- Email: [email protected]
The influence of herbicides on the soil microflora in a plum orchard
Scientia Horticulturae, 23 (1984) 1 9 1 - - 1 9 4
191
Elsevier Science Publishers B.V., A m s t e r d a m - - Printed in The Netherlands
THE INFLUENCE OF HERBICIDES ON THE SOIL MICROFLORA IN A PLUM ORCHARD
V.P. B H U : r A N I I, S. B H A N 2 and S.K. C H O P R A 2
1Department of Pomology and Fruit Technology, H.P. Agricultural University, Palampur-176062 (India) 2Department of Pornology and Fruit Technology, College of Agriculture, Solan-173230 (India) ( A c c e p t e d for publication 19 D e c e m b e r 1983)
ABSTRACT Bhutani, V.P., Bhan, S. and Chopra, S.K., 1984. The influence of herbicides on the soil m i c r o f l o r a in a p l u m orchard. Scientia Hortic., 23: 191--194. The effects of 2.5, 5.0 and 7.5 kg ha -1 of simazine, atrazine, diuron and bromacil, and 2.0, 3.0 and 4.0 kg ha -1 of terbacil on the soil microflora was studied in the soil of a p l u m orchard. A stimulatory effect on the bacterial p o p u l a t i o n and an inhibitory effect on a c t i n o m y c e t e s was observed u n d e r all the herbicidal t r e a t m e n t s up to 60 days f r o m application. Thereafter, the effect levelled off. An inhibitory effect o n fungi was noticed with diuron, bromacil and terbacil, b u t a p r o m o t i v e effect with simazine and atrazine. In general, the herbicide effect lasted up to 60 days and the microbial status of the soil was n o t significantly disturbed at low and m e d i u m concentrations. Keyword:;: herbicides; Japanese plum; soil microflora.
INTRODUCTION
Micrc.organisms living in the surface horizons of the soil help to produce and ma!:ntain a state of fertility adequate for the production of sustained nutrients. The destruction of beneficial microflora or a shift in the balance of their populations due to a change in the soil environment produced by the growing crops or soil treatments may have marked effects on agricultural productivity. Obviously, in the utilization of herbicides for weed control, it is of vital concern that their effect on the soil microflora should be carefully assessed in an a t t e m p t to employ them safely in crop production. Since information on soil microflora, particularly in orchard soil, is lacking, the object of this study was to determine the influence of some herbicidal treatments on the microbial status of the soil in a plum orchard. MATERIALS AND METHODS
The experiment was conducted with 12-year-old 'Santa Rosa' Japanese 0304-4238/84/$03.00
© 1984 Elsevier Science Publishers B.V.
192 plums on wild peach rootstock near Kandaghat, Solan (1600 m above mean sea level). The soil was sandy loam having a pH range of 6.8--7.1, carbon content 3.5% and electrical conductivity 0.28 mmhos cm-'. Commercial formulations of simazine, atrazine, diuron and bromacil at 2.5, 5.0 and 7.5 kg ha-' and terbacil at 2.0, 3.0 and 4.0 kg ha -1 were applied to individual trees in a radius of 2 m in the third week of March 1979. In all, 16 treatments including a control were quadruplicated in a completely randomized block design. Six random soil samples were drawn at intervals of 30, 60 and 90 days from application from 0--15 cm profiles from the drip of each tree, mixed thoroughly and sub-sampled. These composite samples were air-dried, screened (20 mesh) and analysed for microbial status. Population counts on bacteria, actinomycetes and fungi were made by dilution plate techniques employing soil extract agar medium, Ken Knight's agar medium and Martin's rose bengal agar medium, respectively, as suggested by Rangaswamy {1966). RESULTS
AND
DISCUSSION
-The effects of most herbicide treatments on the population of bacteria were stimulatory up to 60 days, whereafter no significant effect could be observed (Table I). Thirty days after application, terbacil at 3.0 and 4.0 kg ha-' yielded the highest bacteria counts. Differences due to concen-
Bacteria.
