Effects of Turning Frequency,Leaves to Grass Mix Ratio and Windrow vs. Pile Configuration on the Composting of Yard Trimmings

Because of proposed bans on the landfilling and incineration of leaves, grass and brush, large-scale composting is fast becoming the primary disposal option for yard trimmings in many states. Few systematic studies have been done to compare the effects of turning regime, feedstock mix ratio, or windrow vs. pile configuration on composting and the characteristics of finished compost. In this study, various ratios of leaves, grass and brush were mixed and composted in two series of windrows; and one set of static piles. One windrow series (#1) was turned seven times every four weeks, while the other windrow series (#2), and the piles, were turned once every four weeks. The effects of the different treatments were examined by measuring compost temperature, oxygen concentration, pH, organic matter and moisture content, volatile fatty acid content, bulk density, stability, humification and seed germination indices, total and available nutrient levels, and particle size distribution. Results showed that turning frequency had little impact on oxygen concentrations, VFA content and temperatures during the composting of yard trimmings in windrows, however, in piles temperatures were substantially higher and oxygen concentrations fluctuated greatly. The composts from all the treatments were stable, (oxygen uptake rates < 0.1 mg O₂/g OM/hr) after 60 days of composting regardless of the turning frequency, mix ratio or configuration. The bulk density inereased much more rapidly in frequently turned windrows than in the other treatments and particle sizes were smaller in these windrows. In most respects however, the final composts (day 136) were remarkably similar and none inhibited Cress seed germination or root elongation. The pH of all the composts, and the soluble salts and nitrate levels in composts made with high levels of grass, exceeded guidelines for greenhouse growth media.     

Cocomposting of Beet Vinasse and Grape Marc In Windrows and Static Pile Systems

Two composts were obtained by cocomposting a concentrated depotassified beet vinasse and grape marc using an aerated static pile and a windrow system. The composting mixtures comprised grape marc (83%) and vinasse (17%) for the aerated static pile system and grape marc (77%), vinasse (20%) and phosphate rock (3%) for the windrow. Changes in temperature followed a similar path for both mixtures, however the thermophilic phase was longer in the aerated static pile (25 days) than in the windrow (10 days). This fact caused differences in both organic matter degradation, weight losses (21% for static pile and 10% for windrow) and gas losses during the process. Nevertheless, the composts obtained by the two systems had a high fertilizer nutrient value (18.2 g kg^?1 N; 3.1 g kg^?1 P; 13.6 g kg^?1 K, C/N 16.1 for compost obtained in static pile and 20.6 g kg^?1 N; 13.7 g kg^?1 P; 13.1 g kg^?1 K; C/N 18 for compost obtained in windrow). A high degree of stability was reached in both composting systems (124 cmol_c kg^?1 CEC for static pile and 153 cmolc kg^?1 CEC for windrow at 80 days of composting). The chemical and physical properties of both vinasse composts suggest their possible use as soil conditioner.     

Nitrogen mineralization in boreal forest stands of isle royale,Northern Michigan

The correlation of soil temperature and moisture with inorganic N concentrations and net mineralization beneath major species types in mature boreal and northern hardwood forests was examined over a two year period. Soils beneath species types where the canopy was dominated byBetula papyrifera, Picea glauca, Alnus rugosa or, in northern hardwoods,Acer saccharum were studied. Net NO₃ ^? mineralization varied by species type and net total inorganic nitrogen (N) mineralization varied by month and the interaction of species type with month. Soil NO₃ ^? concentration and NO₃ ^? mineralization were correlated for spruce, and inversely correlated for alder and maple. Soil NH₄ ⁺ concentration and NH₄ ⁺ mineralization were inversely correlated for alder and maple. In laboratory temperature and moisture treatments of birch, spruce and maple soils, NH₄ ⁺ and total inorganic N-mineralization increased with temperature. The response to moisture was most evident for NO₃ ^? mineralization in maple soils.     

