Use of Raw and Composted Paper Sludge as a Soil Additive or Mulch for Cottonwood Plants

Pulp and paper sludge is a by-product of paper production and may be suitable in agricultural applications as a soil amendment or mulch. The objective of this study was to evaluate raw and composted pulp and paper sludge as soil additives or mulches for cottonwood plants. Primary sludge, a combination of by-products from bleached kraft and neutral sulfite semichemical paper, was mixed with tailings, slaughterhouse paunch, and 10 percent wood ash (by volume), and used raw or composted and cured in the field for 39 weeks. Cuttings of two cottonwood (Populus deltoides Bartr. ex Marsh) clones were planted in a field soil (Quincy loamy fine sand) that was mixed (incorporated) or mulched (placed on top the soil) with raw or composted sludge mixtures at application rates of 0,45,90, 135 and 180 Mg/ha. The plants were grown in a plastic house for nine weeks. Electrical conductivity (EC), cation exchange capacity (CEC), soluble Cl and extractable Na in soil amended with 180 Mg/ha of compost were 37, 22, 197 and 138 percent higher, respectively, than those of soil amended with the raw sludge mixture at the same rate. Bulk density of amended soil decreased, whereas soil aeration and water-holding capacity increased as sludge application rate increased. After nine weeks, raw or composted sludge applied at a rate of 135 Mg/ha, whether used as a mulch or incorporated, improved cottonwood plant height by 40 percent and stem diameter by 20 percent compared to plants grown in nonamended, nonmulched (control) soil. These results indicate that the pulp and paper sludge mixtures, whether raw or composted, improved soil characteristics and aided establishment of cottonwood cuttings.     

Compost Recycling of Wood Fiber Waste Produced by Paper Manufacture

The composting of wood fiber waste from the manufacture of newsprint is described, with a mixture of wood fiber waste:sewage sludge at a ratio of 1:1 giving best results in a trial of shoot growth of Pinus radiata. An alternative chemical nutrient amendment (initial C:N ratio of 60:1) gave a plant response which was not significantly different to that of sewage sludge. Over a five month period volume reductions of up to 39 percent were observed in the composts, providing potential savings in subsequent transport operations. Use of uncomposted materials or addition of fly- or screen-ash compost amendment (12.5 percent or 25 percent v /v) was inhibitory to plant growth. Concentrations of some heavy metals in Hobart city sewage (particularly of chromium) were high, precluding its long-term use as a soil nutrient supplement. In view of the high heavy metal content of sewage sludge and its high volume to nutrient ratio, it was concluded that composting with chemical amendment was the preferred option for future investigation. Such composts would require ash amendment (or lime equivalent) at concentrations lower than those used in this study to counter acidity produced during composting.     

Wood Ash as an Amendment in Municipal Sludge And Yard Waste Composting Processes

Wood ash from a wood-fired, electrical generating plant was examined as a potential amendment in municipal biosolids and yard waste composting applications. The rate of composting and the final compost quality (chemical, physical, and plant growth characteristics) were examined. Yard waste (leaves, grass, and wood chips) and a municipal biosolids-chip mixture were either not amended or amended with wood ash at eight percent or five percent by weight, respectively, and then composted outdoors in insulated, 1700L, aerated reactors. Yard waste piles heated rapidly to 60°C within six to seven days, whereas biosolid piles heated more slowly to a maximum of 52 to 57°C within nine to 11 days. Ash had little, if any, effect on the time-temperature response. In general, ash-amended compost had higher pi I, plant nutrient, and salt contents. Tomato plants (Lycopersicum esculentum) produced 100 percent more shoot biomass in biosolids than in yard waste compost media. Poor plant growth in the yard waste compost was likely due to the high initial pH and salt content of the growth medium. In yard waste media, tomato plants germinated and produced more shoot biomass in the control compost than in the ash-amended compost.

A pH neutralization study indicated that wood fly ash could be used as an economical substitute for lime which is commonly used to stabilize municipal biosolids prior to land filling or land application. Wood fly ash (pH = 13.2-13.4), when added to biosolids at a 2 to 1 ratio by weight, raised the pH of the mixture to 12.0.     

