Pak. J. Weed Sci. Res. 10(3-4):151-156, 2004

Development Of Economical Weed Management Strategies

For Mungbean (Vigna radiata L. Wilczek.)

 Muhammad Mansoor^[1], Haji Khalil Ahmad¹, Himayatullah Khan¹ and Muhammad Yaqoob^[2]

Abstract

An experiment was designed to investigate the efficacy of various weed management strategies in mungbean. Water extracts of sorghum, Eucalyptus and Acacia were used in comparison with hand weeding and pre-emergence herbicide. The experiment was conducted at Agricultural Research Institute Dera Ismail Khan, during 2003. Eight treatments were studied in the experiment viz; check, hand weeding, herbicide pendimethalin and water extracts of sorghum, Eucalyptus and Acacia. Mature sorghum herbage, ground leaves of Eucalyptus and pods of Acacia were used for preparing water extract in 1:5 ratio i.e. 1 kg sorghum herbage soaked in 5 L of water. Water extracts and hand weeding were applied twice i.e., 10 days after sowing and 35 days after sowing. All the treatments significantly affected Number of branches plant^-1, Number of pods plant^-1, 1000 grain weight and grain yield. Application of water extract of Acacia ranked at the top in yield and almost all the yield components followed by Two Hand weeding + Pre-emergence herbicide treatment.

Key words: Vigna radiata, weed management, allelopathy, Acacia, Eucalyptus, sorghum

Introduction

Mungbean (Vigna radiata L. Wilczek.) is emerging to be an important crop, as it is one of the best substitutes to meet the food needs of the large population of the developing countries. In spite of short duration, nutritional superiority and nitrogen fixing character, it is a rainy season crop facing the weeds as main competitor. Weeds are most serious pests reducing the growth and yield of crop. Modern agricultural practices contribute mostly on protection of the crop against competition from weeds. Weeds reduce yield by competing with crop plants for space, light, nutrients and carbon dioxide. There are different views about the intensity of weed losses but it is established fact that weeds cause great losses to crops, depending upon the degree of weed infestation, duration of weed competition, and soil and climatic conditions.

There is no specific way to control weeds of all types because of different kinds of social, economical and environmental factors influence the choice of control method to be used. Quarshi et al (2002) reported that weed could be controlled by manual, cultural and chemical methods. Although weed management practices like hand weeding and herbicide application are effective in weed control but are uneconomical due to higher costs (Cheema et al 2003). Moreover the chemical weed control method is hazardous for health and causes environmental pollution.

Use of sorgaab (sorghum water extract) for weed suppression and increase in crop yield has been reported in field studies by Cheema and Khaliq (2000). Ali et al (2004) reported that allelopathic plants containing allelochemicals in low quantity act as hormones and in high amount act as herbicides. Therefore, Allelopathy has emerged as an important area of weed control research and has been accepted very recently as important ecological phenomena.

The evidence of Allelopathic compounds in sorghum (Sorghum bicolor) and their subsequent effects on other plants inspired the idea of conducting field study to explore the feasibility of using Eucalyptus (Eucalyptus camaldulensis) and Acacia (Acacia nilotica) water extracts also as natural herbicides to control weeds in mungbean crop and to study their effects on growth and yield of mungbean in comparison with hand weeding and herbicides.

Materials and Methods

The experiment was laid out in RCBD with four replications, keeping a net plot size of 1.8 x 4 m ², having plant to plant and row to row spacing 10 and 30cm respectively. NIAB MUNG 98 was used as test variety. Fertilizer was applied @20:50 kg ha^-1 of N:P as basal dose. Weed samples were taken using a quadrate of 1 m² and then oven dried at 70 ⁰C for 48 hours for recording dry weed biomass. Weed management strategies carried out were, use of herbicide before emergence of crop while water extracts and hand weeding was applied 10 and 35 DAS. The water extracts were prepared by soaking the chaffed herbage of the Sorghum, ground leaves of Eucalyptus and pods of Acacia in distilled water in a ratio of 1:5 for 72 hours. It was then filtered to collect the respective extracts. The extracts were concentrated to 20 times by boiling at 100⁰C on a gas burner.

 The detail of treatments was as under:

Treatments

T1=       Control (Check)

T2=       Stomp 330 EC (pre-emergence herbicide)

T3 =      Two hand weeding (10 and 35 days after sowing).

T4=       Pre-emergence herbicide + Two hand weeding (10 and 35 days after sowing).

T5 =      Application of Sorghum extract (10 and 35 days after sowing).

T6=       Application of Eucalyptus extract (10 and 35 days after sowing).

T7 =      Application of Acacia extract (10 and 35 days after sowing).

During the course of studies data were recorded on weed density (g m^-2) 20 and 45 days after sowing, Number of branches plant^-1, Number of pods plant^-1, 1000 grain weight (g) and grain yield (kg ha^-1). The data for the individual traits were subjected to the analysis of variance technique and the significant means were separated by Least Significant Difference Test as outlined by Steel and Torrie (1980).

Results And Discussion

Weed data 20 days after sowing

Weed density m^-2

It is obvious from the Table-1 that mean data regarding weed density m^-2 were significantly affected by various weed management strategies. While the Lowest weed density was shown by Acacia water extract application (4.05), followed by sorghum water extract (4.15) weeds m^-2. Control had the highest weed population of (7.93) m^-2. Cheema et al. (2002) reported similar results that extract application decreased the weed population.

