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Effect of intercropping on rhizosphere population in maize (Zea mays L.) and soybean (Glycine max Merill)
Agriculture and Environment, 3 (1977) 363--368
363
© Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
EFFECT OF INTERCROPPING ON RHIZOSPHERE POPULATION IN MAIZE (ZEA MA YS L.) AND SOYBEAN (GL YCINE MAX MERILL)*
C.L. KESWANI, T.H.M. KIBANI** and M.S. CHOWDHURY
Faculty of Agriculture, Forestry and Veterinary Science, University of Dar es Salaam, P.O. Box 643, Morogoro (Tanzania) **Present Address: Coffee Research and Experimental Station. Lyamungu, P.O. Box 3004, Moshi (Tanzania) (Received 30 November 1976}
ABSTRACT Keswani, C.L., Kibani, T.H.M. and Chowdhury, M.S., 1977. Effect of intercropping on rhizosphere population in maize (Zea mays L.) and soybean (Glycine max Merrill). Agric. Environm., 3: 363--368. Comparative studies on the rhizosphere and non-rhizosphere bacterial and fungal populations of maize and soybean both under solecropping and intercropping were conducted. Intercropping increased the bacterial R : S ratio of maize and soybean, whereas fungal R : S ratio showed a decrease in both cases when compared to solecrop condition. Intercropping of maize with soybean increased the maize yield by 34% and decreased the soybean yield by 51% when compared with their respective yields under solecrop conditions. The dominant fungal species in the rhizosphere and non-rhizosphere soils were also affected by plant species and cropping systems.
INTRODUCTION
Intercropping (mixed or multiple cropping) has been practiced for centuries in many parts of the world, especially by subsistence farmers. Research on the scientific basis of this type of farming has only been started in recent years. Some of the results of these studies indicate a lowering of yields of component crops due to competition for nutrients, water, light or space (Kurtz et al., 1952; Pendleton et al., 1963; Enyi, 1973; Anonymous, 1974) and this is quite expected. But there have been instances of increased production of one component and decreased yields of the other (Agboola and Fayemi, 1971; Finlay, 1975). Although most of the recent studies on intercropping involve the effect on yield, land equivalent ratio and econo*Paper presented in the Symposium on Intercropping in Semi-Arid Areas (SISA) held at the Faculty of Agriculture, Forestry and Veterinary Science, University of Dar es Salaam, Morogoro, May 10--12, 1976.
364 mics of the system, the effects of the subterranean microbial population on the system, or vice versa, have not been investigated under field conditions. A search of literature indicated that only Shantaram and ltangaswami (1967) studied the change in rhizosphere microflora during the growth of mixed crops, using sorghum (Sorghum vulgare Pers.) and sunhemp (Crotolaria juncea Linn.) under greenhouse conditions. Therefore, an attempt was made in this investigation to assess the microbial population in the rhizosphere and non-rhizosphere soils of maize and soybean under intercrop and solecrop conditions in the field. MATERIAL AND METHODS Maize variety Ilonga Composite and soybean cv. 'IH/192' were grown under solecrop and intercropped conditions in the University Farm at Morogoro, Tanzania. The plant spacing was 75 × 30 cm for maize and 75 × 10 cm for soybean under sole crop. In intercropping, two soybean plants were grown in between two maize plants with a spacing of 10 cm between plants in the same row. The experiment was conducted in triplicate plots under rainfed conditions without any fertilizer. Soil samples from the rhizosphere and non-rhizosphere were collected according to a method described by Johnson et al. (1959). Fungal and bacterial counts were made by conventional serial dilution plate technique. Rosebengal-streptomycin agar (Martin, 1950) was used for counting fungal populations, whereas bacterial counts were made on a non-selective agar medium of the following composition: glucose 1.0 g, KH2 PO4 0.08 g, K2 HPO4 0.12 g, KNO3 0.05 g, MgSO4.7H2 O 0.10 g, Bactopeptone (Difco) 1.0 g, yeast extract 1.0 g, soil extract 50.0 ml, Agar 20.0 g and distilled water 950 ml. Soil extract was prepared according to Lochhead and Chase (1943) and the pH of the medium was adjusted to 6.8 prior to sterilisation. All counts were made in triplicate. Yields of the crops were obtained from a 12 m 2 sample plot and the data were converted to kg/ha at 13% moisture level. RESULTS The changes in the bacterial and fungal populations in the rhizosphere and non-rhizosphere soils of maize and soybean under solecrop and intercrop conditions are shown in Fig. 1. Bacterial populations in the rhizosphere of maize and soybean under intercropping were appreciably higher than under solecrop conditions (Fig. 1A). By contrast, intercropping caused a decrease in the number of fungal propagules in soybean rhizosphere; whereas, fungal counts in the maize rhizospheres were little affected by cropping systems (Fig. 1B). Neither cropping system had any appreciable effect on the bacterial and fungal counts in the non-rhizosphere soils, although the intercropped plots had slightly higher numbers of both groups of microorganisms.