TABLE I
I n f l u e n c e of herbicides o n p l u m soft microflora at different i n t e r v a l s Herbicide
Conc. Bacteria (kg h a -1) (X 105/g soft)
Actinomycetes (X 103/g soft)
Fungi (× 10S/g soft) 30 days
60 days
30 days
60 days
90 days
30 days
60 days
90 days
90 days
Control
--
207
240
253
63
57
60
60
73
63
Simazine
2.5 5.0 7.5
187 273 377
233 227 230
230 240 243
30 23 13
40 30 10
50 53 47
80 110 113
73 113 120
60 67 77
Atrazine
2.5 5.0 7.5
350 407 367
363 260 233
257 257 247
50 30 20
60 43 40
57 50 43
117 110 113
90 97 100
70 70 80
Diuron
2.5 5.0 7.5
327 403 433
270 267 280
243 255 277
27 27 23
43 27 23
50 40 23
43 23 17
60 53 37
57 43 37
Bronmcft
2.5 5.0 7.5
280 357 410
287 347 333
240 250 247
23 23 10
47 37 27
50 47 33
20 10 17
33 37 30
60 47 43
Terbacil
2.0 3.0 4.0
410 440 440
220 233 237
227 240 237
47 43 40
53 40 47
50 50 43
33 27 23
53 43 23
57 50 37
29
17
N.S.
15
13
N.S.
12
11
14
L.S.D. ( 0 . 0 5 )
193
trations 30 days after application were significant in all the treatments except terbacil. The stimulatory effect tended to level off after 60 days, and no effect of herbicides on the bacterial counts could be discerned after 90 days. This :is the first report available on the microflora status in a plum orchard. Similar effects of herbicides on the bacterial population have been observed in vitro by Audus (1970) and by Raju and Rangaswamy (1971). Kaufman and Kearney (1964) observed that certain species of bacteria are capable of utilizing simazine and atrazine as the sole or supplementary sources of carbon and nit:rogen. Further certain bacteria such as X a n t h o m o n a s spp., S a r c i n a spp. and P s e u d o m o n a s spp. have been shown to metabolize the uracils and urea as the chief sources of carbon and nitrogen (Hill et al., 1955). This suggests that the increase in bacterial counts could be due to herbicidal application. - - Significant inhibitory effects of different treatments on the actinomycete counts were noticed on the first 2 sampling-dates (Table I). The toxicity increased with the increase in concentration. While at 30 days from application a minimum inhibitory effect was noticed with terbacil, it was highest with simazine, atrazine and bromacil at 7.5 kg h a - ' . The inhibitory effect tended to level off after 60 days from application, and was n o t significant after 90 days. Similar inhibitory effects on actinomycetes counts with simazine, diuron and terbacil have been reported by Rao and Bhutani (1977) :in an apricot orchard.
Actinornycetes.
F u n g i . - - While simazine and atrazine tended to exert a stimulatory effect on the fungi population, diuron, bromacil and terbacil were inhibitory (Table I). The largest fungi populations were recorded with simazine and atrazine at high concentrations on all the sampling-dates, except atrazine at 30 days. A high concentration of atrazine, diuron, bromacil and terbacil continued to exert influence on the fungi population up to the last sampling-date. Uhlig (1966) found that application of simazine at concentrations up to 1000 mg 1-' increased the growth in cultures of mycorrhizal fungi. Frobisher (1961) suggests that the inhibitory effect of diuron, bromacil or terbacil may be due to toxicity, which eventually results in the destruction of the physic~l structure of microorganisms.
REFERENCES
Audus, L.J., 1970. The action of herbicides on the microflora of the soil. Proc. 10th Br. Weed Control Conf., The British Crop Protection Council, Brighton, U.K., pp. 1036-1051. Frobisher, M., 1961. Fundamentals of Microbiology. 6th edn. Saunders, Philadelphia, London, 589 pp. Hill, G.D., McGahen, J.W., Baker, H.M., Finnerty, D.W. and Bingman, C.W., 1955. The fate of substituted urea herbicides in agricultural soils. Agron. J., 47: 93--104.
194 Kaufman, D.D. and Kearney, P.C., 1964. Degradation of simazine by soil microorganism. Abstr. Meet. Weed Sci. Soc. Am., 12 (USDA). Raju, K.S; and Rangaswarny, G., 1971. Studies on the effect of herbicides on soil microflora. Indian J. Microbiol., 11: 25--32. Rangaswamy, G., 1966. Agricultural Microbiology. Asia Publishing House, New York, 385 pp. Rao, A.V. and Bhutani, V.P., 1977. Effect of herbicides on microbial and enzyme activities in the orchard soil. Indian J. Exp. Biol., 15: 943--945. Uhlig, S.K., 1966. Studies on the interaction between chlorbisethylamines-triazine (simazine) and mycorrhiza forming fungi. Wiss. Z. Tech. Univ. Dresden, 1 5 : 6 3 9 - - 6 4 1 (Weed Abstr., 16: 1603).