Recycling of Two-Phase Olive-Mill Cake “Alperujo” by Co-composting with Animal Manures

The use of poultry manure or goat/sheep manure in the co-composting of the two-phase olive-mill cake “alperujo” (ALP) with olive leaf (OL) is compared by studying organic-matter mineralization and humification processes during composting and the characteristics of the end products. For this, two different piles (P1 and P2) were prepared using ALP with OL mixed with poultry manure (PM) and goat/sheep manure (GSM), respectively, and composted by the turned windrow composting system. Throughout the composting process, a number of parameters were monitored, such as temperature, pH, electrical conductivity (EC), organic matter (OM), OM losses, total organic carbon (C_org), total nitrogen (N_t), C_org/N_t ratio, and the germination index (GI). In both piles, the temperature exceeded 55 °C for more than 2 weeks, which ensured maximum pathogen reduction. Organic-matter losses followed a first-order kinetic equation in both piles. The final composts presented a stabilized OM and absence of phytotoxins, as observed in the evolution and final values of the C_org/N_t ratio (C_org/N_t < 20) and the germination index (GI > 50 percent). Therefore, composting can be considered as an efficient treatment to recycle this type of waste, obtaining composts with suitable properties that can be safely used in agriculture.     

Transformations of carbon and nitrogen during composting of animal manure and shredded paper

Composts produced from animal manures and shredded paper were characterized in terms of their carbon (C) and nitrogen (N) forms and C mineralization. Total, water-soluble, acid-hydrolyzable and non-hydrolyzable C and N contents were determined on composts sampled on days 0, 11, 18, 26, 33, 40 and 59 after composting was initiated. Water-soluble and acid-hydrolyzable C and N decreased during composting, whereas non-hydrolyzable C remained relatively constant, and non-hydrolyzable N greatly increased during composting. The water-soluble forms of N were characterized by a decrease of ammomium (NH₄ ⁺-N) at the beginning of composting, followed by an increase of nitrate (NO₃ ^–-N) towards the end of composting. The mineralization of C in composted materials was generally higher at the beginning than at the end of composting, whereas no differences were observed for mineralization of C in non-hydrolyzable materials. The addition of N inhibited C mineralization in composts except in samples collected on days 40 and 59, while C mineralization was strongly stimulated by adding N to the non-hydrolyzable materials. The data suggest that the N forms in the non-hydrolyzable materials were chemically similar and not readily available to microbes, indicating that the C/N ratios often used to assess the biodegradability of organic matter and to develop compost formulations should be based on biologically available N and C and not on total N and C. Received: 12 May 1997     

Mass and Nutrient Losses During the Composting Of Dairy Manure Amended with Sawdust or Straw

Composting has become an increasingly popular manure management method for dairy farmers. However, the design of composting systems for farmers has been hindered by the limited amount of information on the quantities and volumes of compost produced relative to farm size and manure generated, and the impact of amendments on water, dry matter, volume and nitrogen losses during the composting process. Amendment type can affect the free air space, decomposition rate, temperature, C:N ratio and oxygen levels during composting. Amendments also initially increase the amount of material that must be handled. A better understanding of amendment effects should help farmers optimize, and potentially reduce costs associated with composting. In this study, freestall dairy manure (83% moisture) was amended with either hardwood sawdust or straw and composted for 110-155 days in turned windrows in four replicated trials that began on different dates. Initial C:N ratios of the windrows ranged from 25:1 to 50:1 due to variations in the source and N-content of the manure. Results showed that starting windrow volume for straw amended composts was 2.1 to 2.6 times greater than for sawdust amendment. Straw amended composts had low initial bulk densities with high free air space values of 75-93%. This led to lower temperatures and near ambient interstitial oxygen concentrations during composting. While all sawdust-amended composts self-heated to temperatures >55°C within 10 days, maintained these levels for more than 60 days and met EPA and USDA pathogen reduction guidelines, only two of the four straw amended windrows reached 55°C and none met the guidelines. In addition, sawdust amendment resulted in much lower windrow oxygen concentrations (< 5%) during the first 60 days. Both types of compost were stable after 100 days as indicated by CO₂ evolution rates <0.5 mg CO₂-C/g VS/d. Both types of amendments also led to extensive manure volume and weight reductions even after the weight of the added amendments were considered. However, moisture management proved critical in attaining reductions in manure weight during composting. Straw amendment resulted in greater volume decreases than sawdust amendment due to greater changes in bulk density and free air space. Through composting, farmers can reduce the volume and weights of material to be hauled by 50 to 80% based on equivalent nitrogen values of the stabilized compost as compared to unamended, uncomposted dairy manure. The initial total manure nitrogen lost during composting ranged from 7% to 38%. P and K losses were from 14 to 39% and from 1 to 38%, respectively. There was a significant negative correlation between C:N ratio and nitrogen loss (R₂=0.78) and carbon loss (R₂=0.86) during composting. An initial C:N ratio of greater than 40 is recommended to minimize nitrogen loss during dairy manure composting with sawdust or straw amendments.     

