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Effect of the duration of composting on the amount of compost produced and the yield of mushrooms
Scientia Horticulturae, 12 (1980) 351--359
351
Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
EFFECT OF THE D U R A T I O N OF COMPOSTING ON THE AMOUNT OF COMPOST PRODUCED A N D THE YIELD OF MUSHROOMS
P.B. F LEGG and PHYLLIS E. R A N D L E
Glasshouse Crops Research Institute, Worthing Road, Littlehampton, W. Sussex (Gt. Britain) (Accepted for publication 8 November 1979)
ABSTRACT Flegg, P.B. and Randle, P.E., 1980. Effect of the duration of composting on the amount of compost produced and the yield of mushrooms. Scientia Hortic., 12: 351--359. Prolonging duration of composting, especially of Stage II (peak-heating), increased loss of material, reduced bulk density and resulted in a lower weight o f compost prepared per tonne of original straw, Yield of mushrooms (Agaricus bisporus) per tonne of prepared compost was unaffected by prolonging Stage II, but was reduced when expressed per unit area, per tonne of compost filled, or per tonne of original straw, because of loss of materials and reduced bulk density. Fruit bodies of a weed mould, Coprinus sp., were more numerous during mushroom cropping on composts which had been prepared with the shortest Stage II, but there was no correlation between occurrence of Coprinus sp. and the yield of mushrooms per tonne of prepared compost. A basis is proposed for comparing composts prepared by a wide variety of methods. INTRODUCTION
A wide range of procedures and recipes is successfully employed throughout the world for preparing mushroom composts (see Fig. 1), but when an individual process produces unsatisfactory results it can be difficult to apply a successful correction. A greater understanding of the underlying principles and practice of mushroom compost preparation is needed to improve reliability and consistency. Mushroom substrate is usually prepared in 2 stages. In Stage I, the compost is heaped outdoors or in a covered yard and the materials for composting are wetted and mixed during successive turns by machine. For Stage II (peakheating) the compost is transferred to a room, either in wooden containers or heaped in bulk on the floor. There is no further mixing of the material. Usually, the compost is pasteurised by raising the temperature to 60°C for about 6 h and thereafter the temperature is controlled at between 45 and 50°C. When free of ammonia, the compost is cooled to 25°C for spawning. The development of Stage II, since its introduction over 30 years ago, has been reviewed by Randle (1974a).
352 Although Stage II is claimed to be a continuation of Stage I by Lambert (1941) and Gerrits et al. (1967), the contribution of each stage towards the overall composting process has scarcely been studied, probably because of a lack of facilities suitable for replicated trials. This paper describes experiments using a new controlled-environment facility (Flegg and Smith, 1976) having 4 identical chambers. A limited study has been made of the effects of varying the duration of Stages I and II on the substrate and on subsequent mushroom production. MATERIALS AND METHODS The composts were based on the GCRI Formula 2 (Randle, 1974b, Fig.1 A and B), b u t with an increased ratio of deep-litter chicken manure to molassed fibrous meal ("Sporavite" supplied by R u m e n c o Ltd., Burton on Trent), the total nitrogen content of the heap remaining unaltered. The formulation was: Wheat straw 1000 kg Deep-litter chicken manure 275 kg "Sporavite" 103 kg Gypsum 62 kg Water 5360 kg Apart from reducing the number of turns from the usual 8 to 6 during Stage I for all heaps, the composting procedure was the same as for Formula 2. Stage II followed the pattern described in the introduction, and differences in duration were effected by changing the length of time at 45--50 ° C, time taken for the initial pasteurization and final cooling being the same for all treatments. The volume of each peak-heat chamber was 21 m a , sufficient to accommodate 32 trays 90-cm long, 60-cm wide and 18-cm deep, arranged in 8 stacks, 4 trays high. On cooling, each tray of c o m p o s t was machine-spawned, pressed hydraulically, re-stacked in the same relative position within a stack of 4 trays as before and moved to the spawn-running room. The spawn used, Darlington 649, was one in wide commercial use at the time. Because of the differing periods of c o m p o s t preparation, it was n o t possible to spawn all batches of c o m p o s t in an experiment on the same day, b u t when all trays were fully spawn-run, after a b o u t 2 weeks, they were cased with a mix ture of moist sphagnum peat and lump chalk and transferred to the croppingroom. Harvesting lasted a b o u t 6 weeks. Two series of experiments were done. The first series consisted o f 2 experiments begun in April and July 1977, respectively, the same experimental composting-treatments being applied in each. The treatments were 4 or 8 days duration for Stage I in combination with 6 or 10 days duration for Stage II, making 4 batches of c o m p o s t to undergo Stage II separately (Fig. 1 A). Replication of these treatments was in time only, Experiment 2 being a replicate of Experiment 1.
