Effects of irrigation,fertilization and crop straw management on nitrous oxide and nitric oxide emissions from a wheat–maize rotation field in northern China

One-year winter wheat–summer maize rotation is the most popular double cropping system in north-central China, and this highly productive system is an important source of nitrous oxide (N₂O) and nitric oxide (NO) emissions due to the high fertilizer N and irrigation water inputs. To sustain the high crop production and mitigate the detrimental impacts of N₂O and NO emissions, improved management practices are extensively applied. The aim of this study is therefore to evaluate the effects of an improved management practice of irrigation, fertilization and crop straw on grain yield and N₂O and NO emissions for a wheat–maize rotation field in northern China. Using automated and manual chamber measuring systems, we monitored N₂O and NO fluxes for the conventional (CT, 2007–2008), improved (IT, 2007–2008), straw-amended (WS, 2008–2009), straw-not-amended (NS, 2008–2009), and no N-fertilizer treatments (WS–NN, 2008–2009), respectively, for one rotation-year. The grain yields were determined for CT and IT for three rotation-years (2005–2008) and for WS, NS and WS–NN for one rotation-year (2008–2009). The improved management of irrigation and fertilization reduced the annual N fertilization rate and irrigation amount by 17% and 30%, respectively; increased the maize yield by 7–14%; and significantly decreased the N₂O and NO emissions by 7% (p < 0.05) and 29% (p < 0.01), respectively. The incorporation of wheat straw increased the cumulative N₂O and NO emissions in the following maize season by 58% (p < 0.01) and 13%, respectively, whereas the effects of maize straw application were not remarkable. The N₂O and NO emission factors of applied N were 2.32 ± 2.32% and 0.42 ± 1.69% for wheat straw and 0.67 ± 0.23% and 0.54 ± 0.15% for chemical N-fertilizers, respectively. Compared to conventional management practices using high application rates of irrigation water and chemical N-fertilizer as well as the field burning of crop straw, the improved management strategy presented here has obvious environmentally positive effects on grain yield and mitigation of N₂O and NO emissions.     

Soil C storage as affected by tillage and straw management: An assessment using field measurements and model predictions

Soil tillage and straw management are both known to affect soil organic matter dynamics. However, it is still unclear whether, or how, these two practices interact to affect soil C storage, and data from long term studies are scarce. Soil C models may help to overcome some of these problems. Here we compare direct measurements of soil C contents from a 9 year old tillage experiment to predictions made by RothC and a cohort model. Soil samples were collected from plots in an Irish winter wheat field that were exposed to either conventional (CT) or shallow non-inversion tillage (RT). Crop residue was removed from half of the RT and CT plots after harvest, allowing us to test for interactive effects between tillage practices and straw management. Within the 0–30 cm layer, soil C contents were significantly increased both by straw retention and by RT. Tillage and straw management did not interact to determine the total amount of soil C in this layer. The highest average soil C contents (68.9 ± 2.8 Mg C ha^?1) were found for the combination of RT with straw incorporation, whereas the lowest average soil C contents (57.3 ± 2.3 Mg C ha^?1) were found for CT with straw removal. We found no significant treatment effects on soil C contents at lower depths. Both models suggest that at our site, RT stimulates soil C storage largely by decreasing the decomposition of old soil C. Extrapolating our findings to the rest of Ireland, we estimate that RT will lead to C mitigation ranging from 0.18 to 1.0 Mg C ha^?1 y^?1 relative to CT, with the mitigation rate depending on the initial SOC level. However, on-farm assessments are still needed to determine whether RT management practices can be adopted under Irish conditions without detrimental effects on crop yield.     

