Slurry-amended Soils Research Articles

Short-term effect of liquid organic fertilisation and application methods on N2, N2O and CO2 fluxes from a silt loam arable soil

AbstractThe absence of N2 flux measurements in liquid manure-amended soils has resulted in a poor understanding of the effect of manure application on gaseous N losses. The aim of this study was to quantify N2, N2O, CO2, N2O reduction to N2, depth distribution of moisture, water-extractable organic C, NO3−, NH4+, pH, and diffusivity in a laboratory incubation experiment with an arable silt-loam soil. To quantify N processes and gaseous fluxes, 15N tracing was applied. An artificial livestock slurry-mixture was added to the soil in various treatments (control, surface or injected application; slurry-application rate: 42.9 kg N ha− 1; soil water content of either 40% or 60% water-filled pore space (WFPS)). The soil was incubated for 10 days. The depth distribution of the control parameters was measured twice during the experiment on days 5 and 10. The average increase in N2 and N2O fluxes from denitrification was about 900% in slurry-amended soils. The highest N2 and N2O fluxes from denitrification were measured in the slurry injection, 60% WFPS treatment (7.83 ± 3.50 and 11.22 ± 7.60 mg N m− 2 d− 1, respectively). The hypothesis that injected slurry at a higher water content enhances denitrification was confirmed. This study provides important insights into the formation, spatial and temporal variation of the manure-soil hotspot and its impact on the denitrification process. The results will form part of a dataset to develop, improve and test manure application submodules of biogeochemical models and will help to understand in detail the effect of hotspots on N-cycling in manure-treated soils.

Integrated modelling to assess N pollution swapping in slurry amended soils

In the present work, it was hypothesized that through modelling it is possible to overcome the constraints that arise in the quantification of N pollution swapping associated to slurry application practices when using individual experimental data. For this, environmental N losses were assessed under two methods of dairy slurry application to a double cropping system (rainfed oats (Avena strigosa)/irrigated maize (Zea mays)) in two different soils. An integrated experimentation and modelling approach was applied using the RZWQM2 model. The model was first tested using four years of experimental data concerning N fluxes to/from different environmental compartments (soil mineralization, N gas emissions, and N leaching). The model estimated emissions with overall efficiencies of ~70% and r2 ~ 0.75. Total N losses were higher for surface band application (95.4 and 40.2 kg ha−1 for the sandy and sandy loam soils, respectively). However, when slurry was injected, nitrate leaching considerably increased (by 107 and 64% for the sandy and sandy loam soils, respectively), even though gas emissions were minimized. This N swapping among path losses requires targeting of the N mitigation measures to the environmental compartment showing the highest vulnerability. Generally, the estimated emission factors (EFs) were lower than or equal to (slurry injection in the sandy loam soil) the IPCC default. The values showed high variability, reinforcing the need to use agricultural system specific EFs. The methodologies used in this study, focused on scenario analysis, can support policy as they can be used to set up integral strategies to decrease N emissions from livestock farming systems, taking into account possible synergies and antagonisms produced by the measures among NH3 and N2O emissions and NO3− leaching.

Acidification of animal slurry affects the nitrogen dynamics after soil application

Slurry acidification is recommended to minimize ammonia emissions during the whole management chain. However, the impact of the application of acidified slurry to soil has been poorly studied, namely its effect on the nitrogen dynamics (organic nitrogen mineralization and nitrification).In the present study, we hypothesized that a) slurry acidification would slow down nitrification and that this effect would be comparable to that of a nitrification inhibitor (DMPP); b) the alkalinity and/or buffering capacity of some soils would neutralize the acidified slurry and minimize its effect. Thus, a laboratory incubation was run to assess the effect of pig slurry treatment by acidification or DMPP addition on N mineralization and nitrification in five contrasting soils.Our results show that slurry acidification affected the N dynamics after application to the soils, but this effect was closely related to the soil properties. The inhibitory effect of slurry acidification on nitrification was not as evident as that of the nitrification inhibitor, DMPP, but it is noteworthy that, in some soils, the nitrate content remained lower in soil amended with acidified slurry than in soil amended with slurry treated with DMPP. Furthermore, in no case did slurry acidification stimulate nitrification when compared to non-acidified slurry. It can then be concluded that slurry acidification is an efficient way to increase the NH4+ content in slurry amended soils, without intensifying nitrification.

