and one pedon was opened for each and described in the field on a standard description sheet for each slope category. Soil samples were collected from genetic horizons of each pedon for laboratory analysis of the selected physicochemical properties of the soils. The soils were classified into different Reference Soil Groups following the (WRB).The organic carbon (OC) content of the study area ranged from low to medium/moderate (0.64 to 1.83%). Total nitrogen (TN),available.phosphorus (Av.P), cation exchange capacity (CEC) and  percent base saturation (PBS) of the soils were in  the range of (0.066-0.135%), (2.24-4.81 mgkg-1), (39.52-43.52) cmol(+)kg-1) and (77.57- 89.8%), respectively. Accordingly, they were rated as low to medium, very low to low, high to very high and high to very high, respectively. The soil classification revealed that pedon 1 and pedon 2 were Cambic Chernic Phaeozems (Pantoclayic, Humic, Hypereutric); and pedon 4, Cambic Chernic Phaeozem (Pantoclayic, Humic); whereas, pedon 3 is found to be a kind of Luvic Phaeozem (Abruptic, Albic, Clayic, Differentic, Hypereutric). The soils of the study area had low organic matter, available P and total nitrogen content, which can be seen as production constraints of all cultivated lands. To overcome the identified limitations, increasing the organic matter levels through continuous application of manure. Key words: Genetic horizons, morphological properties, pedon, physicochemical properties, slope.

English

Detailed study on soil fertility assessment based on the understanding of the soil system are not available for the most part of Ethiopia. With the cognizance of this fact, the present study was conducted to assess the soil fertility status and to prepare the fertility map of Argo-Gedilala Sub watershed in Dugda District, Central Rift Valley of Ethiopia. Eighteen composite soil samples (0-20cm depth) were taken for fertility assessment of the soil from the land mapping units of the subwatershed and mapping the status of selected soil fertility parameters was done using ordinary kriging technique in ArcGIS 10 software. The bulk density is at an acceptable range 1.3 to 1.4 g cm-3 for mineral agricultural soils. The soil organic matter contents of LUs (04, 05 and 06) 680.47 ha (64.77%) in the study area can be categorized in the range of low soil organic matter content and LUs (01, 02 and 03) 369.31 ha (35.23%) can be categorized in the medium range at the sub-watershed. The average percent total N content of the LUs (02, 04, and 05) 567.7ha (54.05%) were found to be low; LUs (01, 03 and 06) 482.61ha 45.95%) were found to be moderate. The mean available P of soils of LUs (04and05) 443.17 ha (42.19%) was categorized as very low range and LUs (01, 02, 03 and 06) 607.15 ha (57.82%) classified as low range. Exchangeable Ca2+, LUs (01, 02, 03, 05 and 06) 824.88 ha (78.55%) were very high while LU04 which covered an area of 225.44 ha (21.46%) were rated as high. The soils of the study area had low organic matter, available P and total nitrogen content, which can be seen as production constraints of all cultivated lands. To overcome the identified limitations, increasing the organic matter levels through continuous application of manure and/or compost should be integrated with chemical fertilizers.   Key words: Fertility status, land-mapping units, ordinary kriging.

Dissipation of antibiotic resistance genes in manure-amended agricultural soil

Soil antibiotic resistance due to animal manure application is of great concern in recent years. Little is known about the fate of antibiotic resistance genes (ARGs) in agricultural soils associated with long-term manure application. Here we used soil microcosms to investigate the dissipation of ARGs and the change of bacterial community in agricultural soil originated from a vegetable field which had received 24 years' swine manure application. Soil microcosms were conducted at different soil moistures and with or without biochar over a testing period of two years in lab. Results showed that continuous manure application induced an accumulation of ARGs in soil, wherein the dissipation of ARGs differed from those in non-manure amended soil. ARGs persisted in soils at least two years, although their abundance declined gradually. Meanwhile, soil moisture and biochar had significant impact on the fate of ARGs. ARGs dissipated faster in soil with higher moisture. Biochar amendment contributed to the maintenance of bacterial diversity. Within the two years of simulation experiment, biochar enhanced soil ARG retention as they dissipated slowly in the soil amended with biochar. Succession of microbial community may have sustained the transfer and resilience of ARGs. This study provides insight into the dissipation of antibiotic resistance genes in manure-applied agricultural soil.

Responses of soil bacterial community and enzyme activity to organic matter components under long-term fertilization on the Loess Plateau of China

