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Technogenic Soils on Exhausted Peatlands
211
Chapter 9. TECHNOGENIC SOILS ON EXHAUSTED PEATLANDS Enzymological research in the Russian Federation Artem'eva et al (1980) and Shirokikh et al (1987) have studied the low moor peatland Gadovo boloto (Kirov, formerly Vyatka, region) which was dried through open deep draining ditches, and then its peat was extracted by means of rotary cutter. The extraction ended in 1965, but a peat layer remained on the bottom (sand) of the exhausted peatland, on different areas of which the residual peat had the following characteristics: thickness = 10-50 cm (however, in some places there was no peat and so the sand appeared at the surface); decomposition degree = 20-45%; pH = 4.75-6.01; mediocre total N and low plant-available N, P, and K contents. Some plots of the exhausted peatland were submitted to cultivation in 1970, and other plots were reclaimed in the next years. The plots were seeded to awnless bromegrass {Bromus inermis) and fertilised annually with N (NH4NO3), P (superphosphate), K (KCl), NP, NK, PK, or NPK. Each plot was treated with Cu as a trace element at the rate of 7 kg ha"\ Plots not seeded and not fertilised and plots seeded but not fertilised served for comparison. Another peatland, never used for peat extraction, but cultivated with agricultural crops since 1935 and fertilised annually with NPK, also served for comparison. The peat layer of some plots cultivated since the spring of 1973 on the exhausted peatland was sampled by Artem'eva et al (1980) in 1974 and 1975, i.e. in the second and third years of cultivation, for determining invertase and catalase activities. The results presented in Table 25 show that the activities remained low even after 2-3 years of cultivation, excepting the plots fertilised with NPK, in which they increased to some extent in the second and third years and in the third year, respectively. The hay yield was also highest in the NPKfertilised plots. In preliminary reports on these investigations, Nekrasova and Krylova (1975) and Nekrasova et al (1977, 1979) have emphasised that in the NPK-fertilised plots the increase in enzyme activities and hay yield was associated with an increase in numbers of algae. These investigations were also referred to in the book of Zverkov (1982).
212 Table 25 Enzyme activities in technogenic soils of plots cultivated with awnless bromegrass and fertilised annually for two and three years on an exhausted peatland Fertilisers and their rates (kg ha^) Control (unfertilised) N60 P90 K 120 N 60, P 90 N 6 0 , K 120 P 90, K 120 N 60, P 90, K 120 N 90, P 90, K 120 N 120, P 90, K 120
Invertase * Year 3 Year 2 N.D 16.60 8.90 6.50 2.86 7.14 1.59 5.90 6.29 7.74 9.22 8.70 13.07 9.60 15.10 27.53 22.57 17.64 32.11 12.84
Catalase ;* Year 3 Year 2 4.6 3.2 5.6 3.0 5.0 2.9 6.2 3.8 6.6 3.2 7.2 2.5 7.2 3.4 7.6 3.9 7.8 3.3 8.0 4.0
Reproduced from: T.I. Artem'eva, K.A. Nekrasova, I.A. Vertogradskaya, Yu.V. Zverkov, T.M. Borisovich and L.N. Krylova, Pochvennaya Fauna i Biologicheskaya Aktivnost' Osushennykh i Rekul'tiviruemykh Torfyanikov, Moscow, 1980, pp. 86-87. * Expression of enzyme activities: invertase in mg of "glucose" g'^ soil 24 h'^ and catalase in ml of02g"^ soil min'\ N.D. - Not determined. In 1984 and 1985, Shirokikh et al (1987) analysed enzymologically the 0-30-cm layer of some plots cultivated on the exhausted peatland. The plots had a 30-50-cm peat layer over sand and were annually fertilised with NPK. In 1985, their ages were 3, 13, and 16 years, respectively. The analyses indicated that catalase, urease, proteinase, and dehydrogenase activities measured in the 3-year-old plots and in the uncultivated ones were similarly low. The activities were much more pronounced in the 13- and 16-year-old plots and in the control peatland cropped and fertilised since 1935, i.e. for 50 years. Catalase and urease activities were highest in the 13-year-old plots and proteinase and dehydrogenase activities gave the highest values in the peatland cultivated for 50 years. However, other results, published by Shirokikh and Zimenka (1989), indicate that longterm mineral fertilisation of the exhausted peatlands may lead to a general decrease of their enzymatic potential. In the experiments of these authors, the control plots were fertilised only once (at the beginning of the experiments), whereas the other plots were fertilised annually during 16 years with N120P60, N120K120, and N120P60K120, respectively, all fertilisers having been applied in mineral form. Although in the first years mineral fertilisation had a beneficial effect on the enzymatic potential of the exhausted peatland, in the 16th year a decrease was