Paper Mill Sludge Composting and Compost Utilization

Economically viable and environmentally acceptable methods to recycle organic wastes are needed by the pulp and paper industry. We assessed the potential for composting the Virginia Fibre Corporation's (VFC) combined primary and secondary dewatered paper mill sludge (PMS) and evaluated the suitability of the finished product as a potting soil substitute. Composting treatments were: 1) PMS with no supplemental N (control), 2) PMS + 15 kg N/Mg PMS (dry weight), and 3) PMS + 30 kg N/Mg PMS (dry weight). Composting was conducted for 129 days and treatment effects were evaluated by windrow temperature trends. A container plant growth study employing various particle size fractions and proportions of the control PMS compost and a commercial potting medium (Promix^tm) was conducted in a greenhouse to assess the capability of the compost to support growth of radish (Raphanus sativus L.), snap bean (Phaseolus vulgaris L.), marigold (Tagetes erecta L.), and green pepper (Capsicum sp.). Windrow temperatures were lower with no supplemental N than with the N additions during the initial three weeks and were higher with increasing N rate during the last month of composting, which indicated that the unamended sludge may have been N-limited for maximum biological activity. Reduced temperatures in the high N treatments during the midpoint of the composting process may have been induced by ammonia toxicity. However, cured compost chemical properties and stability were not influenced by treatment and were indicative of good quality compost. The lower amount of plant-available water and greater amounts of plant-available nutrients supplied by the compost than the commercial potting medium resulted in less dry matter produced by all plants except green pepper, whose higher nutrient needs were supplied better by the compost than the commercial potting medium alone. Therefore, the paper mill sludge compost may best be used as an organic fertilizer, soil amendment, or supplemental nutrient source for potting media, rather than as a potting medium alone.     

Changes in Thermophilic Bacteria Population and Diversity during Composting of Coal Fly Ash and Sewage Sludge

The thermophilic bacteria in compost made from coal flyash-amended sewage sludge were isolated and identified using theBiolog system to investigate the effect of coal fly ash on thethermophilic decomposition of sewage sludge during composting. Atotal of 8 species of Bacillus were isolated from thecompost and Bacillus brevis was the dominant speciesduring the entire composting process. The present resultsdemonstrate that the Biolog system is a fast and simple methodfor identifying bacterial species in compost, provided thatoptimum conditions could be achieved for the Bacillusculture. Adding coal fly ash as an amendment did not change thedominant bacteria species during composting, but decreased thepopulation and diversity of thermophilic bacteria species due tothe high alkalinity and salinity. Fewer thermophilic bacteriawere detected in ash-amended sewage sludge compost than insludge compost. There was also reduced metabolic activityobserved in the ash-amended sludge compost from the data ofCO₂ evolution and weight loss. Although ash amendmentdemonstrated a negative effect on the population and diversityduring thermophilic phase, it did not cause any significanteffect on compost maturity.     

ADDITION OF PULP MILL ASH RAISES PH,MODIFIES PHYSICAL PROPERTIES,AND ALTERS YOUNG TOMATO PLANT GROWTH AND MINERAL NUTRITION IN A PEAT-BASED SUBSTRATE

Pulp and paper mills often burn wood waste to fuel their boilers. The ash from a Mississippi pulp mill boiler was evaluated for potential use as an amendment to peat moss-based greenhouse substrates for production of young tomato plants. Between 0 and 50% ash was added to a custom-blended peat moss-based substrate, and these were compared to a commercially available substrate without ash. Addition of ash increased substrate pH, conductivity (EC), bulk density and water holding capacity, while reducing airspace and average particle size. In general, tomato plants grown in 0–40% ash had similar growth indexes as plants grown in commercial substrate. Increasing amounts of ash decreased tomato shoot nitrogen (N), potassium (K), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) concentration, and increased concentrations of phosphorus (P), calcium (Ca), sulfur (S), and boron (B). These results indicate that pulp mill ash has the potential to be used as a substrate component for greenhouse container production of tomato.     