Methane and nitrous oxide emissions from an integrated rainfed rice–fish farming system of Eastern India

Integration of fish stocking with rice (Oryza sativa L.) cultivation promises an ecologically sound and environmentally viable management of flooded ecosystem. Rice agriculture contributes to the emission of greenhouse gases CH₄ and N₂O, but little is known on the effect of fish rearing in fields planted to rice on the emission of these two greenhouse gases. In a field study, CH₄ and N₂O fluxes were measured from a sub-humid tropical rice field of Cuttack, eastern India, as affected by integrated rice–fish farming under rainfed lowland conditions. Three Indian major carps, Catla catla H., Labeo rohita H. and Cirrhinus mrigala H., and Puntius gonionotus B. were stocked in rice fields planted to two rice cultivars in a split-plot design with no fish and fish as the main treatments and two rice varieties as sub-treatments with three replicates each. Fish rearing increased CH₄ emission from field plots planted to both the rice cultivars with 112% increase in CH₄ emission in cv. Varshadhan and 74% in case of cv. Durga. On the contrary, fish stocking reduced N₂O emission from field plots planted to both the rice varieties. Movement of fish and associated bioturbation coupled with higher dissolved organic-C and CH₄ contents, and lower dissolved oxygen could be the reasons for release of larger quantities of CH₄ from rice + fish plots, while higher dissolved oxygen content might have influenced release of more N₂O from the rice alone treatment. The total greenhouse gas emission, expressed as CO₂ equivalent global warming potential (GWP), was considerably higher from rice + fish plots with CH₄ contributing a larger share (91%) as compared to rice alone plots (78–81%). On the contrary, N₂O had a comparatively lesser contribution with 19–22% share in rice alone plots that was further reduced to 9% in rice + fish plots. However, considering the profit-loss analysis based on the market price of the produce, rice–fish system provided a net profit of $453.36 ha^?1 over rice alone system in spite of higher carbon credit compliance of a rice–fish ecosystem due to larger cumulative GWP.     

Emissions of N2O and NH3, and nitrogen leaching from direct seeded rice under different tillage practices in central China

Tillage practices affect the fate of fertilizer nitrogen (N) through influencing transformations of N, but few studies have examined N₂O and NH₃ emissions, and N leaching from different rice tillage systems. Thus the objective of this study was to assess N₂O emission, NH₃ volatilization and N leaching from direct seeded rice in conventional tillage (CT) and no-tillage (NT) production systems in the subtropical region of China during the 2008 and 2009 rice growing seasons. Treatments were established following a split-plot design of a randomized complete block with tillage practices as the main plot and N fertilizer level as the sub-plot treatment, and there were four treatments: NT + no fertilizer (NT0), CT + no fertilizer (CT0), NT + compound fertilizer (NTC) and CT + compound fertilizer (CTC), respectively. Results showed that N fertilization significantly increased (p < 0.01) N₂O emissions, NH₃ volatilization and N leaching from rice fields in both years. In general, there was no significant difference in N₂O emissions and NH₃ volatilization between NT0 and CT0 in both years, while NTC had significantly higher (p < 0.05) N₂O emissions and NH₃ volatilization compared to CTC. Over the two rice growing seasons, NTC showed 32% and 47% higher N₂O emissions, and 29% and 52% higher NH₃ losses than CTC. Higher (p < 0.05) N₂O emissions from NTC than CTC were presumably due to higher soil organic C and greater denitrification. Total N and NO₃^? concentrations were higher (p < 0.05) in CTC than NTC, but larger volumes of percolation water in NTC than CTC resulted in no significant difference in leakage of total N and NO₃^?. Hence, application of N fertilizer in combination with NT appeared to be ineffective in reducing N losses from N fertilizer in paddy fields.     

Effect of straw addition on nitrous oxide and methane emissions from stored farmyard manures

Stored solid manure heaps can be a significant source of nitrous oxide (N₂O) and methane (CH₄) emissions. The manure characteristics influence emissions and solid manure heaps can be managed to promote aerobic decomposition during storage. Increasing the carbon (C) content of the manure heap with high-C additives, such as straw, may provide the opportunity for N₂O and CH₄ emission reduction. Greenhouse gas (GHG) emissions from conventionally produced farmyard manure (FYM) have been quantified, but there is little data on emissions from organically produced FYM. N₂O and CH₄ emissions were measured using a small-scale storage method from FYM collected from organic and conventional dairy units under a range of storage conditions with and without extra straw addition.The organic and the conventional FYM were similar in composition except for the higher C and dry matter content in the organic FYM and in the FYM with added straw. This resulted in mean total emissions of N₂O and CH₄ being lower from the organic (27 g N t⁻¹) than the conventional FYM (52 g N t⁻¹) and from the treatments with straw added (32 g N t⁻¹) than those without (47 g N t⁻¹). The initial C:N ratio and dry matter content of the stored FYM were the most important factors affecting N₂O and CH₄ emissions although the FYM temperature also affected CH₄ emissions. Adding high-C additives, such as straw could be a promising strategy for reducing GHG emissions because it influences the dry matter content, C:N ratio and aeration of the manure. The small-scale FYM storage method were shown to be a reliable and an easy method to quantify emissions under a range of environmental conditions and manure manipulations and so develop effective manure management practices to reduce GHG emissions.     

