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Density-dependent interference of Emex australis in wheat at different sowing times

Rana Nadeem Abbas1, Asif Tanveer1, Asghar Ali1 and Zaheer A Zaheer2

1Department of Agronomy, University of Agriculture, Faisalabad, Pakistan. Email: nadeem4u1@hotmail.com
2
Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan.

Abstract

Emex australis Steinh. (Spiny emex) is a newly established invasive annual weed in wheat and other winter crops in Punjab. Decline in grain yield and quality of wheat is a major problem caused by delayed sowing and interference from weeds. The effects of sowing dates (7, 15, 23 Nov) and Emex australis density (0, 18, 36, 54, 72 plants/m2) on growth and yield of wheat and the biology of Emex australis were evaluated over two seasons (2005-06, 2006-07). There was no effect of weed density on the number of days taken to initiate flowering by E. australis. Highest values for E. australis plant height, dry biomass, number of seeds/plant and seed weight were recorded by sowing wheat on 7 November at E. australis density of 18 plants/m2 in both years. The highest number of spike-bearing tillers, plant height, number of grains per spike, 1000-grain weight and grain yield were observed in 7 November sowing with zero E. australis density and minimum values for these parameters were recorded in late sowing (23 November) at maximum weed density of 72 plants/m2. Early sowing and weed-free plots increased wheat grain yield compared to later sowings and higher weed density. The minimum E. australis density level investigated caused significant reduction in grain yield of wheat. Grain yield loss was comparatively less in early sowing than optimum and late sowing. In the study region, wheat should be planted in the first week of November so it can better compete with E. australis, as compared to late sowing when wheat becomes susceptible to competition from E. australis.

Key words

Wheat, Emex australis, Sowing date, Density, Grain yield

Introduction

Planting time and weed management are important factors that influence yield in cereal crops. Sowing date affects the environment of the wheat crop and in turn growth and yield. Timely planting provides greater yields than delayed sowing, due to higher interception of growth period and better utilization of inputs. Cropping intensity has been increased remarkably during the last few years. Owing to this and sowing of rice-wheat and cotton-wheat in succession the interference of weeds in crops has increased greatly. A certain amount of damage and the presence of weeds can be tolerated. An understanding of weed/crop ecology is required to assist development of more cost-effective and targeted weed-management systems. Among the literature weed density and competitiveness are reported as major factors affecting crop yield (Cousens 1985). Conley and Bradley (2005) found that the wheat yield at 18 plants/m2 was not reduced however, at 82 and 155 plants/m2 crop yield was reduced by 13 and 38 %, respectively. Invasion of cropping systems by exotic species like Spiny emex (Emex australis Steinh.) is a threat to agricultural production in general and specifically to wheat. In Pakistan, Emex australis (family Polygonaceae) was first reported in the Chakwal district of Punjab. Currently it is distributed across the country (Nasir and Sultan, 2003) and is known locally as kafar kanda or palak kanda; its English common names are devil’s thorn, three cornered jack, and spiny emex. E. australis is a weed of wheat crops in Australia, adversely effecting the growth and yield of wheat (Hawkins and Black 1958; Gilbey 1974). Although a lot of research has been done on density-dependent competitiveness between wheat and different weeds, research on the combined influence of sowing time and E. australis density is scant. The objectives of this study were to assess the impact of E. australis density on the growth and yield of wheat in relatioin to sown time in order to identify the optimum sowing time to provide wheat with a competitive advantage over E. australis.

Methods

A field experiment was conducted during 2005-06 and 2006-07. Wheat variety Inqulab-91 was sown by manual drill in field on three sowing dates (7, 15, 23 November) with five E. australis densities (0, 18, 36, 54, 72 plants/m2) under irrigated conditions. Fertilizer nitrogen was applied at120 kg/ha1 and phosphorus at 85 kg/ha1 in the form of urea and DAP, respectively. Half of the nitrogen and all of the phosphorus was applied at sowing and the remaining nitrogen was applied at the tillering stage of wheat. At the time of sowing enough seeds of E. australis were sown in order to get the required plant density of E. australis per plot. Excess plants were removed by hand pulling. Other weeds were controlled by hand hoeing. The plots were distributed in randomized complete block design with split arrangement having four replicates of each treatment. At the end of the experiment the wheat and E. australis plants were harvested separately and their parameters of development and yield were measured. The data collected were analysed by using the Fisher’s analysis of variance function of MSTAT C statistical computer package and LSD at 5% probability was used to compare the treatment means (Steel et al., 1997).

Results and Discussion

Effect of sowing date and E. australis densities on E. australis

Interaction involving S1D3 (7 Nov. sowing and 36 plants/m2 of emex) and S1D5 (7 Nov. sowing and 72 plants/m2 of Emex) took the highest number of days (72.10 and 74.65 in 2005-06 and 2006-07, respectively) to initiate flowering in E. australis while interaction S3D3 and S3D4 started flowering significantly earlier in 2005-06 and 2006-07, respectively. In 2005-06 significantly maximum plant height (98.9 cm), dry biomass per plant (43.95 g), number of seeds per plant (442.4) and seed weight per plant (14.56 g) was recorded in interaction of S1D2. A similar trend was observed in 2006-07. Interaction S3D5 resulted in significantly minimum plants height, dry biomass per plants, number of seeds per plant and seed weight per plant in both the years of study (Table 1).