Characteristics of Composts Derived from Waxed Corrugated Cardboard

The characteristics of 12 composts containing, by volume, spent mushroom substrate (SMS, 50 percent), waste waxed corrugated cardboard (WCC, 0 percent, 25 percent or 50 percent), and/or pulverized wood wastes (WW, 50 percent, 25 percent or 0 percent) were measured during two separate windrow composting periods (12-16 weeks). Supplemental N was added to some of the composts in the form of poultry manure, and/or soybean processing wastes. During the first eight to 10 weeks, composts containing 50 percent WCC tended to reach and maintain the highest temperatures, but subsequently cooled most rapidly. Microbial activity (CO₂ evolution) also was initially highest in these composts but fell by the twelfth week to levels comparable to composts containing lower levels of WCC. The paraffin wax in WCC containing composts was almost completely degraded (>95 percent). After 12 weeks of composting N (1.2-1.6 percent DW), P (0.30-0.55 percent), and K (0.9-1.2 percent) concentrations were within typical ranges and N and P were highest in composts containing 50 percent WCC. KC1 extractable NH₄-N (494 mg-N kg^?1) and NO₃+NO₂-N (281 mg-N kg^?1) were highest and lowest, respectively, in composts containing 50 percent WCC. Electrical conductivity (4.5-8.5mS/cm) and pH (7.5-8.5) were high in all composts and highest in composts with 50 percent WCC. Concentrations of phenolic compounds were highest in composts containing 50 percent WCC, manure, and soybean wastes and were positively correlated with NH₄-N. C:N ratios of all composts were within an acceptable range (18-23:1).     

Nitrous oxide flux from soil amino acid mineralization

Nitrous oxide (N₂O) is a greenhouse gas produced during microbial transformation of soil N that has been implicated in global climate warming. Nitrous oxide efflux from N fertilized soils has been modeled using NO₃⁻ content with a limited success, but predicting N₂O production in non-fertilized soils has proven to be much more complex. The present study investigates the contribution of soil amino acid (AA) mineralization to N₂O flux from semi-arid soils. In laboratory incubations (−34 kPa moisture potential), soil mineralization of eleven AAs (100 μg AA-N g⁻¹ soil) promoted a wide range in the production of N₂O (156.0±79.3 ng N₂O-N g⁻¹ soil) during 12 d incubations. Comparison of the δ¹³C content (‰) of the individual AAs and the δ¹³C signature of the respired AA-CO₂-C determined that, with the exception of TYR, all of the AAs were completely mineralized during incubations, allowing for the calculation of a N₂O-N conversion rate from each AA. Next, soils from three different semi-arid vegetation ecosystems with a wide range in total N content were incubated and monitored for CO₂ and N₂O efflux. A model utilizing CO₂ respired from the three soils as a measure of organic matter C mineralization, a preincubation soil AA composition of each soil, and the N₂O-N conversion rate from the AA incubations effectively predicted the range of N₂O production by all three soils. Nitrous oxide flux did not correspond to factors shown to influence anaerobic denitrification, including soil NO₃⁻ contents, soil moisture, oxygen consumption, and CO₂ respiration, suggesting that nitrification and aerobic nitrifier denitrification could be contributing to N₂O production in these soils. Results indicate that quantification of AA mineralization may be useful for predicting N₂O production in soils.     

Composting Olive Mill Waste and Sheep Manure For Orchard Use

An industrial-scale composting plant has been designed for producing organic fertilizers from olive mill waste using the windrow pile system. Materials to be composted, two phase olive mill waste (TPOMW) and sheep litter (SL), were characterized and made into three piles consisting of different proportions of each. Throughout the composting process, temperature (T), moisture (M), organic matter (OM), total organic carbon (C_org), total nitrogen (NT), germination index (GI), pH and electrical conductivity (EC) were monitored. The potential agronomic value of the final composts was ascertained by analyzing the bulk density, OM and Corg concentration, pH, EC, macro and micronutrient content (N, P, K, Ca, Mg, Fe, Cu, Mn, Zn, B), the concentration of humic and fulvic acids and inorganic nitrogen (NH₄⁺,NO₂^?,NO₃^?). Each compost was applied to an area of one hectare within a six year-old olive plantation. Four months after application, the soils showed an increased OM concentration and cationic exchange capacity (CEC).     