Soil bacterial community structure, enzyme activities and their relationships to soil carbon and nitrogen in response to long-term fertilization remain poorly understood. Therefore, the objective of this study was to evaluate soil carbon and nitrogen fractions, enzyme activity, and bacterial community structure at 0–15, 15–30, and 30–60 cm depths after 34-yr of continuous application of manure and inorganic fertilizers. The study had a randomized complete block design with six treatments and three replications. Treatments were inorganic nitrogen fertilizer only (N), nitrogen plus phosphrous fertilizers (NP), manure (M), nitrogen plus manure (NM), nitrogen plus phosphorus plus manure (NPM), and unfertilized control (CK) in a winter wheat (Triticum aestivum L.) monoculture system. Most soil carbon and nitrogen fractions at 0–15 and 15–30 cm were greater with M, NM, and NPM, and winter wheat yield was greater with NPM than other treatments. The NPM increased β-glucosidase, β-xylosidase, and β-N-acetylglucosidase compared to other treatments at all depths. Soil bacterial Shannon index was similar among treatments at 0–15 and 15–30 cm and lower in N and NP than other treatments at 30–60 cm. Compared to CK, inorganic and manure fertilization increased relative abundances of Gemmatimonadetes and Bacteroidetes but decreased those of Nitrospirae, Planctomycetes, and Latescibacteria. Increases in soil enzyme activities and bacterial communities after long-term application of inorganic N and P fertilizers and manure was related to increased substrate availability. Overall, a combination of chemical fertilizers and manure can enhance soil health and quality through increased soil organic matter component, enzyme activity, and bacterial abundance.

Speciation, Transformation, and Accumulation of Manure-derived Cu and Zn in the Soil–Rice System

ABSTRACTPig manure has been successfully utilized as organic fertilizer to field crops in China. In this study, we used the cement pool plot test to investigate the speciation change and bioavailability of Cu and Zn derived from different pig manures (the fresh pig manure [FM1], the composting pig manure [FM2], and the dry-fermentation-bed pig manure [FM3]) in a soil–rice system. Results showed that the soil pH and the carbon content increased after applying pig manures. Cu and Zn contents in soil also remarkably increased but maintained under the safety standards (except Cu content in FM3). The exchangeable and carbonate-associated Cu and Zn both decreased over time, whereas Cu and Zn in Fe-Mn oxide form and organic-bound state increased and were the dominating components in soil. The pig manures, especially FM2, improved the rice biomass and yield. However, FM3 caused high Cu and Zn accumulation in rice. Moreover, the Cu level in grain exceeded the Chinese food hygiene standard, but the Zn level remained under the safety concentration. Collectively, it is imperative to assess the potential risk of Cu and Zn originated from pig manures. Cu more easily exceeded the safety standard than Zn, although Zn levels can reach the limit concentration with continuous manure application.

Antibiotic resistance in grass and soil.

Antibiotic resistance is currently one of the greatest threats to human health. The global overuse of antibiotics in human medicine and in agriculture has resulted in the proliferation and dissemination of a multitude of antibiotic resistance genes (ARGs). Despite a large proportion of antibiotics being used in agriculture, little is understood about how this may contribute to the overall antibiotic resistance crisis. The use of manure in agriculture is a traditional and widespread practice and is essential for returning nutrients to the soil; however, the impact of continuous manure application on the environmental microbiome and resistome is unknown. The use of antibiotics in animal husbandry in therapeutic and sub-therapeutic doses creates a selective pressure for ARGs in the gut microbiome of the animal, which is then excreted in the faeces. Therefore, the application of manure to agricultural land is a potential route for the transmission of antibiotic-resistant bacteria from livestock to crops, animals and humans. It is of vital importance to understand the mechanisms behind ARG enrichment and its maintenance both on the plant and within the soil microbiome to mitigate the spread of this resistance to animals and humans. Understanding this link between human health, animal health, plant health and the environment is crucial to inform implementation of new regulations and practice regarding antibiotic use in agriculture and manure application, aimed at ensuring the antibiotic resistance crisis is not aggravated.

Dissolved organic nitrogen fluxes and crop yield after long-term crop straw incorporation

The transportation of dissolved organic nitrogen (DON) from croplands to aquatic ecosystems potentially negatively influences water quality. Sustaining crop yields while decreasing the environmental impacts of the DON from nitrogen fertilizer application is a key challenge in sustainable agriculture. However, few field datasets have measured the lateral transportation of DON via hydrological routes under different nitrogen fertilizer applications, particularly in sloping croplands. Using lysimeter plots (8 × 4 m2), we measured DON loss via overland flow, interflow, and soil erosion under different fertilizer applications under a long-term field experiment. There were four treatments, including no fertilizer (CK), mineral fertilizer (NPK), mineral fertilizer combined with swine manure (MNPK), and mineral fertilizer combined with crop straw (CNPK). In comparison to the NPK treatment, the annual DON loss fluxes via overland flow, interflow, and soil erosion for the MNPK treatment were significantly (P < 0.05) increased by 68.8, 100.6, and 63.7%, respectively. Conversely, this was significantly decreased by 182.6, − 14.1, and 49.4%, respectively, under the CNPK treatment. Correspondingly, the yield-scaled total DON losses for the MNPK and CNPK treatments were significantly increased by 78.8 and − 18.2% compared to the NPK treatment (0.33 ± 0.04 kg N t−1 grain). Therefore, long-term continuous manure application is associated with an increased risk of DON environmental pollution. Alternatively, the incorporation of crop straw can be recommended as a means of decreasing DON pollution while maintaining crop yield.

