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Soil solarization and chicken manure for the control of Orobanche crenata and other weeds in Lebanon
Crop Protection 19 (2000) 169}173
Soil solarization and chicken manure for the control of Orobanche crenata and other weeds in Lebanon M.A. Haidar*, M.M. Sidahmed Faculty of Agricultural and Food Sciences, American University of Beirut, Beirut, Lebanon Received 16 August 1999; received in revised form 30 September 1999; accepted 4 October 1999
Abstract Field studies were conducted in Lebanon to investigate the e!ect of solarization periods (0}6 wk) with or without chicken manure on Orobanche crenata seeds at various soil depths (0}10 cm), and on weed management in subsequent planting of cabbage. Solarization treatments alone killed Orobanche seeds at 0 depth, but had no signi"cant e!ect on Orobanche seeds below this depth. Solarization with chicken manure killed Orobanche seeds at all depths. Solarization for 2}6 wk with or without chicken manure signi"cantly reduced weed growth and infestation in cabbage. Chicken manure, however, signi"cantly increased the yield of cabbage. 2000 Elsevier Science Ltd. All rights reserved. Keywords: Cabbage; Chicken manure; Weed management
1. Introduction Orobanche crenata Forsk (crenate broomrape) is an obligate root parasite of the family Orobanchaceae (Mitich, 1993). It is widely distributed in the Mediterranean basin region and the Middle East (Parker, 1986). Orobanche crenata parasitizes various winter herbaceous dicots such as broad beans (Vicia faba L.), lentils (Lens esculenta L.) and peas (Pisum sativum L.), but not grasses (Parker and Riches, 1993). In Lebanon, broad beans and peas are the major crops parasitized by O. crenata. Like annual weeds, Orobanche perpetuation depends on production and dormancy of seeds that replenish annual losses from the soil seed bank. A single mature O. crenata plant may produce over 200,000 seeds (Parker and Riches, 1993) that may remain viable in soil for 10 years (Linke and Saxena, 1991). In the "eld, Orobanche seeds germinate only in the presence of chemical stimulants exuded by roots of suitable hosts (Holm et al., 1997), and they require 1}2 wk pre-conditioning period before they respond to the stimulant (Joel, 1995). The emerging radicle moves directly toward the roots of nearby potential hosts. Once the radicle strikes the host root, it immediately forms an appresorium followed by haustoria
* Corresponding author. Tel.: #961-343002; fax: #961-1-744-460. E-mail address: [email protected], [email protected] (M.A. Haidar).
production, where they make physiological connections with host xylem and phloem (Linke et al., 1989). The physiological relationship between Orobanche and its host means conventional methods of controlling Orobanche infestations are expensive and complex, and sometimes unsuccessful. In Lebanon, control is mostly by soil fumigation with methyl bromide, which is expensive, hazardous (Janudi, 1982), and may soon be subject to restrictions. Therefore, the search for non-conventional methods for controlling Orobanche and soil-borne pests has become increasingly important. Among non-conventional methods, soil solarization was found e!ective in controlling Orobanche spp. (Abu-Irmaileh, 1991; Jacobsohn et al., 1980; Saueborn et al., 1989) and various non-parasitic weeds (Elmore, 1991,1995; Haidar and Iskandarani, 1998; Linke, 1994). Soil solarization is achieved by mulching moistened soil with plastic sheets during warm summer months thereby raising soil temperature and controlling various weeds and soil-borne pathogens (Jacobsohn et al., 1980). However, it is well documented that long periods of solarization (6}7 wk) are required for controlling Orobanche (Abu-Irmaileh, 1991; Saueborn et al., 1989). This can be unsatisfactory in intensive agriculture. One way to reduce solarization period is by using soil amendments that augments the weed killing e!ect. Chicken manure is widely used in Lebanon as organic fertilizer, and was e!ective in reducing Orobanche ramosa growth and infestation in potatoes
0261-2194/00/$ - see front matter 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 2 6 1 - 2 1 9 4 ( 9 9 ) 0 0 0 8 3 - 6
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M.A. Haidar, M.M. Sidahmed / Crop Protection 19 (2000) 169}173
(Bibi, 1996). Work by the authors (Haidar et al., 1999) has shown how e!ective this practical procedure can be in the control of other parasitic weeds (Cuscuta spp). The objectives of this study were to determine the e!ects of di!erent periods of soil solarization with or without chicken manure on (1) O. crenata seeds at di!erent soil depths, and (2) on weed infestation in subsequent planting of cabbage.
at soil level, washing the broad bean roots by water, and separating under ground Orobanche attachment from broad bean roots. Dry weight of total Orobanche shoots per pot was recorded. Presented data are the original average of "ve replicates. Means of "ve replications (5 pots or 500 mg of seeds/depth) were analysed for variance and signi"cant di!erences were determined by Duncan's multiple range test at the 5% probability level.
