Soil Nitrogen Dynamics

Головні компоненти системи сполук Нітрогену – комплекс нітрогеновмісних речовин, які утворюють внутрішньоґрунтовий цикл іммобілізації і мобілізації мінеральних форм за допомогою  мікроорганізмів. Участь мікроорганізмів у функціонуванні системи Нітрогену забезпечує високу її чутливість до екзогенних і ендогенних факторів ґрунтового середовища, саморегуляцію і підтримання динамічної рівноваги.

Urban grasslands are turfgrass dominated landscapes of varying functions and uses that are ubiquitous in areas associated with human population growth and urbanization. While these landscapes are perceived to serve a primarily aesthetic function, they provide a multitude of beneficial ecosystem functions that impervious surfaces do not provide. Urban grassland soils have been shown to accumulate carbon (C) and nitrogen (N) for decades, matching native grasslands and eastern hardwood forest soils in terms of C and N densities. The establishment and maintenance of urban grasslands alters many microbially-mediated biogeochemical processes in soils, including soil organic matter (SOM) dynamics. Despite strong evidence of alterations to soil C and N cycling, the impacts of maintaining urban grasslands on soil microbiomes and their functions remain understudied compared to other ecosystems. Typicalmanagement practices can directly and indirectly affect edaphic factors in urban grasslands, which in turn, could impact soil processes mediated by microorganisms. We reviewed the existing literature on urban grassland management, focusing on how mowing, fertilization, irrigation, grass species composition, and soil cultivation could impact the composition and function of soil microorganisms. Although sparse, the literature indicates that the techniques used to maintain urban grassland habitats broadly select for copiotrophic microorganisms adapted to higher resource availability. Additionally, the studies indicate that greater soil fertility and plant productivity found in urban grasslands facilitate the accumulation of soil C and N, as well as SOM as compared to other land-use types. However, effects on soil biology and biogeochemistry depend on specific management practices, which are quite variable. Future research on soil C and N dynamics in urban grasslands should focus on the dominant component of this ecosystem—residential lawns—however, much of the existing scientific literature featuring turfgrass systems focus heavily on golf courses, athletic fields, and major tourist parks.

Agricultural lands are subject to changes in use for a variety of environmental and economic reasons. Among these changes, shifts between crops and grasslands are particularly common. Understanding the effects of these changes on soil functioning is crucial to anticipating crop productivity and environmental impacts and yet has rarely been studied. The purpose of this study was to investigate the in situ temporal dynamics of soil N cycling and C pools after grassland/cropland conversions and risks of N losses from such systems. The experiment was conducted in western France at a long-term experimental site with a temperate oceanic climate. We followed soil N cycling and C pools for four experimental treatments over 36 months: (i) continuous grassland, (ii) continuous rotation of annual crops, (iii) conversion from grassland to a rotation of annual crops, and (iv) conversion from a rotation of annual crops to grassland. Gross N mineralization, potential N immobilization and potential nitrification were estimated using the 15 N dilution/enrichment technique and FLUAZ model, based on samples from the 0e10 cm soil layer (0, 0.75, 3, 12, 24 and 36 months after change in land use) and 10e30 cm soil layer (after 24 and 36 months) in all 4 treatments. Nitrogen pools (NH 4 þ , NO 3 À , and organic N), total carbon (C), dissolved organic C, microbial biomass C, and C mineralization were also determined on all soil samples. The continuous grassland soil had rates of N mineralization and N immobilization twice as high as a rotation of annual crops, as well as a slightly lower rate of nitrification and a higher organic C content. Ploughing the grassland led to a rapid shift of soil organic matter pools, N fluxes and microbial activities towards characteristics of the cropland. These effects were attributed to cultivation mixing the soil layers. In contrast, the restoration of grassland on soil previously cropped with annual species did not significantly change soil N or C characteristics within 24 months although changes began to appear after 36 months. This time lag corresponded to the time needed for the complete establishment of root systems for the grasses. Therefore we found a strong asymmetry in the patterns of change in gross N fluxes and C pools between the two conversions. Overall, we found that responses in N fluxes were strongly correlated to soil C pools, except for nitrification. The ratio of potential nitrification to gross ammonium immobilization, which indicates the risk of N losses in agricultural systems, was greater in annual crop rotation than grassland. This indicates that adding grasslands into a rotation of annual crops does not necessarily reduce the risk of N loss within 2 years but does reduce the risk after 3 years.