213 found in almost each of the activities (catalase, urease, proteinase, nitrogenase, polyphenol oxidase, and peroxidase) determined in the annually fertilised plots as compared to the control plots. It should be added that in the 16th year the hay yields in the annually fertilised plots were at the level of the yields obtained in the control plots. In a short report, Shirokikh and Ulanov (1986) described some biological effects of using sand (800 m^ ha"^) to improve the technogenic soil formed from residual peat on exhausted lov^ moor peatlands. The studies, that were carried out in the 1981-1985 period, showed that, owing to sand treatment, productivity of perennial and annual grasses increased to a large extent; the total number of soil microorganisms manifested a tendency to increase, whereas soil respiration (CO2 evolution), catalase, urease, proteinase, and dehydrogenase activities surprisingly decreased. However, according to another short report, by Shirokikh (1988), activity of oxidoreductase and hydrolase enzymes became higher when the sand or clay treatment of the residual peat was accompanied by organic fertilisation (farmyard manure, green manure, or sewage sludge) and application of mineral fertilisers. Plots recultivated with perennial grasses for 20 years were compared with spontaneously revegetated plots and it was found (Shirokikh and Vertogradskaya, 1992) that accumulation of humus was more pronounced and number and biomass of microorganisms were much higher in the peat under perennial grasses (8-10.10^ cells ml"^ peat and 2.4 t of microbial biomass ha"^) than in that under spontaneous vegetation (0.4-1.10^ cells ml"^ peat and 1.3 t of microbial biomass ha"^). The cellulolytic microflora consisted of fungi, streptomycetes, and myxobacteria in the recultivated peat, whereas in the peat under spontaneous vegetation cellulose was degraded predominantly by fungi. In the recultivated peat peroxidase activity increased 5 times, urease and proteinase activities showed 2-2.5-fold increases, but polyphenol oxidase activity decreased 1.5-2 times as compared to activities measured in the spontaneously revegetated peat. In plots submitted to forest recultivation for 20 years, it was characteristic that the microbial biomass was more abundant, the number of microorganisms and the enzyme (polyphenol oxidase) activity were 2-3 times higher in the litter than in the subjacent peat layer. Shirokikh (1993) found that peroxidase activity behaved like polyphenol oxidase activity.
214 The enzymological investigations carried out by Shirokikh and co-workers were also referred to in two brief review articles (Shirokikh and Shirokikh, 1993; Starodumova and Shirokikh, 1993). Enzymological research related to recultivation of exhausted peatlands was also carried out at the Tolmachevo-Krivodanov peatland (Siberia, Novosibirsk region) (Naplekova and Gorskikh, 1986; Potapova, 1989). Naplekova and Gorskikh (1986) conducted experiments, under field conditions and in vegetation pots, for studying the effect of liquid dung on catalase and proteinase activities, on a lot of microbiological parameters (number of saprophytic microorganisms, respiration, assimilation of organic and mineral N, ammonification, nitrification, N2 fixation, accumulation of amino acids, and aerobic decomposition of cellulose), and on herbage yield in the exhausted peatland cultivated with fodder plants. The liquid dung, applied at high rates, equivalent to 180 and 240 kg of N h a \ had, immediately after its application, a negative effect on the enzymatic activities and microbiological parameters of peat. After 2 months, the negative effect diminished; the diminution was more marked under field conditions than in the vegetation pots. When applied at lower rates, equivalent to 60 and 90 kg of N ha"\ the liquid dung activated the microbiological processes in peat. The yield of fodder plants reflected the changes that occurred in the biological activity of peat. The experiment described by Potapova (1989) was carried out in microplots, in which the exhausted peat was fertilised with P90K90 plus the trace element molybdenum or without Mo, or with N60P90K90 plus Mo or without Mo, and cultivated with oats. Unfertilised microplots were the controls. During the growing season, the peat was sampled fi-om the 0-10- and 10-30-cm depths and analysed for determining cellulase, proteinase, nitrogenase, and catalase activities as well as respiration (CO2 evolution). The determinations showed that, under the influence of fertilisation, the enzyme activities and respiration increased in both peat layers sampled, except for catalase activity which remained unaffected in the 0-10-cm layer, increasing only in the 10-30-cm layer. Cellulase activity and respiration were highest in the microplots fertilised with NPK plus Mo, whereas proteinase and nitrogenase activities gave the highest values in the microplots fertilised with PK plus Mo. Green matter yield of oats was also higher in the microplots that received mineral fertilisers together with molybdenum.
