Greenhouse gas emissions and final compost properties from co-composting bovine specified risk material and mortalities with manure

The increased disposal costs of cattle specified risk materials (SRM) have reduced the competitiveness of the Canadian beef industry. The SRM materials include the skull, brain, trigeminal ganglia, eyes, palatine tonsils, spinal cord and dorsal root ganglia. This study investigates greenhouse gas (GHG) emissions and final compost properties from open windrow co-composting of manure with bovine SRM and mortalities. There were two compost treatments with four replications: SRMC consisting of SRM, cattle manure and barley straw and COWC consisting of cattle mortalities, cattle manure and barley straw. Average windrow temperature was higher (P < 0.05) for SRMC (47.1°C) than for COWC (44.1°C) over the first 139 days. The final compost coliform count, moisture, pH and TC contents were not significantly different between treatments while TN and available N (NH₄ ⁺ + NO₃ ⁻ + NO₂ ⁻) were lower for SRMC than for COWC. The average surface GHG flux from SRMC were 24.3 g C day⁻¹ m⁻² and 0.17 g N day⁻¹ m⁻² for CO₂ and N₂O, respectively, and were not significantly different from those from COWC (31.6 g C day⁻¹ m⁻² and 0.17 g N day⁻¹ m⁻² for CO₂ and N₂O, respectively), but CH₄ emissions from SRMC (0.47 g C day⁻¹ m⁻²) were lower than from COWC (1.57 g C day⁻¹ m⁻²). While a few large bones were left in the cattle mortality treatment, composting decomposed all SRM suggesting that it may be a viable alternative to rendering for SRM disposal.     

Quantifying the Reduction of Greenhouse Gas Emissions as a Resultof Composting Dairy and Beef Cattle Manure

Greenhouse gas emissions from the agricultural sector can be reduced through implementation of improved management practices. For example, the choice of manure storage method should be based on environmental decision criteria, as well as production capacity. In this study, greenhouse gas emissions from three methods of storing dairy and beef cattle manure were compared during the summer period. The emissions of CH₄, N₂O and CO₂ from manure stored as slurry, stockpile, and compost were measured using a flow-through closed chamber. The largest combined N₂O–CH₄ emissions in CO₂ equivalent were observed from the slurry storage, followed by the stockpile and lastly the passively aerated compost. This ranking was governed by CH₄ emissions in relation to the degree of aerobic conditions within the manure. The radiative forcing in CO₂ equivalent from the stockpiled manure was 1.46 times higher than from the compost for both types of cattle manure. It was almost twice as high from the dairy cattle manure slurry and four to seven times higher from the beef cattle manure slurry than from the compost. The potential reduction of GHG was estimated, by extrapolating the results of the study to all of Canada. By composting all the cattle manure stored as slurry and stockpile, a reduction of 0.70 Tg CO₂-eq year⁻¹ would be achieved. Similarly, by collecting and burning CH₄ emissions from existing slurry facilities, a reduction of 0.76 Tg CO₂-eq year⁻¹ would be achieved. New CH₄ emission factors were estimated based on these results and incorporated into the IPCC methodology. For North-America under cool conditions, the CH₄ emission factors would be 45 kg CH₄ hd⁻¹ year⁻¹ for dairy cattle manure rather than 36 kg CH₄ hd⁻¹ year⁻¹, and 3 kg CH₄ hd⁻¹ year⁻¹ for beef cattle manure rather than 1 kg CH₄ hd⁻¹ year⁻¹.     

Greenhouse gas emissions when composting manure from cattle fed wheat dried distillers’ grains with solubles

