Compost Temperature Research Articles

An alternative method of nutrient supplementation in the cultivation of the common mushroom Agaricus bisporus

Addition of cottonseed meal to the casing material, rather than to the compost, was examined as an alternative method of nutrient supplementation in the cultivation of the common mushroom Agaricus bisporus. Formaldehyde and calcium sulfate were used independently to prepare delayed release supplement. Casing supplementation significantly (Pv0.05) increased mushroom production (by 0.5-52% in the different trials) and required significantly less nutrient than compost supplementation. It did not result in the increased compost temperature from microbial thermogenesis that is associated with compost supplementation. A supplementation rate of 6 or 8% (on a fresh weight basis) could be recommended. Increases in mushroom yield from the use of formaldehyde and calcium sulfate were not significantly different but calcium sulfate treatment is quicker and less hazardous than formaldehyde treatment.

The fate of ‘biodegradable’ plastics in municipal leaf compost

Blends of starch with polypropylene, starch with polyethylene, polycaprolactone with polyethylene, and a copolymer of β-hydroxybutyrate and β-hydroxyvalerate (PHB/V) were exposed to degrading leaves in a municipal leaf composting operation. Every month for 6 months, duplicate samples were analyzed for changes in weight and tensile properties, and many of these samples were further analyzed for changes in molecular weight and surface morphology. All results were compared to controls which were incubated for 6 months in moist, sterile leaves at a leaf compost temperature. Very little change was noted for any of the polyolefin blends over the 6-month period. In contrast, PHB/V samples showed massive deterioration with substantial weight loss. Although there was a decrease in molecular weight and a loss of tensile properties in leaf-exposed PHB/V films, the sterile control films also showed similar changes, but without weight loss. Of the microbial isolates from film surfaces, only fungi possessed PHB/V depolymerase activity.

Physical management and interpretation of an environmentally controlled composting ecosystem

Compost for mushroom cultivation was prepared in an environmentally controlled composting(ECC) system of 10 t maximum loading. Early in processing, ventilation was manually controlled to provide aerobic conditions. When the desired compost temperatures were reached, control through temperature feedback was used. Physical uniformity of processing conditions was achieved by recirculating large volumes of air within the reactor. Heat production was found to peak early in the composting process, reaching a maximum of about 8-9 W/kg initial wet (67-71%) substrate. When compost temperatures were allowed to rise to 63�C, maximum heat production occurred at 55-63�C. Total heat production per initial wet weight averaged 1.23 MJ/kg (range 0.92-1.51 MJ/kg), or 5.11 MJ/kg (range 4.04-7.57 MJ/kg) when measured per initial volatile dry matter. Heat evolution averaged 18.3 MJ/kg decomposed (range 15.4-22.0 MJ/kg). Oxygen usage followed a pattern similar to that of heat production reaching a maximum in the 55-63�C range. Peak O2 usage was about 9 x 10-7 kg O2/kg composts, or in volume terms, 2.9 x 10-6 m3 Air/kg comp0st.s. During temperature feedback control, O2 levels were maintained at about 19%. The enclosed ECC system permitted mass balance data to be collected for various components. Trials demonstrated that temperature and O2 could be closely controlled, resulting in-good compost uniformity.

Measurement of soil respiration in the field: influence of temperature, moisture level, and application of sewage sludge compost and agro-chemicals

Soil respiration data were obtained using a portable infrared gas analyzer by measuring the CO2 concentration in a small chamber placed on the ground. The rate of respiration showed a geometrical mean of 11.4 (mmol- h-1 -m-2) and ranged from almost 0 to about 80 (mmol-h-1-m-2) in the experimental field in the farm of Shimane University (103 plots, 1,081 data). The rate was stimulated strongly by the temperature (R2 = 0.76, Q10 = 2.2, 4°C <, < 40°C), and weakly by the moisture level (partial correlation coefficient: 0.4) and input of organic matter. But the influence or agro-chemicals (standard and 5-fold dose of fenitrothion, chlorothalonil, and paraquat dichloride) was too small to be detected in the field.