Cocomposting of Crawfish and Agricultural Processing By-Products

Disposal of crawfish processing residuals (hereinafter, referred to as crawfish residuals) poses a challenging problem to the rapidly expanding crawfish industry. Cocomposting is examined as a waste management alternative to landfill disposal. Four agricultural processing by-products were evaluated for use as bulking agents in composting crawfish residuals: wood chips, rice hulls, bagasse, and bark. Approximately 5 to 6.5 volumes of each bulking agents were mixed with one volume of crawfish residuals in 0.3-m³ composting reactors. Compost temperature was continuously monitored, and moisture content was maintained within a desirable range. Samples were collected twice weekly throughout the 50-d composting process. Use of bagasse as a bulking agent led to the largest reduction in volatile solids (27.6 percent), organic C (55.3 percent), particle size (64.7 percent), and compost volume (52.8 percent). Finished compost using bagasse contained the greatest concentration of N (18.4 g N/kg and 160 mg NH₄-N/kg). Self-heating patterns and decomposition of crawfish residuals were satisfactory using all four bulking agents, and no odor, insect or other nuisance problems were detected. The finished products of all compost mixtures were suitable for use as mulch or reuse as bulking agents.     

Zinc distribution and speciation within rocket plants (Eruca vesicaria L. Cavalieri) grown on a polluted soil amended with compost as determined by XRF microtomography and micro-XANES

Zinc distribution and speciation within different organs (root, petiole, and leaf) of the edible plant Eruca vesicaria L. Cavalieri were determined using synchrotron microbeam X-ray techniques (XRF microtomography and mu-XANES) for plants grown in polluted soil with or without compost amendment. Data on soil derived from different extraction procedures and using mu-XANES analyses on rhizospheric soil indicated that compost amendment did not significantly influence the Zn speciation and availability in soil. However, major differences were observed within the plants. Plants grown in the presence of compost were able to partly block zinc immediately outside the root endodermis in the form of zinc-phytate, while a smaller Zn fraction was allowed to xylem transport as zinc-citrate. In the leaves, zinc was largely excluded from leaf cells, and about approximately 50% was in the form of phosphate precipitates, and the other 50% was complexed by cysteine and histidine residues. The reported data provide new information concerning the mechanisms of zinc tolerance in E. vesicaria L. Cavalieri, a very common edible plant in Mediterranean regions, and on the role of compost in influencing the molecular strategies involved in zinc uptake and detoxification.     

添加不同辅料对污泥堆肥腐熟度及气体排放的影响

选择玉米秸秆和木本泥炭两种辅料添加至脱水污泥中进行联合好氧堆肥,研究了秸秆和木本泥炭作为添加剂对污泥堆肥腐熟度和堆肥过程中气体排放(NH_3、CH_4和N_2O)的影响。两种辅料添加量均为初始物料的15%,堆肥在60 L的密闭反应器中共持续35 d。研究结果表明,秸秆作为添加剂与污泥联合堆肥,堆肥产品可以达到卫生标准和腐熟标准。添加秸秆处理整个堆肥过程中累积NH_3、CH_4和N_2O排放量分别为2.2、0.14和0.09 g/kg,NH_3和CH_4排放主要发生在堆肥的升温期和高温期,N_2O排放主要发生在堆肥的后腐熟阶段。添加木本泥炭作为添加剂不能成功启动堆肥,整个堆置过程中未检测到NH_3和CH_4排放,但是在堆肥前期有大量N_2O产生。对于添加秸秆的处理,CH_4、N_2O和NH_3对总温室气体排放的贡献率分别为45%,36%和19%,CH_4所占比重最高。     

修复植物香薷堆肥对缺铜土壤上冬小麦生长和铜吸收的初步研究

通过堆积腐解处理生长在Cu污染土壤上的修复植物-海州香薷,将其研制成堆肥,作为基肥施用于缺Cu土壤,以矫正作物缺Cu症状。盆栽试验研究了这种堆肥对冬小麦(TriticumaestivumL.)生长和Cu吸收的影响。结果表明,施用海州香薷堆肥可显著提高生长在缺Cu土壤上的小麦的株高、生物量和籽实千粒重。与CK相比,千粒重可提高58.9%,籽实产量提高近1倍;而在这种缺Cu土壤上单纯施加N、P、K化肥,反而降低小麦生物量和籽实千粒重。可见,将Cu污染土壤上生长的修复植物海州香薷制成堆肥,施用于缺Cu土壤是一种可实现修复植物资源化的有效途径。     