Dried distillers’ grains with solubles (DDGS) are a co-product of ethanol production that is increasingly available for use as a livestock feed. Including DDGS in diets could affect animal manure properties and impact manure management strategies. The objectives of this study were to investigate changes in the rate of greenhouse gas (GHG) emissions during composting and final properties of manure compost when DDGS is included in feedlot cattle diets. Treatments were: (1) Control; manure from cattle fed a typical finishing diet containing barley (Hordeum vulgare L.) grain and silage and (2) DDGS; manure from cattle fed a finishing diet with 60% DDGS from wheat (Triticum aestivum L.) in the dietary ration. Manure, consisting of feces, urine and wood shavings, was composted in open windrows. Samples were collected for analysis at initiation and completion of composting. Greenhouse gas surface fluxes were collected weekly during the first 4 weeks and every 2–3 weeks for the remainder of the composting period. The DDGS compost had lower total C, but similar total N (TN) content relative to Control, reflecting the initial manure conditions. The DDGS compost also had higher moisture, higher water-extractable NH₄⁺ and NO₃⁻, a greater fraction of TN in available form, and a lower pH than the Control. The O₂ consumption and N₂O emission from DDGS compost were higher, whereas CO₂ and CH₄ emissions were similar to Control. The higher N₂O emissions from DDGS compost were likely related to the high water-extractable N content in DDGS manure. Increased use of DDGS in feedlot diets may have environmental repercussions that include greater emissions of GHG (N₂O) during manure composting. From an end user perspective, enhanced availability of N could increase the nutrient value of the compost for crop production.     

Inclusion of antibiotics in feed alters greenhouse gas emissions from feedlot manure during composting

In this study, the effects of dietary inclusion of antibiotics on emissions of greenhouse gases (GHG: CO₂, CH₄ and N₂O) from cattle manure during composting were investigated. Manure was collected at the end of two feeding trials in 2005 and 2006 in which feedlot cattle were assigned to one of five dietary groups: (1) Control: no antibiotics added; (2) TYL11: tylosin at 11 mg kg⁻¹ feed; (3) CTC11: chlortetracycline at 11 mg kg⁻¹ feed; (4) CTC44: chlortetracycline at 44 mg kg⁻¹ feed; and CTC44SMZ44: chlortetracycline and sulfamethazine, each at 44 mg kg⁻¹ feed. Open windrows were constructed and the rate of GHG emission was measured periodically. In both years, CO₂ surface emissions were higher (P < 0.05) for treatments CTC11 and CTC44SMZ44 than for the Control. The CO₂ emission rates in 2005 were lower (P < 0.05) than in 2006, reflecting lower total carbon (TC) content in the manure in 2005 (138 ± 2 g kg⁻¹) than in 2006 (245 ± 2 g kg⁻¹). The rate of CH₄ emission varied from 0.006 to 0.232 g C m⁻² day⁻¹. Average values from all four antibiotic treatments were similar (P > 0.05) to the Control in both years. The N₂O emission rates were higher (P > 0.05) with CTC44SMZ44 (2005), TYL11 (2006) and CTC11 (2006) than with Control. While antibiotics do alter GHG emissions from composted feedlot manure, the mechanisms responsible are not clear and warrant further investigation.     

Emissions of NH3, N2O and CH4 from dairy cows housed in a farmyard manure tying stall (housing, manure storage, manure spreading)

Emission measurements from dairy cows housed in a tying stall were carried out with the aim of finding factors that influence the amount of emissions and means to reduce emissions. All sectors of animal husbandry were investigated. This enabled calculations of emissions for the whole management system including housing, storage and spreading of manure. Emissions during aerobic composting and anaerobic stacking of farmyard manure were compared. NH₃ and N₂O emissions from tying stalls for dairy cows are low (5.8 g NH₃ LU⁻¹ d⁻¹, 619.2 mg N₂O LU⁻¹ d⁻¹). Methane emissions from the animal housing are mainly caused by enteric fermentation. During storage and after spreading of farmyard manure substantial differences concerning NH₃, N₂O and CH₄ emissions were observed with composted and anaerobically stacked farmyard manure. The compost emitted more NH₃ than the anaerobically stacked farmyard manure. About one third of the NH₃ emissions from the anaerobically stacked farmyard manure occurred after spreading. Total N losses were at a low level with both storage systems. Greenhouse gas emissions (N₂O and CH₄) were much higher from the anaerobically stacked farmyard manure than from the composted one. As these are ecologically harmful gases, they have to be considered when judging the form of manure treatment. This revised version was published online in August 2006 with corrections to the Cover Date.     

Nitrate accumulation and greenhouse gas emissions during compost storage

Greenhouse gases (CO₂, CH₄ and N₂O) are emitted during livestock manure handling, including composting, storage and land application. However, published data on emission rates of these gases during storage are sparse. In this study, the levels of GHG emissions and N levels during compost storage were investigated. The compost materials were produced by composting livestock manure for 133 d with 0, 10, 20 and 30% phosphogypsum (PG) or 10, 20 and 30% sand amendment. These compost materials were then stored on a clay pad for 233 d. Results from this study indicated that TN content did not change but mineral N content increased significantly during the 233 d storage for all treatments. The higher mineral N content in compost increases its agronomic value. There were only trace amounts of CH₄ and N₂O emissions. The C loss during storage was mainly as CO₂ and accounted for about 2.9 to 10% of total C initially in the compost. This information is vital to livestock manure life cycle analysis, and can be used to develop best manure management strategies that reduce GHG emissions from livestock production. The LRC Contribution No. 387-06006.     