353
Experiments 3 and 4, comprising the second series, were started in October and December 1977, respectively. In Experiment 3, Stage I lasted 4 days and in Experiment 4 it lasted 8 days. Both experiments included 4 periods in Stage II, namely 4.7, 5.7, 6.7 and 7.7 days (see Fig. 1 A). The compost comprising one experimental treatment was allocated at random to 1 of 4 chambers, filled into 32 wooden trays and arranged in the chamber in 8 stacks, each of 4 trays. The experimental treatments were arranged in the cropping-house in 4 randomised blocks. The weight of compost for each treatment was recorded initially and at the end of Stages I and II; moisture determinations on samples taken at these times were used to determine changes in water content and dry matter. Measurement of the volume of compost in the heaps and trays gave estimates of the changes in bulk density (kg m-3). The total nitrogen content of the composts at spawning was determined by a micro-Kjeldahl method (O'Neill and Webb, 1970). The occurrence of a weed mould, Coprinus sp. (ink caps), on the trays during cropping was also recorded. Because of the large bulk of material required to make a satisfactory compost stack, the number of replicate heaps in Stage I is usually limited by the capacity of the composting-machine and by the amount of labour and the area available. Similarly, the number of peak-heating treatments, Stage II, is limited by the availability of specially built chambers. In these experiments the first series (Experiments 1 and 2) was statistically analysed as a split-plot design, assuming no experiment--treatment interaction and that the whole-plot treatments (duration of Stage I) and sub-plot treatments (duration of Stage II) were randomised. The physical limits placed on the amount of replication combined with the natural variability of the composting-process made it difficult to establish significant differences between composting-treatments, particularly in Stage I. The results from the second series (Experiments 3 and 4) could not be satisfactorily analysed statistically. RESULTS
Tables I and II show that prolonging Stage II of composting significantly reduced the weight of compost produced for spawning from a tonne of straw. As Stage II was lengthened, the percentage of the original water remaining in the compost was very significantly reduced (Table I). A similar result was obtained in Experiments 3 and 4 (Table II). Comparable differences in dry matter remaining, while following the same trend as the water remaining, were not statistically significant. A physical factor clearly affected by the duration of Stage II was the bulk density of the compost measured at spawning (Tables I and II). The longer the duration of Stage II, the lower the density; a correlation which possibly reflected decreasing water-content of the compost. The productivity of the compost, expressed as yield of mushrooms per tonne of prepared compost, was not affected by duration of either Stages I or
354 TABLE
I
Effect of duration of Stages I and II of composting on the yield of prepared compost, water and dry matter remaining, and water content and bulk density of the prepared compost (Series 1 = Experiments 1 and 2) Duration of Stage I (days)
Duration of Stage II (days) 6
Mean
10
Yield of prepared compost per tonne of straw (tonnes) 4 2.502 2.101 8 2.411 2.041 Mean 2.456* 2.071"
2.302 2.226
Percentage w a t e r r e m a i n i n g a t s p a w n i n g 4 48.4 8 41.2 Mean 44.8**
44.0 37.9
39.5 34.6 37.1"*
P e r e e n t a g e d r y m a t t e r r e m a i n i n g atspawning 4 60.0 54.0 8 57.5 50.7 Mean 58.8 52.3
57.0 54.1
Percentage w a t e r c o n t e n t o f c o m p o s t a t s p a w n i n g 4 71.8 69.8 8 71.1 70.1 Mean 71.5 70.0
70.8 70.6
Bulk density o f c o m p o s t a f t e r s p a w n i n g ( k g m -3) 4 398 337 8 426 360 Mean 412" 348*
367 393
*Significant at 5% level. **Significant at 1% level.