2. Materials and methods
2.2. Solarization for weed control in cabbage
The experimental procedure and design follow those described by Haidar et al. (1999), except that Orobanche crenata seeds were placed in cotton bags (208;308 lm), and their germination was tested using broad bean as a host. Each bag contained 100 mg of seeds, which is equivalent to about 20,000 seeds (Saghir, 1979).
One month after solarization (October, 1997), 4-wk old cabbage seedlings (cv.O-S-Cross) were transplanted at 25 cm spacing with minimum soil disturbance. Planting was done by driving holes into the soil with a hand chisel. Three rows of cabbage were planted per plot. Fertilizers were not added. One irrigation was applied immediately after transplanting by sprinklers. Weed infestation was estimated by counting the number of weeds/2 m four times during the winter season. Weed fresh and air-dry weight/2 m, number of cabbage heads per plot, cabbage fresh yield per plot and average weight per head were recorded.
2.1. Testing of Orobanche seeds At the end of each duration, the mixture of Orobanche seeds and soil from each bag (100 mg) were mixed with 12 kg of sterilized loam soil: sand: peatmoss mixture (1 : 1 : 1) and placed in 28 cm;25 cm plastic pots. Irrigated pots were left in the greenhouse for 2 wk (preconditioning period), and then planted with three broad bean seeds (cv. Super Aqua Dulce). Pots were thinned to two uniform plants 2 wk later. All pots were irrigated with 1.5 L of water every 5 days. Orobanche infestation was assessed by the number of emerged shoots, underground attachments, and their dry weights. The experiment was terminated 120 days after planting (DAP) broad beans by cutting the crop and Orobanche shoots
3. Results and discussion 3.1. Solarization ewects on Orobanche All solarization treatments signi"cantly reduced Orobanche growth that developed on broad bean grown pots when seeds were solarized at 0 depth (Tables 1 and 2). Orobanche aboveground shoot number (ASN), under-
Table 1 The number of above ground shoot (ASN), underground shoot attachment (USN), and total shoot (TSN) of Orobanche that developed on broad bean grown in pots after treating Orobanche seeds with di!erent period of solarization at 0, 5, and 10 cm soil depth. Each pot contained one bag (100 mg) of Orobanche seeds and two broad bean plants. Each value represents the average of "ve replicates (1 bag or 100 mg/replicate or pot). S and NS indicate solarized and nonsolarized treatments respectively Treatment
Time (wk)
Soil depth (cm) 0
NS!parasite NS#parasite NS#manure S S S S#manure S#manure S#manure
0 0 0 2 4 6 2 4 6
5
10
ASN
USN
TSN
ASN
USN
TSN
ASN
USN
TSN
0.0a 4.0b 2.2ab 0.0a 0.0a 0.2a 0.0a 0.0a 0.0a
0.0a 16.2b 11.0b 0.0a 0.0ac 0.0a 0.2a 0.6a 0.0a
0.0a 20.0b 13.4b 0.0a 0.0a 0.2a 0.2a 0.6a 0.0a
0.0a 4.0bc 6.4c 1.2ab 4.2bc 3.2bc 0.6a 0.0a 0.0a
0.0a 16.2b 9.6ab 11.2ab 4.8a 13.8b 1.4a 0.2a 0.0a
0.0a 20.0b 16.0b 12.4b 8.6ab 17.0b 2.0a 0.2a 0.0a
0.0a 4.0b 3.0ab 3.6b 2.0ab 5.0b 0.8a 0.2a 0.0a
0.0a 16.2b 16.0b 15.4b 15.8b 7.2ab 7.0ab 1.0a 0.0a
0.0a 20.0b 19.0b 19.0b 17.8b 12.2b 7.8ab 1.2a 0.0a
Means followed by same letter, in each column, are not signi"cantly di!erent, according to DMRT (P"0.05).