Despite increasing interest in the effects of climate change on soil processes, the response of nitrification to elevated CO2 remains unclear. Responses may depend on soil nitrogen (N) status, and inferences may vary depending on the methodological approach used. We investigated the interactive effects of elevated CO2 and inorganic N supply on gross nitrification (using 15 N pool dilution) and potential nitrification (using nitrifying enzyme activity assays) in Dactylis glomerata mesocosms. We measured the responses of putative drivers of nitrification (NH4+ production, NH4+ consumption, and soil environmental conditions) and of potential denitrification, a process functionally linked to nitrification. Gross nitrification was insensitive to all treatments, whereas potential nitrification was higher in the high N treatment and was further stimulated by elevated CO2 in the high N treatment. Gross mineralization and NH4+ consumption rates were also significantly increased in response to elevated CO2 in the high N treatment, while potential denitrification showed a significant increase in response to N addition. The discrepancy between the responses of gross and potential nitrification to elevated CO2 and inorganic N supply suggest that these measurements provide different information, and should be used as complementary approaches to understand nitrification response to global change.

Enhancement of soil nitrogen (N) cycling by grazing has been observed in many grassland ecosystems. However, whether grazing affects the activity only of the key microbial functional groups driving soil N dynamics or also affects the size (cell number) and/or composition of these groups remains largely unknown. We studied the enzyme activity, size, and composition of five soil microbial communities (total microbial and total bacterial communities, and three functional groups driving N dynamics: nitrifiers, denitri-fiers, and free N2 fixers) in grassland sites experiencing contrasting sheep grazing regimes (one light grazing [LG] site and one intensive grazing [IG] site) at two topographical locations. Enzyme activity was determined by potential carbon mineralization, nitrification, denitrification, and N2 fixation assays. The size of each community (except N2 fixers) was measured by the most-probable-number technique. The composition of the total soil microbial community was characterized by phospholipid fatty acid analysis (PLFA), and the genetic structure of the total bacterial community was assessed by ribosomal intergenic spacer analysis. The genetic structures of the ammonia-oxidizing, nitrate-reducing, and N2-fixing communities were characterized by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) or by polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE) targeting group-specific genes. Greater enzyme activities, particularly for nitrification, were observed in IG than in LG sites at both to-pographical locations. The numbers of heterotrophs, nitrifiers, and denitrifiers were higher in IG than in LG sites at both topographical locations. The amplitude of changes in community size was higher than that of community enzyme activity. Phospholipid and nucleic acid analyses showed that the composition/structure of all the communities, except nitrate reducers, differed between IG and LG sites at both locations. For each community, changes in activity were correlated with changes in the occurrence of a few individual PLFAs or DNA fragments. Our results thus indicate that grazing enhances the activity of soil microbial communities but also concurrently induces changes in the size and composition/structure of these communities on the sites studied. Although the generality of our conclusions should be tested in other systems, these results are of major importance for predicting the effects of future disturbances or changed grazing regimes on the functioning of grazed ecosystems.

Abstract The potential of a stepwise fusion of proximally sensed portable X-ray fluorescence (pXRF) spectra and electromagnetic induction (EMI) with remote Sentinel-2 bands and a digital elevation model (DEM) was investigated for predicting soil physicochemical properties in pedons and across a heterogeneous 80-ha crop field in Wisconsin, USA. We found that pXRF spectra with partial least squares regression (PLSR) models can predict sand, total nitrogen (TN), organic carbon (OC), silt contents, and clay with validation R2 of 0.81, 0.74, 0.73, 0.68, and 0.64 at the pedon scale but performed less well for soil pH (R2 = 0.51). A combination of EMI, Sentinel-2, and DEM data showed promise in mapping sand, silt contents, and TN at two depths and Ap horizon thickness and soil depth across the field. A clustering analysis using combinations of mapped soil properties or proximal and remote sensing data suggested that data fusion improved the characterization of field-scale variability of soil properties. The cost-benefit analysis showed that the most accurate management zones (MZs) for topsoil can be generated only using estimated soil property maps while it was the most costly as compared to other data sources. For an intermediate-high (for topsoil) and high (subsoil) accuracy and a moderate economic budget, the combination of sensors (proximal + remote sensing + DEM) might be a better approach for effective MZs generation than collecting soil samples for laboratory analysis while the latter produced the most accurate maps for topsoil. It can be concluded that pXRF spectra can be useful for predicting key soil properties (e.g., sand, TN, OC, silt, clay) at different soil depths, and a combination of proximal and remote sensing provides an effective way to delineate soil MZs that are useful for decision-making.