Effect of planting technique and amendment type on pearl millet yield, nutrient uptake, and water use on degraded land in Niger

Due to increased population pressure and limited availability of fertile land, farmers on desert fringes increasingly rely on marginal land for agricultural production, which they have learned to rehabilitate with different technologies for soils and water conservation. One such method is the indigenous zai technique used in the Sahel. It combines water harvesting and targeted application of organic amendments by the use of small pits dug into the hardened soil. To study the resource use efficiency of this technique, experiments were conducted 1999–2000, on-station at ICRISAT in Niger, and on-farm at two locations on degraded lands. On-station, the effect of application rate of millet straw and cattle manure on millet dry matter production was studied. On-farm, the effects of organic amendment type (millet straw and cattle manure, at the rate of 300 g per plant) and water harvesting (with and without water harvesting) on millet grain yield, dry matter production, and water use were studied. First, the comparison of zai vs. flat planting, both unamended, resulted in a 3- to 4-fold (in one case, even 19-fold) increase in grain yield on-farm in both years, which points to the yield effects of improved water harvesting in the zai alone. Zai improved the water use efficiency by a factor of about 2. The yields increased further with the application of organic amendments. Manure resulted in 2–68 times better grain yields than no amendment and 2–7 times better grain yields than millet straw (higher on the more degraded soils). Millet dry matter produced per unit of manure N or K was higher than that of millet straw, a tendency that was similar for all rates of application. Zai improved nutrient uptake in the range of 43–64% for N, 50–87% for P and 58–66% for K. Zai increased grain yield produced per unit N (8 vs. 5 kg kg⁻¹) and K (10 vs. 6 kg kg⁻¹) compared to flat; so is the effect of cattle manure compared to millet straw (9 vs. 4 kg kg⁻¹, and 14 vs. 3 kg kg⁻¹), respectively, Therefore zai shows a good potential for increasing agronomic efficiency and nutrient use efficiency. Increasing the rate of cattle manure application from 1 to 3 t ha⁻¹ increased the yield by 115% TDM, but increasing the manure application rate further from 3 to 5 t ha⁻¹ only gave an additional 12% yield increase, which shows that optimum application rates are around 3t ha⁻¹.     

Long-term application effects of chemical fertilizer and compost on soil carbon under intensive rice–rice cultivation

From a long-term fertilizer experiment on rice–rice cropping in Typic Endoaquept, established at the Central Rice Research Institute, Cuttack, India in 1969, effects of application of composted manure (5 Mg ha⁻¹ year⁻¹) and chemical fertilizers (N, NP, NK, and NPK twice in a year), in series without compost (C₀) or with compost (C₁) on changes in soil carbon and microbial pools were examined by comparing the soils archived in 1984 and those sampled in 2004. Mean concentrations of soil organic carbon (SOC) varied between 5.5 and 7.6 g kg⁻¹ in 1984, and 6.8 and 10.8 g kg⁻¹ in 2004, respectively. Temporal increases in the total amounts of carbon, which reflect the carbon sequestration potential of the soil followed the order: C₁ + NK > C₁ + NP = C₁ + NPK > C₁ + N = C₁-control > C₀ + NP = C₀ + NK > C₀ + NPK > C₀-control > C₀ + N. Fractions of H₂O–C and K₂SO₄–C were higher in 1984, especially in those soil treated without compost. A reverse trend was observed in case of KMnO₄–C and carbohydrate–C fractions. The continuous application of compost enhanced microbial biomass carbon as well as active microbial biomass carbon in 2004. Long-term application of chemical fertilizers in combination, rather than N alone, had beneficial effects on soil carbon and microbial pools. Compost application, even once a year, invariably led to higher increments in both soil carbon and microbial pools and the combinations of chemical fertilizers with compost generally showed comparable effects in the long-term.     

