Beet Residues Research Articles

Optimizing the In-Vessel Composting Process of Sugarbeet Dry-Cleaning Residue

Rapid urbanization and industrialization around the world have created massive amounts of organic residues, which have been prioritized for conversion into valuable resources through the composting process to keep their harmful effect at a minimum. This research aimed to assess the influence of active and passive aeration on composting mass of sugar beet residues in the case of using additives (e.g., charcoal only or manure only or combination). Some physicochemical properties of composting mass were analyzed on certain days of composting. Some parameters including temperature–time profile, carbon to nitrogen ratio (C/N ratio), moisture content, electrical conductivity, pH, germination and microbial population enumeration of compost were measured. Cress germination test was conducted for each medium of germination which contains a mixture of soil and compost (at a ratio of 3:1) taken from each treatment. The results showed that temperature–time profile data of composting mass showed an irregularity. Forcedly aerated composting mass did not demonstrate a thermophilic phase while passively aerated ones did not show a mesophilic phase. Carbon to nitrogen (C/N) ratio reduction was greater in most forcedly aerated composting mass than passively aerated on days from 1 to 33 of composting period. The results further showed that electrical conductivity decreased at the end of the composting period where it ranged from 2.55 to 3.1 dS/m. Germination medium containing forcedly aerated compost treated with a combination of charcoal and manure achieved the highest germination index which was higher than the control sample by 58.63% followed by forcedly aerated composting mass treated by charcoal only which exceeded the control sample by 5.35%. Strong correlation coefficient (r > 0.80) for the relationship between germination index and number of bacteria was obtained on day 17th of composting period.

A Comparison of Combustion Properties in Biomass-Coal Blends Using Characteristic and Kinetic Analyses.

This paper presents comparative research on the combustion of coal, wheat, corn straw (CS), beet residues after extracting sugar (BR), and their blends, coal–corn straw blends (CCSBs), coal–wheat blends (CWBs), and coal–beet residue blends (CBRBs), using thermogravimetric (TG) analysis under 10, 20, 30, 40 and 50 °C/min. The test results indicate that CS and wheat show better combustion properties than BR, which are recommended to be used in biomass combustion. Under the heating rate of 20 °C/min, the coal has the longest thermal reaction time when compared with 10 and 30 °C/min. Adding coal to the biomass can improve the burnout level of biomass materials (BM), reduce the burning speed, and make the reaction more thorough. The authors employed the Flynn–Wall–Ozawa (FWO) method and the Kissinger–Akahira–Sunose (KAS) method to calculate kinetics parameters. It was proven that overall, the FWO method is better than the KAS method for coal, BM, and coal–biomass blends (CBBs), as it provides higher correlations in this study. It is shown that adding coal to wheat and BR decreases the activation energy and makes conversion more stable under particular α. The authors selected a wider range of biomass raw materials, made more kinds of CBB, and conducted more studies on different heating rates. This research can provide useful insights into how to choose agricultural residuals and how to use them.

Soil mulching and deficit irrigation effect on sustainability of nutrients availability and uptake, and productivity of maize grown in calcareous soils

ABSTRACT Plants are subjected to low use efficiency of water and nutrients in marginal lands such as calcareous soils. Moreover, plant wastes are not utilized optimally by the farmers. Hence, field trials were carried out in 2018 and 2019 summer seasons to find the practicable model which can be emerged through addition of sugar beet residues as mulching material and irrigation treatments in maize field. The amount of these residues were 0, 2.4, 7.2 and 12.0 ton ha−1 (denoted ‎ M0 M1 M2 and M3, respectively). Irrigation treatments were 60%, 80% and 100% of crop evapotranspiration (signed as W60, W80 and W100, respectively). The study was established in a strip plots design with three replications. Findings exhibited that W80 x M3 or M2 were as similar as W100 x M2 in improving biological, straw and grain yields ha−1. Similar beneficial effect of W100 or W80 on nutrient uptake was obtained under mulching soil with M3 or M2. Moreover, M1 x W80 or W100 achieved the maximally available phosphorus (P) in soil. As well, M3 x W80 showed stable improvement in water use efficiency during the two studied seasons. Due to irrigation and soil mulching combinations, calcium carbonate (CaCO3) was reduced by 5.6.1–32.6% compared to the initial CaCO3 in soil (25.42%). Generally, application of sugar beet residues at a rate of 7.2 ton ha−1 and moderate irrigation water supply, that is 80% of crop evapotranspiration may be considered a promising quixotic practice for regulating deficit irrigation in maize grown in calcareous soils. Continuous application of compatible irrigation regime and soil mulching, for example, 80% of crop evapotranspiration plus soil mulching could have the potentiality to improve calcareous soil properties year after year.