365
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.= 9.a Q
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~
solecrop non- rhizomphere
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.
.
.
.
.
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SOYBEAN
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SOYBEAN
Fig. 1. Effect of cropping systems on the rhizosphere and non-rhizosphere populations
of bacteria (A) and fungi (B) in maize and soybean.
Rhizosphere : soil (R : S) ratio of bacterial counts in maize and soybean was higher in intercropping than in solecrop system; the difference being most pronounced in maize (Table I). On the other hand, the R : S values o f fungal populations of both the maize and soybean under solecrop system were higher than in intercropped condition. It was observed that maize yield under intercropping increased by 34% in comparison to solecrop condition, although the population of maize plants was same in both the cropping systems. While the plant population of soybean under intercropping was 34% less than in solecrop condition, the soybean yield decreased by 51% under intercropping (Table I).
366
TABLE I Rhizosphere: soil (R : S) ratio of bacterial and fungal popuIations and yield of maize and soybean under solecrop and intercropping conditions Cropping system
Solecrop Solecrop Intercrop Intercrop
Crop
Maize Soybean Maize Soybean
R : S ratio
Yield (kg/ha)
Bacteria
Fungi
23 1 030 773 1 742
387 579 343 138
870.8 545.8 1 166.7 266.7
Results in Table II show that Rhizopus microsporus van Tieghem was the most predominant fungal species in rhizosphere soil of maize under both cropping systems. R. microsporus and Aspergillus niger van Tieghem were predominant in the rhizosphere of soybean under intercrop and solecrop conditions respectively. A. niger, A. terreus Thom. and Penicillium variable Wehmer were found to be predominant in the non-rhizosphere soil of maize and soybean under both cropping systems. Under solecrop conditions Neurospora and Fusarium species were also frequently observed in the rhizosphere and non-rhizosphere soils of maize and soybean. DISCUSSION
Bacterial and fungal populations between the rhizosphere and non-rhizoT A B L E II Prevalence of some of the common fungi in rhizosphere and non-rhizosphere soils of maize and soybean under solecrop and intercropping conditions
Cropping system
Crop
Rhizosphere/ non-rhizosphere
Predominant fungalspecies
Less predominant fungalspecies
Solecrop
Maize
Rhizosphere
Rhizopus
Neurospora spp.
Solecrop
Maize
Non-rhizosphere
Solecrop Solecrop
Soybean Soybean
Rhizosphere Non-rhizosphere
Intercrop Intercrop Intercrop Intercrop
Maize Maize Soybean Soybean
Rhizosphere Non-rhizosphere Rhizosphere Non-rhizosphere
microsporus Aspergillus terreus A. niger A. niger R. microsporus A. niger R. microsporus Penicillium variable A. niger
Neurospara crassa Neurospora spp. Fusarium oxysporum A. R. A. R.
flavus rnicrosporus niger microsporus
Neurospora spp.