II (Tables III and IV). However, yields expressed per tonne of straw used to make the compost were significantly different, the longer Stage II, the lower the yield per tonne of straw. This was because a longer Stage II resulted in less compost being prepared from a tonne of straw, (see Tables I and II). The yields of mushrooms per tonne of compost filled at the end of Stage I were similarly affected, the yields being 141 and 119 kg per tonne for 6 and 10 days in Stage II, respectively. Yields of mushrooms per square metre of mushroom bed were not significantly different between composting-treatments (Tables III and IV), but as bulk density decreased, so did the yield of mushrooms. Clearly, conclusions on the relation between yield of mushrooms and duration of composting depend largely on the basis used for expressing mushroom yields, thus emphasising the care needed in interpreting the results of mush-
355 TABLE II Effect of duration of Stage II of composting on the yield of prepared compost, water and dry matter remaining, and the water content and bulk density of the prepared compost (Series 2 = Experiments 3 and 4) Experiment
Duration of Stage II(days) 4.7
5.7
6.7
7.7
Yield of prepared compost per tonne of straw (tonnes) 3 2.408 2.403 2.291 2.113 4 2.803 2.705 2.697 2.540 Percentage water remaining at spawning 3 44.5 44.4 4 47.7 46.6
42.4 46.0
38.6 43.0
Percentage dry matter remaining at spawning 3 5,1.9 52.8 48.9 4 62.3 57.9 59.7
47.0 57.1
Percentage water content at spawning 3 74.6 74.3 4 73.8 74.8
73.8 73.6
74.9 73.9
Bulk density of compost after spawning (kg m -3) 3 401 412 390 4 579 567 573
365 521
TABLE III Effect of duration of Stages I and II on the yield of mushrooms per tonne of prepared compost, per square metre of bed and per tonne of straw (Series 1 = Experiments 1 and 2) Duration of Stage I (days)
Duration of Stage II (days) 6
10
Yield (kg per tonne of prepared compost) 4 180.6 8 188.8 Mean 184.7 Yield (kg per square metre) 4 8 Mean Yield (kg per tonne of straw) 4 8 Mean *Significant at 5% level.
Mean
185.0 186.4 185.7
182.8 187.6
11.9 13.2 12.5
10.~ 10.8 10.5
11.1 12.0
447.2 447.8 447.5*
389.0 370.8 379.9*
418.1 409.3
356 TABLE IV Effect of duration of Stage II of composting on the yield of mushrooms per tonne of prepared compost, per square metre of bed and per tonne of straw (Series 2 = Experiments 3 and 4) Experiment
Duration of Stage II (days)
Yield (kg per tonne of prepared compost) 3 4 Yield (kg per square metre) 3 4 Yield(kg pertonne ofstraw) 3 4
4.7
5.7
6.7
7.7
115.3 165.3
133.9 165.4
130.8 162.0
138.4 163.3
7.6 15.8
9.1 15.4
8.4 15.3
8.3 14.1
277.6 463.0
321.8 447.4
299.7 436.9
292.4 414.8
TABLE V Effect of duration of Stages I and II of composting on the subsequent occurrence of Coprinus sp. in spawned trays (number of trays with fruit bodies out of 64 per treatment) (Series 1 = Experiments 1 and 2) Duration of Stage I (days)
Duration of Stage II (days)
Total (out of 128)
6
10
4 8
26 16
3 3
29 19
TotM (out of 128)
42
6
48
room composting-experiments. This is demonstrated in considering the relation between duration of Stage II and occurrence of ink caps. Weed moulds are frequently regarded as indicators of the suitability or otherwise of a compost (Sinden, 1971). Fruit bodies of Coprinus sp. were noted on several trays of Experiments 1 and 2 after they were cased. Ink caps occurred mainly on trays spending the shorter period in Stage II, and the greatest number were found on the compost which spent the shortest time in both stages (Table V). Thus, occurrence of ink caps may be related to yield of mushrooms per tonne of straw and per tonne of compost at the end of Stage I, but n o t to the ability of the prepared composts to produce mushrooms. Nitrogen content of composts is also often taken as a measure of the quality of mushroom compost (Atkins, 1966). The total nitrogen contents o f the com-
357
posts of Experiments 1 and 2 at spawning increased as Stage II increased (Table VI), but as with the weed moulds, did not correlate with yield of mushrooms per tonne of prepared compost. Differences in nitrogen content of the composts at spawning probably reflect the increased loss of dry matter associated with prolonged composting. TABLE VI Effect of duration of Stages I and II of composting on the mean nitrogen content of compost at spawning (Series 1 = Experiments 1 and 2) (N% of dry matter) Duration of Stage I (days)
Mean
Duration of Stage II (days) 6
10
1.77 1.89
1.85 2.08
1.83
1.97
Mean
1.81 1.99
DISCUSSION
