Pak J. Weed Sci. Res. 12(1-2): 69-77, 2006

EFFECT OF WILD OATS (Avena fatua) DENSITIES AND PROPORTIONS ON YIELD AND YIELD COMPONENTS OF WHEAT

Ijaz Ahamd Khan and Gul Hassan[1]

ABSTRACT 

In order to study the effect of wild oats densities and propotional on yield and yield components of wheat, field trials were conducted at Malkandher Research Farm, NWFP Agricultural University Peshawar during Rabi 2004-05. The experiment was laid out in Randomize Complete Block (RCB) design with split plot arrangement. Four seed rates viz.100, 130,160-and190 kg ha^-1 were assigned to main plots, while wild oats densities 0,5,10,15,20,25 and 30 seed m^-2 were kept into sub-plots. Data were recorded on number of spikes m^-2, spike length(cm), grains spike^-1, 1000 grain weight (g), tiller wild oat^-1, number of seed/ tiller of wild oat and grain yield (kg ha^-1). Statistical analysis of the data showed that most of the parameters were statistically affected by wild oats densities and seed rates. Maximum number of spikes m^-2 (281.9), spike length (9.33cm), number of grains spike^-1 (50.0), 1000-grain weight (30.26) and were recorded in wheat monoculture (0 wild oat density plot). Seed rate of 160 kg ha^-1 had significantly higher spikes m^-2 (283.4), spike length (8.58 cm), 1000-grain weight (30.87 g) and grain yield. Thus a seed rate of 160 kg ha^-1 is recommended for suppression of wild oats population at wheat crop.

Key words: Wheat density, wild oat density, competition, grain yield

 INTRODUCTION PRIVATE

Wheat belongs to the family Poaceae, tribe Hordae and genus Triticum. Common wheat is hexaploid with 42 chromosomes and botanically known as Triticum aestivum L. em Thell. It is an annual self pollinated and photoperiodically long day plant. Wheat plant consists of roots, leaves and spikes; wheat has both seminal and adventitious roots. The stem consists of nodes and internodes. Normally the plant produce 2-3 tillers under typical eroded field conditions but individual plant on fertile soil with ample space and space and nutrient may produce as many as 100 tillers (Martin et al, 1976). Wheat is the most important crop produced in Pakistan. It is a staple and indispensable food article of the people of Pakistan and occupies more land than any other crop.

In Pakistan, wheat production per unit area is still very low than its potential yield, although Pakistan is among the top ten wheat producers of the world. The average yield of wheat in Pakistan does not go beyond 30-35% of its optimum potential (Sarwar and Nawaz, 1985).

            Weeds are one of the major problems in crop production. They compete with crop plants for light, moisture, nutrients and space. Weeds also increase harvesting costs, reduce quality of the produce, clog waterways, and increase fire hazards (Arnon, 1972). Weed competition with wheat could be either of broadleaf or grasses. Avena fatua, Phalaris minor and Lolium temulentum are the grassy weeds, which have now become a threat to the nutritional requirement of mankind.

            A. fatua has increased tremendously in the rainfed and irrigated areas of the country as well as elsewhere in the world. It is an annual grass and is difficult to eradicate because the seeds shatter before crop maturation and many of the seeds are plowed into the soil, where they lie dormant for one to many years, and germinate when they are turned up near the surface. The roots are small, numerous and fibrous penetrating into the soil to a depth of several feet. The leaves are flat, with broad base and acute apex. The inflorescence is either equilateral (spreading) or unilateral (one sided) panicle. It is of cosmopolitan distribution in cereals where annual precipitation is between 375 to 750 mm. Glumes are lanceolate, ligules up to 6mm long, hairy blades, erect or geniculately ascending. Spikelets pendulous and culms are of 30-150 cm height.

            Ibrahim et al. (1995) conducted four pot experiments in 1992-94 at Giza, Egypt and examined wild oats/wheat competition. Wheat cv. Sakha 69 was grown with wild oats at wheat wild oats numbers/pot of 6.6+5.6+4.6+3.6+2 or 6+1. At these densities, grain yield/plant was decreased by 58, 54, 43, 16 and 7% in 1993-94, respectively, compared with wheat grown alone. In the 2nd experiment, crop weed competition was markedly decreased when emergence of wild oats was delayed by three weeks. In the 3rd experiment wheat and wild oats achieved 100% germination 9 and 15 days after sowing, respectively. In the 4th experiment, wheat and wild oats were sown on 1, 15 and 30 Nov. or 15 Dec. The optimum sowing date for wheat was 30 Nov., while the growth of wild oats was most vigorous when sown on 1 Nov.

            Walia et al. (1998) reported that a field experiment was conducted at Ludhiana, Indian Punjab in 1993-95 to study the effect of artificial infestations of wild oats (A. fatua) in wheat. Crop density was kept constant while wild oats density varied from 0 to 100 plants m^-2. As the density of wild oats increased, wheat yield decreased exponentially. Wheat yield loss was below 1% up to 3 plants of wild oats m^-2, reached 2.2% at 5 plants and was 50-60% at 100 plants of wild oats m^-2. Wheat yield loss could also be related mathematically to the dry weight of wild oats.