Emission of methane, nitrous oxide, and ammonia from dung windrows

Gaseous emissions from livestock waste composting were measured within a project aiming at the determination of the nitrogen balance in biological farming. Gas was collected from windrows of animal waste using gas flux chambers (cover boxes). The gas analysis was performed by a high resolution FT-IR spectrometer. The results showed that ammonia and methane emissions dropped down within two to three weeks, whereas nitrous oxide was emitted mainly in the middle of the composting periods. The mean values of the total emissions per composting period were 57.6 g m⁻² for ammonia, 12.8 g m⁻² for nitrous oxide, and 1346 g m⁻² for methane. The mean ratios of the total gas fluxes related to the carbon dioxide flux were 2.6 10⁻³ for NH₃, 5.9 10⁻⁴ for N₂O and 6.2 10⁻² for CH₄. Both of these factors (total gas flux and mean ratios of total gas fluxes) can serve as indicators to quantify impacts on the environment. This revised version was published online in August 2006 with corrections to the Cover Date.     

Spatial and sectorial disaggregation of N2O emissions from agriculture in Belgium

In this study N₂O emissions from agriculture in Belgium have been split up per agro-pedological region and calculated per farm type. The N₂O emissions were calculated according to the `Revised 1996 IPCC guidelines for national greenhouse gas inventories'. Input data were weighed averages of the N balance of a large number of farms per agro-pedological region and per farm type. As such, the input data represent a theoretical farm in each agro-pedological region and for each distinguished farm type. In a first part, N₂O emissions were calculated for 10 agro-pedological regions in Belgium. The yearly N₂O emissions varied between 225 and 462 kg N₂O-N. The highest N₂O emissions (around 400 kg N₂O-N yr⁻¹) were found in regions with fertile soils, dominated by crop production or a combination of crop production and cattle breeding. The lowest emissions (around 250 kg N₂O-N yr⁻¹) were found in regions with extensive cattle breeding. N₂O emissions of 300 ± 15 kg N₂O-N yr⁻¹ were found in regions with less extensive cattle breeding or in regions with combinations of cattle, pig and poultry breeding. The N₂O emission per ha varied between 6 and 14 kg N₂O-N yr⁻¹. In a second part, N₂O emissions were calculated for 12 different farm types. The yearly N₂O emissions varied between 273 and 512 kg N₂O-N. The highest emissions were found on farms with crop production or a combination of crop production and cattle breeding. The lowest emissions were found on farms specialised in only one activity of animal breeding. Specialised pig farms and farms with combinations of cattle caused the greatest threat with respect to N₂O releases from agriculture. Their N₂O emission per ha was 18–40 kg N₂O-N yr⁻¹, which was significantly higher than the average N₂O release (10 kg N₂O-N yr⁻¹ ha⁻¹) for the other farm types. This revised version was published online in August 2006 with corrections to the Cover Date.     

Emissions of N<Subscript>2</Subscript>O from fertilized and grazed grassland on organic soil in relation to groundwater level

Intensively managed grasslands on organic soils are a major source of nitrous oxide (N₂O) emissions. The Intergovernmental Panel on Climate Change (IPCC) therefore has set the default emission factor at 8 kg N–N₂O ha⁻¹ year⁻¹ for cultivation and management of organic soils. Also, the Dutch national reporting methodology for greenhouse gases uses a relatively high calculated emission factor of 4.7 kg N–N₂O ha⁻¹ year⁻¹. In addition to cultivation, the IPCC methodology and the Dutch national methodology account for N₂O emissions from N inputs through fertilizer applications and animal urine and faeces deposition to estimate annual N₂O emissions from cultivated and managed organic soils. However, neither approach accounts for other soil parameters that might control N₂O emissions such as groundwater level. In this paper we report on the relations between N₂O emissions, N inputs and groundwater level dynamics for a fertilized and grazed grassland on drained peat soil. We measured N₂O emissions from fields with different target groundwater levels of 40 cm (‘wet’) and 55 cm (‘dry’) below soil surface in the years 1992, 1993, 2002, 2006 and 2007. Average emissions equalled 29.5 kg N₂O–N ha⁻¹ year⁻¹ and 11.6 kg N–N₂O ha⁻¹ year⁻¹ for the dry and wet conditions, respectively. Especially under dry conditions, measured N₂O emissions exceeded current official estimates using the IPCC methodology and the Dutch national reporting methodology. The N₂O–N emissions equalled 8.2 and 3.2% of the total N inputs through fertilizers, manure and cattle droppings for the dry and wet field, respectively and were strongly related to average groundwater level (R ² = 0.74). We argue that this relation should be explored for other sites and could be used to derive accurate emission data for fertilized and grazed grasslands on organic soils.     