Compost Maturity Effects on Nitrogen and Carbon Mineralization and Plant Growth

Improved predictive relationships between compost maturity and nitrogen (N) availability are needed. A total of 13 compost samples were collected from a single windrow over a 91 d period. Compost stability and maturity were assessed using both standard chemical analyses (total C and N, mineral N, total volatile solids) and other methods (CO₂ evolution, commercial maturity kits, and neutral detergent fiber, and lignin). Compost N and carbon (C) were evaluated during a 130 d aerobic incubation in a sandy loam soil after each compost was applied at 200 mg total kg^?1 soil. The effect of compost maturity on plant growth was evaluated by growing two ryegrass (Lolium perenne L.) crops and one barley (Hordeum vulgare L.) crop in succession in compost-amended soil under greenhouse conditions. Potential phytotoxicity from compost was assessed by growing tomato (Lypersicum esculentum L.) seedlings in compost-amended soil. Regression and correlation analyses were used to evaluate the relationship between compost maturity parameters, the rate and extent of net N and C mineralization, plant yield and N uptake, and phytotoxicity. Commonly used maturity parameters like total C, total N, and C:N ratio were poorly correlated with the rate and extent of mineralization, and with plant growth parameters. The N mineralization rate during the first 48 d of aerobic incubation was strongly correlated (r= ?0.82 to ?0.86) to compost fiber and lignin concentration, and to the Maturity Index (r=0.85). Trends in C mineralization were similar. There were few differences in C mineralization between composts after 48 d of aerobic incubation in soil. Ryegrass harvested 35 and 70 d after compost application was not strongly affected by compost maturity, and relatively immature composts were phytotoxic to tomato seedlings. Methods of characterizing compost maturity and stability that more realistically reflect the composting process are better predictors of N release and potential plant inhibition after incorporation into soil.     

The relationships among microbial parameters and the rate of organic matter mineralization in forest soils,as influenced by forest type

Vegetation type influences the rate of accumulation and mineralization of organic matter in forest soil, mainly through its effect on soil microorganisms. We investigated the relationships among forest types and microbial biomass C (MBC), basal respiration (R_B), substrate-induced respiration (R_S), N mineralization (N_min), specific growth rate μ, microbial eco-physiology and activities of seven hydrolytic enzymes, in samples taken from 25 stands on acidic soils and one stand on limestone, covering typical types of coniferous and deciduous forests in Central Europe. Soils under deciduous trees were less acidic than soils of coniferous forests, which led to increased mineralizing activities R_B and N_min, and a higher proportion of active microbial biomass (R_S/MBC) in the Of horizon. This resulted in more extractable organic C (0.5 M K₂SO₄) in soils of deciduous forests and a higher accumulation of soil organic matter (SOM) in coniferous forest soil. No effect of forest type on the microbial properties was detected in the Oh horizon and in the 0–10 cm layer. The microbial quotient (MBC/C_org), reflecting the quality of organic matter used for microbial growth, was higher in deciduous forests in all three layers. The metabolic quotient qCO₂ (R_B/MBC) and the specific growth rate μ, estimated using respiration growth curves, did not differ in soils of both forest types. Our results showed that the quality of SOM in coniferous forests supported microorganisms with higher activities of β-glucosidase, cellobiosidase and β-xylosidase, which suggested the key importance of fungi in these soils. Processes mediated by bacteria were probably more important in deciduous forest soils with higher activities of arylsulphatase and urease. The results from the stand on limestone showed that pH had a positive effect on microbial biomass and SOM mineralization.     