Grazing has traditionally been viewed as detrimental to plant growth, but it has been proposed that under certain conditions, grazing may lead to compensatory or overcompensatory growth. However, comprehensive information on the relative role of the main functional processes controlling the response of net primary production (NPP) to grazing is still lacking. In this study, a modelling approach was used to quantify the relative importance of key functional processes in the response of annual canopy NPP to grazing for a West African humid grassland. The PEPSEE-grass model, which represents radiation absorption, NPP, water balance and carbon allocation , was used to compute total and aboveground NPP in response to grazing pressure. Representations of grazing and mineral nitrogen input to the canopy were simplified to focus on the vegetation processes implemented and their relative importance. Simulations were performed using a constant or resource-driven root/shoot allocation coefficient, and dependence or independence of conversion efficiency of absorbed light into dry matter on nitrogen availability. There were three main results. Firstly, the response of NPP to grazing intensity emerged as a complex result of both positive and negative, and direct and indirect effects of biomass removal on light absorption efficiency, soil water availability, grass nitrogen status and productivity, and root/shoot allocation pattern. Secondly, overcompensation was observed for aboveground NPP when assuming a nitrogen-dependent conversion efficiency and a resource-driven root/shoot allocation. Thirdly, the response of NPP to grazing was mainly controlled by the effect of plant nitrogen status on conversion efficiency and by the root/shoot allocation pattern, while the effects of improved water status and reduced light absorption were secondary.

Extensification modify the C and N cycles in grassland ecosystems, but it is not clear whether reduced exploitation increases or decreases soil nitrogen availability, and whether these changes result from a direct effect of the treatment or from an indirect treatment effect through a change in plant species composition. A formerly intensively exploited grassland was submitted to the following treatments: (i) control with one mowing and four grazing periods per year (4G+M), (ii) cessation of mowing (4G), (iii) cessation of mowing and suppression of three grazing periods (1G). During the 13th year of the experiment, the species composition and key indicators of the C and N cycles were measured, using 20 samples per treatment. Lolium perenne and Trifolium repens disappeared in favor of tall caespitose grasses in 4G, and of rhizomatous species in 1G. The species composition and the nitrate concentration of the soil solution suggested an increase in nutrient availability under reduced exploitation, whereas the nitrification and denitrification potentials decreased. More particulate organic matter accumulated in proportion to the below-ground phytomass, whereas the C:N ratio remained constant. Testing treatment effect at similar species composition and plant community effect within the same treatment showed that: (1) the increase in POM residence time was mainly due to the changes in species composition, (2) the decrease in nitrification activity resulted mainly from a direct effect of the treatment, and (3) a compensation between a direct positive and an indirect negative effect of the treatment resulted in no change in extractable N. All results suggested that soil N availability was not decreased, although litter degradability decreased.

Rice production is increasingly limited by water scarcity. Covering paddy rice soils with films (so-called ground cover rice production system: GCRPS) can significantly reduce water demand as well as overcome temperature limitations at the beginning of the growing season, which results in greater grain yields in relatively cold regions and also in those suffering from seasonal water shortages. However, it has been speculated that both increased soil aeration and temperature under GCRPS result in lower soil organic carbon and nitrogen stocks. Here we report on a regional-scale experiment conducted in Shiyan, a typical rice-producing mountainous area of China. We sampled paired adjacent paddy and GCRPS fields at 49 representative sites. Measured parameters included soil carbon (C) and nitrogen (N) stocks (to 1 m depth), soil physical and chemical properties, δ 15 N composition of plants and soils, potential C mineralization rates, and soil organic carbon (SOC) fractions at all sampling sites. Root biomass was also quantified at one intensively monitored site. The study showed that: (1) GCRPS increased SOC and N stocks 5–20 years following conversion from traditional paddy systems; (2) there were no differences between GCRPS and paddy systems in soil physical and chemical properties for the various soil depths, with the exception of soil bulk density; (3) GCRPS increased above-ground and root biomass in all soil layers down to a 40 cm depth; (4) δ 15 N values were lower in soils and plant leaves indicating lower NH 3 volatilization losses from GCRPS than in paddy systems; and (5) GCRPS had lower C mineralization potential than that observed in paddy systems over a 200-day incubation period. Our results suggest that GCRPS is an innovative production technique that not only increases rice yields using less irrigation water, but that it also increases SOC and N stocks.