Methane Emission from Irrigated and Intensively Managed Rice Fields in Central Luzon (Philippines)

Methane (CH₄) emissions were measured with an automated system in Central Luzon, the major rice producing area of the Philippines. Emission records covered nine consecutive seasons from 1994 to 1998 and showed a distinct seasonal pattern: an early flush of CH₄ before transplanting, an increasing trend in emission rates reaching maximum toward grain ripening, and a second flush after water is withdrawn prior to harvesting. The local practice of crop management, which consists of continuous flooding and urea application, resulted in 79–184 mg CH₄ m^–2 d^–1 in the dry season (DS) and 269–503 mg CH₄ m^–2 d^–1 in the wet season (WS). The higher emission in the WS may be attributed to more labile carbon accumulation during the dry fallow period before the WS cropping as shown by higher % organic C. Incorporation of sulfate into the soil reduced CH₄ emission rates. The use of ammonium sulfate as N fertilizer in place of urea resulted in a 25–36% reduction in CH₄ emissions. Phosphogypsum reduced CH₄ emissions by 72% when applied in combination with urea fertilizer. Midseason drainage reduced CH₄ emission by 43%, which can be explained by the influx of oxygen into the soil. The practice of direct seeding instead of transplanting resulted in a 16–54% reduction in CH₄ emission, but the mechanisms for the reducing effect are not clear. Addition of rice straw compost increased CH₄ emission by only 23–30% as compared with the 162–250% increase in emissions with the use of fresh rice straw. Chicken manure combined with urea did not increase CH₄ emission. Fresh rice straw has wider C/N (25 to 45) while rice straw compost has C/N = 6 to 10 and chicken manure has C/N = 5 to 8. Modifications in inorganic and organic fertilizer management and water regime did not adversely affect grain yield and are therefore potential mitigation options. Direct seeding has a lower yield potential than transplanting but is getting increasingly popular among farmers due to labor savings. Combined with a package of technologies, CH₄ emission can best be reduced by (1) the practice of midseason drainage instead of continuous flooding, (2) the use of sulfate-containing fertilizers such as ammonium sulfate and phosphogypsum combined with urea; (3) direct seeding crop establishment; and (4) use of low C/N organic fertilizer such as chicken manure and rice straw compost.     

Methane and carbon dioxide emissions and nitrogen turnover during liquid manure storage

Animal slurry stored in-house and outside is a significant source of atmospheric methane (CH₄). The CH₄ source strength of stored slurry is greatly affected by temperature. To improve emission calculations on a global scale there is a need for knowledge about the relationship between production of CH₄ in slurry and temperature. In this study, the filling of slurry channels was reproduced in the laboratory by gradually filling 1 m-high PVC vessels during 9 days followed by incubation for 100–200 days. A preliminary test showed that little CH₄ was produced from animal slurry during 10 days of incubation at 20°C, if no inoculum (slurry incubated anaerobically at the test temperature for 1.5–2 months) was present. However, the addition of 7.6% inoculum supported an immediate production of CH₄. Vessels amended with inoculum and gradually filled with cattle or pig slurry were then incubated at 10, 15 and 20°C. Methane production from stored pig and cattle slurry was not significant at temperatures below 15°C, where CO₂ was the main product of decomposition processes. In contrast, the anaerobic production of CH₄ was high and significant relative to the production of CO₂ at 20°C. Peak emissions of CH₄ averaging 0.012 and 0.02 g C h⁻¹ kg⁻¹ volatile solids (VS) were reached within about 10 days at 10 and 15°C, respectively. At 20°C, the emission of CH₄ from pig slurry was about 0.01 g C h⁻¹ kg⁻¹ for 10 days, and thereafter emissions increased to about 0.10 g C h⁻¹ kg⁻¹ VS. For cattle slurry a peak emission of 0.08 g C h⁻¹ kg⁻¹ VS was measured after 180 days. Degradation of organic nitrogen (N) in cattle slurry was related to the reduction of organic material as reflected in CO₂ and CH₄ emission. The mineralization of organic N during storage represented 10–80% of organic N in cattle slurry, and 40–80% of the organic N in pig slurry.     