Greenhouse gas emissions and carbon sink capacity of amended soils evaluated under laboratory conditions

Soil sequestration of atmospheric CO₂ through land application of organic residues may have beneficial effects as a strategy to offset the increase in the concentration of greenhouse gases (GHG) in the atmosphere. The significance of different variables on GHG production and soil C sink capacity was investigated by monitoring CO₂ and N₂O fluxes from amended soils under laboratory conditions. In the first experiment, the effects of the chemical composition and complexity of three N-rich organic fertilisers (blood meal, hydrolysed leather, and hoof and horn meal) on the CO₂ and N₂O productions were studied. A second experiment was aimed at evaluating the effects of the degree of transformation of composts prepared from two-phase olive mill waste on soil C sink capacity. The three N-rich organic fertilisers caused different CO₂ and N₂O evolution patterns in the amended soils, despite their similar elemental composition. The total amount of added C that was mineralised in the soil ranged from 10.4% to 15.5%, while N₂O-N originating from horn and hoof meal was 6 and 13 times higher than that coming from hydrolysed leather and blood meal, respectively. Mineralisation of the C added to the soil was inversely correlated to the degree of stabilisation of the composting mixtures. Soils amended with the initial composting mixture evolved from 2 to 7.3 times more CO₂-C than the soil amended with the more stabilised compost. However, the C conservation efficiency of organic residues, calculated by the combined losses during composting, and after land application, was higher for the less transformed organic materials. Both studies showed the key importance of the variables studied on the GHG emissions and C sink efficiency of amended soils under controlled conditions. Laboratory experiments could be a useful tool to assist in the designing of field scale experiments for an effective quantification and monitoring of the overall changes in soil C and N pools.     

Effects of soil moisture on gross N transformations and N2O emission in acid subtropical forest soils

Soil moisture changes, arising from seasonal variation or from global climate changes, could influence soil nitrogen (N) transformation rates and N availability in unfertilized subtropical forests. A ¹⁵?N dilution study was carried out to investigate the effects of soil moisture change (30–90 % water-holding capacity (WHC)) on potential gross N transformation rates and N₂O and NO emissions in two contrasting (broad-leaved vs. coniferous) subtropical forest soils. Gross N mineralization rates were more sensitive to soil moisture change than gross NH₄ ⁺ immobilization rates for both forest soils. Gross nitrification rates gradually increased with increasing soil moisture in both forest soils. Thus, enhanced N availability at higher soil moisture values was attributed to increasing gross N mineralization and nitrification rates over the immobilization rate. The natural N enrichment in humid subtropical forest soils may partially be due to fast N mineralization and nitrification under relatively higher soil moisture. In broad-leaved forest soil, the high N₂O and NO emissions occurred at 30 % WHC, while the reverse was true in coniferous forest soil. Therefore, we propose that there are different mechanisms regulating N₂O and NO emissions between broad-leaved and coniferous forest soils. In coniferous forest soil, nitrification may be the primary process responsible for N₂O and NO emissions, while in broad-leaved forest soil, N₂O and NO emissions may originate from the denitrification process.     

Effect of organic residue amendment on mineralization of nitrogen in flooded rice soils under laboratory conditions

Abstract

This study was undertaken to assess the mineralization of nitrogen (N) in rice soils amended with organic residues under flooded condition. A lab incubation study with a 3x3 factorial design (two replications) was conducted with three rice soils (Joydebpur, Faridpur, and Thakurgaon) receiving the following treatments: 1) control, 2) rice straw (Oryza sativa L.), or 3) pea vine (Pisum sativum L.). The organic residue (25 mg straw g^‐1 soil) was mixed with soil and glass beads (1:1, soil to beads ratio), and transferred into a Pyrex leaching tube, flooded and then incubated at 35°C for up to 12 weeks. The soils in the leaching tubes were leached (while maintaining flooded condition) at 1,2,4, 8, and 12 weeks with deionized water for determination of NH₄‐N, NO₃‐N, pH, and Eh. Nitrogen mineralization in soils amended with rice straw was somewhat different than that of soils treated with pea vine. Soil treated with rice straw had a higher N mineralization rate than soils treated with pea vine, which was due to a lower carbon (C):N ratio for rice straw. The potentially mineralizable N pool (N_o) in soils amended with rice straw and pea vine under flooded conditions, estimated using a 1st order exponential equation, were 7 to 15 times, and 3 to 9 times greater for rice straw N_o values and pea vine, respectively, than the control. The K_N values for unamended soils ranged from 0.35 to 0.52 mg N kg^‐1 wk^‐1 and rice straw and pea vine treated soils were from 0.75 to 1.22 and 0.46 to 0.58 mgN kg^‐1 wk^‐1. The lower N_o and K_N values in pea vine treatments suggested there was greater immobilization of N than in rice straw treatments.     