M.A. Haidar, M.M. Sidahmed / Crop Protection 19 (2000) 169}173 Table 2 Total shoot dry weight of Orobanche that developed on broad bean grown pots after treating Orobanche seeds with di!erent period of solarization at 0, 5, and 10 cm soil depth. Each pot contained one bag (100 mg) of Orobanche seeds and two broad bean plants. Each value represents the average of "ve replicates (1 bag or 100 mg/replicate or pot). S and NS indicate solarized and nonsolarized treatments, respectively Treatments
Time (wk)
Total shoot dry weight (g/pot) Soil depth (cm) 0
NS!parasite NS#parasite NS#manure S S S S#manure S#manure S#manure
0 0 6 2 4 6 2 4 6
0.0a 13.34b 7.78b 0.0a 0.0a 0.34a 0.20a 0.79a 0.0a
5 0.0a 13.34c 12.9c 5.54ab 11.5bc 7.23bc 3.0ab 0.0a 0.00a
10 0.0a 13.34d 9.61cd 11.0cd 7.3bcd 6.75bcd 5.41abc 1.34a 0.00a
Means followed by same letter, in each column, are not signi"cantly di!erent, according to DMRT (P"0.05).
ground shoot number (USN) or attachments, total shoot number (TSN) and dry weight (ODW) were signi"cantly reduced by all solarization treatments when seeds were at 0 depth, compared to the infested control. The greatest e!ect of solar heating on imbibed weed seeds has been observed on the topsoil layer (Rubin and Benjamin, 1984). Soil temperatures at this depth were between 41 and 703C (Haidar et al., 1999), which covers the range lethal to imbibed Orobanche seeds (Holm et al., 1997) and various weed seeds (Egley, 1983). Thus, the reduction in TSN at 0 depth is most likely due to high soil temperatures and #uctuations, which could have damaged Orobanche seeds during solarization. The heating e!ect of solarization on Orobanche seeds at various soil depths was similar to that in Haidar et al. (1999), and indicated that seed depth may be the major protection mechanism for Orobanche seeds against solar heating. While solarization alone caused a signi"cant reduction in TSN only at 0 depth (100%), solarization with chicken manure was signi"cant for all treatments at all soil depths (Table 1). Thus, addition of chicken manure augmented the killing e!ect of solarization, and consequently the required period of solarization for signi"cant reduction in TSN below soil surface (5}10 cm) was 2 wk. The additive e!ect of chicken manure on the reduction of Orobanche was consistent at all tested soil depths. In general, the percent reduction in TSN signi"cantly increased with the solarization period reaching 100% after 6 wk of solarization (Table 1). The e!ect on addition of chicken manure on soil temperature and
171
solarization was similar to that described by Haidar et al. (1999). 3.2. Solarization for weed control in cabbage Common weed species found at harvest were Capsella bursa-pastoris, Diplotaxis erucoides, Raphanus raphanistrum, Sinapis arvensis and Veronica spp. Solarization treatments with or without chicken manure signi"cantly reduced weed infestation at 0, 90 and 180 days after solarization, as compared to the non-solarized treatments (Table 3). Their e!ect on weeds, however, was not consistent after 230 days of solarization. Weed fresh and dry weights were signi"cantly reduced by all solarization treatments (Table 4). Addition of chicken manure did not augment the killing e!ect of solarization on weeds, compared to solar heating alone. The best weed control was obtained with 6 wk of solarization alone or with manure. The results are in agreement with previous "nding by Horowitz et al. (1983), who indicated that solarization with transparent polyethylene plastic sheets resulted in an excellent weed control. Weed growth increased at harvest time of cabbage. At harvest, solarization with or without chicken manure for 6 wk was the most e!ective treatment in reducing weed population (Table 3). Weed population was signi"cantly reduced by 80 and 68% in solarization alone and with chicken manure, respectively, when compared to the control with chicken manure. Thus, chicken manure did not reduce weed infestation, compared to solar heating alone. Although all solarization treatments alone reduced weed infestation, the cabbage yield did not increase in comparison to the non-solarized treatments with chicken manure (Table 5). Amendment of soil with chicken manure signi"cantly increased the cabbage yield. Solarization for 2, 4 and 6 wk with chicken manure increased the Table 3 E!ects of solarization alone or with chicken manure on weed infestation in cabbage. Each value represents the average of "ve replicates. S and NS indicate solarized and nonsolarized treatments respectively Treatments
NS NS#manure S S S S#manure S#manure S#manure
Time (wk)
0 0 2 4 6 2 4 6
No. of weeds/2 m Days after solarization 0
90
180
230
65a 51b 0.5c 0.0c 0.0c 3.0c 0.0c 0.0c
77a 137b 14c 13c 3.0c 8.0c 4.0c 2.0c
91a 147b 38cd 42cd 16d 49c 40cd 31cd
89ab 96a 47cde 34de 19e 58bcd 78abc 30de
Means followed by same letter, in each column, are not signi"cantly di!erent, according to DMRT (P"0.05).