The effect of biological oxygen demand of cattle slurry and soil moisture on nitrous oxide emissions

The application of animal manure slurries to soils may cause high short-term emissions of nitrous oxide (N₂O). We performed studies on N₂O emissions varying the contents of NH₄-N and microbial available organic carbon (measured as biological oxygen demand, BOD) of cattle slurry. Additionally the effect of slurry BOD on N₂O emissions at different soil water contents (35, 54, 71% water filled pore space, WFPS) was studied. Slurries from an anaerobic digestion plant (digested slurry, BOD: 1.2 g O₂ l⁻¹) or untreated slurry (BOD: 6.8 g O₂ l⁻¹) were applied at 30 m³ ha⁻¹ and incubated at 20°C. The higher the WFPS the more N₂O was emitted independent from the type of slurry applied. At low and medium soil water contents, the digested slurry induced significantly lower N₂O emissions than the untreated slurry. The N₂O emissions were directly correlated with the BOD content of the slurry (R ²=0.61, P≤0.001). We also compared the effect of NH₄-N concentration and BOD on emissions from the slurries at 54% WFPS. Again the BOD had a significant influence on N₂O emissions but a reduction of NH₄-N had no effect on the amount of N₂O emitted. The microbially available organic carbon seems to determine the amount of N₂O emitted shortly after slurry application. This revised version was published online in June 2006 with corrections to the Cover Date.     

Nitrogen balance and accumulation pattern in three contrasting prairie soils receiving repeated applications of liquid swine and solid cattle manure

The expansion of intensive livestock operations in western Canada has increased concerns about overloading of nutrients in manured lands. The magnitude of nutrient accumulation and its distribution in the soil profile varies with soil-climatic conditions. The objective of this study was to determine loading and distribution of manure-derived nitrogen (N) in the soil profile as influenced by repeated manure applications. Four field experiments were conducted at three sites (Dixon, Melfort and Plenty) in Saskatchewan under longer-term manure management. The four field experiments provide contrasts in soil type, climatic conditions, manure type, application and cropping history to enable the effect of these factors to be evaluated. Liquid hog manure (LHM—Experiment 1) and solid cattle manure (SCM—Experiment 2) treatments were applied annually over 8 years at Dixon (Black Chernozemic loam soil—Udic Boroll in sub-humid climate), while only LHM was applied at Plenty (Dark Brown Chernozemic heavy clay soil—Typic Boroll in semi-arid climate) over 6 years (Experiment 3), and at Melfort (Dark Gray Luvisol silty clay loam soil—Mollic Cryoboralf in humid climate) over 5 years (Experiment 4). Soil samples were collected in the spring and autumn of 2003 and 2004, and were analyzed for organic N, ammonium-N (NH₄⁺-N) and nitrate-N (NO₃⁻-N) concentrations. Plant samples were collected to determine the impact of manure application rate on plant N uptake and crop N removal. The annual application of LHM (37,000 L ha⁻¹ yr⁻¹) and SCM (7.6 Mg ha⁻¹ yr⁻¹) at agronomic rates at Dixon (added N balances crop demand for that year), or larger rates of LHM (111,000 L ha⁻¹) applied once every 3 years (Melfort) did not significantly elevate NO₃⁻-N in soil compared to the unfertilized control. Lower crop removal and reduced leaching of NO₃⁻-N due to drier conditions as occurred at the Plenty site contributed to greater accumulation of nitrate in the top 60 cm at equivalent rates compared to the other two sites. At large manure rates, excess N from the balance estimates could not be accounted for in soil organic N and was assumed to be lost from the soil-plant system. At the Dixon LHM site, deep leaching of NO₃⁻-N was observed at the excessive rate (148,000 L ha⁻¹ yr⁻¹) up to the 150 cm depth, compared to the control. At Dixon, the large annual application rate of SCM (30.4 Mg ha⁻¹ yr⁻¹) did not significantly increase NO₃⁻-N in the 0–60 cm soil compared to the control, which was attributed to lower mineralization of organic N from the SCM. Over the short and medium term, LHM application at large rates every year poses a greater risk for loading and deep migration of NO₃⁻-N in soil than large rates of SCM. Larger single applications made once every 3 years were not associated with accumulation or deep leaching. To prevent loading, rates of applied manure nitrogen should be reduced when crop N removal potential is diminished by high frequency of drought.     