Dietary Crude Protein and Tannin Impact Dairy Manure Chemistry and Ammonia Emissions from Incubated Soils

Excess crude protein (CP) in dairy cow diets is excreted mostly as urea nitrogen (N), which increases ammonia (NH) emissions from dairy farms and heightens human health and environmental concerns. Feeding less CP and more tannin to dairy cows may enhance feed N use and milk production, abate NH emissions, and conserve the fertilizer N value of manure. Lab-scale ventilated chambers were used to evaluate the impacts of CP and tannin feeding on slurry chemistry, NH emissions, and soil inorganic N levels after slurry application to a sandy loam soil and a silt loam soil. Slurry from lactating Holstein dairy cows (Bos taurus) fed two levels of dietary CP (low CP [LCP], 155 g kg; high CP [HCP], 168 g kg) each fed at four levels of dietary tannin extract, a mixture from red quebracho (Schinopsis lorentzii) and chestnut (Castanea sativa) trees (0 tannin [0T]; low tannin [LT], 4.5 g kg; medium tannin [MT], 9.0 g kg; and high tannin [HT], 18.0 g kg) were applied to soil-containing lab-scale chambers, and NH emissions were measured 1, 3, 6, 12, 24, 36, and 48 h after slurry application. Emissions from the HCP slurry were 1.53 to 2.57 times greater ( < 0.05) than from the LCP slurry. At trial's end (48 h), concentrations of inorganic N in soils were greater ( < 0.05) in HCP slurry-amended soils than in LCP slurry-amended soils. Emissions from HT slurry were 28 to 49% lower ( < 0.05) than emissions from 0T slurry, yet these differences did not affect soil inorganic N levels. Emissions from the sandy loam soil were 1.07 to 1.15 times greater ( < 0.05) than from silt loam soil, a result that decreased soil inorganic N in the sandy loam compared with the silt loam soil. Larger-scale and longer-term field trails are needed to ascertain the effectiveness of feeding tannin extracts to dairy cows in abating NH loss from land-applied slurry and the impact of tannin-containing slurry on soil N cycles.

Altered food web structure and C-flux pathways associated with mineralisation of organic amendments to agricultural soil

Application of organic materials to agricultural soils offers the potential to divert these from conventional waste streams and to reduce the use of mineral fertilisers for crop production. In addition to direct impacts of organic materials on soil physico-chemical conditions, such amendments may also affect the structure and functioning of soil food webs and the coupling of plant- and soil biological activity. In this study we investigated the impact of cattle slurry and municipal green compost applications on soil microbial and nematode communities. Specifically, we applied steady-state 13C-labelling to quantify the impacts of the amendments on transfer of plant-derived C through components of the soil food web and to determine the activity of the soil biota in mineralising amendment- and soil organic matter derived-C. Both the slurry and compost amendments significantly promoted barley N-acquisition and growth. The municipal compost amendment, but not slurry application, strongly affected soil microbial community structure and increased nematode abundance, relative to unamended soil. This was associated with increased flux of plant-derived C through bacterial (particularly Gram negative) populations in compost-amended soil and was associated with increased mineralisation of amendment- and soil organic matter-derived substrates. For slurry-amended soils, the amendment did not alter soil community structure and mineralisation of soil C was not coupled to the flux of plant-derived C through below-ground pools. The results are indicative of N-supply to barley in compost-amended soil being dependent on the functioning of the soil food web (including C-flux to it from living roots), whereas N-supply from slurry was independent of this coupling between plant and soil processes. We suggest that plant/food web interactions are important targets for development of effective management strategies for organic waste applications to agricultural soils in the context of optimising the balance between nutrient supply to crops and the susceptibility of nutrients to losses from soil.