367
sphere soil of maize and soybean under intercrop and solecrop conditions showed marked quantitative differences. In all cases, rhizosphere softs contained more organisms than the non-rhizosphere soils. Such increases of bacterial and fungal numbers in the rhizospheres of the plants under solecrop are in agreement with earlier investigations (Katznelson, 1965). In the present investigation the bacterial population in the rhizospheres of both the cereal and the legume increased considerably under intercropping conditions, whereas Shantaram and Rangaswami (1967) observed a decrease in the rhizosphere bacterial population of legume when intercropped with cereal. If the R : S values are considered to be a measure of rhizosphere effect, the most marked effect of intercropping was found in the bacterial population of maize. This effect may be correlated with higher maize yield. It should be noted that soybean, due to its root nodules, may be releasing additional nitrogen which could be utilized by maize. In other words, the legume may have been contributing fixed nitrogen to maize as was observed by Agboola and Fayemi (1972), whereas, maize was possibly not contributing anything to soybean. However, Barea et al. (1976) observed that many rhizosphere bacteria are capable of producing various growth factors or auxins. The increased rhizosphere population of bacteria in maize under intercropping situation may have included such organisms, and thus contributed to the increased yield of maize. Decreased yield of soybean under intercropping was partly due to 34% less population of soybean plants, but light interception by maize plants and/or nutrient competition may also be contributing to this phenomenon (Pendleton et al., 1963; Enyi, 1973; Anonymous, 1974). Fungal R : S ratio for intercropped maize or soybean did not show a major difference from solecrop, signifying the possible neutral role of rhizosphere fungi in plant nutrition. However, the dilution plate technique may not have detected those fungi that are most beneficial in this respect. Although there were some qualitative differences in fungal populations under intercrop and solecrop conditions, there seems to have been no relationship between these parameters and yield in either maize or soybean. ACKNOWLEDGEMENTS
Thanks are extended to Mr. R.C. Finlay, formerly visiting Research Fellow, Department of Crop Science, University of Dares Salaam, Morogoro for making his experiments available for this study, to Dr. J.H. Monyo, Head, Department of Crop Science for his support and to International Development Research Centre, Ottawa, Ont. for financial assistance. Thanks are also due to the Director, CMI, Kew, Surrey, England for assistance in fungal identifications.
368
REFERENCES Agboola, A.A. and Fayemi, A.A.A., 1971. Preliminary trials on the intercropping of maize with different tropical legumes in Western Nigeria. Jr. Agric. Sci. (Camb)., 77: 219--225. Agboola, A.A. and Fayemi, A.A.A., 1972. Fixation and excretion of nitrogen by tropical legumes. Agron. J., 64: 409--412. Anonymous, 1974. International Rice Research Institute (IRRI). Annual Report for 1973. Los Banos, Phillipines. Barea, J.M., Navarro, E. and Montoya, E., 1976. Production of plant growth regulators by rhizosphere phosphate solubilizing bacteria. J. Appl. Bacteriol., 4 0 : 129--134. Enyi, B.A.C., 1973. Effects of intercropping maize or sorghum with cowpeas, pigeon peas or beans. Exp. Agric., 9: 83--90. Finlay, R.C., 1975. Intercropping soybean with cereals. In: D.K. Whigham (Editor), Soybean Production, Protection and Utilization. Intsoy Series No.6. University of Illinois at Urbana-Champaign, Ill., pp. 77--88. Johnson, L.F., Curl, E.A., Bond J.H. and Friburg, H.A., 1959. Methods of Studying Soil Microflora --Plant disease Relationship. Burgess Publishing Company, St. Paul, Minn., 178 pp. Katznelson, H., 1965. Nature and importance of the rhizosphere. In: K.F. Baker and W.C. Snyder (Editors), Ecology of Soil-borne Plant Pathogens, Univ. Calif. Press, Brekeley, Calif., pp 187--209. Kurtz, T., Mested, S.W. and Bray, R.H., 1952. The importance of water in reducing competition between intercrops and corn. Agron. J., 44: 13--17. Lochhead, A.G. and Chase F.E., 1943. Qualitative studies of soil microorganisms. V. Nutritional requirement of predominant bacterial flora. Soil Sci., 55: 185--195. Martin, J.P., 1950. Use of acid rose-bengal and streptomycin in the plate method for estimating fungi. Soil Sci., 69: 215--232. Pendleton, J.W., Bolen, C.D., and Seif, R.D., 1963. Alternating strips of corn and soybean versus solid plantings. Agron. J., 55: 293--295. Shantaram M.V. and Rangaswami G., 1967. A comparison of the rhizosphere microflora of mixed crops. Mysore J. Agric. Sci., 7: 7--12.