Biogas feedstock potentials and related water footprints from residues in China and the European Union

China encounters heavy air pollution caused by coal consumption. China and the EU aim to decrease greenhouse gas emissions. Shifting to biogas from residues contributes to solving both problems. This study assesses China's biogas potentials and related water footprints (WFs) and compares results with potentials and WFs for the EU. Starting from a literature review on EU biogas potentials, it analyzes information resulting in a calculation methodology, its validation and application to China. Finally, it estimates WFs and makes a comparative assessment of biogas potentials of the EU and China. In the EU, biogas from agricultural, forestry and other residues might contribute 8% (5300 PJ) to primary energy consumption, in China 10% (13,275 PJ.) In the EU, agriculture contributes 41%, forestry 26%, other residues 23%, and manure 10%. The corresponding results for China are agriculture (67%), forestry (23%), manure (7%) and other residues (3%). In the EU, biogas might contribute 45% to total gas demand; in China more biogas can be produced than consumed in 2018 (185% of demand). The EU results fall in the range of residue potentials from earlier studies. Maize, wheat, barley and rapeseed contribute 78% to the EU agricultural biogas potential. In China, dominant crops are maize (49%), rice (18%), wheat (12%) and seed cotton (6%). For water, there are large differences among WFs of specific crop residues, but also between WFs for EU and Chinese crop residues. Most Chinese crop residues have larger WFs than the EU residues. Biogas from sugar beet residues has the smallest WFs, biogas from tobacco residues the largest. Although using residues for energy does not change total national WFs, it reallocates WFs over main products and residues. The comparative assessment supports better use of biogas potentials from residues with lower WFs and is also applicable for other regions and countries.

Conversion of sugar beet residues into lipids by Lipomyces starkeyi for biodiesel production

BackgroundLipids from oleaginous yeasts emerged as a sustainable alternative to vegetable oils and animal fat to produce biodiesel, the biodegradable and environmentally friendly counterpart of petro-diesel fuel. To develop economically viable microbial processes, the use of residual feedstocks as growth and production substrates is required.ResultsIn this work we investigated sugar beet pulp (SBP) and molasses, the main residues of sugar beet processing, as sustainable substrates for the growth and lipid accumulation by the oleaginous yeast Lipomyces starkeyi. We observed that in hydrolysed SBP the yeast cultures reached a limited biomass, cellular lipid content, lipid production and yield (2.5 g/L, 19.2%, 0.5 g/L and 0.08 g/g, respectively). To increase the initial sugar availability, cells were grown in SBP blended with molasses. Under batch cultivation, the cellular lipid content was more than doubled (47.2%) in the presence of 6% molasses. Under pulsed-feeding cultivation, final biomass, cellular lipid content, lipid production and lipid yield were further improved, reaching respectively 20.5 g/L, 49.2%, 9.7 g/L and 0.178 g/g. Finally, we observed that SBP can be used instead of ammonium sulphate to fulfil yeasts nitrogen requirement in molasses-based media for microbial oil production.ConclusionsThis study demonstrates for the first time that SBP and molasses can be blended to create a feedstock for the sustainable production of lipids by L. starkeyi. The data obtained pave the way to further improve lipid production by designing a fed-batch process in bioreactor.Graphical abstract

Changes in biochemical composition of cassava and beet residues during solid state bioprocess with Pleurotus ostreatus

