Allelopathic Potentials of Some Crop Residues on the Germination and Growth of Soybeans
(Glycine max) (l.) Merrill.
M. J. Ayeni and J. Kayode
Department of Plant Science, University of Ado Ekiti, Ado Ekiti, 360101, Nigeria.
Abstract: Allelopathic potentials of aqueous water extracts of sorghum stem, maize inflorescence and rice husks on the germination and growth of soybeans ( Glycine max L.) were investigated. The results showed that the extracts brought about considerable inhibition in the germination of soybean seeds, reductions in radicle and plumule lengths of soybean seedlings. But while the extracts from maize inflorescence and rice husk had more inhibitory effects on soybeans radicle growth, all the three extracts demonstrated pronounced effects on the growth of the plumule.
Key words: Allopathic, allelochemicals, crop residues, Glycine max
Introduction
The presence of allelochemicals compounds in various plants and crops is now widely realized (Rice 1984; Putman 1988; Park 1993). They may be present in any part of the plant- roots, leaves, flowers, fruits or stems-from where they are released to the soil by processes such as volatilization, root exudation, leaching and decomposition (Rice 1984). Ogbe et al., (1994) asserted that these allelochemicals affects plant growth and development of other plants. Such effects, so far identified, included inhibition of seed germination (Patil 1994; Tobe 2000), seedling growth retardation (Bhatt and Todoria 1990) and poor seedling survival (Smith 1990).
Recent initiatives are now suggesting that allelochemicals are equally present in significant proportions in some crop residues.
Consequent on this, Kayode and Ayeni (2009a) demonstrated the allelopathic effects of some crop residues on the germination and growth of cowpea ( Vigna

unguiculata ), Kayode and Ayeni (2009b) on maize ( Zea mays ), Ayeni and Kayode (2009) on
Sphenosylis sternocarpa and Ayeni et al.
, (2010) on Bidens pilosa.
The study being reported here examined the allelopathic potentials of aqueous extracts from residues of sorghum stem, rice husks and maize inflorescence on soybean, an important leguminous food crop widely cultivated in Nigeria.
Materials and Methods
The study was conducted in the laboratory of the Department of Plant Science, University of
Ado-Ekiti, Ado-Ekiti, Nigeria. Soybeans seeds were obtained from the Teaching and Research farm of the University of Ado-Ekiti, Nigeria. Mature sorghum plants and maize inflorescences were harvested from the Department’s experimental farm. The sorghum stems were cut into small pieces to facilitate drying. Fresh rice husks were obtained from Ikere-Ekiti, a town located at about 25 kilometers from the University.
These materials were air dried for three weeks, pounded using pistil and mortal and blended with electric blender. Portions of 5g, 10g, 15g, 20g, and 25g were measured out from the rice husks, sorghum and maize inflorescence. Each portion was soaked in 200ml distilled water in 500ml conical flask. The mixtures were shaken intermittently and left overnight (for 24hrs). The aqueous extracts were filtered using Whatman No .1 filter paper and the filtrates were used afresh or kept in refrigerator for further use.
Petri dishes were double laid with Whatman No .1 filter papers. Five soybeans seeds were put in each Petri dish and each treatment was replicated ten times. The filter papers were moistened daily with the different extract concentrations. Control experiment, whose Petri dishes were moistened with distilled water, was also set up and replicated 10 times. All the Petri dishes were put in growth chamber at room temperature. The seeds were considered germinated upon radicle

emergence. The radicle and plumule growth elongations were recorded at 24hrs interval. The results obtained from the extracts treated seeds were compared to those obtained from the control experiment.
Result and Discussion
The allelopathic effects of the aqueous extracts from sorghum stem, maize inflorescence and rice husks residues on the germination of soybean were recorded until 72hrs experiment time. The results revealed that the germination and growth of soybean seeds were inhibited. The degree of inhibition increased with the increase in the concentration of the extracts. In the sorghum extractstreated seeds (Table 1) 98%, 82%, 68%, 62% and 52% of the extract-treated seeds germinated at 5g,
10g, 15g, 20g and 25g extract concentrations respectively at 96hrs experimental time. Similarly, at
96hrs experimental time, in the maize extracts–treated seeds (Table 2), 98%, 96%, 86%, 78%, 40% and 22% of the extracts-treated seeds germinated at 5g, 10g, 15g, 20g and 25g extract concentrations respectively. Also in the rice husk extracts–treated seeds (Table 3), 94%, 78%, 74%, 68%, 48% and
44% of the extracts-treated seeds germinated at 5g, 10g, 15g, 20g and 25g extract concentrations respectively. In the control experiment, 96% of the seeds had germinated within the 72 hours of the experiment (Tables 1, 2 and 3).These observations agreed with the earlier report of Bora et al .,
(1999) who observed similar inhibitory effects from the leaf extracts of Acacia auriculiformis on the germination of some agricultural crops and whose inhibitory effects were proportional to the concentration of the extracts.
The results of the tests conducted on the effects of aqueous extracts from the three crop residues on the radicle lengths of soybeans were shown in Tables 4, 5, 6 respectively. The growths of radicles from the extracts-treated seeds were retarded when compared to the growth of the seedlings from the control. The rate of retardation increased with the increase in the concentration of