            Lajos et al. (2000) carried out experiments on wheat crop at 5 places under the same condition, but the weed flora differed between sites. Crop density treatments (3, 4, 5 and 6 million wheat seeds ha^-1) were applied to 75 m² plots using the sowing rate as only tool to control weeds had low efficiency. Weeds were least controlled under the lower sowing rates.

High seeding rates also reduced the impacts of weed on crops in a number of previous studies (Barton et al., 1992; Carlson and Hill, 1985; Justice et al., 1994; Radford et al., 1980).

            In view of the importance of the problem for nutrition of human being and national economy, an experiment was designed with these objectives 1) to quantify the losses caused by A. fatua across different populations of wheat and 2) to predict the effect of Avena fatua on wheat and vice versa at various densities.

MATERIALS AND METHODS

            The experiment entitled “Effect of wild oats densities on wheat seeded at varying rates” was conducted at Malkandher Research Farm, NWFP Agricultural University, Peshawar during the Rabi season 2004-2005, using variety Ghaznavi-98. The experiment was laid out in Randomized Complete Block (RCB) design with split plot arrangement, having four replications. In each replication, there were four main plots. Each main plot consisted of seven sub-plots. The wheat seed rates viz. 100, 130, 160 and 190 kg ha^-1 were kept in main plots while the wild oat densities 0, 5, 10, 15, 20, 25, and 30 plants m^-2 were assigned to the subplots. The size of each subplot was 5x1.5m². Row to row distance was kept at 25 cm apart. Wheat seeds were sown with the help of hand hoe. Seeds of wild oat were planted manually, the same day as the wheat. All other weeds were removed manually throughout the wheat season. The data were recorded on number of spikes m^-2, spike length(cm), grains spike^-1 , 1000 grain weight (g), tiller wild oat^-1, number of seed/ tiller of wild oat and grain yield(kg ha^-1). The data recorded for each trait was individually subjected to the ANOVA technique by using MSTATC Computer Software and means were separated by using Fisher's Protected LSD test. (Steel and Torrie, 1980).

RESULTS AND DISCUSSION

Number of spikes m^-2 

Analysis of the data revealed that wild oat densities and seed rates, had significant effect on number of spike m^-2, while their interaction showed non-significant variation .The data in (Table-1) exhibit that maximum (281.6) spikes m^-2 were recorded in control plots, while the minimum (269.9) spikes m^-2 were noted in 30 wild oats seeded m^-2. Among the seed rates the highest (283.4) spikes m^-2 were noted in 160 kg ha^-1, while the lowest (269.9) spikes m^-2 were recorded in 190 kg ha^-1. For interaction of seed rates with wild oats densities the differences although were non-significant statistically yet the maximum (288.5) spikes m^-2 were recorded in 160 kg ha^-1 x 0 wild oat density. The minimum (263.0) number of spikes m^-2 were noted in 190 kg ha^-1 x25 wild oats seeded m^-2. Weed competition in wheat reduced yield due to decreases in spike numbers (Bell and Nalewaja, 1969;Cudney et al.1989; Liebl and Worsham, 1984) and spike length (Burrows and Olson, 1955).

Spike length (cm)

The analysis of the data showed that differences among the wild oats densities and seed rates were significant statistically while the interaction of wild oats densities with seed rates showed non-significant variation. The minimum (7.78) spike length was recorded in 30 wild oat seed m^-2, while the highest (9.34) spike length was recorded in control (0) plots. Among the seed rates, the highest (8.58) spike length was noted in 160 kg ha^-1, while lowest spike length (8.09) was recorded in 190 kg ha^-1. The data (Table-2) further depicts that the interaction though failed to reach the statistical significance level, the maximum spike length (9.52) was recorded in 160kg ha^-1 x 0 wild oat density .The minimum (7.62) spike length was noted in 190kg ha^-1 x30 seed m^-2 treatment. Similar results were reported by Fang and Wang (1990). They reported that weeds affected the yield of wheat mainly through reducing spike length. Earlier researchers have also concluded that weed competition in wheat caused yield reduction via decreases in spike numbers (Bell and Nalewaja, 1969; Cudney, et al .1989; Liebl and Worsham, 1984) spike length (Burrows and Olson, 1955) and number of grains per spike (Wilson and Peters, 1982).