The development of the Pleurotus ostreatus in cassava ( Manihot esculenta ) and beet ( Beta vulgaris ) residues via solid state bioprocess (SSB) was evaluated in terms of variation of proximate composition, phenolic compounds, minerals, in vitro digestibility, fungal growth and lipase activity. The substrates were cultured at 30 °C for 35 days and sampled every 5 days. The amount of protein, and fibers of cassava residues, increased by 125.7%, and 253.2%, respectively. The beet residue showed a protein increment of 57.6%, and fibers of 232.7%. In beet residues, the lipid increase was of 261.7% while that for cassava residues was of 136.2%. The cassava residue showed a reduction in phenolic compounds from 18.07 mg of acid galic equivalent (AGE)/g to 4.17 mg AGE/g and beet from 30.96 mg to 3.50 mg. In vitro digestibility increased by 5.24% in cassava residues and 29.38% in beet residues. P. ostreatus reached 8.63 CFU/g (15 days) in cassava residue and 6.08 CFU/g (25 days) in beet residue. Maximum lipase activity was 0.71 U/g (35 days) in beet residues and 0.46 U/g (20 days) in cassava residues. Both beet and cassava residues presented nutritional enrichment (carbohydrate reduction and increase of other compounds) and increased in vitro digestibility with P. ostreatus via SSB. This application presents great biotechnological potentiality, e.g. the utilization as a low-cost nutrient source for animal feed.

Comparative assessment of bioethanol supply chain: insights from Iran

Biofuels are important alternative fuel in recent years. In this work, the bioethanol supply chain planning is performed by BioEnergy Supply Model to optimally find the best pathways using economic and environmental objective functions in Iran. Then, different sustainability criteria focusing on environmental, economic, and social concerns are assessed for possible routes of the bioethanol production from available resources. Although agriculture residues and wastes, decrease the greenhouse gas emissions but municipal solid wastes are more economic and require less water. The agricultural wastes and residues improve the sustainability. Then, criteria focusing on environmental, economic, and social concerns are assessed for available agricultural resources. The most cost-intensive bioethanol is obtained from the rice and barley wastes with 52.6 and 42.4 billion dollars over 25 years, respectively. The lowest total cost of the supply chain belongs to sugarcane and sugar beet wastes with the amounts of 10.7 and 13.56 billion dollars, respectively. The bioethanol form wastes of rice, barely, and wheat cultivation mitigates the global warming more than other resources while they have negative carbon cycles. Similarly, the highest and lowest number of created jobs of bioethanol supply chain belong to the rice wastes and the sugar beet and corn residues.

Use of laboratory incubation techniques to estimate greenhouse gas footprints from conventional and no-tillage organic agroecosystems

Organic agroecological systems “produce goods using methods that preserve the environment” but can be a substantial source of greenhouse gases (GHG) if not managed properly. The objective of this experiment was to monitor nitrogen (N) and carbon (C) transformations in soils resulting from N additions, water filled pore space (WFPS) and prior tillage management during a simulated freeze-thaw. Incubated soils were taken from two USDA certified organic five-year small grain rotations with mixed legume cover crops that varied only in tillage, conventional (CT) vs. no-tillage (NT) for 3 yr prior to sampling. Soils incubated for 149 d were left unamended or amended with 15N labelled urea or sugar beet residue and maintained at 40, 60 and 80% WFPS. Non-metric multidimensional scaling (NMS) verified that soils amended with beet vs urea clustered separately in ordination space. A two way PerMANOVA analysis confirmed a significant interaction between WFPS and N amendment (p = 0.0002). Prior tillage management, N treatment and WFPS had a significant effect on GHG emission from soils. At 40% WFPS, soil previously in NT amended with beet residues emitted more nitrous oxide (N2O) and carbon dioxide (CO2) relative to soil previously in CT. At 60% WFPS, soil previously in CT amended with beet residues emitted greater N2O and less CO2 relative to soil previously in NT. Our research indicates that climate, carbon stocks and duration of prior tillage management determined the potential of no-till to reduce GHG emissions during a simulated freeze-thaw. Growers should note that as much as 4.51% of nitrates (NO3−) in residues can be lost as N2O at an average soil temperature of 10 °C.

Supercritical water gasification of beet residues: From batch to continuous reactor

A residue obtained after the distillation of agricultural alcohol called beet residues is gasified in supercritical water to form a mixture of fuel gas. A parametric study and thermodynamic calculations are first proposed in batch reactor. The results show a significant effect of temperature on the overall mass yields. Gasification efficiencies range from 0.60 to 0.90gg−1 when temperature increases from 450 to 600°C. The gas low heating value increases under these conditions from 7.4 to 13.2MJkg−1 of initial dry feedstock. After that, a continuous system designed for hydrothermal oxidation processes has been used. For supercritical water gasification, the reduction of total organic carbon in the liquid effluent output presents a little variation, between 59 and 69%, when the operating conditions are changed. To increase the reaction temperature, supercritical water partial oxidation has been conducted. The highest carbon gasification yield is obtained for the highest equivalent molar ratio, indicating a great interest of partial oxidation. Moreover, the results indicate that this process configuration accepts biomass flow variations without influencing the global efficiency.