Table 1. Effect of sowing date and E. australis densities on E. australis.

2005-06

Sowing Date

Emex densitym2

Days to flowering

Plant height (cm)

Dry weight (cm)

Number of seeds/ plant

Seed weight per weight (g)


S1= 7 Nov

D2=18

71.50

98.90

43.95

442.4

14.56

D3=36

72.10

85.68

42.13

435.9

13.12

D4=54

71.95

76.88

36.13

274.8

9.51

D5=72

71.50

69.70

30.27

202.6

7.75


S2= 15 Nov

D2=18

68.60

93.45

38.85

421.5

13.60

D3=36

68.05

78.55

27.65

274.5

9.64

D4=54

68.01

72.47

27.27

212.1

8.77

D5=72

68.75

63.47d

24.30

203.8

7.54


S3= 23 Nov

D2=18

63.05

81.42

28.67

300.0

10.03

D3=36

62.80

69.05

24.67

243.4

8.81

D4=54

63.60

50.15

20.48

169.3

5.98

D5=72

62.90

44.65

17.90

142.6

4.90

LSD

 

1.269

19.44

13.25

107.4

2.894

2006-07


S1= 7 Nov

D2=18

74.25

96.00

46.30

349.9

13.35

D3=36

74.55

88.32

43.47

293.5

11.40

D4=54

73.65

74.18

31.17

206.4

7.90

D5=72

74.65

73.07

29.05

172.4

6.47


S2= 15 Nov

D2=18

68.50

87.30

36.20

300.3

11.18

D3=36

68.50

76.88

25.88

223.1

8.44

D4=54

68.30

71.63

24.08

185.3

6.82

D5=72

68.55

67.20

21.25

162.4

5.74


S3= 23 Nov

D2=18

62.50

83.22

31.92

245.1

9.30

D3=36

63.50

70.20

22.42d

208.5

7.58

D4=54

62.40

63.08

19.52

128.4

4.67

D5=72

63.00

55.67

17.70

121.9

4.38

LSD

 

1.225

14.110

9.604

61.00

1.940

Extensive growth of Emex as a result of its competition for nutrient and water with wheat resulted in reduced thousand grain weight and grain yield of wheat. El-Khatib and Hegazy (1999) reported that wild oats competed with wheat for nutrients, water, space and light resulting in reduced yields. Interaction of Italian ryegrass and wheat was quantified by Hasham and Radosevich (1991). They reported that Italian ryegrass had more competitive ability than wheat. The interaction involving the higher Emex density and delayed sowing caused lower Emex height, dry biomass, number of seeds and seed weight per plant due to interspecific competition with wheat. In addition increase in population of Emex plants per plot caused intraspecific competition for nutrients, water space and competition offered by wheat resulted in reduced growth and physiological traits of Emex plant. Highest values for E. australis plant height, dry biomass, number of seed per plant and seed weight on 7 November sowing at E. australis density of 18 plants/m2 in both years showed that Emex grew at its full because of proper climatic conditions and absence of drastic competition which otherwise present in other treatments. To control E. australis in first week of November chemical weed control may be used to avoid competition in current wheat crop and increase in soil seed bank of this weed.

Effect of sowing date and E. australis densities on wheat

Interaction between sowing date and E. australis densities was significant for all the parameters recorded during both years. In 2005-06, significantly (P≤ 0.05) highest spike-bearing tillers (429.8), plant height (94.30 cm), number of grains per spike (52.60), 1000-grain weight (41.43 g) and grain yield (5495 Kg) were recorded when wheat was sown on 7 November in E. australis-free plots. Significantly lowest plant height (78.30 cm), spike bearing tillers/m2 (300.5), number of grains per spike (38.35), 1000-grain weight (34.69 g) and grain yield (3033 Kg) was recorded in interaction of S3 D5. In 2006-07, similar trend was observed for all recorded parameters. Highest number of spike bearing tillers was recorded in early sowing (S1) where Emex density was zero.

Table 2. Effect of sowing date and E. australis densities on wheat.