Integrated environmental assessment of biodiesel production from soybean in Brazil

This paper presents the results of an environmental impact assessment of biodiesel production from soybean in Brazil. In order to achieve this objective, environmental impact indicators provided by Emergy Accounting (EA), Embodied Energy Analysis (EEA) and Material Flow Accounting (MFA) were used. The results showed that for one liter of biodiesel 8.8 kg of topsoil are lost in erosion, besides the cost of 0.2 kg of fertilizers, about 5.2 m² of crop area, 7.33 kg of abiotic materials, 9.0 tons of water and 0.66 kg of air and about 0.86 kg of CO₂ were released. About 0.27 kg of crude oil equivalent is required as inputs to produce one liter of biodiesel, which means an energy return of 2.48 J of biodiesel per Joule of fossil fuel invested. The transformity of biodiesel (3.90E + 05 seJ J^?1) is higher than those calculated for fossil fuels as other biofuels, indicating a higher demand for direct and indirect environmental support. Similarly, the biodiesel emergy yield ratio (1.62) indicates that a very low net emergy is delivered to consumers, compared to alternatives. Obtained results show that when crop production and industrial conversion to fuel are supported by fossil fuels in the form of chemicals, goods, and process energy, the fraction of fuel that can actually be considered renewable is very low (around 31%).     

CaCO3 production using liquid waste from Solvay method

Process of obtaining CaCO₃ from the waste post-distillation liquid DS and post-filtration liquid from Solvay method of the soda production at 303 K was investigated. Reagents were dosed in a stoichiometric ratio without dilution, for different concentrations of the DS and post-filtration liquids. The dosage time was varied in the range 2–30 min, the reagent stirring rate was 500 rpm. For the obtained samples of CaCO₃, the bulk and packing densities, water, paraffin oil and dibutyl phthalate absorption capacities, distribution of the particle size as well as the crystalline form were determined.     

Bird use of rice field strips of varying width in the Kanto Plain of central Japan

Bird communities in flooded rice strips of different widths were surveyed in 71 fields around Lake Kasumigaura, on the Kanto Plain (central Japan). Strips categorized into four width classes (<50, 50–100, 100–300 and >300 m) and two locations (core >100 and <100 m from edges) were censused from May to July 1998, and mean species number and density of birds were compared. Both density and mean species differed significantly between classes, strips >300 m wide favoring bird diversity and number of marsh and grassland species. Breeding skylarks and fan-tailed warblers hardly occurred in fields adjacent to edges. Strips <50 m wide were not suitable feeding site of egret species (Ardeidae), but supported diurnal activity of black-crowned night herons and species requiring both rice fields and adjacent environment. As a consequence, bird conservation in rice field strips needs to consider both their width and location within the environment.     

Analysis of temperature effects on seasonal and interannual variation in CH4 emission from rice-planted pots