Fresh Weed Biomass (g m^-2)

Analysis of the data showed that all the weed control treatments had significant effect on fresh weed biomass. The lowest fresh weight of weeds 7.56 and 7.69 g m^-2 were recorded in plots sprayed with Acacia and Sorghum water extracts, respectively. The highest fresh weed biomass (10.79 g m^-2) was noted in control treatment. Cheema et al. (2002) reported that sorghum water extract application reduced fresh weight of weeds by 48%.

Dry weed Biomass (g m^-2)

The analyzed data of dry weed biomass revealed that the differences between dry weeds biomass of weed management strategies and check treatment were significant, which means that weed control treatments significantly reduced the dry weight of weeds. The lowest dry weeds weight of 3.61g m^-2 was recorded in plots sprayed with Acacia water extract followed by 4.48 and 4.51g m^-2 in the plots which were sprayed with Sorghum water extract and pre-emergence herbicide + Two hand weeding, respectively. Cheema et al. (2002) also reported that extract application reduced dry weight of weed by 50%.

Table-1. Weed parameters as affected by various weed management strategies

Means sharing common letter are not significantly different at alpha = 0.05.

Weed data 45 days after sowing

Weed density m^-2

The performance of Acacia water extract application was the best amongst all weed management strategies in controlling the weed population, with the value of 4.04 weed m^-2. Sorghum water extract application has very close results with 4.35 weed m^-2 The control treatment had the highest weed density (16.59). Similar results were obtained by Cheema et al, (2003) who noted that extract application gave better weed control. Khan et al. (2004a&b) have also reported the inhibitory effect of tree extracts on the germination of weeds of wheat crop.

Fresh Weed Biomass (g m^-2)

The analyzed data of Fresh weed biomass at 45 days after sowing of mungbean revealed that all the weed management strategies had significant effect on the fresh weight of weeds. The lowest fresh weed weight of 5.46 g m^-2 was recorded in plots sprayed with Acacia water extract followed by 6.25 g m^-2 in the plot, which had been sprayed with the Sorghum water extract. Among all the treatments, the highest fresh weed weight of 19.60 g m^-2 was noted in control treatment. Similar results was obtained by Bhatti et al., (2000) with the application of water extract in other crops. Khan et al. (2004 a&b) have reported the inhibitory effect of tree species on associated weeds of wheat crop.

Dry weed Biomass (g m^-2)

The statistical analysis of the data showed that all the weed control treatments had significant effect on dry weeds weight. The differences between dry weed weights of weed management treatments and control plots were significant. Three treatments i.e. Application of Acacia, sorghum water extracts and treatment with two hand weeding + Pre-emergence herbicide were statistically at par with 4.09, 4.34 and 4.48 g m^-2.  While the highest dry weed biomass (16.58 g m^-2) was noted in control treatment. Water extracts resulted in reduction of weed biomass in the presence of either phytotoxic or allelopathic compounds. The results may have value in enabling weed control based on natural plant extracts. Similar results were obtained by Cheema et al (2002) who reported reduction of dry weed biomass in treatments where water extracts were applied.

Table-2. Mungbean yield parameters as affected by weed management strategies

Means sharing common letter are not significantly different at alpha = 0.05.

Number of branches plant^-1

The perusal of Table-2 indicated that weed management strategies significantly differed  (P=0.05) in affecting branches plant^-1. The number of branches plant^-1 ranged from 4.58 to 6.53. The highest number of branches plant^-1 (6.53) were recorded when Acacia extract was applied followed by pre-emergence herbicide + two hand weeding and Sorghum water extract application ( 6.19 and 6.01, respectively). The lowest branches (4.58) were obtained in control plots which were significantly less than all the weed management strategies. Similar results were reported by Cheema et al. (2001) they reported that with the application of water extracts number of branches were increased.

Number of Pods plant^-1

Data regarding number of pods plant^-1 on given in Table-2 were found significantly different. Number of pods plant^-1 ranged from 40.83 to 66.10. The highest number (66.10) of pods plant^-1 were counted in the Acacia extract application followed by Pre-emergence herbicide + two hand weeding giving 62.60 pods plant^-1. The lowest pods (40.83) were obtained in control treatment. Cheema et al. (2001) also reported the increase in number of pods plant^-1 with application of water extracts.

1000 grain weight (g)

Data regarding 1000 grain weight as affected by different weed management strategies was non-significant at P=0.05, and ranged from 39.22 to 43.28 g. The highest value (43.28 g) was observed in control treatment followed by hand weeding treatment (41.60 g), while the lowest value (39.22 g) was recorded in Pre-emergence herbicide + Two hand weeding treatment.

Grain Yield kg ha^-1

The data given in Table-2 shows that grain yield was significantly affected by various weed management strategies applied for weed control. It ranged from 750 to 1266 kg ha^-1. The highest grain yield (1266) was recorded in Acacia extract application treatment closely followed by Pre-emergence herbicide + Two hand weeding treatment with grain yield of 1253 kg ha^-1 was obtained.  While the lowest yield (750 kg ha^-1) was obtained in control treatment. Ali et al. (2004) reported similar results that water extract application increased the grain yield of crops.