215 Enzymological research in Belorussia Polyakov et al (1987) performed enzymological investigations related to the influence of forecrops on the efficiency of using perennial grasses for the recultivation of an exhausted peatland belonging to the "Berdovka" farm (Lida district, Grodno region). Thickness of the residual peat layer on the bottom (fine sand) was 50-70 cm. Decomposition degree of peat was 35-40% and pH in KCl solufion 5.3-5.6. The following plants were used as forecrops: a pea-oats mixture; a foxtail clover-timothy grass-meadow fescue mixture; an awnless bromegrass-timothy grass-meadow fescue mixture; annual grasses; barley; lupine; and potato. The plots were installed in 1982. Some of them were seeded to perennial grasses in the same year and others were sown in 1982 with forecrops which were replaced by perennial grasses after 1 year (in 1983), 2 years (in 1984), and 3 years (in 1985). The plots were fertilised with NPK. Plots kept free of plants served for comparison. Yields of perennial grasses and activity of some enzymes in plots were estimated in 1985. Yields of perennial grasses were lowest in plots cultivated only with these plants for 4 years, increased in plots cultivated with forecrops for 1, 2, and 3 years and then sown with perennial grasses. The highest yield was recorded in plots cultivated with forecrops in the first year and then with perennial grasses for 3 years. Of the forecrops, the pea-oats mixture, barley, and lupine proved to be the best. Catalase, urease, and dehydrogenase activities were lower in the control plots than in the cultivated ones. Catalase activity was highest in the plots cultivated with perennial grasses for 4 years, whereas urease and dehydrogenase activities exhibited the highest values in plots cultivated with forecrops for 2 years followed by cultivation of perennial grasses also for 2 years. The conclusion has been drawn that cultivation of forecrops is also recommended for enhancing the enzymatic potential of technogenic soils formed on exhausted peatlands.
Chapter 9. TECHNOGENIC SOILS ON EXHAUSTED PEATLANDS Enzymological research in the Russian Federation Artem'eva et al (1980) and Shirokikh et al (1987) have studied the low moor peatland Gadovo boloto (Kirov, formerly Vyatka, region) which was dried through open deep draining ditches, and then its peat was extracted by means of rotary cutter. The extraction ended in 1965, but a peat layer remained on the bottom (sand) of the exhausted peatland, on different areas of which the residual peat had the following characteristics: thickness = 10-50 cm (however, in some places there was no peat and so the sand appeared at the surface); decomposition degree = 20-45%; pH = 4.75-6.01; mediocre total N and low plant-available N, P, and K contents. Some plots of the exhausted peatland were submitted to cultivation in 1970, and other plots were reclaimed in the next years. The plots were seeded to awnless bromegrass {Bromus inermis) and fertilised annually with N (NH4NO3), P (superphosphate), K (KCl), NP, NK, PK, or NPK. Each plot was treated with Cu as a trace element at the rate of 7 kg ha"\ Plots not seeded and not fertilised and plots seeded but not fertilised served for comparison. Another peatland, never used for peat extraction, but cultivated with agricultural crops since 1935 and fertilised annually with NPK, also served for comparison. The peat layer of some plots cultivated since the spring of 1973 on the exhausted peatland was sampled by Artem'eva et al (1980) in 1974 and 1975, i.e. in the second and third years of cultivation, for determining invertase and catalase activities. The results presented in Table 25 show that the activities remained low even after 2-3 years of cultivation, excepting the plots fertilised with NPK, in which they increased to some extent in the second and third years and in the third year, respectively. The hay yield was also highest in the NPKfertilised plots. In preliminary reports on these investigations, Nekrasova and Krylova (1975) and Nekrasova et al (1977, 1979) have emphasised that in the NPK-fertilised plots the increase in enzyme activities and hay yield was associated with an increase in numbers of algae. These investigations were also referred to in the book of Zverkov (1982).