Rice (Oryza sativa L.) paddies are one of the major sources of atmospheric methane (CH₄), a greenhouse gas. To elucidate the quantitative relationship between CH₄ emission from rice paddies and temperature, 6 years data of CH₄ emission from pot experiments were analyzed in terms of the sum of effective temperature (∑(T−15); T is the daily mean air temperature (°C)). The base temperature of 15 °C was adopted as the 0 °C physiological temperature for methanogens. Significant positive correlations between total CH₄ emission throughout the rice growth period and ∑(T−15) were observed for pots with rice straw (RS) application at a rate of 6 g kg⁻¹ soil, which corresponds to 6 t ha⁻¹ (r=0.830⁷¹), and those without RS application (r=0.818⁷¹). It was confirmed that temperature is a major factor affecting the interannual variation in CH₄ emission. For the 1993 and 1995 data sets that include seven and four levels of RS application, the relationship between seasonal CH₄ emission and RS application rate could be expressed using linear functions (r=0.988⁷¹, 0.996⁷¹), the slopes of which were similar to each other. Based on these findings, we confirmed that the dependence of seasonal CH₄ emission on both temperature and RS application rate can be described by a single linear equation.     

Mitigation of greenhouse gas emissions by anaerobic digestion of cattle slurry

Biogas treatment of animal manures is an upcoming technology because it is a way of producing renewable energy (biogas). However, little is known about effects of this management strategy on greenhouse gas (GHG) emissions during fermentation, storage, and field application of the substrates compared to untreated slurries. In this study, we compared cattle slurry and cattle slurry with potato starch as additive during the process of fermentation, during storage and after field application. The addition of potato starch strongly enhanced CH₄ production from 4230 l CH₄ m⁻³ to 8625 l CH₄ m⁻³ in the fermenter at a hydraulic retention time (HRT) of 29 days. Extending the HRT to 56 days had only a small effect on the CH₄ production. Methane emissions from stored slurry depended on storage temperature and were highest from unfermented slurry followed by the slurry/starch mixture. Gas emissions from untreated and fermented slurry during storage were further analyzed in a pilot-scale experiment with different levels of covering such as straw cover, a wooden lid and no cover. Emissions of greenhouse gases (CH₄, N₂O, NH₃) were in the range of 14.3–17.1 kg CO₂ eq. m⁻³ during winter (100 day storage period) and 40.5–90.5 kg CO₂ eq. m⁻³ during summer (140 day storage period). A straw cover reduced NH₃ losses, but not overall GHG emissions, whereas a solid cover reduced CH₄ and NH₃ emissions. After field application, there were no significant differences between slurry types in GHG emissions (4.15–8.12 kg CO₂ eq. m⁻³ a⁻¹). GHG emissions from slurry stores were more important than emissions after field application. Co-digestion of slurry with additives such as starch has a large potential to substitute fossil energy by biogas. On a biogas plant, slurry stores should be covered gas-tight in order to eliminate GHG emissions and collect CH₄ for electricity production.     

Soil-profile organic carbon and total nitrogen during 12 years of pasture management in the Southern Piedmont USA

Soil organic C (SOC) and total soil N (TSN) sequestration estimates are needed to improve our understanding of management influences on soil fertility and terrestrial C cycling related to greenhouse gas emission. We evaluated the factorial combination of nutrient source (inorganic, mixed inorganic and organic, and organic as broiler litter) and forage utilization (unharvested, low and high cattle grazing pressure, and hayed monthly) on soil-profile distribution (0–150 cm) of SOC and TSN during 12 years of pasture management on a Typic Kanhapludult (Acrisol) in Georgia, USA. Nutrient source rarely affected SOC and TSN in the soil profile, despite addition of 73.6 Mg ha^?1 (dry weight) of broiler litter during 12 years of treatment. At the end of 12 years, contents of SOC and TSN at a depth of 0–90 cm under haying were only 82 ± 5% (mean ± S.D. among treatments) of those under grazed management. Within grazed pastures, contents of SOC and TSN at a depth of 0–90 cm were greatest within 5 m of shade and water sources and only 83 ± 7% of maximum at a distance of 30 m and 92 ± 14% of maximum at a distance of 80 m, suggesting a zone of enrichment within pastures due to animal behavior. During 12 years, the annual rate of change in SOC (0–90 cm) followed the order: low grazing pressure (1.17 Mg C ha^?1 year^?1) > unharvested (0.64 Mg C ha^?1 year^?1) = high grazing pressure (0.51 Mg C ha^?1 year^?1) > hayed (?0.22 Mg C ha^?1 year^?1). This study demonstrated that surface accumulation of SOC and TSN occurred, but that increased variability and loss of SOC with depth reduced the significance of surface effects.     