172
M.A. Haidar, M.M. Sidahmed / Crop Protection 19 (2000) 169}173
Table 4 E!ects of solarization alone or with chicken manure on weed fresh and dry weight in cabbage. Each value represents the average of "ve replicates. S and NS indicate solarized and nonsolarized treatments respectively Treatments
Time (wk)
Fresh weight (g/2 m)
Air dry weight (g/2 m)
NS NS#manure S S S S#manure S#manure S#manure
0 0 2 4 6 2 4 6
1136a 2122b 282c 238c 200c 424c 428c 230c
322a 557b 98c 94c 68c 112c 184d 65c
Acknowledgements This research was supported by a grant from the University Research Board, American University of Beirut, Beirut, Lebanon.
References
Means followed by the same letter, in each column, are not signi"cantly di!erent, according to DMRT (P"0.05).
Table 5 E!ects of solarization alone or with chicken manure on yield of head cabbage. Each value represents the average of "ve replicates. S and NS indicate solarized and nonsolarized treatments, respectively Treatments
Time (wk)
Heads/plot No.
Yield/plot (kg)
Av. wt/ head (kg)
NS NS#manure S S S S#manure S#manure S#manure
0 0 2 4 6 2 4 6
25a 26a 27a 27a 25a 26a 25a 26a
20.5a 52.1b 47.2b 42.5b 42.3b 80.2c 84.0c 90.5c
0.8a 2.0b 1.8b 1.6b 1.7b 3.1c 3.4c 3.5c
Means followed by same letter, in each column, are not signi"cantly di!erent, according to DMRT (P"0.05).
average weight of cabbage plant by 55, 70 and 75%, respectively, compared to the control with chicken manure. The highest fresh weight was obtained with 6 wk solarization with chicken manure. This increase may be due to the death of plant pests and increase in soil fertility (Chen and Katan, 1980; DeVay, 1991). Nevertheless, the contribution of other biological and chemical factors associated with the addition of manure to the improvement of cabbage yield cannot be excluded.
4. Conclusion This work indicates that combination of solarization and chicken manure for 2}6 wk is an e!ective weed management practice to control Orobanche and suppress the infestation of other weeds in subsequent planting of cabbage. Amendment of soil with chicken manure increased the cabbage yield.
Abu-Irmaileh, B.E., 1991. Soil solarization controls broomrapes (Orobanche spp.) in host vegetable crops in the Jordan valley. Weed Technol. 5, 575}581. Bibi, W., 1996. Response of broomrape (Orobanche ramosa) growth and development to various animal manures in potato. M.Sc. Thesis, American University of Beirut, Beirut, Lebanon, 87 pp. Chen, Y., Katan, J., 1980. E!ect of solar heating of soils by transparent polyethylene mulching on their chemical properties. Soil Sci. 130, 271}277. DeVay, J.E., 1991. Use of soil solarization for control of fungal and bacterial plant pathogens including biocontrol. In: DeVay, J.E., Stapleton, J.J., Elmore, C.L., (Eds.), Soil Solarization. FAO Plant Production and Protection Paper Vol. 109, pp. 79}93. Egley, G.H., 1983. Weed seed seedling reductions by soil solarization with transparent polyethylene sheets. Weed Sci. 31, 404}409. Elmore, C.L., 1991. Use of solarization for weed control. In: Devay, J.E. Stapletonb, J.J., Elmore, C.L. (Eds.), Soil Solarization. FAO Plant Production and Protection Paper. Vol. 109 129}138 Elmore, C.L., 1995. Solarization: an environmentally friendly technology for weed control. Arab J. Plant Prot. 13, 53}55. Haidar, M.A., Iskandarani, N., 1998. Soil sorlarization for control of dodder (Cuscuta spp.) and other weeds in cabbage. In: Stapleton, J.J., DeVay, J.E., Elmore, C.L. (Eds.), Soil Solarization and Integrated Management of Soilborne Pests. FAO Plant Production and Protection Paper, Vol. 147, pp. 264}274. Haidar, M.A., Iskandarani, N., Sidahmed, M., Baalbaki, R., 1999. Response of "eld dodder (Cuscuta campastris) seeds to solarization and chicken manure. Crop Prot. 18, 253}258. Holm, L., Doll, J., Holm, E., Pancho, J., Herberger, J., 1997. World Weeds-natural Histories and Distribution. Wiley, pp. 511}530. Horowitz, M., Regev, Y., Herzlinger, G., 1983. Solarization for weed control. Weed Sci. 31, 170}179. Jacobsohn, R., Greenberger, A., Katan, J., Levi, M., Alon, H., 1980. Control of Egyptian broomrape (Orobanche aegyptiaca) and other weeds by means of solar heating of the soil by polyethylene mulching. Weed Sci. 28, 312}316. Janudi, A.K., 