Changes in mineral nitrogen, soil organic matter fractions and microbial community level physiological profiles after application of digested pig slurry and compost from municipal organic wastes to burned soils

Abstract In this study, mineralization of digested pig slurry and compost from municipal organic wastes in burned soils was followed for 60 days. The effects of amendments on organic matter fractions and microbial community level physiological profiles (CLPP) were also investigated at the end of the incubation period. Soil from a forest 10 days after a fire had a greater basal respiration, and more organic matter that a nearby soil that was not affected by fire, presumably as a consequence of black ash addition following the wildfire. Nitrification was inhibited in soils treated at 105 and 250 °C in the laboratory, but amendment application allowed nitrification to take place in the latter soil, and led to significant flushes of mineralization. Slurry amendment resulted in greater increases in mineral N compared with compost. Soil treated at 250 °C had the greatest content of water-extractable compounds (WE) at the expense of acid-extractable compounds (AE), but during the incubation the variations in these two fractions had an opposite trend, i.e. soil gained AE and lost WE fractions. The variation in N-acetyl-glucosamine-induced respiration was different between compost- and slurry-amended soils, with the greater values in the former. The effect of amendments could be further differentiated by principal component (PCA) and cluster analyses based on the variations in organic matter fractions and CLPP between the beginning and the end of the incubation period. Amendment application led to shifts on the PCA maps that depended both on the amendment and soil treatment. In fresh soil and in that treated at 250 °C, the unamended, compost- and slurry-amended treatments remained relatively close on the PCA maps and had linkage distances 1.0. Pig slurry led to the greatest changes in burned soil, while compost induced the greatest shifts in soil treated at 105 °C. This study suggests that an application of organic amendments after a severe fire event may contribute to a faster recovery of soil functions.

Degradation of Lindane (γ-HCH) in a Mollisol as Effected by Different Soil Amendments

Soil amendments play an important role in management of pesticide residues. In this study, incubation experiment was conducted using the surface (0 - 15 cm) sample of a mollisol supplied with different soil amendments (farmyard manure, cow-dung slurry, pyrite and gypsum) to investigate the effect of amendments on the dissipation of lindane in mollisols. Dissipation of lindane in soil was studied at eight consecutive samplings (0, 1, 3, 5, 7, 10, 15 and 30 d). The results indicated that soil amendments could promote the degradation of lindane in soil. After 30 d of incubation 79% degradation was observed in the untreated soil (without any amendment) whereas, in the case of farmyard manure and cow-dung slurry amended soils, 83% and 91% degradation was observed, respectively. The pyrite and gypsum amendments also enhanced the degradation of lindane in soils, but the effect was less pronounced as compared to the organic amendments. Enhanced degradation in soil treated with organic amendments could be attributed to stimulated microbial activity after the addition of organic amendments. These addition, under different soil management conditions, minimize the persistence of lindane and consequently the risk of leaching and seepage into aquifers.

Effect of cow slurry amendment on atrazine dissipation and bacterial community structure in an agricultural Andisol