Pathogenicity, Symptom Development, and Mycotoxin Formation in Wheat by Fusarium Species Frequently Isolated from Sugar Beet

Crop rotations with putative non-host crops such as sugar beet are often recommended to reduce Fusarium head blight (FHB) in cereals. However, recent observations have shown pathogenic, endophytic, and saprotrophic colonization of sugar beet with various Fusarium spp. Therefore, strains of seven species frequently isolated from sugar beet were tested for pathogenicity on wheat. Species-specific symptoms on heads and kernels were evaluated and the grains were analyzed for 20 mycotoxins with liquid chromatography-tandem mass spectrometry. Fusarium graminearum, F. culmorum, and F. cerealis from sugar beet caused typical FHB symptoms and mycotoxin contamination with deoxynivalenol and nivalenol, while a high incidence of black point was observed in heads inoculated with F. tricinctum or F. equiseti. Black point kernels revealed 3.4 to 14.5 times higher mycotoxin concentrations than symptomless grains, containing enniatin B1 at 38,000 μg/kg, moniliformin at 4,900 μg/kg, and 2-amino-14,16-dimethyloctadecan-3-ol at 5,500 μg/kg, as well as monoacetoxyscirpenol at 2,600 μg/kg and nivalenol at 3,800 μg/kg. Monitoring of these latter two species in the field is hampered by the lack of typical head symptoms after infection. In further experiments, the impact of sugar beet residues on FHB severity and the correlation between mycotoxin contamination of cereal lots and the amount of black point have to be evaluated.

Flame retarded composite panels from sugar beet residues

Sugar beet residues and various additives were used to prepare panels by forming the semi-dry or wet mixtures and pressing the composites at a temperature of 150 °C and pressures of 100–5410 kPa for up to 105 min. The highest panel density and second highest thickness were observed when a combination of calcium hydroxide and boric acid were used as additives using the semi-dry procedure. SEM images revealed that at pressures over 1000 kPa the cell wall structure of sugar beet was completely unrecognizable. The FTIR results indicated that the non-cellulosic polysaccharides contributed significantly to the properties of the panels by acting as adhesives. The best flame retardant parameters were also obtained with the calcium hydroxide/boric acid formulation. In comparison to composites prepared from recycled paper and mixtures of sugar beet shreds with recycled paper, higher density panels were prepared at lower pressure from sugar beet sources.

Direct Polymerase Chain Reaction-Based Detection of Cercospora beticola in Field Soils.

Cercospora beticola, the causal agent of Cercospora leaf spot of sugar beet, survives as pseudostromata in infected sugar beet residues in the soil. Under optimal conditions, overwintering propagules germinate and produce conidia that are dispersed as primary inoculum to initiate infection in sugar beet. We developed a polymerase chain reaction (PCR) technique for rapid detection of C. beticola in field soils. Total DNA was first isolated from soil amended with C. beticola culture using the PowerSoil DNA Kit. The purified DNA was subjected to PCR in Extract-N-Amp PCR mix with CBACTIN primers over 35 cycles. The amplified products were resolved and compared by electrophoresis in 1% agarose gels. The PCR fragment size of C. beticola from the amended field soil correlated in size with the amplicon from control C. beticola culture DNA extract. Additionally, sample soils were collected from sugar beet fields near Sidney, MT and Foxholm, ND. Total DNA was extracted from the samples and subjected to PCR and resolved as previously described. The amplicons were purified from the gels and subjected to BigDye Terminator Cycle sequencing. All sequences from field soils samples, C. beticola-amended field soil, and pure culture were compared by alignment with a C. beticola actin gene sequence from GenBank. The result of the alignment confirmed the amplicons as products from C. beticola. Rapid screening for the presence of C. beticola in the soil by PCR will improve research capabilities in biological control, disease forecasting, and management of this very important sugar beet pathogen.