Biological Evaluation of Seaweed Composting

Large quantities of green seaweed, linked probably to eutrophication, are cast ashore every summer on the Puerto Madryn beaches (Patagonia, Argentina, 42°S, 65°W). This algal biomass interferes with recreational uses of the beach, and therefore must be periodically collected and disposed. Part of this algal biomass was composted with the objective to produce an amendment to improve physical and nutritional characteristics of some local soils used in intensive horticulture, and at the same time to find a way to reduce environmental pollution. The compost was then biologically evaluated by determining the growth rate of tomato plants cultivated on various substrata (washed sand, sandy loam soil, and sandy loam soil plus inorganic fertilizers) to which different doses of compost were added. Results showed that in all cases the addition of compost increased water holding capacity and plant growth. The increase of tomato plants (Licopersicum esculentum var. platense) was proportional to the compost doses. Also, plants grown on sustrata containing at least ten percent compost had significant benefits compared to control plants, improving growth and water stress resistance. Although the quality of this seaweed compost was limited by excessive amounts of sand and low nitrogen content, it proved to be a good amendment that improved both physical and nutritional characteristics of local sandy loam soils used in intensive horticulture. According to these results, composting is a useful technology both to solve environmental pollution problems and to produce a valuable organic fertilizer for soils.     

The Accumulation of Boron in Agropyron elongatum Grown in Coal Fly Ash and Sewage Sludge Mixture

A greenhouse pot experiment was conducted to investigate the boron (B) release capacity of coal fly ash and sewage sludge mixtures, and the accumulation of B in Agropyron elongatum after two consecutive growing seasons. Sludge was amended with fly ash at application rates of 0, 5, 10, 35, and 50% (w/w), and each mixture was then mixed with a loamy soil at either 1:1 or 1:5 (v/v). Both water soluble B (WS-B) and hot water soluble B (HWS-B) increased with increasing fly ash amendment rate. Shoot B concentrations also increased significantly according to the rate of ash amendment. The ash-sludge mixture improved plant growth with the highest total dry weight yield at 10% ash amendment rate. Boron toxicity symptoms in leaf tips were observed at 35% and 50% ash amendment rate at both soil mixing ratios. Hot water soluble B and WS-B decreased significantly after consecutive cropping of Agropyron especially at low ratio of mixure with soil i.e., 1:5 (v/v). However, soil available B contents at ≥ 35% ash application rate and 1:1 (v/v) soil mixing ratio were still excessive for normal plant growth, suggesting that deleterious effects on plant growth would be experienced in later seasons owing to the high amounts of residual B.     

Pilot and Full Scale Evaluations of Leaves as an Amendment in Sewage Sludge Composting

The use of leaf amendment in woodchips/sludge composting was studied in pilot-scale and full-scale operations. Use of leaves at a rate of 20 percent by volume was compatible with present practices and equipment at the Columbus Compost Facility, but higher rates caused materials handling and curing problems and would necessitate system modifications. Only very slight reduction in new woodchip usage was observed for the 20 percent leaf amendment, but output of sieved-finished compost was doubled. Leaf usage increased airflow requirement per unit dry matter during the initial stage of composting but decreased ammonia release throughout the composting process. On the other hand, use of recycled materials, compost and sieved woodchips, increased ammonia release. Adequate moisture and periodic turning in the pilot-scale studies enhanced composting for all treatments. Leaf usage may necessitate forced aeration during curing to keep full size piles aerobic. In addition, leaf usage increased the total materials handling requirement for operating the full-scale system by 16 percent, and it was concluded that careful consideration of materials handling is the major concern for a system's operating efficiency.     

The Effect of Sewage Sludge Compost On the Viability of the Eggs of a Parasitic Nematode

Ascariasis affects approximately one quarter of the world's population and is particularly prevalent in developing countries. As improvements in sanitation in most of these countries becomes more widespread, composting of human excreta and sewage sludge has become a popular and cost-effective method of treatment, as well as offering a valuable source of organic fertilizer and a soil amendment. If, however, the composting process is not properly controlled there may be a potential risk from pathogens, helminths and other infections to workers handling the compost and to consumers of foodstuffs grown on land treated with the compost.