Atrazine is a commonly used herbicide for maize production in Chile, but it has recently been shown to be ineffective in soils that receive applications of cow slurries generated from the dairy industry. This effect may be caused either by the sorption of the pesticide to organic matter or more rapid degradation in slurry-amended soils. The objectives of this study were to evaluate the effects of cow slurry on atrazine dissipation, the formation of atrazine metabolites and the modification of bacterial community in Andisol. The cow slurry was applied at doses of 100,000–300,000 L ha − 1 . After 4 weeks, atrazine was applied to the slurry-amended soils at concentrations of 1–3 mg kg − 1 . The amounts of atrazine and its metabolites were determined by high performance liquid chromatography (HPLC). The soil microbial community was monitored by measurement of CO 2 evolution and changes in bacterial community using PCR–DGGE of 16S rRNA genes. The results show that cow slurry applications had no effect on atrazine dissipation, which had a half-life of 15–19 days. The atrazine metabolites were detected after 20 days and were significantly higher in soils amended with the slurry at both 20 and 40 days after application of the herbicide. Respiration rates were elevated after 10 days in all soils with atrazine addition. Both the atrazine and slurry amendments altered the bacterial community structures, indicated by the appearance of specific bands in the DGGE gels after 10 days. Cloning and sequencing of the 16S rRNA genes from the DGGE gels showed that the bands represented various genera of β-proteobacteria that appeared in response to atrazine. According to our results, further field studies are required to explain the lower effectiveness of atrazine in weed control. These studies may include the effect of dissolved organic carbon on the atrazine mobility.

Microbial activity in pig slurry-amended soils under aerobic incubation

A 120-day aerobic incubation experiment was conducted to study the effects of pig slurry application on soil microbial activity. Pig slurry was added to soil at rates of 0 (control treatment), 150 and 300 m(3) ha(-1). Soil samples were taken after 0, 7, 14, 30, 45, 60, and 120 days of incubation and analyzed for total organic C and microbial biomass C contents, and basal respiration. Most of the organic C applied to soil with pig slurry was readily decomposed within 30 days. During the first phase (0 to 14-30 days), the addition of pig slurry to the soil, especially at the larger rate, increased microbial biomass C content, microbial biomass C/total organic C ratio, basal respiration, and metabolic quotient. The microbial growth and the increase of their activity that these results reflected were not persistent, since the initially measured values in pig slurry-amended soils decreased and reached those of the control soil in a relatively short time.

Detection of Copper(II) and zinc(II) binding to humic acids from pig slurry and amended soils by fluorescence spectroscopy

The effect of the consecutive annual additions of pig slurry at rates of 0 (control), 90 and 150 m 3 ha −1 yr −1 after a 7-year period on the Cu(II) and Zn(II) binding behavior of soil HAs was investigated in a field experiment. A fluorescence titration method and a single site model were used for determining metal ion complexing capacities and stability constants of metal ion complexes of HAs isolated from pig slurry and unamended and amended soils. With respect to control soil HA, pig-slurry HA featured much smaller Cu(II) and Zn(II) binding capacities and stability constants. Pig-slurry application to soil decreased Cu(II) and Zn(II) complexing capacities and binding affinities of soil HA. These effects increased with increasing the rate per year of PS application to soil, and are expected to have a large impact on bioavailability, mobilization, and transport of Cu(II) and Zn(II) ions in pig slurry-amended soils.

Proton Binding by Humic and Fulvic Acids from Pig Slurry and Amended Soils

The knowledge of acid-base characteristics of humic acid (HA) and fulvic acid (FA) fractions of organic amendments and amended soils is of considerable importance for assessing their agronomic efficacy and environmental impact. In this work, the acid-base properties of HAs and FAs isolated from pig slurry, soils amended with either 90 or 150 m(3) ha(-1) yr(-1) of pig slurry for 3 yr, and the corresponding nonamended control soil were investigated by using a current potentiometric titration method. The nonideal competitive adsorption (NICA) model that describes proton binding by two classes of binding sites (carboxylic- and phenolic-type groups) was successfully fit to titration data. With respect to the control soil HA and FA, pig-slurry HA and FA were generally characterized by smaller carboxylic-type group contents, slightly smaller phenolic-type group contents, larger affinities for proton binding by the carboxylic-type groups, and much smaller, in the case of the HA fraction, or similar, in the case of the FA fraction, affinities for proton binding by the phenolic-type groups. Amendment with pig slurry determined a number of modifications in soil HAs and FAs, including decrease of acidic functional group contents, and slight increase of the proton affinity of the carboxylic-type groups. Further, a slight decrease of the affinities for proton binding by the phenolic-type groups of HAs was observed. These effects can have a large impact on the biological availability, mobilization, and transport of macro- and micronutrients, toxic metal ions, and xenobiotic organic cations in pig slurry-amended soils.