2005-06

Sowing Date

Emex Density/m2

Spike bearing tillers/m2

Plant height (cm)

Grain per spike

1000-grain weight (g)

Grain yield (kg)


S1= 7 Nov

D1= Control

429.8

94.30

52.60

41.43

5495

D2= 18

387.8

91.35

47.80

40.03

5035

D3= 36

376.0

88.45

47.25

39.17

4721

D4= 54

360.3

86.75

46.25

38.03

4215

D5= 72

346.3

85.22

44.50f

37.18

4009



S2= 15 Nov

D1= Control

415.5

92.55

50.75

40.91

5463

D2= 18

384.0

88.55

46.00

39.33

4706

D3= 36

362.8

86.35

44.05

37.97

4250

D4= 54

349.3

85.60

42.40

36.89

3926

D5= 72

342.0

84.00

40.95

35.76

3639



S3= 23 Nov

D1= Control

393.3

87.35

48.80

39.26

4739

D2= 18

355.5

83.15

44.65

37.90

4131

D3= 36

339.8

81.70

40.50

37.29

3604

D4= 54

322.0

80.35

39.65

35.64

3306

D5= 72

300.5

78.30

38.35

34.69

3033

LSD

 

20.81

2.260

2.692

1.095

322.7

2006-07


S1= 7 Nov

D1= Control

435.0

93.50

49.15

41.65

5625

D2= 18

407.8

90.68

47.50

40.26

5204

D3= 36

380.8

89.50

46.50

38.71

4606

D4= 54

365.5

87.85

45.35

38.57

4288

D5= 72

352.8

86.45

45.00

37.42

4070



S2= 15 Nov

D1= Control

419.8

91.20

49.00

40.53

5370

D2= 18

387.0

88.05

46.92

39.21

4758

D3= 36

362.3

86.05

44.55

38.02

4435

D4= 54

348.0

85.20

43.55

37.43

3961

D5= 72

338.5

84.00

42.00

36.81

3628



S3= 23 Nov

D1= Control

397.8

89.25

47.88

38.81

4834

D2= 18

362.5

85.20

44.60

37.65

4366

D3= 36

345.5

83.25

42.30

36.73

3950

D4= 54

331.0

80.70

40.25

36.63

3670

D5= 72

311.0

79.55

39.08

35.47

3236

LSD

 

21.04

1.505

2.605

0.5190

239.1

The increased number of tillers could be due to lower temperature and no weed competition that encouraged tiller production during the early growth period and maximum number of tillers was reached by the end of the vegetative phase after which it declines (Khalifa et al. 1977). In the treatments where sowing was delayed and Emex density was high, tillers were significantly reduced because of the short period for tillering stage and in addition, competition from weed plants restricted the wheat plant to fewer tillers per plot. The fact that the number of tillers was affected by the length of the duration of tiller initiation as well as by plant density suggests that interaction between sowing date and plant population density were bound to influence yield (Dennett 1999). Interaction of late wheat sowing and Emex densities reduced wheat grain yield and yield components during both the years. This was due to the shorter growth period with added effect of Emex competition.

Conclusion

The results showed that wheat sown on 7 November was significantly superior to that sown on 15 or 23 November for all studied aspects of growth and yield of wheat. Emex densities, even at lower levels (18 plants/m2) showed significant reduction in yield. This suggests a target sowing time of the first week of November for wheat in this region, though Emex must be controlled as early as possible, even at low densities, in order to get maximum grain yield.

References

Akhtar M, Cheema MS, Jamil M and Ali L (2006). Effect of time of sowing on some important characteristics of wheat, Triticum aestivum genotypes. Journal of Agriculture Research 44, 255-259.

Conley S and Bradley KW (2005). Wheat (Triticum aestivum) yield response to henbit (Lamium amplexicaule) interference and simulated winterkill. Weed Technology 19, 902–906.

Cousens R (1985). An empirical model relating crop yield to weed and crop density and a statistical comparison with other models. Journal of Agriculture Research 105, 513-521.

Dennett MD (1999) Effects of sowing date and the determination of optimum sowing date. In: Wheat, Ecology and Physiology of Yield Determination Eds. EH Sattore, GS Slafer pp. 123-140. Food Products Press, New York, USA.

El-Khatib AA and Hegazy AK (1999). Growth and physiological responses of wild oats to the allelopathic potential of wheat. Acta-Agronomica Hungarica 47, 11-18.

Gilbey DJ (1974). Estimating yield losses in wheat resulting from infestation by doublegee (Emex australis). Australian Journal of Experimental Agriculture and Animal Husbandry 14, 656–657.

Hawkins HS and Black JN (1958). Competition between wheat and three-cornered jack. Journal of the Australian Institute of Agricultural Science 24, 45–50.

Hashem A and Radosevich SR (1991). Effect of density, proportion, and spatial arrangement on winter wheat and Italian ryegrass. Ph.D. Dissert., Oregon State Univ., Corvallis, USA.

Khalifa MA, Akasha MH and Said MB (1977). Growth and N uptake by wheat as influenced by sowing date and N in irrigated semi-arid conditions. Journal of Agriculture 89, 1-255.

Nasir, ZA and Sultan, S (2003). Weed communities in the wheat fields of district chakwal. Sarhad Journal of Agriculture 19, 113-120.

Steel RGD, Torrie JH and Dickey DA (1997) Principles and Procedures of Statistics. A Biometrical Approach 3rd Ed. McGraw Hill Book Co., Inc., Singapore: pp.172-177.

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