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Effects of two Compositae plant species and two types of fertilizer on nematodes in an alluvial soil, India
Applied Soil Ecology 10 (1998) 21±25
Effects of two Compositae plant species and two types of fertilizer on nematodes in an alluvial soil, India Mohammad Akhtar* Department of Plant Protection, Institute of Agriculture, Aligarh Muslim University, Aligarh 202002, India Received 2 October 1997; accepted 3 March 1998
Abstract In a ®eld study conducted at Aligarh, India, Compositae plants were used alone and in combination with two types of fertilizers to investigate their effects on the community of soil nematodes. Organic fertilizer (composted manure ± an organic source of nitrogen) and synthetic fertilizer (urea ± a non-organic source of nitrogen) were incorporated in a ®eld soil at two different dosages. All treatments decreased the number of plant-parasitic nematodes, however, doubling the dosage of fertilizer further decreases nematode numbers. Combination of both fertilizer treatments with Compositae plants were the most effective in suppressing plant-parasitic nematode populations. Both fertilizer types signi®cantly increased number of microbivorous (free-living) nematodes relative to untreated control plots; however, Compositae plant species (Tagetes erecta and Helianthus annuus) did not affect the free-living nematode populations. Populations of predatory nematodes (Mononchus aquaticus and Dorylaimus elongatus) were signi®cantly different in all the treatments. Few differences between the two plant species were found for any of the nematode community measurements. # 1998 Elsevier Science B.V. Keywords: Composted manure; Ecology; Fertilizer; Free-living nematode; Plant parasitic nematode; Urea
1. Introduction Damage caused by plant-parasitic nematodes can limit crop production (Akhtar, 1997). As nematicide usage becomes more limited, it will be necessary to develop other methods for managing plant-parasitic nematodes. Attention of nematologists is now focused on alternative control strategies, including cultural and biological methods. Numerous cultural practices can be bene®cial by reducing population densities of plant-parasitic nematodes. Organic soil amendments are now widely recognized as a `non-conventional' nematode management option (Muller and Gooch, *Corresponding author. 0929-1393/98/$19.00 # 1998 Elsevier Science B.V. All rights reserved. PII S0929-1393(98)00046-8
1982; Akhtar and Mahmood, 1996a). A number of plant species are receiving greater attention as an effective means of biological control of nematode pests (Akhtar and Mahmood, 1994). Compost manure, a mixture of animal and plant wastes, is a potential cause of pollution. Conversely, it is considered a valuable organic fertilizer rich in all macro and micro nutrients necessary for plant growth (Wilkinson, 1979). Utilization of compost manure might offer an inexpensive alternative for both fertilization and plant-parasitic nematode control, and at the same time provide a safe disposal (Akhtar and Alam, 1993). Plants of the family Compositae are receiving increased attention as novel tools for the management
22
M. Akhtar / Applied Soil Ecology 10 (1998) 21±25
of plant-parasitic nematodes. Decomposition products from Compositae can be suppressive to plant-parasitic nematodes (Akhtar and Alam, 1992). Many of these plants are recommended as intercrops grown in close vicinity to the crop plants, and the detrimental effects of weed plants such as Tagetes and an oil crop sun¯ower (Helianthus annuus) on crop yield often outweigh the bene®cial effects of nematode control. These plants have been shown to have some nematicidal potential by decomposition of plant residues or release some chemicals from their roots. Tagetes plants are characterized by the presence of a-terthinielyl compounds, which act as natural deterrents of nematode pests and serve as bio-nematicide (Akhtar and Mahmood, 1996b). Soil fauna can enhance soil organic matter decomposition and nutrient mineralization. Free-living (microbivorous) nematodes contribute to both decomposition processes of organic soil amendments and increase the mineralization of nitrogen and phosphorus (nutrient cycling), and may have an indirect bene®cial effect on plant growth (Yeates and Colemann, 1982; Ingham et al., 1985). Interest