Effects of continuous manure application on methanogenic and methanotrophic communities and methane production potentials in rice paddy soil

Livestock manures are broadly used in agriculture to improve soil productivity; however, the impact of continuous manure application on the behaviors of methanogens (mcrA) and methanotrophs (pmoA) is poorly understood. The objective of this study was to determine the influence of continuous pig manure application on methanogenic and methanotrophic communities and the methane production potentials (MPPs) of rice paddy soil. The results show that adding manure induced significantly higher mcrA gene abundance than chemical fertilizer treatments, and that manure led to higher mcrA gene abundance when it was applied together with full NPK fertilizers than it did when applied with N or NP fertilizers. However, there were no obvious effects of continuous manure application on pmoA gene abundance. The community structures of mcrA and pmoA were distinctly altered by continuous manure application, and their variation was closely associated with fertilizer-induced changes in dissolved organic C, total P, and available P and K in the soil. We also observed that manure application along with full NPK fertilizers caused significantly higher MPPs compared to chemical fertilization alone, while manure application with N or NP fertilizers had no obvious effect on MPPs. Moreover, MPPs were positively correlated with mcrA gene abundance, suggesting that continuous manure application may enhance methane emissions by stimulating methane production. Therefore, long-term manure application can affect both the abundance and composition of methanogens, and thus, enhance methane production. This effect is largely dependent on soil nutritional status.

The long-term role of organic amendments in building soil nutrient fertility: a meta-analysis and review

An exhaustive meta-analysis of 132 long-term (≥ 10 years) studies worldwide was carried out to determine the effects of the use of organic amendments (OA) and OA + inorganic fertiliser (IF) on soil nutrient fertility. The responses of (1) crop yield [over the whole duration of the period (yieldm) and at the end of the experiment (yieldf)], (2) soil organic carbon (OC), (3) size of microbial biomass, and (4) Olsen phosphorus (P) to OA and OA + IF compared with IF only (standard control) and no fertilisation (nil control) were investigated. The overall effect of OA alone on yield was significant when compared with the nil control, but not when compared with the standard control. Only when OA and IF were added to soils that met specific conditions (low initial fertility, sandy texture, near-neutral pH values, under tropical climate) they rendered a significantly greater yieldf than the corresponding standard controls. The continuous application of manure caused greater relative and absolute gains in soil OC than straw + IF but did not produce significant greater yields while causing a considerable increase in Olsen P over time. The use of OA and OA + IF increased the resilience of agronomic systems over that of IF alone, as inferred from the smaller coefficient of variation of crop yield over time. We conclude that while the use of OA along with IF provides some additional benefits on yields as compared with IF application alone (especially under the above-mentioned conditions), the selection of the OA type and application rate should be carefully considered in order to maximise the nutrient use efficiency and minimise any undesirable effects to the environment.

Comparison of Nutrient and Metal Loadings with the Application of Swine Manure Slurries and Their Liquid Separates to Soils.

The accumulation of phosphorus (P) and metals is a serious concern with the continuous application of manure to agricultural soils. Solid-liquid separation of swine slurry is a promising approach to reduce P and metal loadings through application of separated liquid (SL) as a nutrient source. However, little information is available on nutrient and metal loadings with the application of SL compared with unseparated raw manure (RM). We analyzed element concentrations and calculated nutrient and metal loadings for RM and their respective SL applications, considering an application rate of 100 kg total nitrogen (N) ha. Samples of SL were obtained through three separation techniques: (i) centrifugation without a flocculant, (ii) centrifugation with a flocculant, and (iii) rotary press with a flocculant. Irrespective of separation technique, calculated P loadings with the application of SL were only 50 to 70% of that of RM at equivalent rates of total N yet exceeded crop removal rate. In contrast, calculated K and Na loadings with SL application were significantly greater than with RM, indicating a possible build-up of K and Na in soil. Calculated Ca and Mg loadings were significantly greater with RM than with SL. Loadings of Al, As, Ba, Cd, Cr, Fe, Mn, Ni, Pb, Sn, Se, Ti, and V were low, whereas Cu and Zn loadings were above crop removal rates for RM and SL. For solid-liquid separation to provide a lasting solution to the problem of P and metal accumulation, the SL must be supplemented with commercial N fertilizer to meet crop N demand.

Comparative studies on lentic environment of Mai Pokhari, Ilam and Kechana jheel wetland ecosystems, Jhapa, Nepal (With reference to bottom dwelling fauna)

Mai Pokahri is a mountain lake situated in midland at an altitude of 2150 m from sea level whereas Kechana jheel is situated in lowland (Tarai) at an altitude of 63 m from the sea level respectively. The lentic environments of the both lakes vary in the composition of bottomdwelling fauna and limnetic fauna respectively. The comparative studies were carried out in two different years by sampling the macroinvertebrates periodically. The bottom-fauna at Mai pokhari was found higher than Kechana jheel. Mai pokhari is still in natural condition but Kechana jheel is losing its native entity because of aquaculture. Mainly, the abundance of Chironomids showed the stratification in Mai pokhari but abundance of Trichoptera and Coleoptera in Kechana jheel indicate unstable bottom condition because continuous application of manure for pre-conditioning it as a fish pond. DOI: http://dx.doi.org/10.3126/njbs.v1i0.7467 Nepalese Journal of Biosciences 1: 32-36 (2011)