Since the 1930s, many composting-methods have been developed. There has been a trend to shorten Stage I and to encourage microbial activity in Stage II (Randle, 1974a). Figure 1 compares a wide range of compostingmethods with different durations of Stages I and II. Sinden and Hauser (1950, 1953) claimed that their "short" composting-process gave better utilisation of raw materials, with savings in labour, time and space for composting, than did the traditional "long" methods (Fig. 1 D). Similar claims have been made for rapidly prepared composts (Fig. 1 E) made in up to 5 days (e.g. Till, 1962; Laborde and Delmas, 1969; Smith, 1979), compared with composts prepared in about 10--20 days. Experimental evidence provided in this paper supports the hypothesis that the shorter the composting-period the greater the conservation of raw materials without impairing the ability of the prepared composts to produce mushrooms. Composting-methods which are represented on the left and bottom of Fig. 1, while capable of producing satisfactory yields of mushrooms, do so with better conservation of raw materials than those represented on the right and top. O t h e r factors vary with respect to duration of Stages I and II, for example a relatively high nitrogen content may be acceptable or even desirable in composts to the upper right of Fig. 1, while composts with lower levels of nitrogen appear at the bottom left. The nitrogen content of 16-day composts (Rasmussen, 1962, Fig. 1 F) tended to exceed 2.0% at stacking, whereas Sinden and Hauser (1953) recommend 1.5%, warning that 2.0% should not be ex~ ceeded. Smith (1979) found that nitrogen levels less than 1.5% in his rapid
358
composts were more likely to produce a satisfactory compost in 5--7 days than higher levels. It is suggested that the comparison of composting-methods shown in Fig. 1 is a useful way of relating methods which otherwise appear to be a widely different collection of procedures and recipes. Obviously more work is needed to validate this suggestion which, if successful, would lead to a greater overall understanding of mushroom composting. 15-
100
=U'}
c o-L 0
[] I 10
I 15
I I 20
D I 25
I I
3o
Stage I, days
Fig. 1. A p p r o x i m a t e d u r a t i o n s o f S t a g e s I and II in a range o f composting-methods. A, Experiments 1--4. B, GCRI F2 compost (Randle, 1974b). C, " S h o r t " composts (Sinden and Hauser, 1950, 1953). D, " L o n g " composts (Atkins, 1966). E, " R a p i d " composts (Till, 1962; Lahorde and Delmas, 1969; Smith and Spencer, 1976). F, " 1 6 - d a y " composts (Rasmussen, 1962). G, " D u t c h " composts (Gerrits, 1974, 1977).
ACKNOWLEDGEMENTS
We thank R.J. White for help and advice with the statistical analysis and Miss M. Trussler, J. White and C. Penn for help with the experiments. REFERENCES Atkins, F.C., 1966. Mushroom Growing Today. Faber and Faber, London, pp. 55--63. Flegg, P.B. and Smith, J.F., 1977. Controlled-environment facilities for mushroom research at Glasshouse Crops Research Institute. Rep. Glasshouse Crops Res. Inst. 197.6, 155--162 Gerrits, J.P.G., 1974. Development of a synthetic compost for mushroom growing based on wheat straw and chicken manure. Neth. J. Agric. Sci., 22: 175--194. Gerrits, J.P.G., 1977. The supplementation of horse manure compost and synthetic compost with chicken manure and other nitrogen sources. Mushroom Sci., 9: Pt 2, 77--98. Gerrits, J.P.G., Bels-Koning, H.C. and Muller, F.M., 1967. Changes in compost constituents during composting, pasteurization and cropping. Mushroom Sci., 6: 225--243.
359 Laborde, J. and Delmas, J., 1969. La preparation express des substrats. Bulletin de la F~deration Nationale des Syndicats Agricoles des Cultivateurs de Champignons, No. 184, 2093--2109. Lambert, E.B., 1941. Studies on the preparation of mushroom compost. J. Agric. Res., 62: 415--422. O'Neill, J.V. and Webb, R.A., 1970. Simultaneous determination of nitrogen, phosphorus and potassium in plant material by automatic methods. J. Sci. F o o d Agric., 21: 217-219. Randle, P.E., 1974a. A review of peak-heating for mushroom composts. Mushroom J., 22: 388--393. Randle, P.E., 1974b. Compost. Rep. Glasshouse Crops Res. Inst. 1973, pp. 82--84. Rasmussen, C.R., 1962. The 16-day normal + 75% inactive composting process. Mushroom Sci., 5: 91--102. Sinden, J.W., 1971. Ecological control of pathogens and weed moulds in mushroom culture. Annu. Rev. Phytopathol., 9: 411--432. Sinden, J.W. and Hauser, E., 1950. The short method of composting. Mushroom Sci., 1: 52--60. Sinden, J.W. and Hauser, E., 1953. The nature of the composting process and its relation to short composting. Mushroom Sci., 2: 123--131. Smith, J.F., 1980. Conservation of materials during composting. Mushroom Sci., 10: in press. Smith, J.F. and Spencer, D.M., 1976. Rapid preparation of composts suitable for the production of the cultivated mushroom. Scientia Hortic., 5: 23--31. Till, O., 1962. Champignonkultur auf sterilisiertem N~ihrsubstrat und die Wiederverwendung yon abgetragenem Kompost. Mushroom Sci., 5: 127--133.