1982. Comparative studies on GR-24 and herbicide for Orobanche ramosa control in tomato. M.Sc. Thesis. American University of Beirut, Beirut, 66 pp. Joel, D.M., 1995. Germination of weedy root parasites. In: Kigel, J., Galili, G. (Eds.), Seed development and germination. MarcelDekker, New York, pp. 567}597. Linke, K.H., 1994. E!ects of soil solarization on arable weeds under Mediterranean conditions: control, lack of response or stimulation. Crop Prot. 13, 115}120. Linke, K.H., Saxena, M.C. 1991. Study the viability and longevity of Orobanche seed under laboratory conditions. In: Wegmann, K., Musselman, L.J. (Eds.), Proceedings of the International Workshop on Orobanche Research, Obermarchtal, 1989. Eberhard-KarlsUniversitat, Tubingen, pp. 110}114. Linke, K.H., Sauerborn, J., Saxena, M.C., 1989. Orobanche Field Guide. University of Hohenheim and ICARDA, p. 42. Mitich, L.W., 1993. Orobanche * the broomrapes. Weed Technol. 7, 532}535. Parker, C., Riches C.R., 1993. Parasitic Weeds of the World: Biology and Control. Cab International, Wallingford, UK, 332 pp.
M.A. Haidar, M.M. Sidahmed / Crop Protection 19 (2000) 169}173 Parker, C., 1986. Scope of the agronomic problems caused by Orobanche species. In: Proceedings of Workshop on Biology and Control of of Orobanche. ter Borg, S.J. (Ed.), LH/VPO Wageningen, The Netherlands, pp. 11}17. Rubin, B., Benjamin, A., 1984. Solar heating of the soil: involvement of environmental factors in the weed control process. Weed Sci. 32, 138}142.
173
Saghir, A.R., 1979. Di!erent chemicals and their potential for Orobanche control. Second Symposium on Parasitic weeds, pp. 41}47. Saueborn, J., Linke, K.-H., Saxena, M.C., Koch, W., 1989. Solarization; a physical control method for weeds and parasitic plants (Orobanche spp.) in Mediterranean agriculture. Weed Res. 29, 391}397.
Soil solarization and chicken manure for the control of Orobanche crenata and other weeds in Lebanon M.A. Haidar*, M.M. Sidahmed Faculty of Agricultural and Food Sciences, American University of Beirut, Beirut, Lebanon Received 16 August 1999; received in revised form 30 September 1999; accepted 4 October 1999
Abstract Field studies were conducted in Lebanon to investigate the e!ect of solarization periods (0}6 wk) with or without chicken manure on Orobanche crenata seeds at various soil depths (0}10 cm), and on weed management in subsequent planting of cabbage. Solarization treatments alone killed Orobanche seeds at 0 depth, but had no signi"cant e!ect on Orobanche seeds below this depth. Solarization with chicken manure killed Orobanche seeds at all depths. Solarization for 2}6 wk with or without chicken manure signi"cantly reduced weed growth and infestation in cabbage. Chicken manure, however, signi"cantly increased the yield of cabbage. 2000 Elsevier Science Ltd. All rights reserved. Keywords: Cabbage; Chicken manure; Weed management
1. Introduction Orobanche crenata Forsk (crenate broomrape) is an obligate root parasite of the family Orobanchaceae (Mitich, 1993). It is widely distributed in the Mediterranean basin region and the Middle East (Parker, 1986). Orobanche crenata parasitizes various winter herbaceous dicots such as broad beans (Vicia faba L.), lentils (Lens esculenta L.) and peas (Pisum sativum L.), but not grasses (Parker and Riches, 1993). In Lebanon, broad beans and peas are the major crops parasitized by O. crenata. Like annual weeds, Orobanche perpetuation depends on production and dormancy of seeds that replenish annual losses from the soil seed bank. A single mature O. crenata plant may produce over 200,000 seeds (Parker and Riches, 1993) that may remain viable in soil for 10 years (Linke and Saxena, 1991). In the "eld, Orobanche seeds germinate only in the presence of chemical stimulants exuded by roots of suitable hosts (Holm et al., 1997), and they require 1}2 wk pre-conditioning period before they respond to the stimulant (Joel, 1995). The emerging radicle moves directly toward the roots of nearby potential hosts. Once the radicle strikes the host root, it immediately forms an appresorium followed by haustoria
* Corresponding author. Tel.: #961-343002; fax: #961-1-744-460. E-mail address: [email protected], [email protected] (M.A. Haidar).