363
© Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
EFFECT OF INTERCROPPING ON RHIZOSPHERE POPULATION IN MAIZE (ZEA MA YS L.) AND SOYBEAN (GL YCINE MAX MERILL)*
C.L. KESWANI, T.H.M. KIBANI** and M.S. CHOWDHURY
Faculty of Agriculture, Forestry and Veterinary Science, University of Dar es Salaam, P.O. Box 643, Morogoro (Tanzania) **Present Address: Coffee Research and Experimental Station. Lyamungu, P.O. Box 3004, Moshi (Tanzania) (Received 30 November 1976}
ABSTRACT Keswani, C.L., Kibani, T.H.M. and Chowdhury, M.S., 1977. Effect of intercropping on rhizosphere population in maize (Zea mays L.) and soybean (Glycine max Merrill). Agric. Environm., 3: 363--368. Comparative studies on the rhizosphere and non-rhizosphere bacterial and fungal populations of maize and soybean both under solecropping and intercropping were conducted. Intercropping increased the bacterial R : S ratio of maize and soybean, whereas fungal R : S ratio showed a decrease in both cases when compared to solecrop condition. Intercropping of maize with soybean increased the maize yield by 34% and decreased the soybean yield by 51% when compared with their respective yields under solecrop conditions. The dominant fungal species in the rhizosphere and non-rhizosphere soils were also affected by plant species and cropping systems.
INTRODUCTION
Intercropping (mixed or multiple cropping) has been practiced for centuries in many parts of the world, especially by subsistence farmers. Research on the scientific basis of this type of farming has only been started in recent years. Some of the results of these studies indicate a lowering of yields of component crops due to competition for nutrients, water, light or space (Kurtz et al., 1952; Pendleton et al., 1963; Enyi, 1973; Anonymous, 1974) and this is quite expected. But there have been instances of increased production of one component and decreased yields of the other (Agboola and Fayemi, 1971; Finlay, 1975). Although most of the recent studies on intercropping involve the effect on yield, land equivalent ratio and econo*Paper presented in the Symposium on Intercropping in Semi-Arid Areas (SISA) held at the Faculty of Agriculture, Forestry and Veterinary Science, University of Dar es Salaam, Morogoro, May 10--12, 1976.
364 mics of the system, the effects of the subterranean microbial population on the system, or vice versa, have not been investigated under field conditions. A search of literature indicated that only Shantaram and ltangaswami (1967) studied the change in rhizosphere microflora during the growth of mixed crops, using sorghum (Sorghum vulgare Pers.) and sunhemp (Crotolaria juncea Linn.) under greenhouse conditions. Therefore, an attempt was made in this investigation to assess the microbial population in the rhizosphere and non-rhizosphere soils of maize and soybean under intercrop and solecrop conditions in the field. MATERIAL AND METHODS Maize variety Ilonga Composite and soybean cv. 'IH/192' were grown under solecrop and intercropped conditions in the University Farm at Morogoro, Tanzania. The plant spacing was 75 × 30 cm for maize and 75 × 10 cm for soybean under sole crop. In intercropping, two soybean plants were grown in between two maize plants with a spacing of 10 cm between plants in the same row. The experiment was conducted in triplicate plots under rainfed conditions without any fertilizer. Soil samples from the rhizosphere and non-rhizosphere were collected according to a method described by Johnson et al. (1959). Fungal and bacterial counts were made by conventional serial dilution plate technique. Rosebengal-streptomycin agar (Martin, 1950) was used for counting fungal populations, whereas bacterial counts were made on a non-selective agar medium of the following composition: glucose 1.0 g, KH2 PO4 0.08 g, K2 HPO4 0.12 g, KNO3 0.05 g, MgSO4.7H2 O 0.10 g, Bactopeptone (Difco) 1.0 g, yeast extract 1.0 g, soil extract 50.0 ml, Agar 20.0 g and distilled water 950 ml. Soil extract was prepared according to Lochhead and Chase (1943) and the pH of the medium was adjusted to 6.8 prior to sterilisation. All counts were made in triplicate. Yields of the crops were obtained from a 12 m 2 sample plot and the data were converted to kg/ha at 13% moisture level. RESULTS The changes in the bacterial and fungal populations in the rhizosphere and non-rhizosphere soils of maize and soybean under solecrop and intercrop conditions are shown in Fig. 1. Bacterial populations in the rhizosphere of maize and soybean under intercropping were appreciably higher than under solecrop conditions (Fig. 1A). By contrast, intercropping caused a decrease in the number of fungal propagules in soybean rhizosphere; whereas, fungal counts in the maize rhizospheres were little affected by cropping systems (Fig. 1B). Neither cropping system had any appreciable effect on the bacterial and fungal counts in the non-rhizosphere soils, although the intercropped plots had slightly higher numbers of both groups of microorganisms.