Nickel mine spoils in New Caledonia represent an extreme environment, rich in nickel and strongly deficient in elementary elements such as carbon and nitrogen. To rehabilitate these sites, revegetation attempts are performed with endemic plant species establishing dinitrogen-fixation symbiosis (Gymnostoma webbianum and Serianthes calycina). As this biological fixation process provides the major source of available nitrogen in this extreme environment, it could be expected that nitrogen cycling would be stimulated. To study the revegetation effect on mine spoils, the effect of the two pioneer plants on the structure and activity of two functional bacterial communities involved in the N-cycle was investigated. nifH and narG genes were used as molecular markers for dinitrogen-fixers and dissimilatory nitrate reducers respectively. In order to assess the influence of the plants on both communities, nine clone libraries were constructed for each targeted gene. Libraries containing 602 and 513 nifH and narG clones, respectively, were screened by restriction fragment length poly-morphism (RFLP) analysis. One hundred and forty-one and 78 representative clones from at least all RFLP families containing more than one clone were sequenced from nifH and narG clone libraries respectively. Both pioneer plants modified the diversity and activity of the two functional communities. However, distinct effects were observed depending on the plant species and the community considered. Serianthes calycina strongly selected a diazotroph phylotype and restored the potential activity of both communities. In contrast, G. webbianum selected no particular phylotype and only restored a fixing activity.

Stimulation of nitrification and denitrification by long term (from years to decades) grazing has commonly been reported in different grassland ecosystems. However, grazing generally induces important changes in plant species composition, and whether changes in nitrification and denitrification are primarily due to changes in vegetation composition has never been tested. We compared soil nitrification-and denitrification-enzyme activities (NEA and DEA, respectively) between semi-natural grassland sites experiencing intensive (IG) and light (LG) grazing/mowing regimes for 13 years. Mean NEA and DEA (i.e. observed from random soil sampling) were higher in IG than LG sites. The NEA/DEA ratio was higher in IG than LG sites, indicating a higher stimulation of nitrification. Marked changes in plant species composition were observed in response to the grazing/mowing regime. In particular, the specific phytomass volume of Elymus repens was lower in IG than LG sites, whereas the specific volume of Lolium perenne was higher in IG than LG sites. In contrast, the specific volume of Holcus lanatus, Poa trivialis and Arrhenatherum elatius were not significantly different between treatments. Soils sampled beneath grass tussocks of the last three species exhibited higher DEA, NEA and NEA/DEA ratio in IG than LG sites. For a given grazing regime, plant species did not affect significantly soil DEA, NEA and NEA/DEA ratio. The modification of plant species composition is thus not the primary factor driving changes in nitrification and denitrification in semi-natural grassland ecosystems experiencing long term intensive grazing. Factors such as trampling, N returned in animal excreta, and/or modification of N uptake and C exudation by frequently defoliated plants could be responsible for the enhanced microbial activities.

Management by combined grazing and mowing events is commonly used in grasslands, which influences the activity and composition of soil bacterial communities. Whether observed effects are mediated by management-induced disturbances, or indirectly by changes in the identity of major plant species, is still unknown. To address this issue, we quantified substrate-induced respiration (SIR), and the nitrification, denitrification and free-living N2-fixation enzyme activities below grass tufts of three major plant species (Holcus lanatus, Arrhenatherum elatius and Dactylis glomerata) in extensively or intensively managed grasslands. The genetic structures of eubacterial, ammonia oxidizing, nitrate reducing, and free-living N 2-fixing communities were also characterized by ribosomal intergenic spacer analysis, and denaturing gradient gel electrophoresis (DGGE) or restriction fragment length polymorphism (RFLP) targeting group-specific genes. SIR was not influenced by management and plant species, whereas denitrification enzyme activity was influenced only by plant species, and management–plant species interactions were observed for fixation and nitrification enzyme activities. Changes in nitrification enzyme activity were likely largely explained by the observed changes in ammonium concentration, whereas N availability was not a major factor explaining changes in denitrification and fixation enzyme activities. The structures of eubacterial and free-living N2-fixing communities were essentially controlled by management, whereas the diversity of nitrate reducers and ammonia oxidizers depended on both management and plant species. For each functional group, changes in enzyme activity were not correlated or were weakly correlated to overall changes in genetic structure, but around 60% of activity variance was correlated to changes in five RFLP or DGGE bands. Although our conclusions should be tested for other ecosystems and seasons, these results show that predicting microbial changes induced by management in grasslands requires consideration of management–plant species interactions.