extracts thus indicating that the retardation was concentration-dependent. In the sorghum extractstreated seeds, the radicle lengths at 144hr experimental time were 21.82cm, 20.68cm, 13.98cm,
11.60cm, and 8.70cm respectively (Table 4) at 5g, 10g, 15g, 20g and 25g extract concentrations.
These constituted 36%, 33%, 57%, 64% and 73% reductions respectively from that of the control experiment.
In the maize extracts-treated seeds, the radicle lengths at 144hr experimental time were
14.42cm, 9.22cm, 8,20cm, 8.14cm and 4.38cm respectively (Table 5) at 5g, 10g, 15g, 20g and 25g extract concentrations, thus constituting 55%, 72%, 75%, 75% and 86% reductions respectively from that of the control experiment. Also at the 144hr experimental time, the radicle lengths in the rice husk extract-treated seeds were 26.32cm, 16.24cm, 14.66cm, 6.88cm and 5.72cm respectively
(Table 6) at 5g, 10g, 15g, 20g and 25g extract concentrations. These constituted 19%, 50%, 55%,
79% and 82% reductions respectively from that of the control experiment. The radicle length was
32.40cm in the control experiment at the same experimental time. The results tend to suggest that extracts derived from the maize inflorescence and rice husk had more inhibitory effects on the growth of radicle in soybean as no growths were recorded in these extracts until 72hours of the experiment in all the extracts concentrations.
The plumule lengths of soybeans were also retarded by the three extracts (Tables 7, 8, and 9).
In the sorghum-extract treated seeds (Table 7), the plumule lengths at 144hr experimental time were
7.72cm, 2.92cm, 0.90cm, 0.72cm and 0.36cm at 5g, 10g, 15g, 20g and 25g extract concentrations while the plumule length of the control experiment was 16.92cm. The degree of retardation also increased with the increase in the concentration of the extracts. The retardations obtained from the extract-treated seeds were 54%, 83%, 95%, 96% and 98% respectively. In the maize inflorescenceextract treated seeds (Table 8), the plumule lengths at 144hr experimental time were 7.04cm,

6.24cm, 4.22cm, 3.18cm and 0.30cm at 5g, 10g, 15g, 20g and 25g extract concentrations, thus constituting reductions of 58%, 63%, 75%, 81% and 98% respectively from that of the control experiment. Also in the rice husk extract-treated seeds (Table 9), the plumule lengths at 144hr experimental time were 12.72cm, 5.80cm, 5.60cm, 1.22cm and 0.88cm at 5g, 10g, 15g, 20g and 25g extract concentrations, thus constituting reductions of 25%, 66%, 67%, 89% and 95% reductions respectively from that of the control experiment. Thus the effects of these extracts on plumule could also be said to be oncentration dependent. The results tend to suggest that all extracts treated seeds experienced considerable inhibitory effects in the growth of their plumule.
The results obtained from this study agreed with the previous findings of Jadhar and Goyanar
(1992) who observed that the percentage germination, plumule and radicle lengths of rice and cowpea were decreased with increasing concentration of the extracts from leaf leachates of Acacia auriculiformis , and also with Qudhia (1999) who asserted that extract from C . gigantean inhibited the growth of radicle and plumule of Lathyrus sativa . Similarly Chou and Lin (1976) as well as
Irshad and Cheema (2004) reported that aqueous extracts from rice residues inhibited root growth of lettuce, rice seedlings and Barnyard grass respectively. Previous studies revealed that the inhibitory compounds occurring in these crop residues are mostly phenols (Guenzi and McCalla 1996). The phenols in sorghum plants are benzoic acid, p -hydrobenzoic acid, vanillic acid, m -comedic acid, p coumaric acid, gallic acid, ferulic acid and chlorogenic acid (Cheema 1988). The rice husks, according to Chuo and Lin (1976) contained p-hydroxyl benzoic acid, yanillic, ferullic, p -coumeric and o -hydroxylphenylacetic acids. Chou et al. (1981) had also reported the presence of syringic acid in rice husks.
In Nigeria, these crop residues are often left uncared for on farms where they decomposed and consequently release considerable proportion of allelochemicals into the soil. Further studies on