production, where they make physiological connections with host xylem and phloem (Linke et al., 1989). The physiological relationship between Orobanche and its host means conventional methods of controlling Orobanche infestations are expensive and complex, and sometimes unsuccessful. In Lebanon, control is mostly by soil fumigation with methyl bromide, which is expensive, hazardous (Janudi, 1982), and may soon be subject to restrictions. Therefore, the search for non-conventional methods for controlling Orobanche and soil-borne pests has become increasingly important. Among non-conventional methods, soil solarization was found e!ective in controlling Orobanche spp. (Abu-Irmaileh, 1991; Jacobsohn et al., 1980; Saueborn et al., 1989) and various non-parasitic weeds (Elmore, 1991,1995; Haidar and Iskandarani, 1998; Linke, 1994). Soil solarization is achieved by mulching moistened soil with plastic sheets during warm summer months thereby raising soil temperature and controlling various weeds and soil-borne pathogens (Jacobsohn et al., 1980). However, it is well documented that long periods of solarization (6}7 wk) are required for controlling Orobanche (Abu-Irmaileh, 1991; Saueborn et al., 1989). This can be unsatisfactory in intensive agriculture. One way to reduce solarization period is by using soil amendments that augments the weed killing e!ect. Chicken manure is widely used in Lebanon as organic fertilizer, and was e!ective in reducing Orobanche ramosa growth and infestation in potatoes
0261-2194/00/$ - see front matter 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 2 6 1 - 2 1 9 4 ( 9 9 ) 0 0 0 8 3 - 6
170
M.A. Haidar, M.M. Sidahmed / Crop Protection 19 (2000) 169}173
(Bibi, 1996). Work by the authors (Haidar et al., 1999) has shown how e!ective this practical procedure can be in the control of other parasitic weeds (Cuscuta spp). The objectives of this study were to determine the e!ects of di!erent periods of soil solarization with or without chicken manure on (1) O. crenata seeds at di!erent soil depths, and (2) on weed infestation in subsequent planting of cabbage.
at soil level, washing the broad bean roots by water, and separating under ground Orobanche attachment from broad bean roots. Dry weight of total Orobanche shoots per pot was recorded. Presented data are the original average of "ve replicates. Means of "ve replications (5 pots or 500 mg of seeds/depth) were analysed for variance and signi"cant di!erences were determined by Duncan's multiple range test at the 5% probability level.
2. Materials and methods
2.2. Solarization for weed control in cabbage
The experimental procedure and design follow those described by Haidar et al. (1999), except that Orobanche crenata seeds were placed in cotton bags (208;308 lm), and their germination was tested using broad bean as a host. Each bag contained 100 mg of seeds, which is equivalent to about 20,000 seeds (Saghir, 1979).
One month after solarization (October, 1997), 4-wk old cabbage seedlings (cv.O-S-Cross) were transplanted at 25 cm spacing with minimum soil disturbance. Planting was done by driving holes into the soil with a hand chisel. Three rows of cabbage were planted per plot. Fertilizers were not added. One irrigation was applied immediately after transplanting by sprinklers. Weed infestation was estimated by counting the number of weeds/2 m four times during the winter season. Weed fresh and air-dry weight/2 m, number of cabbage heads per plot, cabbage fresh yield per plot and average weight per head were recorded.