Number of Grains spike ^-1

Statistical analysis of the data showed that wild oat densities have a significant effect while seed rates and their interaction have non-significant influence on grains spike^-1. The data in Table-3 showed that maximum (50.0) grains spike^-1 were recorded in control (0 wild oat density m^-2). Minimum (45.01) number of grains were recorded in 30 wild oats seeded m^-2. Among the seed rates, the highest number of grains spike^-1 (46.99) were recorded in 160 kg ha^-1, which was closely followed by other seed rates included in the studies. For the interaction of seed rates with the wild oats densities the differences although were non-significant statistically, yet the maximum  (50.60) grains spike^-1 were noted in 160 kg x 0 wild oats m^-2. The minimum number of grains spike^-1 (43.97) were recorded in 190 kg x 30 wild oats m^-2 plot. Martin et al. (1987) also found that increasing wheat density decreased the losses from wild oats. Weed competition in wheat resulted in yield reduction due to decrease in spike numbers (Bell and Nalewaja 1969, Cudney et al. 1989; Liebl and Worsham 1984) or number of grains per spike (Wilson and Peters, 1982).

1000-grain weight (g)

Analysis of the data revealed that 1000-grain weight was significantly affected by wild oats densities and seed rate, while interaction of seed rates with wild oat densities were non-significant statistically. The data (Table-4) revealed that maximum (30.26) 1000 grain weight were recorded in control plot. Minimum (29.4) 1000 grain weight was noted in 30 wild oat seed m^-2. Among the seed rate the maximum (30.8) 1000 grain weight was recorded in 160kg ha^-1 while the minimum (29.6) 1000 grain weight was noted in 190kg ha^-1 seed rates which was closely followed by the other seed rates included in the studies. The data in Table-6 further depicts that the interaction though failed to reach the statistical significance level, the maximum 1000-grain weight (31.30) was recorded in 160 kg ha^-1 x0 wild oat seed m^-2. Minimum (28.90) 1000 grain weight was noted in 190 kg ha^-1 x 25 wild oat seed m^-2 plot.  These findings are in agreement with the work of Justice et al. (1994), Radford et al. (1989) and Barton et al. (1992), who concluded the strong relation of seeding rates with the wild oats management.

Tillers wild oat plant^-1

Statistical analysis of the data showed that the number of tillers of wild oats plant^-1 were significantly affected by wild oats densities while the seed rates and interaction of wild oats densities with the seed rates were non-significant statistically. The data (Table-5) revealed that the maximum (13.1) tillers of wild oats plant^-1 were recorded in 5 wild oats seed m^-2 plots. The minimum (11.8) tillers of wild oat plant^-1 was noted in 30 wild oat seed m^-2. Among the seed rates the highest (11.2) number of tiller wild oat plant^-1 were recorded in 100 kg ha^-1, while the lowest (10.2) number of tiller wild oat plant^-1 were recorded in 160 kg ha^-1, However, it was statistically similar with 130 and 190 kg ha^-1 seed rates. For the interaction of seed rates with the wild oat densities, the differences although were non-significantly yet the maximum (13.7) number of tillers wild oat plant^-1 were noted in 100kg ha^-1 x5 wild oat densities m^-2. The minimum number of tillers (11.5) wild oat plant^-1 were recorded in 160 kg ha^-1 x30 wild oat densities m^-2 treatment.

Seeds/Tiller of wild oats

Analysis of the data revealed that wild oat densities had significant effect on seeds/tiller of wild oat, while seed rates and their interaction had showed non-significant variation. The data in Table–6 indicated that among the mixtures of all the densities had almost equal number of seeds/tiller of wild oats. Similarly, among the seed rates similar number of seeds/tiller of wild oats were recoded for each seed rate.

Table-1. Effect of wheat and wild oats density on number of spikes m^-2 of wheat.

Table-2. Effect of wheat and wild oats density on spike length (cm) of wheat.

Table –3.          Effect of wheat and wild oats density on grains spike^-1 of wheat.

Table -4.          Effect of wheat and wild oats density on 1000-grain weight (g) of wheat..

Table-5.           Effect of wheat and wild oats density on tillers of wild oat/plant.

Table-6.           Effect of wheat and wild oats density on seed/tiller of wild oat of wheat.

Grain yield (kg ha^-1)

Statistical analysis of the data revealed that wild oats seed rates and densities were significant, while their interaction was non-significant statistically. The data in Table-7 show that the maximum (2938kg ha^-1) grain yield among the wild oats densities was recorded in 0 wild oats seed m^–2 while minimum (2283kg ha^-1) grain yield was recorded in 30 wild oats seeded m^-2 treatment. For interaction of seed rates with the wild oats densities, the highest yield (3121.0kg ha^-1) was observed in 160 kg ha^-1 X 0 wild oats seed m^-2, while minimum grain yield  (2022.50 kg ha^-1) was observed in 190 kg ha^-1 x 30 wild oats seed m^-2. Wheat yield loss due wild oats competition, involving weed densities as a variable, has been extensively reported in the world literature (Dew, 1972, Tessema and Tanner, 1997; Tessema et al .1996a; 1996b) and various models have been reviewed by Zimdahl (1980) and Cousens (1985). Wilson et al. (1990) also reported that increased seeding rates of barley reduced the initial growth of wild oats seedlings.

 Table-7. Effect of wheat and wild oats density on grain yield (kg ha^-1) of wheat.

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