During this study the effect of sewage sludge compost on the viability of ascarid eggs was examined. Eggs of Ascaridia galli were used as a model for the eggs of the human pathogen Ascaris lumbricoides. Fully-developed A. galli eggs were added to sewage sludge compost suspensions, to microorganism-free compost filtrate suspensions and to distilled water controls. The results from these experiments showed that the compost environments had a destructive effect on the A. galli eggs suspended in the compost. The viability of the eggs sampled from the compost environments became reduced with increased exposure to these conditions. No reduction in the viability of the A. galli eggs from the microorganism-free compost filtrates or from the distilled water controls was observed. A thorough microscopic examination of the eggs from the three environments was undertaken. Degenerate eggs from the compost suspensions were seen to be enlarged and swollen. No swelling was observed in the eggs from the control nor from the microorganism-free compost. The observations were believed to have been a result of action by microorganisms, possibly fungi, present in the compost suspensions but not in the microorganism free compost filtrates or the distilled water controls.     

Assessment of Arsenic and Selenium Concentration with Chlorophyll Contents of Sugar Beet (Beta vulgaris var.saccharifera) and Wheat (Triticum aestivum) Exposed to Municipal Sewage Sludge Doses

The present study was conducted to assess the suitability of sewage sludge amendment in soil for Beta vulgaris var. saccharifera (sugar beet) and Triticum aestivum (wheat) by evaluating the arsenic and selenium accumulation and physiological responses of plants grown at 10%, 25%, and 50% sewage sludge amendment rate. Sewage sludge amendment was modified by the physicochemical properties of soil, thus increasing the availability of heavy metals in the soil and consequently with higher accumulation in plant parts. The chlorophyll contents increased after the sewage sludge treatments except for 50%. The sewage sludge amendment led to a significant increase in arsenic and selenium concentrations of the soil. The heavy metal accumulation in the soil after the treatments did not exceed the limits for the land application of sewage sludge recommended by the US Environmental Protection Agency. The increased concentration of heavy metals in the soil due to the sewage sludge amendment led to increases in heavy metal uptake in the leaves and root concentrations of arsenic and selenium in plants as compared to those grown on unamended soil. Accumulation was more in roots than shoots and leaves for most of the heavy metals. Concentrations of arsenic and selenium were more than the permissible limits of national standards in the edible portion of sugar beet and wheat grown on different sewage sludge amendments ratios. The study concludes that the sewage sludge amendment in the soil for growing sugar beet and wheat may not be a good option due to risk of contamination of arsenic and selenium.     

Growth of Rudbeckia and Leaching of Nitrates in Potting Media Amended with Composted Coffee Processing Residue,Municipal Solid Waste and Sewage Sludge

Composts made from coffee processing residue (CFPR), source separated municipal solid waste (MSW), sewage sludge and wood chips (SSWC), and sewage sludge, wood ash, wood chips and leaves (SSACL) were examined as replacements for the peat, perlite and sand found in a conventional potting medium. The perennial flower Rudbeckia hirta L. ‘Goldilocks’ (Black-Eyed Susan) was grown in media composed of 0, 10, 25, 50, 80, and 100 (percent by vol) of each compost. Leachate from media containing 0, 25, 50, and 100% compost was tested for NO₃-N and NH₃-N + NH₄-N to determine if compost would increase the potential for potting media to be a source of nitrate in surface and ground water. The effects of two mid season applications of liquid fertilizer on plant growth and nitrogen leaching were also examined.

Compared to a conventional medium without compost, differences in the growth of Rudbeckia in media with compost were few. Statistically significant decreases in growth occurred in media containing 80 and 100% CFPR, and 80% SSACL. None of the composts caused a statistically significant increase in growth. Leaching of nitrogen increased from media containing 100% CFPR, SSWC and SSACL compared to the medium with no compost. Media containing 25, 50, and 100% MSW leached less N the conventional medium. Liquid fertilizer did not significantly change the growth of Rudbeckia or the amount of nitrogen found in the leachate from any medium.     

Percolation and leachate composition in a disturbed soil layer mulched with sewage biosolids