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright Abstract In a context of frequent intensification or de-intensification of management in grasslands, a better understanding of how quickly soil microbiota responds to changes in management is required. The kinetics of changes in the structure of the bacterial community (using ribosomal intergenic spacer analysis) was studied in grassland mesocosms after changes of aboveground grazing regime, taking into account bacteria micro-localisation by separating the bacteria located inside stable aggregates (inner soil fraction) and the bacteria easily washed out, i.e. mainly located in macropores (outer soil fraction). Four treatments were used: (i) control grazed mesocosms, (ii) control ungrazed mesocosms, (iii) application of grazing on previously ungrazed mesocosms, (iv) cessation of grazing on previously grazed mesocosms. Each grazing event was simulated by application of synthetic sheep urine and plant clipping. Application of grazing led to a change in the structure of the whole soil bacterial community within 5 months, whereas changes were observed only 12 months after cessation of grazing. Changes in plant species composition and soil organic carbon content observed after cessation of grazing were found to be possible drivers of the changes in the bacterial community structure. However, after application of grazing, changes of the bacterial community structure occurred prior to changes in plant species composition and soil organic carbon content, suggesting that supply of urine and/or impact of labile carbon were likely the main drivers of changes. After 12 months, the application of grazing significantly affected the bacterial community structure in both inner and outer soil fractions. Conversely, 12 months after cessation of grazing, community structure was affected only for bacteria located in the outer fraction. This study shows that the bacterial community structure responded faster and more deeply after application than after cessation of grazing, and may be driven by different environmental factors between both scenarios. This study also shows that, 2 years after the changes in grazing regime, the bacterial community structure was determined by both the past and new grazing regimes.

Згідно з теорією внутрішньоґрунтового циклу Нітрогену, пул органічних сполук N поділяється на активну фазу, яка складається з негуміфікованих
рослинних залишків, відмерлої мікробної біомаси і продуктів її деструкції та пасивну фазу – стійку до мікробного розкладу частину органічної речовини,
яка практично не бере участі у внутрішньо ґрунтовому циклі N.

Many studies have assessed the responses of soil microbial functional groups to increases in atmospheric CO2 or N deposition alone and more rarely in combination. However, the effects of elevated CO2 and N on the (de)coupling between different microbial functional groups (e.g., different groups of nitrifiers) have been barely studied, despite potential consequences for ecosystem functioning. Here, we investigated the short-term combined effects of elevated CO2 and N supply on the abundances of the four main microbial groups involved in soil nitrification: ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and nitrite-oxidizing bacteria (belonging to the genera Nitrobacter and Nitrospira) in grassland mesocosms. AOB and AOA abundances responded differently to the treatments: N addition increased AOB abundance, but did not alter AOA abundance. Nitrobacter and Nitrospira abundances also showed contrasted responses to the treatments: N addition increased Nitrobacter abun...