the release and effects of these allochemicals are being advocated in the continued efforts to boost food production in the country.
REFERENCES
Ayeni, J. M. Kayode, J 2009 The effects of aqueous extracts from maize roots and sorghum stem on the germination and growth of Sphenostylis sternocapa Hochst ex. Rich. (African Yam beans).
African Journal of General Agriculture 5 (3) 117-121.
Ayeni, J. M. Kayode, J. Tedela, P. O 2010 Allelopathic potentialities of some crop residues on the germination and growth of Bidens pilosa L. Journal of Agricultural Science and Technology 4 (1) 21-
24.
Bhatt, B. P. Todoria, N. P 1990 Studies on the allelopathic effects of some agro forestry tree crops of
Garhwal Himalaya, Agroforestry Systems 12 251-255.
Bora, I. Singh, J. J. Borthakur, R. Bora, E. 1999 Allelopathic effects of leaf extract of Acacia auriculiformis on seed germination of some agricultural crops. An Ann. For .
7 143-146.
Cheema, Z. A 1988 Weed control in weeds through sorghum allelochemicals. Unpublished Ph.D
Thesis, Department of Agronomy, University of Agriculture, Faisalahad.
Chuo, C. I. Lin, H. J. 1976 Autointoxication mechanism of Oryza sativa L. Phytotoxic effects of decomposing rice residues in Soil . J. Chem. Eco.
2 353-367.
Chou, C. H. Chiang, Y.C. Cheng, H. H 1981 Autointoxincation mechanism of I. sativa III. Effect of temperature on phytotoxic production during rice straw decpmposition in soil. J. ChemEcol. 7 741-
752.
Guenzi, W. D. McCalla, T. M 1996 Phenolic acids in oats wheat, sorghum and corn residues and their phytoxicty . Agron. J. 58 303-304.
Irshad, A. Cheema, Z. A 2004 Influence of some plant water extracts on the germination and seedling growth of Barnyard grass ( E. crus- galli L.) . Pak . J. Sci . Ind. Res.
43 (3) 222-226.
Jadhar, B. B. Gayanar, I. 1992 Allelopathic affects of Acacia auriculiformis on the germination of rice and cowpea. Indian J. Plant Phys .
1 86-89.
Kayode, J. Ayeni, J. M. 2009a Allelopathic Effects of Some Crop Residues on the Germination an
Growth of Cowpea( Vigna unguiculata L. Walp.) Ethnobotanical Leaflets 13 343-350.
Kayode, J. Ayeni, J. M 2009b Allelopathic Effects of Some Crop Residues on the Germination and
Growth of Maize( Zea mays L.). The Pacific Journal of Science and Tecnology 10 (1) 345-349.

Ogbe, F.M.O. Gill, L. S. Iserhein, E. O. O 1994 Effects of aqueous extracts of C. odorata L. on the radical and plumule growth and seedling height of maize, Z. mays L. Compositae Newsletters 25
31-38.
Park, K.H. Ku, Y. C. Oh, Y.J. Cho, S. Y 1993 A potential weed control by alleloopathic rice germplasm. Korean J. Weed Sc . 13 (2) 95-96.
Patil, B.P 1994 Effects of Gliricidia maculata L. extracts on field crops. Allelopathy J.
1 118-120.
Putnam, A. R 1984 Allelochemicals from plant as herbicides. Weed Technology 2 510-518.
Qudhia, A 1999 Allelopathic effects of some obnoxious weeds on germination and seedlings Vigor of Lathyrus sativas , FABIS Newsletter 42 .
Rice, E. L 1984 Allelopathy. Academic Press, New York, USA.
Smith, A. E 1990 The potential alleloopathic characteristics of bitter sneezeweed ( Helenium amaraum ), Weed Sci . 37 665-669.
Tobe, K. Li, X. Omasa, K 2000 Seed germination and radicule growth of halophyte Kalidium capsicum (Chenopediaceae), Annals of Botany , 85 (3) 391-396.

Table1: Effects of aqueous extracts from sorghum stem on the germination of soybeans ( Glycine max) seeds.
Extracts g/200ml
% Seed germination / Experimental Time (Hrs)
24 48 72 96 120 144
5
10
15
20
25
Control
15
20
25
5
10
Control
0 8 64 26 - -
0 0 60 22 6 -
0 0 48 20 6 -
0 0 44 18 4 -
0 0 38 14 2 -
0 50 46 2 - -
Table 2: Effects of the aqueous extract from maize inflorescence on the germination of Soybeans
( Glycine max ) seeds.
Extracts
(g/200ml)
% Seed germination / Experimental Time (Hrs)
24 48 72 96 120 144
0 0 66 30 - -
0 0 56 30 2 -
0 0 46 28 16 -
0 0 16 24 16 -
0 0 0 22 14 -
0 50 46 2 - -