in using predatory nematodes, e.g., Dorylaimus sp. and Mononchus sp. for suppressing populations of plant-parasitic nematodes in the soil is receiving less attention. However, few studies have investigated predatory nematodes as bio-control agents in the soil (Akhtar, 1989, 1995). The objective of the experiment reported in the present paper was to determine the effects of different amounts of two fertilizer types, organic fertilizer (composted-manure an organic source of nitrogen) and synthetic fertilizer (urea ± a non-organic source of nitrogen), and two Compositae plants, Tagetes erecta and sun¯ower (Helianthus annuus), on populations of plant-parasitic, free-living (microbivorous) and predatory nematodes. 2. Materials and methods Experiments were established at Aligarh Muslim University Agricultural Research Farm, Aligarh, India. The ®eld had been previously cultivated and ploughed by chisel thoroughly to a depth of 25±30 cm and divided into small plots measuring 2.52.5 m separated from each other by a 0.5 m strips. The ®eld
soil was an alluvial soil (60% sand, 27% silt, and 13% clay) of pH 8.3 and organic matter 1.0%. Plots were separately treated with composted manure and urea, each at 110 and 220 kg N haÿ1. Untreated plots, not receiving organic or inorganic fertilizer were also included. Another set of experiments was simultaneously established with the Compositae plant species Tagetes erecta grown alone, sun¯ower (Helianthus annuus) grown alone, and both grown with fertilizers at the same rates described earlier. A bare-fallow treatment was also included. The experimental design was a randomised complete block with ®ve replications of each treatment including control plots within each treatment plot nine mounds (20 cm diameter, 10 cm high, 40 cm apart) were hand-formed. Five seeds of marigold or sun¯ower were planted per mound, except for the barefallow treatment. Plots were watered to ®eld capacity for 2 h on alternate days. Weeds were also removed by hand when necessary. Soil samples consisting of 32 cores (5 cm diameter, 20±25 cm deep) per treatment were collected 3 days before treatments in October, 1996 and at the end of growing season in January 1997, the plant stems were cut off and removed. Cores were bulked, mixed and sieved before sub-sampling and a 100 g sub-sample was used for nematode extraction by Baermann funnel (Hooper, 1986). All nematodes were preserved in 4% formalin. In every sub-sample, nematodes were identi®ed and counted separately as free-living, predatory (Dorylaimus elongatus de Man and Mononchus aquaticus Coetzee) or plant-parasitic nematodes (Hoplolaimus indicus sher, Helicotylenchus indicus Siddiqi, Rotylenchulus reniformis Linford and Oliveira, and Meloidogyne incognita Kofoid and white chitwood). Data were analysed by analysis of variance (ANOVA) and Fischer's least signi®cant differences (FLSD) were calculated for separation of means. Unless otherwise stated, all differences referred to in the text were signi®cant at P0.05. 3. Results 3.1. Effect of populations of plant-parasitic nematodes In untreated soil, the populations of plantparasitic nematodes were not signi®cantly different
M. Akhtar / Applied Soil Ecology 10 (1998) 21±25
23
Table 1 Effect of synthetic fertilizer and organic fertilizer on nematode population Treatment Initial population Synthetic fertilizer Organic fertilizer Untreated control
Dose
No. of nematode/100 g soil
(kg N/ha)
Plant-parasitic
Predatory
Free-living
110 220 110 220 ±
1119 279 230 1140 1107 1149
215 316 420 895 1150 249
2249 2897 3044 3792 5667 2674
ANOVA effects: Synthetic fertilizer Organic fertilizer
a Ns
a a
a a
a ± Analysis of variance (ANOVA) effect significant at P0.05. Ns ± Not significant.
as compared to initial populations (Table 1). In general, both plant species differed in their effects on nematode populations (Table 2). Population of plantparasitic nematodes signi®cantly decreased in all treated plots (Tables 1±3). The greatest reduction in plant-parasitic nematode populations was observed with organic fertilizer plus Tagetes (Table 3). Increased dosages (220 kg N/ha) of both treatments were found effective in further reducing the populations of plant-parasitic nematodes. The ef®cacy of different treatments and the rates of application differed between different species of plant-parasitic nematodes (data not shown).