Steam disinfestation is an ecologically less harmful alternative to synthetic chemical fumigants such as methyl bromide, which is being phased out of use due to its ozone-depleting properties. Although previous studies have characterized the effects of steaming on targeted pests, soil microorganisms, including beneficial ones, may be strongly influenced by this agricultural practice, since: (1) high temperature disturbs most soil microorganisms; and (2) disinfestation-induced changes in the soil environment can indirectly affect soil microbiota. The impact of soil disinfestation on functional bacterial communities was evaluated particularly in view of their role in nitrogen cycling. The short-term effects of steam disinfestation on heterotrophic bacteria, denitrifying and nitrifying bacteria, and their ability to recover after this disturbance were examined by surveying the enzyme activity, size and genetic structure of each community. Our results show that: (1) steaming immediately induced significant de- crease in community activity and size, and changes in community composition, nitrifying bacteria being mostly affected; (2) abundances of each community reached values equal or higher than those observed in control soil within 15–60 days after steaming, but community structures remained very different as compared to those in control soil; and (3) for each activity, no complete recovery was observed after the disturbance: substrate induced respiration and denitrification increased but remained lower in steamed soil, whereas nitrification was not detectable after 62 days. Our results show that these effects of steaming on key soil functional communities can have important, long-lasting implications for nitrogen cycle that should be taken into account when evaluating the influence of such an agricultural practice.

Nitrogen (N) availability in grasslands varies with agricultural land use. Traditional management regimes of mowing for hay and manuring in subalpine meadows maintain plant communities with exploitative functional strategies suited to fertile soils with fast turnover of nutrients. We investigated whether the neglect of traditional practices has led to a reduction in N availability in two parallel ecosystems (terraced and unterraced fields). Soil nitrate and ammonium contents were assessed using soil cores and ion exchange resins over a 1-year period, and assays of microbial nitrifying and denitrifying enzyme activities, made early in the growing season. A large difference in pH between the two ecosystems, caused by historical ploughing, facilitated greater N availability in terraced than unterraced fields. Abandonment of manuring and mowing caused a reduction in N availability and N transformation processes, which correlated with a shift in the plant community towards more-conservative functional strategies and greater dominance by grasses. We propose that positive feedback between the grassland management regime and dominant plant functional strategy maintained high N availability in these managed subalpine grasslands. When traditional practices of mowing and manuring are neglected, direct management effects combined with the spread of grass species with conservative strategies force down N availability in the soil, reduce microbial activity, change the pH, and lead to a long-term loss of characteristic herbaceous subalpine-meadow species.

• The objective of this study was to better identify the mechanisms by which elevated CO2 (c. 665 µmol mol − 1) alters soil nitrifying and denitrifying enzyme activity (NEA and DEA), and the dynamics of plant and microbial N pools. • We measured the effects of elevated CO2 on plant biomass and N, soil microbial biomass N, soil ammonium and nitrate concentrations, NEA and DEA in mono-specific grassland mesocosms (Holcus lanatus and Festuca rubra) grown for 15 months in reconstituted grassland soil. • NEA strongly decreased at elevated CO2 in the Holcus mesocosms, but was not affected in Festuca systems. DEA was less sensitive to elevated CO2 than NEA. In Holcus mesocosms, microbial N showed an initial growth phase that appeared to limit plant N acquisition, but was only transient. • CO2-induced changes in NEA and DEA were best explained by factors that could reduce soil [O2 ] (increased soil water content and organic C). Elevated CO2 may increase microbial immobilisation in highly disturbed systems, this effect weakening as the system gets closer to equilibrium.

Source materials and manure management may affect compost nutrient availability to plants. A laboratory experiment
was conducted to determine the impact of these factors on the N and P release from 23 on-farm and 6 industrial composts.
Composts were mixed with the Ap horizon of an Arago sandy loam (Humo-Ferric Podzol), at 200 mg N kg–1, and incubated for
13 wk in glass jars at 35°C. The soil mineral N content at the end of incubation was the highest from poultry litter, sheep manure, horse manure and vegetable residue sources whereas the fresh solid, beef and young dairy manure composts resulted in high N immobilization. The release of N from the compost organic N fraction was in most cases negative. The soil Mehlich-3 P content at the end of the incubation period was higher from the poultry litter than from any other sources, whereas P was strongly immobilized from week 1 to week 13 in the fresh solid, beef and young dairy manure compost amended soils. Septic tank sludge compost was the least efficient N and P source among industrial products whereas the others showed N and/or P release comparable to most on-farm composts. In dairy manure compost, use of wood in bedding, turning compost windrow, increasing composting
duration and sheltering material against precipitation all reduced P immobilization during incubation. Organic N mineralization in soil was only significantly increased by composting duration. This study indicated that the short-term N and P potential nutrient value of composts are dependent upon compost source materials and manure management, and should be based on their inorganic N and P content.