Modeling of Ammonia Emissions from Soils

Using a dynamic flow-through chamber system in conjunction with a Thermo Environmental 17C Chemiluminescence ammonia (NH3) analyzer, emissions from slurry-amended, that is, effluent from the lagoon (∼33 kg N ha-1) and nonamended soils were calculated at a swine farm in eastern North Carolina. The average NH3-N flux values during the period when the soils were not amended with any slurry were ∼54 ng N m-2 s-1, while the average NH3-N flux values measured immediately following the application of slurry to the soil were 1723.9 ng N m-2 s-1. An empirical model relating soil temperature to NH3 flux for nonamended soils explained over 70% of the variability in NH3 emissions; however, a similar empirical model relating soil temperature to NH3 flux for slurry-amended soils was able to explain only 39% of the variability in NH3 emissions. A mass transport model, based on physical and chemical processes to estimate NH3 emissions from recently amended soils is also presented and compared and contrasted to the empirical model. The variables used in the mechanistic model are pH, soil temperature, and total ammoniacal nitrogen content. When using the mass transport model, the percentage difference between predicted and measured values for the nonamended and slurry-amended soils were 164 and 16%, respectively, indicating that the mechanistic model is only applicable for periods when nitrification/denitrification, plant uptake, and immobilization are small enough in comparison to the chemical and physical processes following slurry application that they can be ignored. The percentage of the nitrogen (N) applied, which was emitted as NH3, increased at its greatest rate immediately following slurry application (1–2 days) and then began to level out at a value of approximately 20% by day 4. Previous laboratory studies found these volatilization events to be short lived (few days–2 weeks), and this study corroborates those findings.

Effects of pig slurry application on soils and soil humic acids.

The effect of three annually consecutive additions of pig slurry at two rates (90 and 150 m3 x ha(-1) x year(-1) on soils and soil humic acids (HAs) was investigated in a field experiment under semiarid conditions. Soils and pig slurries were analyzed by standard methods. The HAs were isolated from soils and pig slurry by a conventional procedure based on alkaline extraction, acidic precipitation to pH 1, purification by repeated alkaline dissolutions and acidic precipitations, water washing, dialysis, and final freeze-drying. The HAs obtained were analyzed for elemental (C, H, N, S, and O) and acidic functional group (carboxylic and phenolic) composition, and by UV-vis, FT-IR, fluorescence, and ESR spectroscopies. With respect to the control soil, the pig slurry amended soils had greater pH and electrical conductivity, slightly larger total N content, and smaller values of C/N ratio. A decrease of total organic C was observed only in soils amended for 2 and 3 years at the higher slurry rate. With respect to control soil HA, pig slurry HA was characterized by larger contents of S- and N-containing groups, smaller acidic functional group and organic free radical contents, a prevalent aliphatic character, extended molecular heterogeneity, and smaller aromatic polycondensation and humification degrees. Amendment with pig slurry HA determines a number of modifications in soil HAs, including increase of C, S, and COOH contents, C/N ratios, and aliphaticity and decrease of extraction yields and N, O, phenolic OH, and organic free radical contents. These effects are generally more evident after the first year of slurry application and tend to disappear with increasing number of treatments. Most probably, over the years the slightly humified slurry HA is mineralized through extended microbial oxidation, whereas only the most recalcitrant components, such as S-containing, phenolic, and aliphatic structures, are partially accumulated by incorporation into soil HA.