Table 3: Effects of the aqueous extracts from rice husk on the germination of Soybeans ( Glycine max ) seeds.
Extracts
(g/200ml)
% Seeds germination / Experimental Time (Hrs)
24 48 72 96 120 144
15
20
25
5
10
Control
0 4 68 24 2 -
0 0 56 22 12 -
0 0 52 22 10 -
0 0 48 20 6 -
0 0 30 18 2 -
0 56 40 4 - -
Table 4: Effects of the aqueous extracts from sorghum stem on the radicle length (cm) of Soybeans
( Glycine max ) seeds
Extract g(/200ml)
5
Radicle length (cm) / Experimental Time (Hrs).
24 48 72 96 120 144*
10
15
20
25
Control
0 0.06 4.14 11.78 15.38 20.68
(36%)
0 0 2.94 6.98 21.62 21.82
(33%)
0 0 1.00 4.44 14.50 13.98
(57%)
0 0 0.58 4.04 10.48 11.60
(64%)
0 0 0.36 3.68 8.12 8.70
(73%)
0 0.46 7.16 16.38 19.60 32.40
* Figures in brackets are the proportions of inhibition from the control

Table 5: Effects of the aqueous extracts from maize inflorescence on the radicle length (cm) of soybeans ( Glycine max ).
Extracts
(g/200ml)
5
Radicle length (cm) / Experimental Time (Hrs).
24 48 72 96 120 144*
0 0 7.40 9.76 13.88 14.42
(55%)
10
15
20
25
Control
0 0 0.64 7.82 8.82 9.22
(72%)
0 0 0.26 5.82 7.98 8.20
(75%)
0 0 0 5.30 7.78 8.14
(75%)
0 0 0 0.92 2.38 4.38
(86%)
0 0.46 7.16 16.38 19.60 32.40
* Figures in brackets are the proportions of inhibition from the control

Table 6: Effects of the aqueous extracts from rice husk on the radicle length (cm) of soybeans
( Glycine max ) seeds.
Extracts
(g/200ml)
5
Radicle length (cm) / Experimental Time (Hrs).
24 48 72 96 120 144*
10
15
20
0 0 3.98 15.08 23.86 26.32
(19%)
0 0 0.54 9.48 14.52 16.24
(50%)
0 0 0.38 8.88 14.14 14.66
(55%)
0 0 0.36 6.58 6.08 6.88
(79%)
25
Control
0 0 0.16 5.34 5.88 5.72
(82%)
0 0.46 7.16 16.38 19.60 32.40
* Figures in brackets are the proportions of inhibition from the control

TABLE 7: Effects of the aqueous extracts from sorghum stem on the plumule length (cm) of soybeans ( Glycine max ).
Extracts
(g/200ml)
5
Soybeans seed germination (%)/Experiment Time (Hrs)
24 24 72 96 120 144
10
15
20
25
Control
0 0 0.10 1.64 7.58 7.72
(54%)
0 0 0 0.76 1.72 2.92
(83%)
0 0 0 0.48 0.60 0.90
(95%)
0 0 0 0.36 0.48 0.72
(96%)
0 0 0 0.16 0.40 0.36
(98%)
0 0.04 1.30 3.32 9.70 16.92
* Figures in brackets are the proportions of inhibition from the control

Table 8: Effects of the aqueous extracts fom maize inflorescence on the plumule length (cm) of soy beans (Glycine max).
Extracts
(g200ml)
5
Soy beans germination (%)/Experimental Time (Hrs)
24 48 72 96 120 144
10
15
20
25
Control
0 0 0 1.48 4.26 7.04
(58%)
0 0 0 0.56 3.42 6.24
(63%)
0 0 0 0.50 3.02 4.22
(75%)
0 0 0 0.46 2.36 3.18
(81%)
0 0 0 0 0.06 0.30
(98%)
0 0.04 1.30 3.32 9.70 16.92
* Figures in brackets are the proportions of inhibition from the control

Table 9: Effects of the aqueous extracts from rice husks on the plumule length (cm) of soybeans
(Glycine max).
Extracts
(g/200ml)
5
Soybeans seeds germination (%) Experimental Time(Hrs)
24 48 72 96 120 144*
10
15
20
25
Control
0 0 0 3.64 8.46 12.72
(25%)
0 0 0 0.18 2.42 5.80
(66%)
0 0 0 0.16 1.00 5.60
(67%)
0 0 0 0.10 0.76 1.22
(89%)
0 0 0 0 0.42 0.88
(95%)
0 0.04 1.30 3.32 9.70 16.92
* Figures in brackets are the proportions of inhibition from the control