212 Table 25 Enzyme activities in technogenic soils of plots cultivated with awnless bromegrass and fertilised annually for two and three years on an exhausted peatland Fertilisers and their rates (kg ha^) Control (unfertilised) N60 P90 K 120 N 60, P 90 N 6 0 , K 120 P 90, K 120 N 60, P 90, K 120 N 90, P 90, K 120 N 120, P 90, K 120
Invertase * Year 3 Year 2 N.D 16.60 8.90 6.50 2.86 7.14 1.59 5.90 6.29 7.74 9.22 8.70 13.07 9.60 15.10 27.53 22.57 17.64 32.11 12.84
Catalase ;* Year 3 Year 2 4.6 3.2 5.6 3.0 5.0 2.9 6.2 3.8 6.6 3.2 7.2 2.5 7.2 3.4 7.6 3.9 7.8 3.3 8.0 4.0
Reproduced from: T.I. Artem'eva, K.A. Nekrasova, I.A. Vertogradskaya, Yu.V. Zverkov, T.M. Borisovich and L.N. Krylova, Pochvennaya Fauna i Biologicheskaya Aktivnost' Osushennykh i Rekul'tiviruemykh Torfyanikov, Moscow, 1980, pp. 86-87. * Expression of enzyme activities: invertase in mg of "glucose" g'^ soil 24 h'^ and catalase in ml of02g"^ soil min'\ N.D. - Not determined. In 1984 and 1985, Shirokikh et al (1987) analysed enzymologically the 0-30-cm layer of some plots cultivated on the exhausted peatland. The plots had a 30-50-cm peat layer over sand and were annually fertilised with NPK. In 1985, their ages were 3, 13, and 16 years, respectively. The analyses indicated that catalase, urease, proteinase, and dehydrogenase activities measured in the 3-year-old plots and in the uncultivated ones were similarly low. The activities were much more pronounced in the 13- and 16-year-old plots and in the control peatland cropped and fertilised since 1935, i.e. for 50 years. Catalase and urease activities were highest in the 13-year-old plots and proteinase and dehydrogenase activities gave the highest values in the peatland cultivated for 50 years. However, other results, published by Shirokikh and Zimenka (1989), indicate that longterm mineral fertilisation of the exhausted peatlands may lead to a general decrease of their enzymatic potential. In the experiments of these authors, the control plots were fertilised only once (at the beginning of the experiments), whereas the other plots were fertilised annually during 16 years with N120P60, N120K120, and N120P60K120, respectively, all fertilisers having been applied in mineral form. Although in the first years mineral fertilisation had a beneficial effect on the enzymatic potential of the exhausted peatland, in the 16th year a decrease was
213 found in almost each of the activities (catalase, urease, proteinase, nitrogenase, polyphenol oxidase, and peroxidase) determined in the annually fertilised plots as compared to the control plots. It should be added that in the 16th year the hay yields in the annually fertilised plots were at the level of the yields obtained in the control plots. In a short report, Shirokikh and Ulanov (1986) described some biological effects of using sand (800 m^ ha"^) to improve the technogenic soil formed from residual peat on exhausted lov^ moor peatlands. The studies, that were carried out in the 1981-1985 period, showed that, owing to sand treatment, productivity of perennial and annual grasses increased to a large extent; the total number of soil microorganisms manifested a tendency to increase, whereas soil respiration (CO2 evolution), catalase, urease, proteinase, and dehydrogenase activities surprisingly decreased. However, according to another short report, by Shirokikh (1988), activity of oxidoreductase and hydrolase enzymes became higher when the sand or clay treatment of the residual peat was accompanied by organic fertilisation (farmyard manure, green manure, or sewage sludge) and application of mineral fertilisers. Plots recultivated with perennial grasses for 20 years were compared with spontaneously revegetated plots and it was found (Shirokikh and Vertogradskaya, 1992) that accumulation of humus was more pronounced and number and biomass of microorganisms were much higher in the peat under perennial grasses (8-10.10^ cells ml"^ peat and 2.4 t of microbial biomass ha"^) than in that under spontaneous vegetation (0.4-1.10^ cells ml"^ peat and 1.3 t of microbial biomass ha"^). The cellulolytic microflora consisted of fungi, streptomycetes, and myxobacteria in the recultivated peat, whereas in the peat under spontaneous vegetation cellulose was degraded predominantly by fungi. In the recultivated peat peroxidase activity increased 5 times, urease and proteinase activities showed 2-2.5-fold increases, but polyphenol oxidase activity decreased 1.5-2 times as compared to activities measured in the spontaneously revegetated peat. In plots submitted to forest recultivation for 20 years, it was characteristic that the microbial biomass was more abundant, the number of microorganisms and the enzyme (polyphenol oxidase) activity were 2-3 times higher in the litter than in the subjacent peat layer. Shirokikh (1993) found that peroxidase activity behaved like polyphenol oxidase activity.