191
Elsevier Science Publishers B.V., A m s t e r d a m - - Printed in The Netherlands
THE INFLUENCE OF HERBICIDES ON THE SOIL MICROFLORA IN A PLUM ORCHARD
V.P. B H U : r A N I I, S. B H A N 2 and S.K. C H O P R A 2
1Department of Pomology and Fruit Technology, H.P. Agricultural University, Palampur-176062 (India) 2Department of Pornology and Fruit Technology, College of Agriculture, Solan-173230 (India) ( A c c e p t e d for publication 19 D e c e m b e r 1983)
ABSTRACT Bhutani, V.P., Bhan, S. and Chopra, S.K., 1984. The influence of herbicides on the soil m i c r o f l o r a in a p l u m orchard. Scientia Hortic., 23: 191--194. The effects of 2.5, 5.0 and 7.5 kg ha -1 of simazine, atrazine, diuron and bromacil, and 2.0, 3.0 and 4.0 kg ha -1 of terbacil on the soil microflora was studied in the soil of a p l u m orchard. A stimulatory effect on the bacterial p o p u l a t i o n and an inhibitory effect on a c t i n o m y c e t e s was observed u n d e r all the herbicidal t r e a t m e n t s up to 60 days f r o m application. Thereafter, the effect levelled off. An inhibitory effect o n fungi was noticed with diuron, bromacil and terbacil, b u t a p r o m o t i v e effect with simazine and atrazine. In general, the herbicide effect lasted up to 60 days and the microbial status of the soil was n o t significantly disturbed at low and m e d i u m concentrations. Keyword:;: herbicides; Japanese plum; soil microflora.
INTRODUCTION
Micrc.organisms living in the surface horizons of the soil help to produce and ma!:ntain a state of fertility adequate for the production of sustained nutrients. The destruction of beneficial microflora or a shift in the balance of their populations due to a change in the soil environment produced by the growing crops or soil treatments may have marked effects on agricultural productivity. Obviously, in the utilization of herbicides for weed control, it is of vital concern that their effect on the soil microflora should be carefully assessed in an a t t e m p t to employ them safely in crop production. Since information on soil microflora, particularly in orchard soil, is lacking, the object of this study was to determine the influence of some herbicidal treatments on the microbial status of the soil in a plum orchard. MATERIALS AND METHODS
The experiment was conducted with 12-year-old 'Santa Rosa' Japanese 0304-4238/84/$03.00
© 1984 Elsevier Science Publishers B.V.
192 plums on wild peach rootstock near Kandaghat, Solan (1600 m above mean sea level). The soil was sandy loam having a pH range of 6.8--7.1, carbon content 3.5% and electrical conductivity 0.28 mmhos cm-'. Commercial formulations of simazine, atrazine, diuron and bromacil at 2.5, 5.0 and 7.5 kg ha-' and terbacil at 2.0, 3.0 and 4.0 kg ha -1 were applied to individual trees in a radius of 2 m in the third week of March 1979. In all, 16 treatments including a control were quadruplicated in a completely randomized block design. Six random soil samples were drawn at intervals of 30, 60 and 90 days from application from 0--15 cm profiles from the drip of each tree, mixed thoroughly and sub-sampled. These composite samples were air-dried, screened (20 mesh) and analysed for microbial status. Population counts on bacteria, actinomycetes and fungi were made by dilution plate techniques employing soil extract agar medium, Ken Knight's agar medium and Martin's rose bengal agar medium, respectively, as suggested by Rangaswamy {1966). RESULTS
AND
DISCUSSION
-The effects of most herbicide treatments on the population of bacteria were stimulatory up to 60 days, whereafter no significant effect could be observed (Table I). Thirty days after application, terbacil at 3.0 and 4.0 kg ha-' yielded the highest bacteria counts. Differences due to concen-
Bacteria.