351
Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
EFFECT OF THE D U R A T I O N OF COMPOSTING ON THE AMOUNT OF COMPOST PRODUCED A N D THE YIELD OF MUSHROOMS
P.B. F LEGG and PHYLLIS E. R A N D L E
Glasshouse Crops Research Institute, Worthing Road, Littlehampton, W. Sussex (Gt. Britain) (Accepted for publication 8 November 1979)
ABSTRACT Flegg, P.B. and Randle, P.E., 1980. Effect of the duration of composting on the amount of compost produced and the yield of mushrooms. Scientia Hortic., 12: 351--359. Prolonging duration of composting, especially of Stage II (peak-heating), increased loss of material, reduced bulk density and resulted in a lower weight o f compost prepared per tonne of original straw, Yield of mushrooms (Agaricus bisporus) per tonne of prepared compost was unaffected by prolonging Stage II, but was reduced when expressed per unit area, per tonne of compost filled, or per tonne of original straw, because of loss of materials and reduced bulk density. Fruit bodies of a weed mould, Coprinus sp., were more numerous during mushroom cropping on composts which had been prepared with the shortest Stage II, but there was no correlation between occurrence of Coprinus sp. and the yield of mushrooms per tonne of prepared compost. A basis is proposed for comparing composts prepared by a wide variety of methods. INTRODUCTION
A wide range of procedures and recipes is successfully employed throughout the world for preparing mushroom composts (see Fig. 1), but when an individual process produces unsatisfactory results it can be difficult to apply a successful correction. A greater understanding of the underlying principles and practice of mushroom compost preparation is needed to improve reliability and consistency. Mushroom substrate is usually prepared in 2 stages. In Stage I, the compost is heaped outdoors or in a covered yard and the materials for composting are wetted and mixed during successive turns by machine. For Stage II (peakheating) the compost is transferred to a room, either in wooden containers or heaped in bulk on the floor. There is no further mixing of the material. Usually, the compost is pasteurised by raising the temperature to 60°C for about 6 h and thereafter the temperature is controlled at between 45 and 50°C. When free of ammonia, the compost is cooled to 25°C for spawning. The development of Stage II, since its introduction over 30 years ago, has been reviewed by Randle (1974a).
352 Although Stage II is claimed to be a continuation of Stage I by Lambert (1941) and Gerrits et al. (1967), the contribution of each stage towards the overall composting process has scarcely been studied, probably because of a lack of facilities suitable for replicated trials. This paper describes experiments using a new controlled-environment facility (Flegg and Smith, 1976) having 4 identical chambers. A limited study has been made of the effects of varying the duration of Stages I and II on the substrate and on subsequent mushroom production. MATERIALS AND METHODS The composts were based on the GCRI Formula 2 (Randle, 1974b, Fig.1 A and B), b u t with an increased ratio of deep-litter chicken manure to molassed fibrous meal ("Sporavite" supplied by R u m e n c o Ltd., Burton on Trent), the total nitrogen content of the heap remaining unaltered. The formulation was: Wheat straw 1000 kg Deep-litter chicken manure 275 kg "Sporavite" 103 kg Gypsum 62 kg Water 5360 kg Apart from reducing the number of turns from the usual 8 to 6 during Stage I for all heaps, the composting procedure was the same as for Formula 2. Stage II followed the pattern described in the introduction, and differences in duration were effected by changing the length of time at 45--50 ° C, time taken for the initial pasteurization and final cooling being the same for all treatments. The volume of each peak-heat chamber was 21 m a , sufficient to accommodate 32 trays 90-cm long, 60-cm wide and 18-cm deep, arranged in 8 stacks, 4 trays high. On cooling, each tray of c o m p o s t was machine-spawned, pressed hydraulically, re-stacked in the same relative position within a stack of 4 trays as before and moved to the spawn-running room. The spawn used, Darlington 649, was one in wide commercial use at the time. Because of the differing periods of c o m p o s t preparation, it was n o t possible to spawn all batches of c o m p o s t in an experiment on the same day, b u t when all trays were fully spawn-run, after a b o u t 2 weeks, they were cased with a mix ture of moist sphagnum peat and lump chalk and transferred to the croppingroom. Harvesting lasted a b o u t 6 weeks. Two series of experiments were done. The first series consisted o f 2 experiments begun in April and July 1977, respectively, the same experimental composting-treatments being applied in each. The treatments were 4 or 8 days duration for Stage I in combination with 6 or 10 days duration for Stage II, making 4 batches of c o m p o s t to undergo Stage II separately (Fig. 1 A). Replication of these treatments was in time only, Experiment 2 being a replicate of Experiment 1.