tode community. In both fertilizer treated plots, however, the nematode populations signi®cantly increased especially at double dosages of organic fertilizer (Table 1). Bare-fallow plots had a higher population than plots with Tagetes followed by sun¯ower plots (Table 2). However, there was an increase in the populations in plots treated with fertilizers plus plant species (Table 3). In general, all treatments differed greatly in their effects on populations of free-living nematodes. Populations of free-living nematodes were most strongly increased by the incorporation of organic fertilizer at double dosage.
3.2. Effect of population of free-living nematodes
3.3. Effect on populations of predatory nematodes
Free-living (microbivorous) nematodes were the most abundant averaging 40%±55% of the total nema-
Predatory nematodes (Dorylaimus elongatus and Mononchus aquaticus) made up to 10%±15% of soil nematode community as evident from the initial population levels. Populations of Dorylaimus sp. usually appear higher than Mononchus sp. (data not shown). Populations of both nematodes increased in organic fertilizer treatments with increasing dosages of the treatment (Table 1) and signi®cantly decreased in plots with plants (Table 2). In plots treated with fertilizers plus plant species, there was an improvement in the plant growth (data not shown), and a signi®cant increase in populations of predatory nematodes, but not as much as in both fertilizer alone treatments (Tables 1 and 3).
Table 2 Effect of Compositae plants on nematode populations Treatment
No. of nematode/100 g soil Plant parasitic
Predatory
Free-living
Initial population Tagetes erecta Helianthus annuus No plant-control ANOVA effects
1119 242 388 1149 a
215 112 130 249 a
2249 2200 2214 2674 a
a ± Analysis of variance (ANOVA) effect significant at P0.05.
24
M. Akhtar / Applied Soil Ecology 10 (1998) 21±25
Table 3 Combined effects of synthetic fertilizer (SF), organic fertilizer (OF) with Tagetes erecta (TE) and Helianthus annuus (HA) on nematode population Treatment Initial population SFTE SFHA OFTE OFHA Untreated-control ANOVA effects: SFTE SFHA OFTE OFHA
Dose
No. of nematodes/100 g soil
Kg N/ha
Plant-parasitic
Predatory
Free-living
110 220 110 220 110 220 110 220
1119 212 198 298 277 128 98 124 104 1149
215 268 293 299 279 736 1029 812 1079 249
2249 2747 2872 3112 5216 3924 5772 3972 5882 116
a Ns a Ns
a Ns a a
a a a a
a ± Analysis of variance (ANOVA) effects significant at P0.05. Ns ± Not significant.
4. Discussion
References
The present ®ndings indicate that the addition of organic fertilizers promotes the build-up of populations of free-living and predatory nematodes. Akhtar (1995) observed that the symptoms caused by the rootknot nematode Meloidogyne incognita were suppressed by the predatory nematode Mononchus aquaticus. The addition of neem and castor leaves into soil further decreased the root-knot nematode attack. Organic fertilizer provides organic matter to the soil for growth and development of predatory nematodes. Predatory nematodes generally feed on all nematodes including free-living nematodes. Therefore, the contribution of Mononchus sp. and Dorylaimus sp. to the reduction of populations of plantparasitic nematodes can not be assessed from the present data. Based on the present ®ndings, Compositae family members such as marigold and sun¯ower were highly effective in maintaining low populations of plant-parasitic nematodes. Therefore, these plants species may be useful in intercropping or crop rotations to reduce populations of plant-parasitic nematodes.