2.1. Testing of Orobanche seeds At the end of each duration, the mixture of Orobanche seeds and soil from each bag (100 mg) were mixed with 12 kg of sterilized loam soil: sand: peatmoss mixture (1 : 1 : 1) and placed in 28 cm;25 cm plastic pots. Irrigated pots were left in the greenhouse for 2 wk (preconditioning period), and then planted with three broad bean seeds (cv. Super Aqua Dulce). Pots were thinned to two uniform plants 2 wk later. All pots were irrigated with 1.5 L of water every 5 days. Orobanche infestation was assessed by the number of emerged shoots, underground attachments, and their dry weights. The experiment was terminated 120 days after planting (DAP) broad beans by cutting the crop and Orobanche shoots
3. Results and discussion 3.1. Solarization ewects on Orobanche All solarization treatments signi"cantly reduced Orobanche growth that developed on broad bean grown pots when seeds were solarized at 0 depth (Tables 1 and 2). Orobanche aboveground shoot number (ASN), under-
Table 1 The number of above ground shoot (ASN), underground shoot attachment (USN), and total shoot (TSN) of Orobanche that developed on broad bean grown in pots after treating Orobanche seeds with di!erent period of solarization at 0, 5, and 10 cm soil depth. Each pot contained one bag (100 mg) of Orobanche seeds and two broad bean plants. Each value represents the average of "ve replicates (1 bag or 100 mg/replicate or pot). S and NS indicate solarized and nonsolarized treatments respectively Treatment
Time (wk)
Soil depth (cm) 0
NS!parasite NS#parasite NS#manure S S S S#manure S#manure S#manure
0 0 0 2 4 6 2 4 6
5
10
ASN
USN
TSN
ASN
USN
TSN
ASN
USN
TSN
0.0a 4.0b 2.2ab 0.0a 0.0a 0.2a 0.0a 0.0a 0.0a
0.0a 16.2b 11.0b 0.0a 0.0ac 0.0a 0.2a 0.6a 0.0a
0.0a 20.0b 13.4b 0.0a 0.0a 0.2a 0.2a 0.6a 0.0a
0.0a 4.0bc 6.4c 1.2ab 4.2bc 3.2bc 0.6a 0.0a 0.0a
0.0a 16.2b 9.6ab 11.2ab 4.8a 13.8b 1.4a 0.2a 0.0a
0.0a 20.0b 16.0b 12.4b 8.6ab 17.0b 2.0a 0.2a 0.0a
0.0a 4.0b 3.0ab 3.6b 2.0ab 5.0b 0.8a 0.2a 0.0a
0.0a 16.2b 16.0b 15.4b 15.8b 7.2ab 7.0ab 1.0a 0.0a
0.0a 20.0b 19.0b 19.0b 17.8b 12.2b 7.8ab 1.2a 0.0a
Means followed by same letter, in each column, are not signi"cantly di!erent, according to DMRT (P"0.05).
M.A. Haidar, M.M. Sidahmed / Crop Protection 19 (2000) 169}173 Table 2 Total shoot dry weight of Orobanche that developed on broad bean grown pots after treating Orobanche seeds with di!erent period of solarization at 0, 5, and 10 cm soil depth. Each pot contained one bag (100 mg) of Orobanche seeds and two broad bean plants. Each value represents the average of "ve replicates (1 bag or 100 mg/replicate or pot). S and NS indicate solarized and nonsolarized treatments, respectively Treatments
Time (wk)
Total shoot dry weight (g/pot) Soil depth (cm) 0
NS!parasite NS#parasite NS#manure S S S S#manure S#manure S#manure
0 0 6 2 4 6 2 4 6
0.0a 13.34b 7.78b 0.0a 0.0a 0.34a 0.20a 0.79a 0.0a
5 0.0a 13.34c 12.9c 5.54ab 11.5bc 7.23bc 3.0ab 0.0a 0.00a
10 0.0a 13.34d 9.61cd 11.0cd 7.3bcd 6.75bcd 5.41abc 1.34a 0.00a
Means followed by same letter, in each column, are not signi"cantly di!erent, according to DMRT (P"0.05).
ground shoot number (USN) or attachments, total shoot number (TSN) and dry weight (ODW) were signi"cantly reduced by all solarization treatments when seeds were at 0 depth, compared to the infested control. The greatest e!ect of solar heating on imbibed weed seeds has been observed on the topsoil layer (Rubin and Benjamin, 1984). Soil temperatures at this depth were between 41 and 703C (Haidar et al., 1999), which covers the range lethal to imbibed Orobanche seeds (Holm et al., 1997) and various weed seeds (Egley, 1983). Thus, the reduction in TSN at 0 depth is most likely due to high soil temperatures and #uctuations, which could have damaged Orobanche seeds during solarization. The heating e!ect of solarization on Orobanche seeds at various soil depths was similar to that in Haidar et al. (1999), and indicated that seed depth may be the major protection mechanism for Orobanche seeds against solar heating. While solarization alone caused a signi"cant reduction in TSN only at 0 depth (100%), solarization with chicken manure was signi"cant for all treatments at all soil depths (Table 1). Thus, addition of chicken manure augmented the killing e!ect of solarization, and consequently the required period of solarization for signi"cant reduction in TSN below soil surface (5}10 cm) was 2 wk. The additive e!ect of chicken manure on the reduction of Orobanche was consistent at all tested soil depths. In general, the percent reduction in TSN signi"cantly increased with the solarization period reaching 100% after 6 wk of solarization (Table 1). The e!ect on addition of chicken manure on soil temperature and