365
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0II g.5
.= 9.a Q
-= !~!i!
~
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~
interorQP rhizoephere
~
solecrop non- rhizomphere
~
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.
.
.
.
.
t
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:!I:
~ iS.8, 6.0 MAIZE
SOYBEAN
® 7 !iii:
MAIZE
SOYBEAN
Fig. 1. Effect of cropping systems on the rhizosphere and non-rhizosphere populations
of bacteria (A) and fungi (B) in maize and soybean.
Rhizosphere : soil (R : S) ratio of bacterial counts in maize and soybean was higher in intercropping than in solecrop system; the difference being most pronounced in maize (Table I). On the other hand, the R : S values o f fungal populations of both the maize and soybean under solecrop system were higher than in intercropped condition. It was observed that maize yield under intercropping increased by 34% in comparison to solecrop condition, although the population of maize plants was same in both the cropping systems. While the plant population of soybean under intercropping was 34% less than in solecrop condition, the soybean yield decreased by 51% under intercropping (Table I).
366
TABLE I Rhizosphere: soil (R : S) ratio of bacterial and fungal popuIations and yield of maize and soybean under solecrop and intercropping conditions Cropping system
Solecrop Solecrop Intercrop Intercrop
Crop
Maize Soybean Maize Soybean
R : S ratio
Yield (kg/ha)
Bacteria
Fungi
23 1 030 773 1 742
387 579 343 138
870.8 545.8 1 166.7 266.7
Results in Table II show that Rhizopus microsporus van Tieghem was the most predominant fungal species in rhizosphere soil of maize under both cropping systems. R. microsporus and Aspergillus niger van Tieghem were predominant in the rhizosphere of soybean under intercrop and solecrop conditions respectively. A. niger, A. terreus Thom. and Penicillium variable Wehmer were found to be predominant in the non-rhizosphere soil of maize and soybean under both cropping systems. Under solecrop conditions Neurospora and Fusarium species were also frequently observed in the rhizosphere and non-rhizosphere soils of maize and soybean. DISCUSSION
Bacterial and fungal populations between the rhizosphere and non-rhizoT A B L E II Prevalence of some of the common fungi in rhizosphere and non-rhizosphere soils of maize and soybean under solecrop and intercropping conditions
Cropping system
Crop
Rhizosphere/ non-rhizosphere
Predominant fungalspecies
Less predominant fungalspecies
Solecrop
Maize
Rhizosphere
Rhizopus
Neurospora spp.
Solecrop
Maize
Non-rhizosphere
Solecrop Solecrop
Soybean Soybean
Rhizosphere Non-rhizosphere
Intercrop Intercrop Intercrop Intercrop
Maize Maize Soybean Soybean
Rhizosphere Non-rhizosphere Rhizosphere Non-rhizosphere
microsporus Aspergillus terreus A. niger A. niger R. microsporus A. niger R. microsporus Penicillium variable A. niger
Neurospara crassa Neurospora spp. Fusarium oxysporum A. R. A. R.
flavus rnicrosporus niger microsporus
Neurospora spp.