TABLE I
I n f l u e n c e of herbicides o n p l u m soft microflora at different i n t e r v a l s Herbicide
Conc. Bacteria (kg h a -1) (X 105/g soft)
Actinomycetes (X 103/g soft)
Fungi (× 10S/g soft) 30 days
60 days
30 days
60 days
90 days
30 days
60 days
90 days
90 days
Control
--
207
240
253
63
57
60
60
73
63
Simazine
2.5 5.0 7.5
187 273 377
233 227 230
230 240 243
30 23 13
40 30 10
50 53 47
80 110 113
73 113 120
60 67 77
Atrazine
2.5 5.0 7.5
350 407 367
363 260 233
257 257 247
50 30 20
60 43 40
57 50 43
117 110 113
90 97 100
70 70 80
Diuron
2.5 5.0 7.5
327 403 433
270 267 280
243 255 277
27 27 23
43 27 23
50 40 23
43 23 17
60 53 37
57 43 37
Bronmcft
2.5 5.0 7.5
280 357 410
287 347 333
240 250 247
23 23 10
47 37 27
50 47 33
20 10 17
33 37 30
60 47 43
Terbacil
2.0 3.0 4.0
410 440 440
220 233 237
227 240 237
47 43 40
53 40 47
50 50 43
33 27 23
53 43 23
57 50 37
29
17
N.S.
15
13
N.S.
12
11
14
L.S.D. ( 0 . 0 5 )
193
trations 30 days after application were significant in all the treatments except terbacil. The stimulatory effect tended to level off after 60 days, and no effect of herbicides on the bacterial counts could be discerned after 90 days. This :is the first report available on the microflora status in a plum orchard. Similar effects of herbicides on the bacterial population have been observed in vitro by Audus (1970) and by Raju and Rangaswamy (1971). Kaufman and Kearney (1964) observed that certain species of bacteria are capable of utilizing simazine and atrazine as the sole or supplementary sources of carbon and nit:rogen. Further certain bacteria such as X a n t h o m o n a s spp., S a r c i n a spp. and P s e u d o m o n a s spp. have been shown to metabolize the uracils and urea as the chief sources of carbon and nitrogen (Hill et al., 1955). This suggests that the increase in bacterial counts could be due to herbicidal application. - - Significant inhibitory effects of different treatments on the actinomycete counts were noticed on the first 2 sampling-dates (Table I). The toxicity increased with the increase in concentration. While at 30 days from application a minimum inhibitory effect was noticed with terbacil, it was highest with simazine, atrazine and bromacil at 7.5 kg h a - ' . The inhibitory effect tended to level off after 60 days from application, and was n o t significant after 90 days. Similar inhibitory effects on actinomycetes counts with simazine, diuron and terbacil have been reported by Rao and Bhutani (1977) :in an apricot orchard.
Actinornycetes.
F u n g i . - - While simazine and atrazine tended to exert a stimulatory effect on the fungi population, diuron, bromacil and terbacil were inhibitory (Table I). The largest fungi populations were recorded with simazine and atrazine at high concentrations on all the sampling-dates, except atrazine at 30 days. A high concentration of atrazine, diuron, bromacil and terbacil continued to exert influence on the fungi population up to the last sampling-date. Uhlig (1966) found that application of simazine at concentrations up to 1000 mg 1-' increased the growth in cultures of mycorrhizal fungi. Frobisher (1961) suggests that the inhibitory effect of diuron, bromacil or terbacil may be due to toxicity, which eventually results in the destruction of the physic~l structure of microorganisms.
REFERENCES
Audus, L.J., 1970. The action of herbicides on the microflora of the soil. Proc. 10th Br. Weed Control Conf., The British Crop Protection Council, Brighton, U.K., pp. 1036-1051. Frobisher, M., 1961. Fundamentals of Microbiology. 6th edn. Saunders, Philadelphia, London, 589 pp. Hill, G.D., McGahen, J.W., Baker, H.M., Finnerty, D.W. and Bingman, C.W., 1955. The fate of substituted urea herbicides in agricultural soils. Agron. J., 47: 93--104.
194 Kaufman, D.D. and Kearney, P.C., 1964. Degradation of simazine by soil microorganism. Abstr. Meet. Weed Sci. Soc. Am., 12 (USDA). Raju, K.S; and Rangaswarny, G., 1971. Studies on the effect of herbicides on soil microflora. Indian J. Microbiol., 11: 25--32. Rangaswamy, G., 1966. Agricultural Microbiology. Asia Publishing House, New York, 385 pp. Rao, A.V. and Bhutani, V.P., 1977. Effect of herbicides on microbial and enzyme activities in the orchard soil. Indian J. Exp. Biol., 15: 943--945. Uhlig, S.K., 1966. Studies on the interaction between chlorbisethylamines-triazine (simazine) and mycorrhiza forming fungi. Wiss. Z. Tech. Univ. Dresden, 1 5 : 6 3 9 - - 6 4 1 (Weed Abstr., 16: 1603).