Changes in maturity indicators during the degradation of organic wastes subjected to simple composting procedures

Selected maturity indicators were monitored over a period of 335 days during the degradation of organic wastes subjected to four simple composting procedures, which varied in raw material (garden refuse with and without market refuse) and turning frequency (0×, 6×). All procedures produced mature composts. The inclusion of market refuse and frequent turning generally increased the cation exchange capacity of compost on an ash-free basis. Until day 118 of the composting process, compost samples which contained market refuse in their raw material mixture had the lowest redox potentials after anaerobic incubation. Cress grown on these composts also produced the lowest fresh mass. At a later stage of the composting process, the same composts displayed increased cellulolytic activity. Frequent turning of the compost heaps resulted in greater fluorescein diacetate hydrolysis, a greater occurrence of low-molecular-weight humic compounds and, occasionally, an inhibition of cellulolytic activity. The arginine ammonification assay gave information on the N-status of the composts, rather than on the compost maturity, and suggested that all the composts could be safely applied to soil with no risk of microbial immobilisation of soil N.     

Use of mineralization kinetics to estimate the potentially mineralizable nitrogen of rock phosphate-enriched composts-amended soil

Predicting nitrogen (N) mineralization has been one of the greatest challenges to improving N management in agriculture. A laboratory incubation experiment was conducted to study the N mineralization of soil amended with rock phosphate (RP)-enriched composts. The RP-enriched rice straw compost amended soil mineralized highest N as compared to compost prepared from mustard stover and tree leaves. The first-order model was found to be the most suitable for N because it provided the best fit to the experimental data and for its simplicity. The model predicted that potentially mineralized N (N₀) was varied from 4.0 to 52.1 mg kg^?1 and the mineralization rate k varied from 0.015 to 0.066 day^?1. The rice straw compost amended soil had higher N₀ value than mustard stover and tree leaves compost amended soil. This study demonstrated the importance of application of rock phosphate-enriched composts in improving N supplying capacity of soil.     

N mineralization process of the surface soils under shifting cultivation in northern Thailand

N mineralization process (ammonification plus nitrification) in the surface 0-5 cm soil layers under shifting cultivation in northern Thailand was studied. Labile pool of organic matter extracted with a K₂S0₄ solution at 1l0°C in an autoclave (fraction A) or by shaking at room temperature (fraction B) was used as factor to evaluate the N mineralization process which was examined in an incubation experiment. In the soils, in which the N mineralization pattern was fitted to a first order kinetics model, the content of (organic + NH₄ ⁺)-N in fraction B determined the initial rate of N mineralization. The soils, which showed a short lag time of less than 7 d both in the N mineralization and nitrification processes, had a high ratio of organic C to (organic + NH₄ ⁺)-N in fraction B, exceeding the value of 7. The soils, which showed a long lag time of more than 7 d only in the nitrification process, had a low pH(KCI) (less than 4.2). Thus, the rate of N mineralization was affected by the labile pool in fraction B or soil pH. On the other hand, there was a correlation between the N ₀ + N _max (inorganic N at 0 d + maximum amount of mineralizable N) value and the labile pool in the fraction A, suggesting that the N ₀ + N _max value depended on the contents of the labile pool.     

Chemical Amendments and Process Controls To Reduce Ammonia Volatilization During In-House Composting

Composting inside high-rise, caged layer facilities can produce atmospheric ammonia (NH₃) concentrations exceeding standards for human and poultry health. Control measures that reduce NH₃ volatilization are necessary for in-house composting to be sustainable. Due to differences specific to in-house composting — low carbon to nitrogen ratios of composting material, continuous manure addition, and frequent turning — it is not known whether NH₃ control measures used previously for poultry manure will work. The objectives of this study were to evaluate various amendment and process controls on NH₃ produced during simulated in-house composting in the lab, and to evaluate select chemical control measures during composting inside a high-rise layer facility. Ten amendments (aluminum sulfate; chloride salts of aluminum, calcium, magnesium, and potassium; gypsum; sodium bisulfate; zeolite (clinoptilolite); straw; and cellulose) and four process controls (moisture; temperature; turning frequency; and particle size) were evaluated in lab incubations in 1 L vessels wherein samples of poultry manure compost were incubated to simulate composting. Vials of boric acid solution were used to capture NH₃ evolved during incubations. With the exception of zeolite and cellulose, all amendments reduced NH₃ capture. Low moisture and temperature also reduced NH₃ capture, although managing temperature and moisture to achieve low NH_g would adversely impact microbial activity and other desired benefits of composting. When evaluated inhouse, aluminum sulfate, calcium chloride and magnesium chloride did not reduce NH evolution from compost measured on three different dates with a gas sensor. Spatial variability along treated segments of windrow apparently masked amendment effects. At the end of a six-week composting cycle, total nitrogen content was higher in compost treated with aluminum sulfate than control or chloride salt treatments. Aluminum sulfate and process controls such as moisture content, carbon source and particle size have potential to reduce NH₃ loss from poultry manure composted inside high-rise layer structures. In-house compost management to reduce NH₃ volatilization must consider the cost of amendments, effectiveness, and impacts on the composting process.     