Second generation diesel fuel from renewable sources

The study is devoted to the issue of direct transformation of triacylglycerols (TAG) to diesel fuels applying a commercially available NiMo and NiW hydrorefining catalysts. It was proved that during hydrodesulphurisation also hydrodeoxygenation occurs and TAG can be converted to the fuel biocomponent by adding 6.5 % vol. of TAG to atmospheric gas oil. In this way, after hydroprocessing at mild conditions (temperature 320–360 °C, pressure 3.5–5.5 MPa, LHSV: 1.0 h^?1 and ratio H₂:HC = 500–1000 Nm³/m³, catalyst presence), gas oil containing 5–5.5% of biocomponent was prepared, characterized with standard performance and emission parameters. Performance and emission tests documented that even 5% vol. portion of bio-components reduces the controlled and uncontrolled emissions.     

Linking spatio-temporal variation of crop response with sediment deposition along paddy rice terraces

In tropical mountainous regions of South East Asia, intensive cultivation of annual crops on steep slopes makes the area prone to erosion resulting in decreasing soil fertility. Sediment deposition in the valleys, however, can enhance soil fertility, depending on the quality of the sediments, and influence crop productivity. The aim of the study was to assess (i) the spatio-temporal variation in grain yield along two rice terrace cascades in the uplands of northern Viet Nam, (ii) possible linkage of sediment deposition with the observed variation in grain yield, and (iii) whether spatial variation in soil water or nitrogen availability influenced the obtained yields masking the effect of inherent soil fertility using carbon isotope (¹³C) discrimination and ¹⁵N natural abundance techniques. In order to evaluate the impact of seasonal conditions, fertilizer use and sediment quality on rice performance, ¹⁵N and ¹³C stable isotope compositions of rice leaves and grains taken after harvest were examined and combined with soil fertility information and rice performance using multivariate statistics. The observed grain yields for the non-fertilized fields, averaged over both cascades, accounted for 4.0 ± 1.4 Mg ha^?1 and 6.6 ± 2.5 Mg ha^?1 in the spring and summer crop, respectively, while for the fertilized fields, grain yields of 6.5 ± 2.1 Mg ha^?1 and 6.9 ± 2.1 Mg ha^?1 were obtained. In general, the spatial variation of rice grain yield was strongly and significantly linked to sediment induced soil fertility and textural changes, such as soil organic carbon (r 0.34/0.77 for Cascades 1 and 2, respectively) and sand fraction (r ?0.88/?0.34). However, the observed seasonal alteration in topsoil quality, due to sediment deposition over two cropping cycles, was not sufficient to fully account for spatial variability in rice productivity. Spatial variability in soil water availability, assessed through ¹³C discrimination, was mainly present in the spring crop and was linearly related to the distance from the irrigation channel, and overshadowed in Cascade 2 the expected yield trends based on sediment deposition. Although δ¹⁵N signatures in plants indicated sufficient N uptake, grain yields were not found to be always significantly influenced by fertilizer application. These results showed the importance of integrating sediment enrichment in paddy fields within soil fertility analysis. Furthermore, where the effect of inherent soil fertility on rice productivity is masked by soil water or nitrogen availability, the use of ¹³C and ¹⁵N stable isotopes and its integration with conventional techniques showed potential to enhance the understanding of the influence of erosion – sedimentation and nutrient fluxes on crop productivity, at toposequence level.     

Yield formation of CO2-enriched inter-subspecific hybrid rice cultivar Liangyoupeijiu under fully open-air field condition in a warm sub-tropical climate