353
Experiments 3 and 4, comprising the second series, were started in October and December 1977, respectively. In Experiment 3, Stage I lasted 4 days and in Experiment 4 it lasted 8 days. Both experiments included 4 periods in Stage II, namely 4.7, 5.7, 6.7 and 7.7 days (see Fig. 1 A). The compost comprising one experimental treatment was allocated at random to 1 of 4 chambers, filled into 32 wooden trays and arranged in the chamber in 8 stacks, each of 4 trays. The experimental treatments were arranged in the cropping-house in 4 randomised blocks. The weight of compost for each treatment was recorded initially and at the end of Stages I and II; moisture determinations on samples taken at these times were used to determine changes in water content and dry matter. Measurement of the volume of compost in the heaps and trays gave estimates of the changes in bulk density (kg m-3). The total nitrogen content of the composts at spawning was determined by a micro-Kjeldahl method (O'Neill and Webb, 1970). The occurrence of a weed mould, Coprinus sp. (ink caps), on the trays during cropping was also recorded. Because of the large bulk of material required to make a satisfactory compost stack, the number of replicate heaps in Stage I is usually limited by the capacity of the composting-machine and by the amount of labour and the area available. Similarly, the number of peak-heating treatments, Stage II, is limited by the availability of specially built chambers. In these experiments the first series (Experiments 1 and 2) was statistically analysed as a split-plot design, assuming no experiment--treatment interaction and that the whole-plot treatments (duration of Stage I) and sub-plot treatments (duration of Stage II) were randomised. The physical limits placed on the amount of replication combined with the natural variability of the composting-process made it difficult to establish significant differences between composting-treatments, particularly in Stage I. The results from the second series (Experiments 3 and 4) could not be satisfactorily analysed statistically. RESULTS
Tables I and II show that prolonging Stage II of composting significantly reduced the weight of compost produced for spawning from a tonne of straw. As Stage II was lengthened, the percentage of the original water remaining in the compost was very significantly reduced (Table I). A similar result was obtained in Experiments 3 and 4 (Table II). Comparable differences in dry matter remaining, while following the same trend as the water remaining, were not statistically significant. A physical factor clearly affected by the duration of Stage II was the bulk density of the compost measured at spawning (Tables I and II). The longer the duration of Stage II, the lower the density; a correlation which possibly reflected decreasing water-content of the compost. The productivity of the compost, expressed as yield of mushrooms per tonne of prepared compost, was not affected by duration of either Stages I or
354 TABLE
I
Effect of duration of Stages I and II of composting on the yield of prepared compost, water and dry matter remaining, and water content and bulk density of the prepared compost (Series 1 = Experiments 1 and 2) Duration of Stage I (days)
Duration of Stage II (days) 6
Mean
10
Yield of prepared compost per tonne of straw (tonnes) 4 2.502 2.101 8 2.411 2.041 Mean 2.456* 2.071"
2.302 2.226
Percentage w a t e r r e m a i n i n g a t s p a w n i n g 4 48.4 8 41.2 Mean 44.8**
44.0 37.9
39.5 34.6 37.1"*
P e r e e n t a g e d r y m a t t e r r e m a i n i n g atspawning 4 60.0 54.0 8 57.5 50.7 Mean 58.8 52.3
57.0 54.1
Percentage w a t e r c o n t e n t o f c o m p o s t a t s p a w n i n g 4 71.8 69.8 8 71.1 70.1 Mean 71.5 70.0
70.8 70.6
Bulk density o f c o m p o s t a f t e r s p a w n i n g ( k g m -3) 4 398 337 8 426 360 Mean 412" 348*
367 393
*Significant at 5% level. **Significant at 1% level.