Co‐incorporation of biodegradable wastes with crop residues to reduce nitrate pollution of groundwater and decrease waste disposal to landfill

AbstractReturn of high nitrogen (N) content crop residues to soil, particularly in autumn, can result in environmental pollution resulting from gaseous and leaching losses of N. The EU Landfill Directive will require significant reductions in the amounts of biodegradable materials going to landfill. A field experiment was set up to examine the potential of using biodegradable waste materials to manipulate losses of N from high N crop residues in the soil. Leafy residues of sugar beet were co‐incorporated into soil with materials of varying C:N ratios, including molasses, compactor waste, paper waste, green waste compost and cereal straw. The amendment materials were each incorporated to provide approximately 3.7 t C per hectare. The most effective material for reducing nitrous oxide (N2O) production and leaching loss of NO3− was compactor waste, which is the final product from the recycling of cardboard. Adding molasses increased N2O and NO3− leaching losses. Six months following incorporation of residues, the double rate application of compactor waste decreased soil mineral N by 36 kg N per hectare, and the molasses increased soil mineral N by 47 kg N per hectare. Compactor waste reduced spring barley grain yield by 73% in the first of years following incorporation, with smaller losses at the second harvest. At the first harvest, molasses and paper waste increased yields of spring barley by 20 and 10% compared with sugar beet residues alone, and the enhanced yield persisted to the second harvest. The amounts of soil mineral N in the spring and subsequent yields of a first cereal crop were significantly correlated to the lignin and cellulose contents of the amendment materials. Yield was reduced by 0.3–0.4 t/ha for every 100 mg/g increase in cellulose or lignin content. In a second year, cereal yield was still reduced and related to the cellulose content of the amendment materials but with one quarter of the effect. Additional fertilizer applied to this second crop did not relieve this effect. Although amendment materials were promising as tools to reduce N losses, further work is needed to reduce the negative effects on subsequent crops which was not removed by applying 60 kg/ha of fertilizer N.

Effect of tillage intensity on N mineralization of different crop residues in a temperate climate

To evaluate the effect of tillage intensity on the N mineralization pattern of winter wheat residues, sugar beet residues, Italian ryegrass and maize residues undisturbed soil samples were taken from six sites under different tillage management. Site NT K had been managed for 10 years under reduced tillage (RT), whereby the last 4 years the crops were sown using direct seeding (NT). Site RT CSE had been managed for 20 years under reduced tillage (RT) and site RT H for 3 years. For each site under RT a nearby site under conventional tillage (CT) was selected (CT K, CT CSE and CT H). On site NT K and site RT CSE a significantly higher amount of SOC in the 0–10 cm was accumulated compared to the respective CT sites. Between site RT H and site CT H no such significant difference was found. However, the content of microbial biomass C (MB-C) and the β-glucosidase and urease activities were higher on all RT sites compared to the respective CT sites. This indicates that these microbiological and biochemical parameters seem to be very sensitive for alterations in management intensity. After 98 days, more N was immobilized under NT K than under CT K by adding winter wheat residues (expressed as kg ha −1 and as % of total added N). This higher immobilization potential can be explained by a higher microbial activity and a change in microbial population. Under RT CSE and RT H net N immobilization of the winter wheat residues was found, but the pattern was less pronounced than for NT K. However, when expressed as % of total N added, N immobilization of winter wheat residues was higher under CT than under RT, which indicates that high C:N residues when incorporated, decompose more slowly under RT than under CT. Similar results were found comparing the N mineralization pattern of maize residues under RT H and CT H. The residues of sugar beet and Italian ryegrass at site CT H released N more rapidly and to a higher extent, 74.1% and 66.2%, respectively (expressed as % of total N added) than under RT H at the end of the incubation. The slower mineralization of N rich crop residues under RT compared to CT means that there is less potential risk for nitrate leaching to occur, which may result in a higher N efficiency in RT compared to CT.

Incubation Experiments on Net Nitrogen Mineralization in Organic Greek Soils

Aerobic incubation experiments were conducted in organic surface samples collected from arable soils of Philippoi, in Northern Greece. Laboratory experiments were carried out to investigate the nitrogen (N) mineralized from soils and sugar beet residues incorporated into the soils. Cumulative mineralization of N, potentially mineralizable nitrogen (N0), and mineralization rate constant k were estimated after 30 continuous incubation weeks at 35°C. Total N content of soils ranged between 6.6 and 19.2 g kg−1, total soil carbon from 119 to 309 g kg−1, soil organic carbon ranged from 119 to 308 g kg−1, and the C∶N ratio varied from 13.5 to 18.3. The cumulative net mineralized N ranged between 132 and 426 mg kg−1 for nonamended soil and between 165 and 586 mg kg−1 for residue‐amended soil. Nitrate was the main form of mineralized N, although appreciable amounts of ammonium were measured. Potentially mineralizable nitrogen (N0) varied between 254 and 1067 mg kg−1 for nonamended soil and 311–1465 mg N kg−1 in residue‐treated soil. The mineralization constant k was between 0.052 and 0.068 (week−1). Close relationships between total soil N and soil organic carbon, and between cumulative mineralization and total soil N were found. Mineralization occurred rather rapidly, although the amount of mineralized N per week was reduced in the later weeks of incubation. Variation in net mineralization among soil samples can be attributed to soil organic matter content, origin, and state of decomposition, as well as differences in management histories, and soil and microenvironmental conditions. Monitoring of mineralization process may ensure a basis for increasing nitrogen use efficiency.