Akhtar, M., 1989. Studies on the predatory behaviour of Mononchus aquaticus. Int. Nematol. Network Newsl. 6, 8± 9. Akhtar, M., 1995. Biological control of the root-knot nematode Meloidogyne incognita in tomato by the predatory nematode Mononchus aquaticus. Int. Pest Control 37, 18±19. Akhtar, M., 1997. Current options in integrated management of plant-parasitic nematodes. Integ. Pest Manag. Reviews 2, 187± 197. Akhtar, M., Alam, M.M., 1992. Effect of crop residues amendments to soil for the control of plant-parasitic nematodes. Biores. Technol. 41, 113±115. Akhtar, M., Alam, M.M., 1993. Utilization of waste materials in nematode control: A review. Biores. Technol. 4, 1±7. Akhtar, M., Mahmood, I., 1994. Potentiality of phytochemicals in nematode control: A review. Biores. Technol. 47, 189± 201. Akhtar, M., Mahmood, I., 1996a. Organic soil amendments in relation to nematode management with particular reference to India. Integ. Pest Manag. Reviews 1, 201±215. Akhtar, M., Mahmood, I., 1996b. Control of plant-parasitic nematodes with organic and inorganic amendments to agricultural soil. Applied Soil Ecol. 4, 243±247. Hooper, D.J., 1986. Extraction of free-living stages from soil. In: Southey, J.F. (Ed.), Laboratory Methods for Work with Plant and Soil Nematodes. Min. Agr. Fish and Food, HMSO, London, UK, pp. 5±22.
M. Akhtar / Applied Soil Ecology 10 (1998) 21±25 Ingham, R.E., Trofymow, J.A., Ingham, E.R., Coleman, D.C., 1985. Interactions of bacteria, fungi, and their nematodes grazers. Effect of nutrient cycling and plant growth. Ecological Monographs 55, 119±140. Muller, R., Gooch, P.S., 1982. Organic amendments in nematode control. An examination of the literature. Nematropica 12, 319± 326.
25
Wilkinson, S.R., 1979. Plant nutrient and economic value of animal manures. J. Animal Sci. 48, 121±133. Yeates, G.W., Colemann, D.C., 1982. Nematodes and decomposition. In: Freckman, D.W. (Ed.), Nematodes in Soil Ecosystems. University of Texas Press, Austin, USA, pp. 55±80.
Effects of two Compositae plant species and two types of fertilizer on nematodes in an alluvial soil, India Mohammad Akhtar* Department of Plant Protection, Institute of Agriculture, Aligarh Muslim University, Aligarh 202002, India Received 2 October 1997; accepted 3 March 1998
Abstract In a ®eld study conducted at Aligarh, India, Compositae plants were used alone and in combination with two types of fertilizers to investigate their effects on the community of soil nematodes. Organic fertilizer (composted manure ± an organic source of nitrogen) and synthetic fertilizer (urea ± a non-organic source of nitrogen) were incorporated in a ®eld soil at two different dosages. All treatments decreased the number of plant-parasitic nematodes, however, doubling the dosage of fertilizer further decreases nematode numbers. Combination of both fertilizer treatments with Compositae plants were the most effective in suppressing plant-parasitic nematode populations. Both fertilizer types signi®cantly increased number of microbivorous (free-living) nematodes relative to untreated control plots; however, Compositae plant species (Tagetes erecta and Helianthus annuus) did not affect the free-living nematode populations. Populations of predatory nematodes (Mononchus aquaticus and Dorylaimus elongatus) were signi®cantly different in all the treatments. Few differences between the two plant species were found for any of the nematode community measurements. # 1998 Elsevier Science B.V. Keywords: Composted manure; Ecology; Fertilizer; Free-living nematode; Plant parasitic nematode; Urea
1. Introduction Damage caused by plant-parasitic nematodes can limit crop production (Akhtar, 1997). As nematicide usage becomes more limited, it will be necessary to develop other methods for managing plant-parasitic nematodes. Attention of nematologists is now focused on alternative control strategies, including cultural and biological methods. Numerous cultural practices can be bene®cial by reducing population densities of plant-parasitic nematodes. Organic soil amendments are now widely recognized as a `non-conventional' nematode management option (Muller and Gooch, *Corresponding author. 0929-1393/98/$19.00 # 1998 Elsevier Science B.V. All rights reserved. PII S0929-1393(98)00046-8