II (Tables III and IV). However, yields expressed per tonne of straw used to make the compost were significantly different, the longer Stage II, the lower the yield per tonne of straw. This was because a longer Stage II resulted in less compost being prepared from a tonne of straw, (see Tables I and II). The yields of mushrooms per tonne of compost filled at the end of Stage I were similarly affected, the yields being 141 and 119 kg per tonne for 6 and 10 days in Stage II, respectively. Yields of mushrooms per square metre of mushroom bed were not significantly different between composting-treatments (Tables III and IV), but as bulk density decreased, so did the yield of mushrooms. Clearly, conclusions on the relation between yield of mushrooms and duration of composting depend largely on the basis used for expressing mushroom yields, thus emphasising the care needed in interpreting the results of mush-
355 TABLE II Effect of duration of Stage II of composting on the yield of prepared compost, water and dry matter remaining, and the water content and bulk density of the prepared compost (Series 2 = Experiments 3 and 4) Experiment
Duration of Stage II(days) 4.7
5.7
6.7
7.7
Yield of prepared compost per tonne of straw (tonnes) 3 2.408 2.403 2.291 2.113 4 2.803 2.705 2.697 2.540 Percentage water remaining at spawning 3 44.5 44.4 4 47.7 46.6
42.4 46.0
38.6 43.0
Percentage dry matter remaining at spawning 3 5,1.9 52.8 48.9 4 62.3 57.9 59.7
47.0 57.1
Percentage water content at spawning 3 74.6 74.3 4 73.8 74.8
73.8 73.6
74.9 73.9
Bulk density of compost after spawning (kg m -3) 3 401 412 390 4 579 567 573
365 521
TABLE III Effect of duration of Stages I and II on the yield of mushrooms per tonne of prepared compost, per square metre of bed and per tonne of straw (Series 1 = Experiments 1 and 2) Duration of Stage I (days)
Duration of Stage II (days) 6
10
Yield (kg per tonne of prepared compost) 4 180.6 8 188.8 Mean 184.7 Yield (kg per square metre) 4 8 Mean Yield (kg per tonne of straw) 4 8 Mean *Significant at 5% level.
Mean
185.0 186.4 185.7
182.8 187.6
11.9 13.2 12.5
10.~ 10.8 10.5
11.1 12.0
447.2 447.8 447.5*
389.0 370.8 379.9*
418.1 409.3
356 TABLE IV Effect of duration of Stage II of composting on the yield of mushrooms per tonne of prepared compost, per square metre of bed and per tonne of straw (Series 2 = Experiments 3 and 4) Experiment
Duration of Stage II (days)
Yield (kg per tonne of prepared compost) 3 4 Yield (kg per square metre) 3 4 Yield(kg pertonne ofstraw) 3 4
4.7
5.7
6.7
7.7
115.3 165.3
133.9 165.4
130.8 162.0
138.4 163.3
7.6 15.8
9.1 15.4
8.4 15.3
8.3 14.1
277.6 463.0
321.8 447.4
299.7 436.9
292.4 414.8
TABLE V Effect of duration of Stages I and II of composting on the subsequent occurrence of Coprinus sp. in spawned trays (number of trays with fruit bodies out of 64 per treatment) (Series 1 = Experiments 1 and 2) Duration of Stage I (days)
Duration of Stage II (days)
Total (out of 128)
6
10
4 8
26 16
3 3
29 19
TotM (out of 128)
42
6
48
room composting-experiments. This is demonstrated in considering the relation between duration of Stage II and occurrence of ink caps. Weed moulds are frequently regarded as indicators of the suitability or otherwise of a compost (Sinden, 1971). Fruit bodies of Coprinus sp. were noted on several trays of Experiments 1 and 2 after they were cased. Ink caps occurred mainly on trays spending the shorter period in Stage II, and the greatest number were found on the compost which spent the shortest time in both stages (Table V). Thus, occurrence of ink caps may be related to yield of mushrooms per tonne of straw and per tonne of compost at the end of Stage I, but n o t to the ability of the prepared composts to produce mushrooms. Nitrogen content of composts is also often taken as a measure of the quality of mushroom compost (Atkins, 1966). The total nitrogen contents o f the com-
357
posts of Experiments 1 and 2 at spawning increased as Stage II increased (Table VI), but as with the weed moulds, did not correlate with yield of mushrooms per tonne of prepared compost. Differences in nitrogen content of the composts at spawning probably reflect the increased loss of dry matter associated with prolonged composting. TABLE VI Effect of duration of Stages I and II of composting on the mean nitrogen content of compost at spawning (Series 1 = Experiments 1 and 2) (N% of dry matter) Duration of Stage I (days)
Mean
Duration of Stage II (days) 6
10
1.77 1.89
1.85 2.08
1.83
1.97
Mean
1.81 1.99
DISCUSSION