N2O emission and CH4 uptake in arable fields managed under conventional and reduced tillage cropping systems in northern Japan

Nitrous oxide (N2O) emission and methane (CH4) uptake were measured in an experimental long‐term tillage field (Andosol) in Hokkaido, northern Japan, to assess their contributions to net global warming, associated with arable crop production. From May 2001 to August 2002, the field was cultivated with winter wheat, adzuki bean, sugar beet, potato, and cabbage, where the total N applied was 110, 40, 150, 60, and 220 kg N ha−1 yr−1, respectively. Under conventional tillage (CT) cropping systems, basal N fertilization and plowing for residue incorporation had little effect on N2O fluxes, but vigorous N2O emission was observed when rotary harrowing was used for incorporating N‐rich cabbage residues into soil in summer. Also, high N2O emissions occurred when there was heavy rainfall after a large amount of N fertilizer had been applied to sugar beet and also when there was thawing of frozen soil and snow in the winter wheat treatment. Despite the differing N2O flux patterns among the crops, the annual N2O emissions from each crop were positively correlated with the total N applied as fertilizer. Under CT systems, across all five crops, the mean N2O emission factor (the percent ratio of N2O‐N emitted out of total N applied as fertilizer) was 0.36%. Under reduced tillage (RT) cropping systems, where crop residues were left on the ground over winter, large quantities of N2O were emitted from adzuki bean and sugar beet residues when the frozen soil and snow thawed. Therefore, total N2O emissions from adzuki bean and sugar beet cultivated under RT systems were much greater than under CT systems. The rates of CH4 uptake by arable soils were less sensitive to crop type, field management practices, and fertilizer application rates, but the rates were strongly influenced by long‐term tillage management. For fallow, winter wheat, adzuki bean, and sugar beet treatments, the CH4 uptake rates in the CT soils (1.36 kg CH4 ha−1 yr−1), which had a 20‐year history of intensive plowing, were lower than those in the RT soils (2.40 kg CH4 ha−1 yr−1). Thus RT production systems improved CH4 uptake by arable soils, although they adversely affected N2O emissions for adzuki bean and sugar beet production.

Management of N mineralization from crop residues of high N content using amendment materials of varying quality

Abstract. A potential technique for reducing overwinter leaching from high N containing crop residues is to immobilize the N released during decomposition by co‐incorporating materials of a wider C : N ratio. This article describes the use of laboratory incubation experiments to investigate the effects of a wide range of such amendment materials on the mineralization of N from sugar beet and brassica leaf residues in a sandy loam and a silt loam. These materials were of varying quality, with C : N ratio ranging from 15 : 1 to 520 : 1, and cellulose content from 0 to 34%. Amendments were added at a fixed rate of 3.5 mg C g−1 of dry soil, equivalent to around 10 t ha−1 C (to 20 cm depth). The soils were then incubated at 15°C, and net mineral N derived from the leaves was measured at regular intervals over 168 days. Net mineralization of residue N was greatest with molasses (C : N ratio of 18 : 1), whereas paper waste (C : N ratio of 520 : 1) reduced N mineralized by up to 90% compared with a soil‐only control. As the concentration of cellulose and lignin in the amendment materials increased, so the amounts of N mineralized decreased, with 62 and 54% of variance in N mineralized explained by cellulose and lignin content, respectively. Reduced levels of mineral N were associated with higher levels of biomass‐N. The levels of N2O‐N lost from sugar beet residues on day 14 were significantly reduced from 66 to 5 g ha−1 where compactor (cardboard) waste had been mixed into sandy loam, but this effect was not observed in the silt loam. These techniques could lead to greater efficiency of N use in rotations through reduction in N losses, and provide alternative routes for disposal of wastes when the EC Landfill Directive is implemented.