1982; Akhtar and Mahmood, 1996a). A number of plant species are receiving greater attention as an effective means of biological control of nematode pests (Akhtar and Mahmood, 1994). Compost manure, a mixture of animal and plant wastes, is a potential cause of pollution. Conversely, it is considered a valuable organic fertilizer rich in all macro and micro nutrients necessary for plant growth (Wilkinson, 1979). Utilization of compost manure might offer an inexpensive alternative for both fertilization and plant-parasitic nematode control, and at the same time provide a safe disposal (Akhtar and Alam, 1993). Plants of the family Compositae are receiving increased attention as novel tools for the management
22
M. Akhtar / Applied Soil Ecology 10 (1998) 21±25
of plant-parasitic nematodes. Decomposition products from Compositae can be suppressive to plant-parasitic nematodes (Akhtar and Alam, 1992). Many of these plants are recommended as intercrops grown in close vicinity to the crop plants, and the detrimental effects of weed plants such as Tagetes and an oil crop sun¯ower (Helianthus annuus) on crop yield often outweigh the bene®cial effects of nematode control. These plants have been shown to have some nematicidal potential by decomposition of plant residues or release some chemicals from their roots. Tagetes plants are characterized by the presence of a-terthinielyl compounds, which act as natural deterrents of nematode pests and serve as bio-nematicide (Akhtar and Mahmood, 1996b). Soil fauna can enhance soil organic matter decomposition and nutrient mineralization. Free-living (microbivorous) nematodes contribute to both decomposition processes of organic soil amendments and increase the mineralization of nitrogen and phosphorus (nutrient cycling), and may have an indirect bene®cial effect on plant growth (Yeates and Colemann, 1982; Ingham et al., 1985). Interest in using predatory nematodes, e.g., Dorylaimus sp. and Mononchus sp. for suppressing populations of plant-parasitic nematodes in the soil is receiving less attention. However, few studies have investigated predatory nematodes as bio-control agents in the soil (Akhtar, 1989, 1995). The objective of the experiment reported in the present paper was to determine the effects of different amounts of two fertilizer types, organic fertilizer (composted-manure an organic source of nitrogen) and synthetic fertilizer (urea ± a non-organic source of nitrogen), and two Compositae plants, Tagetes erecta and sun¯ower (Helianthus annuus), on populations of plant-parasitic, free-living (microbivorous) and predatory nematodes. 2. Materials and methods Experiments were established at Aligarh Muslim University Agricultural Research Farm, Aligarh, India. The ®eld had been previously cultivated and ploughed by chisel thoroughly to a depth of 25±30 cm and divided into small plots measuring 2.52.5 m separated from each other by a 0.5 m strips. The ®eld
soil was an alluvial soil (60% sand, 27% silt, and 13% clay) of pH 8.3 and organic matter 1.0%. Plots were separately treated with composted manure and urea, each at 110 and 220 kg N haÿ1. Untreated plots, not receiving organic or inorganic fertilizer were also included. Another set of experiments was simultaneously established with the Compositae plant species Tagetes erecta grown alone, sun¯ower (Helianthus annuus) grown alone, and both grown with fertilizers at the same rates described earlier. A bare-fallow treatment was also included. The experimental design was a randomised complete block with ®ve replications of each treatment including control plots within each treatment plot nine mounds (20 cm diameter, 10 cm high, 40 cm apart) were hand-formed. Five seeds of marigold or sun¯ower were planted per mound, except for the barefallow treatment. Plots were watered to ®eld capacity for 2 h on alternate days. Weeds were also removed by hand when necessary. Soil samples consisting of 32 cores (5 cm diameter, 20±25 cm deep) per