171
solarization was similar to that described by Haidar et al. (1999). 3.2. Solarization for weed control in cabbage Common weed species found at harvest were Capsella bursa-pastoris, Diplotaxis erucoides, Raphanus raphanistrum, Sinapis arvensis and Veronica spp. Solarization treatments with or without chicken manure signi"cantly reduced weed infestation at 0, 90 and 180 days after solarization, as compared to the non-solarized treatments (Table 3). Their e!ect on weeds, however, was not consistent after 230 days of solarization. Weed fresh and dry weights were signi"cantly reduced by all solarization treatments (Table 4). Addition of chicken manure did not augment the killing e!ect of solarization on weeds, compared to solar heating alone. The best weed control was obtained with 6 wk of solarization alone or with manure. The results are in agreement with previous "nding by Horowitz et al. (1983), who indicated that solarization with transparent polyethylene plastic sheets resulted in an excellent weed control. Weed growth increased at harvest time of cabbage. At harvest, solarization with or without chicken manure for 6 wk was the most e!ective treatment in reducing weed population (Table 3). Weed population was signi"cantly reduced by 80 and 68% in solarization alone and with chicken manure, respectively, when compared to the control with chicken manure. Thus, chicken manure did not reduce weed infestation, compared to solar heating alone. Although all solarization treatments alone reduced weed infestation, the cabbage yield did not increase in comparison to the non-solarized treatments with chicken manure (Table 5). Amendment of soil with chicken manure signi"cantly increased the cabbage yield. Solarization for 2, 4 and 6 wk with chicken manure increased the Table 3 E!ects of solarization alone or with chicken manure on weed infestation in cabbage. Each value represents the average of "ve replicates. S and NS indicate solarized and nonsolarized treatments respectively Treatments
NS NS#manure S S S S#manure S#manure S#manure
Time (wk)
0 0 2 4 6 2 4 6
No. of weeds/2 m Days after solarization 0
90
180
230
65a 51b 0.5c 0.0c 0.0c 3.0c 0.0c 0.0c
77a 137b 14c 13c 3.0c 8.0c 4.0c 2.0c
91a 147b 38cd 42cd 16d 49c 40cd 31cd
89ab 96a 47cde 34de 19e 58bcd 78abc 30de
Means followed by same letter, in each column, are not signi"cantly di!erent, according to DMRT (P"0.05).
172
M.A. Haidar, M.M. Sidahmed / Crop Protection 19 (2000) 169}173
Table 4 E!ects of solarization alone or with chicken manure on weed fresh and dry weight in cabbage. Each value represents the average of "ve replicates. S and NS indicate solarized and nonsolarized treatments respectively Treatments
Time (wk)
Fresh weight (g/2 m)
Air dry weight (g/2 m)
NS NS#manure S S S S#manure S#manure S#manure
0 0 2 4 6 2 4 6
1136a 2122b 282c 238c 200c 424c 428c 230c
322a 557b 98c 94c 68c 112c 184d 65c
Acknowledgements This research was supported by a grant from the University Research Board, American University of Beirut, Beirut, Lebanon.
References
Means followed by the same letter, in each column, are not signi"cantly di!erent, according to DMRT (P"0.05).
Table 5 E!ects of solarization alone or with chicken manure on yield of head cabbage. Each value represents the average of "ve replicates. S and NS indicate solarized and nonsolarized treatments, respectively Treatments
Time (wk)
Heads/plot No.
Yield/plot (kg)
Av. wt/ head (kg)
NS NS#manure S S S S#manure S#manure S#manure
0 0 2 4 6 2 4 6
25a 26a 27a 27a 25a 26a 25a 26a
20.5a 52.1b 47.2b 42.5b 42.3b 80.2c 84.0c 90.5c
0.8a 2.0b 1.8b 1.6b 1.7b 3.1c 3.4c 3.5c
Means followed by same letter, in each column, are not signi"cantly di!erent, according to DMRT (P"0.05).
average weight of cabbage plant by 55, 70 and 75%, respectively, compared to the control with chicken manure. The highest fresh weight was obtained with 6 wk solarization with chicken manure. This increase may be due to the death of plant pests and increase in soil fertility (Chen and Katan, 1980; DeVay, 1991). Nevertheless, the contribution of other biological and chemical factors associated with the addition of manure to the improvement of cabbage yield cannot be excluded.
4. Conclusion This work indicates that combination of solarization and chicken manure for 2}6 wk is an e!ective weed management practice to control Orobanche and suppress the infestation of other weeds in subsequent planting of cabbage. Amendment of soil with chicken manure increased the cabbage yield.
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