Since the 1930s, many composting-methods have been developed. There has been a trend to shorten Stage I and to encourage microbial activity in Stage II (Randle, 1974a). Figure 1 compares a wide range of compostingmethods with different durations of Stages I and II. Sinden and Hauser (1950, 1953) claimed that their "short" composting-process gave better utilisation of raw materials, with savings in labour, time and space for composting, than did the traditional "long" methods (Fig. 1 D). Similar claims have been made for rapidly prepared composts (Fig. 1 E) made in up to 5 days (e.g. Till, 1962; Laborde and Delmas, 1969; Smith, 1979), compared with composts prepared in about 10--20 days. Experimental evidence provided in this paper supports the hypothesis that the shorter the composting-period the greater the conservation of raw materials without impairing the ability of the prepared composts to produce mushrooms. Composting-methods which are represented on the left and bottom of Fig. 1, while capable of producing satisfactory yields of mushrooms, do so with better conservation of raw materials than those represented on the right and top. O t h e r factors vary with respect to duration of Stages I and II, for example a relatively high nitrogen content may be acceptable or even desirable in composts to the upper right of Fig. 1, while composts with lower levels of nitrogen appear at the bottom left. The nitrogen content of 16-day composts (Rasmussen, 1962, Fig. 1 F) tended to exceed 2.0% at stacking, whereas Sinden and Hauser (1953) recommend 1.5%, warning that 2.0% should not be ex~ ceeded. Smith (1979) found that nitrogen levels less than 1.5% in his rapid
358
composts were more likely to produce a satisfactory compost in 5--7 days than higher levels. It is suggested that the comparison of composting-methods shown in Fig. 1 is a useful way of relating methods which otherwise appear to be a widely different collection of procedures and recipes. Obviously more work is needed to validate this suggestion which, if successful, would lead to a greater overall understanding of mushroom composting. 15-
100
=U'}
c o-L 0
[] I 10
I 15
I I 20
D I 25
I I
3o
Stage I, days
Fig. 1. A p p r o x i m a t e d u r a t i o n s o f S t a g e s I and II in a range o f composting-methods. A, Experiments 1--4. B, GCRI F2 compost (Randle, 1974b). C, " S h o r t " composts (Sinden and Hauser, 1950, 1953). D, " L o n g " composts (Atkins, 1966). E, " R a p i d " composts (Till, 1962; Lahorde and Delmas, 1969; Smith and Spencer, 1976). F, " 1 6 - d a y " composts (Rasmussen, 1962). G, " D u t c h " composts (Gerrits, 1974, 1977).
ACKNOWLEDGEMENTS
We thank R.J. White for help and advice with the statistical analysis and Miss M. Trussler, J. White and C. Penn for help with the experiments. REFERENCES Atkins, F.C., 1966. Mushroom Growing Today. Faber and Faber, London, pp. 55--63. Flegg, P.B. and Smith, J.F., 1977. Controlled-environment facilities for mushroom research at Glasshouse Crops Research Institute. Rep. Glasshouse Crops Res. Inst. 197.6, 155--162 Gerrits, J.P.G., 1974. Development of a synthetic compost for mushroom growing based on wheat straw and chicken manure. Neth. J. Agric. Sci., 22: 175--194. Gerrits, J.P.G., 1977. The supplementation of horse manure compost and synthetic compost with chicken manure and other nitrogen sources. Mushroom Sci., 9: Pt 2, 77--98. Gerrits, J.P.G., Bels-Koning, H.C. and Muller, F.M., 1967. Changes in compost constituents during composting, pasteurization and cropping. Mushroom Sci., 6: 225--243.
359 Laborde, J. and Delmas, J., 1969. La preparation express des substrats. Bulletin de la F~deration Nationale des Syndicats Agricoles des Cultivateurs de Champignons, No. 184, 2093--2109. Lambert, E.B., 1941. Studies on the preparation of mushroom compost. J. Agric. Res., 62: 415--422. O'Neill, J.V. and Webb, R.A., 1970. Simultaneous determination of nitrogen, phosphorus and potassium in plant material by automatic methods. J. Sci. F o o d Agric., 21: 217-219. Randle, P.E., 1974a. A review of peak-heating for mushroom composts. Mushroom J., 22: 388--393. Randle, P.E., 1974b. Compost. Rep. Glasshouse Crops Res. Inst. 1973, pp. 82--84. Rasmussen, C.R., 1962. The 16-day normal + 75% inactive composting process. Mushroom Sci., 5: 91--102. Sinden, J.W., 1971. Ecological control of pathogens and weed moulds in mushroom culture. Annu. Rev. Phytopathol., 9: 411--432. Sinden, J.W. and Hauser, E., 1950. The short method of composting. Mushroom Sci., 1: 52--60. Sinden, J.W. and Hauser, E., 1953. The nature of the composting process and its relation to short composting. Mushroom Sci., 2: 123--131. Smith, J.F., 1980. Conservation of materials during composting. Mushroom Sci., 10: in press. Smith, J.F. and Spencer, D.M., 1976. Rapid preparation of composts suitable for the production of the cultivated mushroom. Scientia Hortic., 5: 23--31. Till, O., 1962. Champignonkultur auf sterilisiertem N~ihrsubstrat und die Wiederverwendung yon abgetragenem Kompost. Mushroom Sci., 5: 127--133.