treatment were collected 3 days before treatments in October, 1996 and at the end of growing season in January 1997, the plant stems were cut off and removed. Cores were bulked, mixed and sieved before sub-sampling and a 100 g sub-sample was used for nematode extraction by Baermann funnel (Hooper, 1986). All nematodes were preserved in 4% formalin. In every sub-sample, nematodes were identi®ed and counted separately as free-living, predatory (Dorylaimus elongatus de Man and Mononchus aquaticus Coetzee) or plant-parasitic nematodes (Hoplolaimus indicus sher, Helicotylenchus indicus Siddiqi, Rotylenchulus reniformis Linford and Oliveira, and Meloidogyne incognita Kofoid and white chitwood). Data were analysed by analysis of variance (ANOVA) and Fischer's least signi®cant differences (FLSD) were calculated for separation of means. Unless otherwise stated, all differences referred to in the text were signi®cant at P0.05. 3. Results 3.1. Effect of populations of plant-parasitic nematodes In untreated soil, the populations of plantparasitic nematodes were not signi®cantly different
M. Akhtar / Applied Soil Ecology 10 (1998) 21±25
23
Table 1 Effect of synthetic fertilizer and organic fertilizer on nematode population Treatment Initial population Synthetic fertilizer Organic fertilizer Untreated control
Dose
No. of nematode/100 g soil
(kg N/ha)
Plant-parasitic
Predatory
Free-living
110 220 110 220 ±
1119 279 230 1140 1107 1149
215 316 420 895 1150 249
2249 2897 3044 3792 5667 2674
ANOVA effects: Synthetic fertilizer Organic fertilizer
a Ns
a a
a a
a ± Analysis of variance (ANOVA) effect significant at P0.05. Ns ± Not significant.
as compared to initial populations (Table 1). In general, both plant species differed in their effects on nematode populations (Table 2). Population of plantparasitic nematodes signi®cantly decreased in all treated plots (Tables 1±3). The greatest reduction in plant-parasitic nematode populations was observed with organic fertilizer plus Tagetes (Table 3). Increased dosages (220 kg N/ha) of both treatments were found effective in further reducing the populations of plant-parasitic nematodes. The ef®cacy of different treatments and the rates of application differed between different species of plant-parasitic nematodes (data not shown).
tode community. In both fertilizer treated plots, however, the nematode populations signi®cantly increased especially at double dosages of organic fertilizer (Table 1). Bare-fallow plots had a higher population than plots with Tagetes followed by sun¯ower plots (Table 2). However, there was an increase in the populations in plots treated with fertilizers plus plant species (Table 3). In general, all treatments differed greatly in their effects on populations of free-living nematodes. Populations of free-living nematodes were most strongly increased by the incorporation of organic fertilizer at double dosage.
3.2. Effect of population of free-living nematodes
3.3. Effect on populations of predatory nematodes
Free-living (microbivorous) nematodes were the most abundant averaging 40%±55% of the total nema-
Predatory nematodes (Dorylaimus elongatus and Mononchus aquaticus) made up to 10%±15% of soil nematode community as evident from the initial population levels. Populations of Dorylaimus sp. usually appear higher than Mononchus sp. (data not shown). Populations of both nematodes increased in organic fertilizer treatments with increasing dosages of the treatment (Table 1) and signi®cantly decreased in plots with plants (Table 2). In plots treated with fertilizers plus plant species, there was an improvement in the plant growth (data not shown), and a signi®cant increase in populations of predatory nematodes, but not as much as in both fertilizer alone treatments (Tables 1 and 3).
Table 2 Effect of Compositae plants on nematode populations Treatment
No. of nematode/100 g soil Plant parasitic
Predatory
Free-living
Initial population Tagetes erecta Helianthus annuus No plant-control ANOVA effects
1119 242 388 1149 a
215 112 130 249 a
2249 2200 2214 2674 a
a ± Analysis of variance (ANOVA) effect significant at P0.05.