Growth and phosphorus uptake of maize cultivated alone, in mixed culture with other crops or after incorporation of their residues

AbstractIntercropping or rotating of P‐efficient crop species which mobilize sparingly soluble P by their root exudates can have beneficial effects on growth and P uptake of P‐inefficient species. We aimed at studying the effect of intercropping or incorporating of crop residues of P‐efficient crops on the components of maize P‐uptake, i.e. the root‐system size and P influx (P‐uptake rate per unit root length). This was studied in 3 pot experiments in a low‐P sandy soil. In the first experiment, maize was intercropped with white lupine, sugar beet or oilseed rape, and with groundnut in the second experiment. In the third experiment, maize was grown after incorporating the crop residues of white lupine, sugar beet or oilseed rape. Maize growth and yield was strongly inhibited when intercropped with white lupine, sugar beet or oilseed rape, probably because of competition for nutrients. But with groundnut as the accompanying species, maize yield was increased by a factor of 3, mainly because of an enhanced P influx. Crop residues of oilseed rape and sugar beet increased the yield of maize by factors 2 and 1.6, respectively, because of a 3 and 2 times higher P uptake as compared to maize grown after maize without incorporation of crop residue. The reason for the higher maize P‐uptake after oilseed rape was an 11 times higher P influx as compared to maize without crop residues, and after sugar beet residues because of an enhanced root growth and a 4 times higher P influx. Lupine residues did not improve maize growth, mainly because of a low P influx, which was even less than that of maize grown without crop residues. The soil solution P concentration and calcium acetate lactate‐extractable P (CAL P) measured in this study did not reflect the P availability as indicated by the plants (P uptake, P influx). This indicates that other mechanisms such as P mobilization in the rhizosphere by root exudates or cell‐wall components were responsible for the increased P availability. These mechanisms need further investigation.

Reduced Ammonia Emissions from Slurry after Self-Acidification with Organic Supplements

Ammonia volatilisation from field applied slurries causes environmental hazards and loss of fertilizer value. Acidification of slurry, usually with inorganic or organic acids has previously been used to reduce NH3 emissions. In this study, we present an alternative technique for the acidification of slurry, namely the use of fermentation by endogenous microbes to form organic acids from readily degradable organic compounds. In laboratory experiments, the addition of different sugars (sucrose in dosages of 0.003, 0.01, 0.03, 0.1 and 0.3 mol l−1, glucose in dosages of 0.05 and 0.1 mol l−1) and organic residues (sugar beet residues in dosages of 33 and 330 g fresh weight l−1, biowaste at 50 g fresh weight l−1) to cattle slurry resulted in a considerable decrease in pH, with a minimum pH of 4.7. A subsequent pH increase indicated that the organic acids were probably further degraded with a resultant loss of acidity in the slurry. In a field study, the NH3 emissions from untreated and acidified (pH = 6) slurries were compared after field application (20 m3 ha−1). During the first 20 hours, the acidified slurry showed NH3 emissions of less than 5% of the applied ammonia compared to a 26% loss from the untreated slurry. The total emissions of NH4 +-N were 32% for acidified and 54% for untreated slurry. Easily degradable organic amendments therefore have the potential to effectively reduce NH3 emissions from slurries and may be an alternative for the use of acids.

Nitrous oxide emission from soils amended with crop residues

Crop residues incorporated in soil are a potentially important source of nitrous oxide (N2O), though poorly quantified. Here, we report on the N2O emission from 10 crop residues added to a sandy and a clay soil, both with and without additional nitrate (NO3). In the sandy soil, total N2O emission from wheat, maize, and barley residues was not significantly different from the control. The total N2O emission from white cabbage, Brussels sprouts, mustard, sugar beet residues and broccoli ranged from 0.13 to 14.6 % of the amount of N added as residue and were higher with additional NO3 than without additional NO3. In the clay soil, similar effects of crop residues were found, but the magnitude of the N2O emission was much smaller than that in the sandy soil: less than 1 % of the residue N evolved as N2O. The C-to-N ratio of the residue accounted for only 22–34% and the mineralizable N content of the residue for 18–74% of the variance in N2O emission. We suggest that the current IPCC methodology for estimating N2O emission from crop residues may be considerably improved by defining crop specific emission factors instead of one emission factor for all crop residues.