Hybrid rice (Oryza sativa L.) cultivars play an important role in rice production due to its heterosis, resistance to environmental stress and high yield potential. However, no attention has been given to its yield responses to rising atmospheric CO₂ concentration ([CO₂]). To address this need, we conducted a Free Air CO₂ Enrichment (FACE) experiment at Yangzhou, Jiangsu, China, in 2004–2006. A two-line inter-subspecific hybrid rice variety Liangyoupeijiu, recently bred in China, was grown at ambient or elevated (c. 570 μmol mol^?1) [CO₂] under two levels of nitrogen (N) application (12.5 and 25 g N m^?2). Elevated [CO₂] slightly accelerated phenological development (1–2 days), and substantially enhanced grain yield (+30%). The magnitude of yield response to [CO₂] was independent of N fertilization, but greatly varied among years. On average, elevated [CO₂] increased panicle number per unit land area by 8%, due to an increase in maximum tiller number under FACE, while productive tiller ratio remained unaffected. Spikelet number per panicle showed an average increase of 10% due to elevated [CO₂], which was also supported by increased plant height and dry weight per stem. Meanwhile, Elevated [CO₂] caused a significant enhancement in both filled spikelet percentage (+5%) and individual grain mass (+4%). Compared with previous rice FACE studies, this hybrid cultivar appears to profit much more from elevated [CO₂] than inbred japonica cultivars (c. +13%), not only due to its stronger sink generation, but also enhanced capacity to utilize the carbon sources in a high [CO₂] environment. As sufficient intraspecific variation in yield response exists under field conditions, there is a pressing need to identify genotypes which would produce maximum grain yield under projected future [CO₂] levels.     

Lodging in rice can be alleviated by atmospheric CO2 enrichment

The projected increase of atmospheric CO₂ concentration [CO₂] is expected to increase yield of agricultural C₃ crops, but little is known about effects of [CO₂] on lodging that can reduce yield. This study examined the interaction between [CO₂] and nitrogen (N) fertilization on the lodging of rice (Oryza sativa L.) using free-air CO₂ enrichment (FACE) systems installed in paddy fields at Shizukuishi, Iwate, Japan (39°38′N, 140°57′E). Rice plants were grown under two levels of [CO₂] (ambient = 365 μmol mol⁻¹; elevated [CO₂] = 548 μmol mol⁻¹) and three N fertilization regimes: a single initial basal application of controlled-release urea (8 g N m⁻², CRN), split fertilization with a standard amount of ammonium sulfate (9 g N m⁻², MN), and ample N (15 g N m⁻², HN). Lodging score (six ranks at 18° intervals, with larger scores indicating greater bending), yield, and yield components were measured at maturity. The lodging score was significantly higher under HN than under CRN and MN, but lodging was alleviated by elevated [CO₂] under HN. This alleviation was associated with the shortened and thickened lower internodes, but was not associated with a change in the plant's mass moment around the culm base. A positively significant correlation between lodging score and ripening percentage indicated that ripening percentage decreased by 4.5% per one-unit increase in lodging score. These findings will be useful to develop functional algorithm that can be incorporated into mechanistic crop models to predict rice production more accurately in a changing climate and with different cultural practices.     

Micro-flood (MF) technology for sustainable manufacturing operations that are coolant less and occupationally friendly

This paper presents a new technology for minimizing the use of metalworking fluids (MWFs) during the machining process that is atomization-less and occupational friendly. Micro-flood (MF) technology utilizes direct contact between the cutting tool and the MWF without the interaction of a gas medium. Experiments were conducted in high volume mass production environment turning HSLA (high strength low alloy) SAE 070Y steel. Machining performance and total air mass particulates were investigated in dry machining, Near dry machining (NDM) via atomized spray mist and MF technology. Open-atmosphere air monitoring indicated that total mass particulates behaved in an almost linear fashion with respect to gas atomization pressure, whereas the MWF flow rate demonstrated logarithmic trends in NDM applications using an atomized spray. Nozzle orientations directed upward into the air also produced higher mg/m³ concentrations (such as flank) than chip and rake face orientations that were directed down. Greater separation existed at higher gas atomization pressures, MWF flow rates and by changing the MWF type. At extreme limits, nozzle orientation affected mg/m³ concentration as much as 4–5 mg/m³ for water-miscible MWFs and 15–22 mg/m³ for non-water-miscible MWFs. Tool-life performance varied greatly among MWF type and flow rate, and in all cases MF technology performed better than NDM using an atomized spray mist. Direct and consistent MWF penetration to cutting zone using MF technology lowered tool-wear on the average of 12–75% compared to NDM at the same MWF flow rate. Compared to dry machining, NDM improved tool-wear on the average by 20–243%. In one case, tool-wear performance was improved by 616% at 0.15 mm using MF technology compared to dry machining at a nominal 0.925 mm tool-wear. Overall, a large mass reduction of particulates can be achieved employing MF technology that would have been unrealistic for an open-atmosphere machining environment employing an atomized spray mist. On the average, MF technology can maintain a total air mass particulate of less than 0.4 mg/m³ in the occupational work zone using MWF flow rates up to 1260 ml/h, regardless of the MWF classification. Atomized spray mist applications are capable meeting the 5 mg/m³ OSHA limit if MWF flow rates are less than 160 ml/h, air pressures are less than 0.137 MPa (20 psi) using water-miscible MWFs and air pressures are less than 0.0344 MPa (5 psi) using non-water-miscible MWFs.     