Nitrogen and carbon losses from dung storage in urban gardens of Niamey,Niger

Intensive vegetable production in urban and peri-urban agriculture (UPA) of West African cities is characterized by high nutrient inputs. However, little is known about nitrogen (N) and carbon (C) losses in these systems, in particular during the storage of manure, the main organic fertilizer in these systems. We therefore aimed at quantifying gaseous emissions of ammonia (NH₃), nitrous oxide (N₂O), carbon dioxide (CO₂) and methane (CH₄) as well as leaching losses of C, N, phosphorus (P) and potassium (K) from animal manure stored in vegetable gardens of Niamey, Niger. During a first 3.5-month experiment in the hot dry season, cumulative gaseous N losses, measured with a closed-chamber system, were with 0.11 g kg⁻¹ manure DM highest (P < 0.05) in the uncovered control treatment accounting for 1.8% of total manure N. Nitrogen losses decreased by 72% under plastic sheet roofing and by 50% under roofing + ground rock phosphate (RP) application at 333 g kg⁻¹ manure DM. Carbon losses from manure amounted to 73 g kg⁻¹ DM in the control and to 92 g kg⁻¹ DM and 68 g kg⁻¹ DM under roofing and under roofing + RP, respectively. In a second 3.5-month experiment conducted in the rainy season, C losses from the control were 164 g kg⁻¹ manure DM and reduced to 77 and 65% of the control by roofing and roofing + RP, respectively. Leaching losses during the rainy season were only observed for the unroofed control and averaged 2.1 g C, 0.05 g N, 0.07 g P and 1.8 g K kg⁻¹ manure DM.     

Effects of fertiliser type and the presence or absence of plants on nitrous oxide emissions from irrigated soils

Nitrous oxide (N₂O) emissions and denitrification losses from an irrigated sandy loam soil amended with composted municipal solid waste (MSW), sheep manure (SM), surface applied pig slurry (SPS), incorporated pig slurry (IPS) or urea (U) were studied under Mediterranean conditions. We quantified emissions, in both the presence and absence of maize and N₂O production, via denitrification and nitrification pathways using varying concentrations of acetylene. Discounting the N₂O lost in the Control, the percentages of N₂O lost in relation to the total N applied were greater for urea (1.80%) than for MSW (0.50%), SM (0.46%), SPS (1.02%) or IPS (1.27%). In general, plots treated with organic fertilisers emitted higher amounts of N₂O when under maize than bare soil plots. On the other hand, greater denitrification losses were also recorded for plots in the absence of plants (between 9.7 and 29.3 kg N₂O-N ha⁻¹) than for areas with plants (between 7.1 and 24.1 kg N₂O-N ha⁻¹). The proportion of N₂O produced via denitrification was greater from fertiliser treatments than for the controls and also greater without plants (between 66 and 91 % of the N₂O emitted) than with plants (between 48 and 81%).     

Organic amendment effects on crop productivity and nutrient uptake on reclaimed natural gas wellsites

Restoration of productivity on agricultural soils disturbed by industrial activity is important for agronomic and environmental reasons. Because of the role of organic matter in soil health and quality, organic amendments have been widely used in the reclamation of disturbed soils such as those on abandoned oil and natural gas wellsites. This study examined the effects of one-time applications of alfalfa (Medicago sativa L.) hay or beef cattle (Bos taurus) feedlot manure compost on wheat (Triticum aestivum L.) yield and nutrient uptake on two abandoned natural gas wellsites that had recently been reclaimed in southern Alberta, Canada. The base amendment rate (1×) [dry wt.] was 5.3 Mg ha⁻¹ for compost and 3.1 Mg ha⁻¹ for alfalfa. The five treatment amendment rates of 0, 1×, 2×, 4×, and 8× were soil-incorporated at the wellsites. Yields and plant nutrient uptake were generally higher at Hussar than at Turin, reflecting the higher inherent fertility of the soil at Hussar. Grain yields were similar for alfalfa and compost amendments, indicating that either amendment can be used depending on availability and/or transportation costs. Our results show that spring wheat yields on these reclaimed soils can be optimized at alfalfa and compost rates of no more than 6 and 10 Mg ha⁻¹, respectively. Continued monitoring of crop productivity and soil properties may provide insight into the long-term benefits of alfalfa and compost amendments in wellsite reclamation schemes. Lethbridge Research Centre contribution no. 387-07030.     