214 The enzymological investigations carried out by Shirokikh and co-workers were also referred to in two brief review articles (Shirokikh and Shirokikh, 1993; Starodumova and Shirokikh, 1993). Enzymological research related to recultivation of exhausted peatlands was also carried out at the Tolmachevo-Krivodanov peatland (Siberia, Novosibirsk region) (Naplekova and Gorskikh, 1986; Potapova, 1989). Naplekova and Gorskikh (1986) conducted experiments, under field conditions and in vegetation pots, for studying the effect of liquid dung on catalase and proteinase activities, on a lot of microbiological parameters (number of saprophytic microorganisms, respiration, assimilation of organic and mineral N, ammonification, nitrification, N2 fixation, accumulation of amino acids, and aerobic decomposition of cellulose), and on herbage yield in the exhausted peatland cultivated with fodder plants. The liquid dung, applied at high rates, equivalent to 180 and 240 kg of N h a \ had, immediately after its application, a negative effect on the enzymatic activities and microbiological parameters of peat. After 2 months, the negative effect diminished; the diminution was more marked under field conditions than in the vegetation pots. When applied at lower rates, equivalent to 60 and 90 kg of N ha"\ the liquid dung activated the microbiological processes in peat. The yield of fodder plants reflected the changes that occurred in the biological activity of peat. The experiment described by Potapova (1989) was carried out in microplots, in which the exhausted peat was fertilised with P90K90 plus the trace element molybdenum or without Mo, or with N60P90K90 plus Mo or without Mo, and cultivated with oats. Unfertilised microplots were the controls. During the growing season, the peat was sampled fi-om the 0-10- and 10-30-cm depths and analysed for determining cellulase, proteinase, nitrogenase, and catalase activities as well as respiration (CO2 evolution). The determinations showed that, under the influence of fertilisation, the enzyme activities and respiration increased in both peat layers sampled, except for catalase activity which remained unaffected in the 0-10-cm layer, increasing only in the 10-30-cm layer. Cellulase activity and respiration were highest in the microplots fertilised with NPK plus Mo, whereas proteinase and nitrogenase activities gave the highest values in the microplots fertilised with PK plus Mo. Green matter yield of oats was also higher in the microplots that received mineral fertilisers together with molybdenum.
215 Enzymological research in Belorussia Polyakov et al (1987) performed enzymological investigations related to the influence of forecrops on the efficiency of using perennial grasses for the recultivation of an exhausted peatland belonging to the "Berdovka" farm (Lida district, Grodno region). Thickness of the residual peat layer on the bottom (fine sand) was 50-70 cm. Decomposition degree of peat was 35-40% and pH in KCl solufion 5.3-5.6. The following plants were used as forecrops: a pea-oats mixture; a foxtail clover-timothy grass-meadow fescue mixture; an awnless bromegrass-timothy grass-meadow fescue mixture; annual grasses; barley; lupine; and potato. The plots were installed in 1982. Some of them were seeded to perennial grasses in the same year and others were sown in 1982 with forecrops which were replaced by perennial grasses after 1 year (in 1983), 2 years (in 1984), and 3 years (in 1985). The plots were fertilised with NPK. Plots kept free of plants served for comparison. Yields of perennial grasses and activity of some enzymes in plots were estimated in 1985. Yields of perennial grasses were lowest in plots cultivated only with these plants for 4 years, increased in plots cultivated with forecrops for 1, 2, and 3 years and then sown with perennial grasses. The highest yield was recorded in plots cultivated with forecrops in the first year and then with perennial grasses for 3 years. Of the forecrops, the pea-oats mixture, barley, and lupine proved to be the best. Catalase, urease, and dehydrogenase activities were lower in the control plots than in the cultivated ones. Catalase activity was highest in the plots cultivated with perennial grasses for 4 years, whereas urease and dehydrogenase activities exhibited the highest values in plots cultivated with forecrops for 2 years followed by cultivation of perennial grasses also for 2 years. The conclusion has been drawn that cultivation of forecrops is also recommended for enhancing the enzymatic potential of technogenic soils formed on exhausted peatlands.