Changes in soil fertility parameters and the environmental effects in a rapidly developing region of China

An extensive knowledge of the temporal variability of soil fertility parameters and how this variation affects the environment is imperative to a wide range of disciplines within agricultural science for optimal crop production and ecosystem preservation. This paper examines the temporal variability of soil pH, organic matter (OM), cation exchange capacity (CEC), total nitrogen (TN), total phosphorus (TP), available phosphorus (P_Av), and available potassium (K_Av) on Cambosols (Entisols) (n = 179) and Anthrosols (Inceptisols) (n = 95) in Zhangjiagang County, China from 1980 to 2004. Nutrient input was monitored from 1983 to 2004. Annual N fertilizer rates were significantly different during three periods (1983–1989, 1989–1999, 1999–2004), where annual rates increased significantly after 1989 and then decreased after 1999. Annual P fertilizer rates were significantly different during two periods (1983–1993, 1993–2004) where annual rates increased after 1993. No change was found in K fertilizer rates. Soil pH marginally increased by 0.14 units in Cambosols, but significantly decreased by 1.02 units in Anthrosols. OM, CEC, and TN increased in both soil orders an average of 2.15 g kg^?1, 1.6 cmol kg^?1, and 0.21 g kg^?1, respectively. TP decreased in Anthrosols by 70 mg kg^?1, P_Av increased in Cambosols by 4.83 mg kg^?1, and K_Av decreased in Cambosols by 15 mg kg^?1. Fertilizer input rates are causing nutrient imbalances, contributing to acidification in Anthrosols, and decreasing C/N ratios. Nutrient loading of N and deficiency of K is also a potential problem in the area. Efforts should be made to readjust soil nutrient inputs to reach an optimal, sustainable level.     

Disaggregated greenhouse gas emission inventories from agriculture via a coupled economic-ecosystem model

Estimates of regional greenhouse gas emissions from agricultural systems are needed to evaluate possible mitigation strategies with respect to environmental effectiveness and economic feasibility. Therefore, in this study, we used the GIS-coupled economic-ecosystem model EFEM–DNDC to assess disaggregated regional greenhouse gas (GHG) emissions from typical livestock and crop production systems in the federal state of Baden-Württemberg, Southwest Germany. EFEM is an economic farm production model based on linear programming of typical agricultural production systems and simulates all relevant farm management processes and GHG emissions. DNDC is a process-oriented ecosystem model that describes the complete biogeochemical C and N cycle of agricultural soils, including all trace gases.Direct soil emissions were mainly related to N₂O, whereas CH₄ uptake had marginal influence (net soil C uptake or release was not considered). The simulated N₂O emissions appeared to be highly correlated to N fertilizer application (R² = 0.79). The emission factor for Baden-Württemberg was 0.97% of the applied N after excluding background emissions.Analysis of the production systems showed that total GHG emissions from crop based production systems were considerably lower (2.6–3.4 Mg CO₂ eq ha⁻¹) than from livestock based systems (5.2–5.3 Mg CO₂ eq ha⁻¹). Average production system GHG emissions for Baden-Württemberg were 4.5 Mg CO₂ eq ha⁻¹. Of the total 38% were derived from N₂O (direct and indirect soil emissions, and manure storage), 40% were from CH₄ (enteric fermentation and manure storage), and 22% were from CO₂ (mainly fertilizer production, gasoline, heating, and additional feed). The stocking rate was highly correlated (R² = 0.85) to the total production system GHG emissions and appears to be a useful indicator of regional emission levels.     