Short-term C and N dynamics in a soil amended with pig slurry and barley straw: a field experiment

Interactions between animal slurries and crop residues can impact on soil N availability during decomposition. Our objective was to study the short-term decomposition of pig slurry and barley straw incorporated alone or in combination. A field experiment was conducted on a sandy loam unamended (control) or amended with 60 m3 ha–1 pig slurry (PS) or 4 Mg ha–1 barley straw (BS), or both (PSBS). Surface CO2 and N2O fluxes, soil water content and temperature, microbial biomass C, and NO3− and NH4+ contents were monitored during 28 d in the 0- to 20-cm soil layer. Large CO2 fluxes occurred during the first 4 h of the experiment in slurry-amended plots that were attributed to carbonate dissociation when slurry was mixed to the soil. Specific respiration activity (ratio of CO2-C fluxes-to-microbial biomass C) was increased in slurry-amended soils for the first 7 d, likely due to the rapid oxidation of volatile fatty acids present in slurry. After 28 d, 26% more C had been evolved in PSBS than the sum of C released from PS and BS, indicating a synergistic interaction during decomposition of combined amendments. Adding straw caused a net but transient immobilisation of soil N, especially in PSBS plots where 36% of slurry-added NH4+ was immobilised after 3 d. Slurry-NH4+ was rapidly nitrified (within 10 d), but N2O production was not a significant source of N loss during this study, representing less than 0.3% of slurry-added NH4+. Nevertheless, about twice the amount of N2O was produced in PS than in PSBS after 28 d, reflecting lower soil N availability in the presence of straw. Our study clearly illustrates the strong interaction existing between soil C and N cycles under field conditions as slurry mineral N appeared to stimulate straw-C mineralisation, whereas straw addition caused a net immobilisation of slurry N. Key words: Animal slurry, crop residues, C-N relationships, organic amendments

Methane fluxes following slurry applications to grassland soils: laboratory experiments

The effect of soil and slurry type on methane (CH 4) emissions were investigated under laboratory conditions. CH 4 emissions were influenced by soil type only when the slurries applied had low dry matter contents. Pig and dairy slurries were applied at 25 m 3 ha −1 to intact soil cores of a sandy loam and a silty clay. CH 4 emissions were immediate from all slurry amended soils and emissions decreased to background levels after 48 h. There was no effect of slurry type on CH 4 emissions from the sandy loam (sand), but emissions were greater following pig slurry additions to the silty clay (clay) than following dairy slurry additions. Emissions were significantly greater from the clay than the sand for both slurry types. In contrast, a second experiment demonstrated no significant effect of soil type on CH 4 emissions. This experiment also showed that most of the CH 4 emitted was derived from the slurry itself and not from the soil. The explanation for such contrasting effects of soil type on CH 4 emissions is discussed.

Nitrous oxide and methane emissions from pig slurry amended soils

Nitrous oxide and methane emissions from pig slurry amended soils

Effect of cattle slurry in grassland on microbial biomass and on activities of various enzymes

We examined the long-term effects of cattle slurry, applied at high rates, on microbial biomass, respiration, the microbial quotient (qCO2) and various soil enzyme activities. In March, June, July, and October 1991, slurry-amended grassland soils (0–10 cm) contained significantly higher levels of microbial biomass, N mineralization and enzyme activities involved in N, P, and C cycling. With microbial biomass as the relative value, the results revealed that the slurry treatment influenced enzyme production by the microbial biomass. High levels of urease activity were the result not only of a larger microbial biomass, but also of higher levels of enzmye production by this microbial biomass. The ratio of alkaline phosphatase and xylanase to microbial biomass was nearly constant in the different treatments. The metabolic quotient (qCO2) declined with increased levels of slurry application. Therefore it appears that microorganisms in slurry-amended soils require less C and energy if there is no competition for nutrients. The results of this study suggest that urease activity, nitrification, and respiration (metabolic quotient) can be used as indicators of environmental stress, produced by heavy applications of cattle slurry.