367
sphere soil of maize and soybean under intercrop and solecrop conditions showed marked quantitative differences. In all cases, rhizosphere softs contained more organisms than the non-rhizosphere soils. Such increases of bacterial and fungal numbers in the rhizospheres of the plants under solecrop are in agreement with earlier investigations (Katznelson, 1965). In the present investigation the bacterial population in the rhizospheres of both the cereal and the legume increased considerably under intercropping conditions, whereas Shantaram and Rangaswami (1967) observed a decrease in the rhizosphere bacterial population of legume when intercropped with cereal. If the R : S values are considered to be a measure of rhizosphere effect, the most marked effect of intercropping was found in the bacterial population of maize. This effect may be correlated with higher maize yield. It should be noted that soybean, due to its root nodules, may be releasing additional nitrogen which could be utilized by maize. In other words, the legume may have been contributing fixed nitrogen to maize as was observed by Agboola and Fayemi (1972), whereas, maize was possibly not contributing anything to soybean. However, Barea et al. (1976) observed that many rhizosphere bacteria are capable of producing various growth factors or auxins. The increased rhizosphere population of bacteria in maize under intercropping situation may have included such organisms, and thus contributed to the increased yield of maize. Decreased yield of soybean under intercropping was partly due to 34% less population of soybean plants, but light interception by maize plants and/or nutrient competition may also be contributing to this phenomenon (Pendleton et al., 1963; Enyi, 1973; Anonymous, 1974). Fungal R : S ratio for intercropped maize or soybean did not show a major difference from solecrop, signifying the possible neutral role of rhizosphere fungi in plant nutrition. However, the dilution plate technique may not have detected those fungi that are most beneficial in this respect. Although there were some qualitative differences in fungal populations under intercrop and solecrop conditions, there seems to have been no relationship between these parameters and yield in either maize or soybean. ACKNOWLEDGEMENTS
Thanks are extended to Mr. R.C. Finlay, formerly visiting Research Fellow, Department of Crop Science, University of Dares Salaam, Morogoro for making his experiments available for this study, to Dr. J.H. Monyo, Head, Department of Crop Science for his support and to International Development Research Centre, Ottawa, Ont. for financial assistance. Thanks are also due to the Director, CMI, Kew, Surrey, England for assistance in fungal identifications.
368
REFERENCES Agboola, A.A. and Fayemi, A.A.A., 1971. Preliminary trials on the intercropping of maize with different tropical legumes in Western Nigeria. Jr. Agric. Sci. (Camb)., 77: 219--225. Agboola, A.A. and Fayemi, A.A.A., 1972. Fixation and excretion of nitrogen by tropical legumes. Agron. J., 64: 409--412. Anonymous, 1974. International Rice Research Institute (IRRI). Annual Report for 1973. Los Banos, Phillipines. Barea, J.M., Navarro, E. and Montoya, E., 1976. Production of plant growth regulators by rhizosphere phosphate solubilizing bacteria. J. Appl. Bacteriol., 4 0 : 129--134. Enyi, B.A.C., 1973. Effects of intercropping maize or sorghum with cowpeas, pigeon peas or beans. Exp. Agric., 9: 83--90. Finlay, R.C., 1975. Intercropping soybean with cereals. In: D.K. Whigham (Editor), Soybean Production, Protection and Utilization. Intsoy Series No.6. University of Illinois at Urbana-Champaign, Ill., pp. 77--88. Johnson, L.F., Curl, E.A., Bond J.H. and Friburg, H.A., 1959. Methods of Studying Soil Microflora --Plant disease Relationship. Burgess Publishing Company, St. Paul, Minn., 178 pp. Katznelson, H., 1965. Nature and importance of the rhizosphere. In: K.F. Baker and W.C. Snyder (Editors), Ecology of Soil-borne Plant Pathogens, Univ. Calif. Press, Brekeley, Calif., pp 187--209. Kurtz, T., Mested, S.W. and Bray, R.H., 1952. The importance of water in reducing competition between intercrops and corn. Agron. J., 44: 13--17. Lochhead, A.G. and Chase F.E., 1943. Qualitative studies of soil microorganisms. V. Nutritional requirement of predominant bacterial flora. Soil Sci., 55: 185--195. Martin, J.P., 1950. Use of acid rose-bengal and streptomycin in the plate method for estimating fungi. Soil Sci., 69: 215--232. Pendleton, J.W., Bolen, C.D., and Seif, R.D., 1963. Alternating strips of corn and soybean versus solid plantings. Agron. J., 55: 293--295. Shantaram M.V. and Rangaswami G., 1967. A comparison of the rhizosphere microflora of mixed crops. Mysore J. Agric. Sci., 7: 7--12.