Methane,nitrous oxide and ammonia emissions during storage and after application of dairy cattle slurry and influence of slurry treatment

Slurries are a significant source of CH₄, NH₃ and N₂O emissions to the atmosphere. The research project aimed at quantifying CH₄, NH₃ and N₂O emissions from liquid manure stores and after manure application under field conditions. The influence of the manure treatment options “no treatment”, “slurry separation”, “anaerobic digestion”, “slurry aeration” and “straw cover” on the emission level was investigated. Approximately 10 m³ of differently treated slurry were stored in pilot scale slurry tanks. Emissions were followed for c. 80 days. After the storage period, slurries were applied to permanent grassland. Greenhouse gas emissions from slurry were mainly caused by methane emissions during storage and by nitrous oxide emissions after field application of manures. Mitigation of GHG emissions can be achieved by a reduction in slurry dry matter and easily degradable organic matter content. Ammonia emissions mainly occurred after field application. Untreated slurry emitted 226.8 g NH₃ m⁻³ and 92.4 kg CO₂ eq. m⁻³ (storage and field application). Slurry separation (liquid fraction and composting of the solid fraction) resulted in NH₃ losses of 402.9 g m⁻³ and GHG losses of 58.5 kg CO₂ eq. m⁻³. Anaerobic digestion was a very effective means to reduce GHG emissions. 37.9 kg CO₂ eq. m⁻³ were lost. NH₃ emissions were similar to those from untreated slurry. Covering the slurry store with a layer of chopped straw instead of a wooden cover increased NH₃ emissions to 320.4 g m⁻³ and GHG emissions to 119.7 kg CO₂ eq. m⁻³. Slurry aeration nearly doubled NH₃ emissions compared to untreated slurry. GHG emissions were reduced to 53.3 kg CO₂ eq. m⁻³.     

Biogas production from maize and dairy cattle manure—Influence of biomass composition on the methane yield

There is an increasing world wide demand for energy crops and animal manures for biogas production. To meet these demands, this research project aimed at optimising anaerobic digestion of maize and dairy cattle manures. Methane production was measured for 60 days in 1 l eudiometer batch digesters at 38 °C. Manure received from dairy cows with medium milk yield that were fed a well balanced diet produced the highest specific methane yield of 166.3 Nl CH₄ kg VS⁻¹. Thirteen early to late ripening maize varieties were grown on several locations in Austria. Late ripening varieties produced more biomass than medium or early ripening varieties. On fertile locations in Austria more than 30 Mg VS ha⁻¹ can be produced. The methane yield declined as the crop approaches full ripeness. With late ripening maize varieties, yields ranged between 312 and 365 Nl CH₄ kg VS⁻¹ (milk ripeness) and 268–286 Nl CH₄ kg VS⁻¹ (full ripeness). Silaging increased the methane yield by about 25% compared to green, non-conserved maize. Maize (Zea mays L.) is optimally harvested, when the product from specific methane yield and VS yield per hectare reaches a maximum. With early to medium ripening varieties (FAO 240–390), the optimum harvesting time is at the “end of wax ripeness”. Late ripening varieties (FAO ca. 600) may be harvested later, towards “full ripeness”. Maximum methane yield per hectare from late ripening maize varieties ranged between 7100 and 9000 Nm³ CH₄ ha⁻¹. Early and medium ripening varieties yielded 5300–8500 Nm³ CH₄ ha⁻¹ when grown in favourable regions. The highest methane yield per hectare was achieved from digestion of whole maize crops. Digestion of corns only or of corn cob mix resulted in a reduction in methane yield per hectare of 70 and 43%, respectively. From the digestion experiments a multiple linear regression equation, the Methane Energy Value Model, was derived that estimates methane production from the composition of maize. It is a helpful tool to optimise biogas production from energy crops. The Methane Energy Value Model requires further validation and refinement.