Emission of ammonia (NH3), nitrous oxide (N2O) and methane (CH4) from a dairy hardstanding in the UK

Emissions of ammonia (NH₃), nitrous oxide (N₂O) and methane (CH₄) from uncovered yard areas (hardstandings) of a UK dairy farm were measured between October 1997 and August 1999. Measurements were concentrated after morning milking when the yard had been scraped, and at positions accounting for differences in slurry coverage and manure type. Over two seasons, the mean NH₃ emission from a number of season and position categories on the hardstanding were 0.27 g N m⁻² h⁻¹ in winter and spring, 0.45 g N m⁻² h⁻¹ in summer when the feeding/loafing area was not included, increasing to 1.51 g N m⁻² h⁻¹ when this area was included, and 5.0 g N m⁻² h⁻¹ for the feeding/loafing area alone. The feeding/loafing area was close to the slurry lagoon where excreta were continuously deposited and not scraped to the slurry lagoon, as was the rest of the hardstanding. A diurnal study of emissions in the summer showed a marked decrease with time after the yard was scraped following the first milking, with emissions increasing again after evening milking when fresh excreta were deposited. Nitrous oxide emissions were more variable than NH₃, with an order of magnitude difference between lowest and highest emissions measured at the same time. Mean N₂O emission rates were 3.3 μg N m⁻² h⁻¹ in winter and spring, 6.5 μg N m⁻² h⁻¹ in summer when the feeding/loafing area was not included, increasing to 7.8 μg N m⁻² h⁻¹ when this area was included, and 17.9 μg N m⁻² h⁻¹ for the feeding/loafing area alone. Large mean methane emissions were measured, 185 mg C m⁻² h⁻¹ in winter and spring, decreasing to 57.3 mg C m⁻² h⁻¹ in summer when the feeding/loafing area was not included, increasing to 72.9 mg C m⁻² h⁻¹ when this area was included, and 151.2 mg C m⁻² h⁻¹ for the feeding/loafing area alone. Therefore in summer, emissions measured directly from a dung pat [0–5 cm] that had not been scraped from the loafing area were much greater than from scraped hardstanding areas, but in winter there were still significant emissions from the remaining slurry post-scraping. The experimental design was not sufficient to elucidate the physico-chemical variables controlling the measured emissions, but the data were put into context by estimating the annual emission of these pollutant gases from this one dairy farm. These were estimated at 0.43 t NH₃-N y⁻¹, 0.3 kg N₂O-N y⁻¹ and 1.0 kg CH₄-C y⁻¹. Therefore, uncovered farmyard areas that regularly have excreta deposited on them are significant but previously unaccounted for sources of NH₃ loss, less so for N₂O and CH₄, and require further study to assess the significance of these emission sources within the UK and worldwide. This revised version was published online in August 2006 with corrections to the Cover Date.     

Nutrient evolution in soil and cereal yield under different fertilization type in dryland

Under semiarid conditions the response of crops to synthetic fertilizers is often reduced. Organic fertilizers can be used to provide a continuous source of nutrients for the crops. The soil nitrogen and crop yield in a rotation of durum wheat (Triticum durum)–fallow-barley (Hordeum vulgare)–vetch (Vicia sativa) were studied during 4 years when synthetic fertilizer (chemical), compost (organic) or no fertilizer (control) were applied in a field with high initial contents of soil NO₃–N (> 400 kg N ha⁻¹), phosphorus (22 mg kg⁻¹) and potassium (> 300 mg kg⁻¹). Changes in soil organic matter, phosphorus and potassium were also measured. During the crop period, chemical fertilization significantly increased the content of soil NO₃–N in the first 0.30 m of soil with respect to organic fertilization and the control. The yield of wheat and barley was not increased after applying chemical or organic fertilizer with respect to the unfertilized plots. The estimated losses of nitrogen were similar for the three types of fertilization, as well as the uptake of nitrogen for the total biomass produced. The initial levels of organic matter and phosphorus were maintained, even in the plots that were not fertilized, while the potassium decreased slightly. Thus, the rotation and burying of crop residues were enough to maintain the crop yield and the initial content of nutrients.