Modification and testing of a domestic freezer for use in studies of plant growth and survival at low temperatures

SUMMARYModifications of a domestic freezer are described, which convert it to a versatile controlled environment chamber capable of maintaining temperatures between ambient and ‐ 18 °C and therefore useful in investigations both of plant growth at low positive temperatures and of survival of sub‐zero temperatures. The temperature control mechanism can provide a wide range of diurnal temperature regimes and of cooling and warming rates.Measurements in two such chambers showed air temperatures were always uniform to within ° 1 °C of set temperature except in a 6 cm band round the inside walls, where they were lower by 0°6 °C, at most; CO2 concentration was always close to 300 v.p.m.; relative humidity was usually in the range 80–90% and photon flux densities during the light period were 180 ° 10 μmol m‐2 s‐1.The uniformity of environmental conditions within each chamber was confirmed by measurements of leaf growth and plant survival of tillers of a single genotype of perennial ryegrass growing in pots of compost. These tests also confirmed the lower temperature of the 6 cm band adjacent to the chamber walls.Although temperature settings were identical, air and compost temperatures were 0°3 °C higher in one of the two chambers tested. Although this difference did not result in significant differences in plant survival, significant differences in leaf lamina extension were found between cabinets.Problems encountered in the design and testing of the chambers are discussed.

Lignocellulose degradation in mushroom composts

The edible mushroomAgaricus bisporus is grown commercially on composted manure/straw mixtures. However, this proven composting procedure is wasteful of raw materials. A nonmanure compost was developed (Smith, 1980) with two main aims: A “conservation compost” (wheat straw, bran, whey, urea, peat, and gypsum) is ready for inoculation with mushroom mycelium (spawning) after 7 d preparation, i.e., 2 d pre-wetting of straw, then 4–5 d composting under controlled conditions. Whereas a traditional manure/wheat straw compost is produced by composting in windrows (8–11 d) followed by a controlled pasteurization phase (5–7 d). In the preparation of a traditional mushroom compost, as much as 60% of the initial dry matter is lost by microbial degradation prior to spawning. By shortening the composting process to 7 d conservation of cellulose and hemicellulose is achieved with only some 30% loss in dry matter. Straw hemicelluloses are degraded much quicker than cellulose during composting. Hence, the measurable extracellular laminarinase and xylanase activities of the compost microflora appear much greater than their cellulase activities at this period in both composts. A peak in laminarinase and xylanase activity after 48 h in manure compost corresponds with the increase in microbial populations. A pronounced increase in thermophilic bacterial and actinomycete populations occurs in “conservation composts” as readily available soluble carbohydrates are assimilated. Initially, this results in higher uniform compost temperatures (60‡C+) and leads to a reduced thermophilic fungal population (103 viable propagules g-1 dry wt compost), which may explain the lowered enzyme activities found in the “conservation composts” and thus the reduced degradation of lignocellulose. The compost microflora showed no laccase activity during composting, and little if any lignin was degraded. However,Agaricus bisporus does possess a moderately active lignolytic system and a strongly active cellulolytic system. Subsequent experiments have shown that increased mushroom yields may be obtained from these composts when urea is replaced by chicken manure as the nitrogen supplement (Smith, 1983); this has not affected compost “selectivity” for mushroom growth, dry matter loss, or the duration of the process. Although yield of mushrooms, based on compost weights at spawning tend to be lower than what would be expected from traditional composts, yield calculated on the basis of weight of starting materials is usually much higher.

The influence of greenhouse covering, propagating bench design and pot type on environmental temperature

Because of radiation and evaporation, the temperature of the compost in plant pots generally differs from that of the greenhouse air, whereas convection tends to equalise temperatures within the greenhouse. Following some preliminary experimental observations, the nocturnal heat balance of pots and benches was considered theoretically. Using different types of pot, designs of bench and greenhouse coverings, pot compost temperatures were measured at night during a tomato propagating period of eight weeks. At the end of this period, plant dry weight was found to be correlated with mean nocturnal compost temperature.