Initial recovery of soil carbon and nitrogen pools and dynamics following disturbance in jack pine forests: A comparison of wildfire and clearcut harvesting

Forests naturally maintained by stand-replacing wildfires are often managed with clearcut harvesting, yet we know little about how replacing wildfire with clearcutting affects soil processes and properties. We compared the initial recovery of carbon (C) and nitrogen (N) pools and dynamics following disturbance in jack pine (Pinus banksiana) stands in northern Lower Michigan, USA, by sampling soils (Oa+A horizons) from three “treatments”: 3-6-year-old harvest-regenerated stands, 3-6-year-old wildfire-regenerated stands and 40-55-year-old intact, mature stands (n=4 stands per treatment). We measured total C and N; microbial biomass and potentially mineralizable C and N; net nitrification; and gross rates of N mineralization and nitrification. Burned stands exhibited reduced soil N but not C, whereas clearcut and mature stands had similar quantities of soil organic matter. Both disturbance types reduced microbial biomass C compared to mature stands; however, microbial biomass N was reduced in burned stands but not in clearcut stands. The experimental C and N mineralization values were fit to a first-order rate equation to estimate potentially mineralizable pool size (C₀ and N₀) and rate parameters. Values for C₀ in burned and clearcut stands were approximately half that of the mature treatment, with no difference between disturbance types. In contrast, N₀ was lowest in the wildfire stands (170.2 μg N g⁻¹), intermediate in the clearcuts (215.4 μg N g⁻¹) and highest in the mature stands (244.6 μg N g⁻¹). The most pronounced difference between disturbance types was for net nitrification. These data were fit to a sigmoidal growth equation to estimate potential NO₃⁻ accumulation (Nit_max) and kinetic parameters. Values of Nit_max in clearcut soils exceeded that of wildfire and mature soils (149.2 vs. 83.5 vs. 96.5 μg NO₃⁻-N g⁻¹, respectively). Moreover, the clearcut treatment exhibited no lag period for net NO₃⁻ production, whereas the burned and mature treatments exhibited an approximate 8-week lag period before producing appreciable quantities of NO₃⁻. There were no differences between disturbances in gross rates of mineralization or nitrification; rather, lower NO₃⁻ immobilization rates in the clearcut soils, 0.20 μg NO₃⁻ g⁻¹ d⁻¹ compared to 0.65 in the burned soils, explained the difference in net nitrification. Because the mobility of NO₃⁻ and NH₄⁺ differs markedly in soil, our results suggest that differences in nitrification between wildfire and clearcutting could have important consequences for plant nutrition and leaching losses following disturbance.     

Optimization of Medlar Pruning Waste Composting Process by Cattle Manure Addition

In this study, medlar pruning waste (MPW) was composted with and without cattle manure (CM). Two piles were prepared: one contained only MPW (pile 1) and one contained MPW augmented with CM (pile 2). Both piles were composted in an enclosed composting vessel with passive aeration and aeration by turning. During the composting process, temperature, pH, electrical conductivity (EC), organic matter (OM), OM losses, total organic carbon (C_org), total nitrogen (N_T), C_org/N_T ratio, and germination index (GI) were measured. Pile 2 produced a faster increase of the temperature and had a longer thermophilic phase than pile 1. However, the rate of OM degradation was faster in pile 1 than in the pile containing CM (pile 2). The addition of CM also resulted in an increased pH and salt content. In both piles, C/N ratio decreased throughout the process, presumably as a result of the faster organic carbon degradation compared to N mineralization. However, only pile 2 had a final C/N ratio <20, the limit accepted for compost by the Spanish legislation on fertilizer. Also, both composts had GI > 50 percent, indicating an absence of phytotoxicity.