24
M. Akhtar / Applied Soil Ecology 10 (1998) 21±25
Table 3 Combined effects of synthetic fertilizer (SF), organic fertilizer (OF) with Tagetes erecta (TE) and Helianthus annuus (HA) on nematode population Treatment Initial population SFTE SFHA OFTE OFHA Untreated-control ANOVA effects: SFTE SFHA OFTE OFHA
Dose
No. of nematodes/100 g soil
Kg N/ha
Plant-parasitic
Predatory
Free-living
110 220 110 220 110 220 110 220
1119 212 198 298 277 128 98 124 104 1149
215 268 293 299 279 736 1029 812 1079 249
2249 2747 2872 3112 5216 3924 5772 3972 5882 116
a Ns a Ns
a Ns a a
a a a a
a ± Analysis of variance (ANOVA) effects significant at P0.05. Ns ± Not significant.
4. Discussion
References
The present ®ndings indicate that the addition of organic fertilizers promotes the build-up of populations of free-living and predatory nematodes. Akhtar (1995) observed that the symptoms caused by the rootknot nematode Meloidogyne incognita were suppressed by the predatory nematode Mononchus aquaticus. The addition of neem and castor leaves into soil further decreased the root-knot nematode attack. Organic fertilizer provides organic matter to the soil for growth and development of predatory nematodes. Predatory nematodes generally feed on all nematodes including free-living nematodes. Therefore, the contribution of Mononchus sp. and Dorylaimus sp. to the reduction of populations of plantparasitic nematodes can not be assessed from the present data. Based on the present ®ndings, Compositae family members such as marigold and sun¯ower were highly effective in maintaining low populations of plant-parasitic nematodes. Therefore, these plants species may be useful in intercropping or crop rotations to reduce populations of plant-parasitic nematodes.
Akhtar, M., 1989. Studies on the predatory behaviour of Mononchus aquaticus. Int. Nematol. Network Newsl. 6, 8± 9. Akhtar, M., 1995. Biological control of the root-knot nematode Meloidogyne incognita in tomato by the predatory nematode Mononchus aquaticus. Int. Pest Control 37, 18±19. Akhtar, M., 1997. Current options in integrated management of plant-parasitic nematodes. Integ. Pest Manag. Reviews 2, 187± 197. Akhtar, M., Alam, M.M., 1992. Effect of crop residues amendments to soil for the control of plant-parasitic nematodes. Biores. Technol. 41, 113±115. Akhtar, M., Alam, M.M., 1993. Utilization of waste materials in nematode control: A review. Biores. Technol. 4, 1±7. Akhtar, M., Mahmood, I., 1994. Potentiality of phytochemicals in nematode control: A review. Biores. Technol. 47, 189± 201. Akhtar, M., Mahmood, I., 1996a. Organic soil amendments in relation to nematode management with particular reference to India. Integ. Pest Manag. Reviews 1, 201±215. Akhtar, M., Mahmood, I., 1996b. Control of plant-parasitic nematodes with organic and inorganic amendments to agricultural soil. Applied Soil Ecol. 4, 243±247. Hooper, D.J., 1986. Extraction of free-living stages from soil. In: Southey, J.F. (Ed.), Laboratory Methods for Work with Plant and Soil Nematodes. Min. Agr. Fish and Food, HMSO, London, UK, pp. 5±22.
M. Akhtar / Applied Soil Ecology 10 (1998) 21±25 Ingham, R.E., Trofymow, J.A., Ingham, E.R., Coleman, D.C., 1985. Interactions of bacteria, fungi, and their nematodes grazers. Effect of nutrient cycling and plant growth. Ecological Monographs 55, 119±140. Muller, R., Gooch, P.S., 1982. Organic amendments in nematode control. An examination of the literature. Nematropica 12, 319± 326.
25
Wilkinson, S.R., 1979. Plant nutrient and economic value of animal manures. J. Animal Sci. 48, 121±133. Yeates, G.W., Colemann, D.C., 1982. Nematodes and decomposition. In: Freckman, D.W. (Ed.), Nematodes in Soil Ecosystems. University of Texas Press, Austin, USA, pp. 55±80.