The effect of sludge and sludge compost as a mulch for dissipating raindrop impact and maintaining a relatively high percolation rate was studied using a Paleudalf from South Africa. Three kg soil were packed in perforated boxes in a making a two cm layer, and subjected to five consecutive simulated rainstorms during a period of 26 days. A 4-day incubation was allowed between the first 4 storms and 10 days before the 5th storm. The soil was amended with either a dry waste activated sludge or a sludge compost at a rate equivalent to 45 Mg ha⁻¹. The amendments (<2-mm) were applied either on the surface or mixed with the whole soil. The application of both sludge and sludge compost reduced the final percolation rate (FPR) compared with the unamended control. The effect of the consecutive rainstorms on the average FPR from all the treatments was as follows: FPR after 1st storm 2nd3rd4th>5th. The effect of amendment on average FPR from all storms was: control>sludge mixed with the soil>surface-applied sludge>sludge compost mixed with the soil≥ surface-applied sludge compost. The decrease of FPR was not related to the electrical conductivity or clay concentration of the leachates. The main chemical species that appeared in the leachates from the treated soils, and persisted throughout the five rainstorms, were ammonium and sulfate. Other ions, such as calcium and magnesium, were present in high concentrations in the leachate during the first storm but at low concentrations in subsequent storms. Nitrate concentrations were high during the first and fifth storms. It is suggested that the adverse effect of the amendments resulted from mechanical and microbial clogging of soil pores.     

Biomass and Cu and Zn Uptake of Two Turfgrass Species Grown in Sludge Compost–soil Mixtures

Two kinds of common turfgrass, fescue and ryegrass, were grown in soils amended with 20?×?80% sludge compost (SC) in this research. The effects of SC on two kinds of soil and response of fescue and ryegrass to the SC amendment were studied. The results showed that urease activity, extractable content of Cu and Zn and Electrical conductivity of both soils increased while pH decreased with the increase of SC amendment. However, the change of these parameters also depended strongly on soil characteristics. Sludge compost at the ≤40 and ≤60% levels can improve growth of fescue and ryegrass, respectively. The biomass of fescue grown in substrate with 40% SC increased 27% in a red soil and 44% in a yellow loamy soil compared to the control. The biomass of ryegrass grown in substrate with 60% SC increased 120% in the red soil and 86% in the yellow loamy soil. Sludge compost amendment at these levels did not significantly affect soluble salt contents of soil or Cu and Zn in plant tissue. Therefore, rational use of sludge compost can take advantage of its beneficial effect as a nutrient source for plant production while avoiding the potential deleterious effects on soil and plant.     

Growth,Yield and Nutrition of Potato in Fumigated or Nonfumigated Soil Amended with Spent Mushroom Compost and Straw Mulch

Four cultural amendments; spent mushroom compost, straw mulch, both compost and straw mulch, or neither, were applied to soils that were either fumigated or not fumigated in a field of potatoes subject to early dying and Colorado potato beetle defoliation. Two plant samples were harvested at two week intervals to measure shoot and tuber growth and mineral nutrition, and two rows were harvested for yield at maturity. Amending the soil with compost increased vegetative growth and shoot weight more than final yield of tubers. Compost amendment delayed tuber filling by several days. Fumigation partly controlled the loss of leaf area due to early dying, but it did not increase tuber yields, and in 1994 fumigation reduced tuber yield in compost amended soils. The effects of compost and straw mulch on tuber yield were related to the concentrations of N and P in leaves. The potato crop did not benefit from compost amendment combined with fumigation, because in fumigated soil there was no improvement in plant nutrition due to compost.     

Composting By-Products from a Bleached Kraft Pulping Process: Effect of Type and Amount Of Nitrogen Amendments

Over 70% of solid wastes (by-products) generated in the manufacture of paper pulp are presently disposed of in landfills. Most of these by-products are compostable and reusable in horticulture, landscaping and agriculture. This work addresses the questions of nitrogen amendments required for composting a mix of four bleached kraft pulp mill by-products — namely, primary sludge, bark, grit and ash. Two nitrogen amendments, ammonium nitrate and chicken litter were compared to determine which provided a more rapid mass reduction and stabilization. Different amounts of ammonium nitrate addition were evaluated to determine if decreasing the C:N ratio of the initial mix (from 130.9 to 28.3) resulted in more rapid composting. A blend of sludge, grit, bark and ash in dry weight percentages of 56, 25, 6 and 13% respectively, stabilized (measured using oxygen respirometry) in a period of 28 days. Although in the initial stages of composting there were differences resulting from the effect of the two types of nitrogen amendments, at the 28th day no significant difference was observed. It was also found that decreasing the C:N ratio did not accelerate the composting process. A composting mix with a C:N ratio of 130.9 had similar mass reduction compared to others with C:N of 95.3, 79.5 and 28.3. Lower C:N ratios were in fact less preferable because of high soluble salt content and greater amendment requirements.