Influence of Weed Management Practices on Growth Parameters and Economics of Cowpea [ Vigna unguiculata (L.) Wasp.]

and (quizalofop-ethyl + 1 HW + 1 IC) very effective in weed control and had positive impact on plant height, plant spread, number of branch per plant, number of pods per plant and number of seeds per pods. These treatments were as good as weed free plot. These integrated weed management treatments gave broad spectrum weed control and higher gross, net return and B:C ratio. By adopting appropriate weed management practices farmer can get 3000 to 4000 net increase in return over the other treatment. So integrated weed management is better option and cowpea grower combine cultural practices with suitable pre and post herbicides like as pendimethalin, quizalofop-ethyl and imazethapyr to get similar return as weed free plot.


INTRODUCATION
Pulses are part of a healthy, balanced diet and also important to maintain soil health by fixing nitrogen biologically. India has key position in global pulses production and contributes about 25% of the total global pulse production. According to the third advance estimates (ministry of agriculture and farmers welfare, government of India) pulses production in the country in the year 2016-17 will be 22.4 million tones, this is 35% higher than previous year (2015 -16).
Cowpea [Vigna unguiculata (L.) is one of the key food legume crop in the arid and semiarid part of the world including Asia, Africa, Southern Europe, and Central and South America. A droughttolerant in nature and warm-weather suited crop, cowpeas are well-adapted to the drier regions of the tropics, where other food legumes do not perform well. It also has the ability to fix atmospheric nitrogen through its root nodules, and it grows well in nutrient deficient soil with more than 85% sand and with less than 0.2% organic matter and low levels of phosphorus. [1,2]. Also, it is shade tolerant in character and, therefore, well-suited as an intercrop with cereal crops like as sorghum, millet and maize. It is also acknowledged as Crowpea, black-eyed pea or southern pea etc. and has multiple uses like food, feed, forage, fodder green manuring and vegetable. Cowpea seed is a nourishing component in the human diet, and low-priced livestock feed as well. The tender green leaves are also used by small and marginal farmer in the rural areas for vegetable purpose. It also leave 30-40 Kg N ha in the soil for the succeeding crop all of these character make cowpea potential crops for cowpea growers under rainfed condition. Despite several advantages cowpeas have very low productivity 500 kg ha -1 at world level grown on an area of 10.89 million ha with 5.45 million tones total production in 2011 [3]. A survey of 316 cowpea grower conducted in western Rajasthan revealed that among different production constraint weed control through herbicides is technically complex phenomenon (89.25%, I rank) followed by lack of knowledge about inoculation of seed through culture (85.12%, II rank), sandy storm, high wind velocity and high temperature affect the growth of crop and productivity (83.23%, III rank) and lack of knowledge about seed treatment (81.02%, IV rank), respectively [4].
Different researchers reported that critical period of weed competition in cowpea vary from 10-45 DAS [5,6,7] but it can be extended up to harvest in rainy season [8]. During rainy season the crop suffers severely due to weed infestation resulting into heavy loss in crop yield. Therefore, weed control measure desired to be undertaken during early stage of crop growth. Till date cowpea farmer mainly depended on hand weeding for weed control, but day by day shortage of family labour arise because of nuclear family concept. In such situation farmers forced to look towards hired labour which reduce farmers saving. Many researchers conducted experiment on integrated approach. For example, studies conducted on application of pendimethalin (1.5 or 2.0 L ha -1 ) or fluchloralin (1.0 or 1.5 L ha -1 ) at 3 days + handweeding twice at 30 DAS, resulted in significant reduction in weed density and weed dry matter [9]. Pendimethalin at 1.0 kg ha -1 + hand-weeding at 30 DAS gave the maximum cowpea yield and lowest weed population and weed dry weight [10]. Same as evaluate weed management tactic for cow pea and found pre-emergence application of pendimethalin at 0.75 kg a.i. ha -1 + weeding at 5 week after sowing gave a higher grain yield (511 kg ha -1 ) and net return (Rs. 4705 ha -1 ) compared to other weed management practices [8]. Chemical-weeding (Stomp @ 3.75 L ha -1 ) at 2-3 leaf stage of weeds + hand-weeding at 50 DAS gave significant increase (68%) in grain yield of cowpea and positive impact on growth parameter like as number of pods per plant, number of seeds per pod, 1000 grain weight [11]. Keeping above fact in mind, the present study was carried out to evaluate appropriate and cost effective weed management option to cut back negative impact of weeds on growth parameter and economics below threshold level and increase cowpea growers saving.

Experimental Site
A field study was conducted in C 8 block of the Instructional Farm, Department of Agronomy, Junagadh Agriculture University (JAU), Junagadh, Gujarat in the kharif season of 2007. This place is located at 21.50 N latitudes and 70.50 E longitudes with an altitude of 60 m above mean sea level (AMSL). Jungadh districts fall in subtropical region familiar with moderately cold and dry winter, hot and dry summer and fairly humid monsoon season. During July and September, the rainfall was above average and well distributed. Maximum and minimum temperature recorded during the crop growth period ranged between 28.5 to 38°C and 18.5 to 27.6°C, respectively.

Experimental Soil
Soil was clayey in nature on the basis of sand, silt and clay composition. It was slightly alkaline in nature (pH 7.9 0-15 cm), average in organic carbon (0.61%) on the basis of available nitrogen (220.0 kg ha -1 ), phosphorus (18.9 kg ha -1 ) and potassium (378.0 kg ha -1 ) in 0-15 cm soil depth it characterized as low in nitrogen and phosphorus and high in potassium at the beginning of the trial.

Cropping History
In the Kharif season (July to October) 2005-06 pigeon pea was grown continued in rabi (November to March) and summer (April to June) kept as fallow in Kharif season 2006-07 pearmillet grown in rabi wheat grown and summer kept as fallow.

Experimental Detail
The trial was laid out in Random block design (RBD) consisting 12 treatments with 4 replications. The total area of experimental plot was 1216.80 m 2 gross plot sizes maintained as 5.0 × 3.6 m and net 4.0 × 2.7 m, respectively.

Detail of the Treatments
Full detail about the treatments like as herbicides dose, time of application and combination of culture practices with herbicides are given in (Table 1).

Agronomic Practices
The field was manually seeded 45×10 cm with 25 kg of seed ha

Growth parameter
The five plants were randomly selected from each net plot. Selected plant was labeled for easy identification. The same five plants were harvested separately for post harvest studies.

Plant height (cm)
The plant height was measured at harvest by taking height of five randomly selected plants in each net plot. The average value for each net plot was computed and recorded.

Plant spread (cm)
Plant spread (cm) or crown diameter was recorded at harvest of the crop on the basis of average spread of five randomly selected plants from each net plot.

Number of branches per plant
All the branches arising from the main shoot were counted from the selected five plants in each plot at harvest.

Number of pods per plant
Average number of pods per plant was counted at harvest on the basis of five randomly selected plants from each net plot.

Number of seeds per pod
Average number of seeds per pod was calculated by counting the number of seeds in five pods collected from five randomly selected plants from each net plot.

Grain weight (g) per plant
Pods of five selected plants were harvested first and allowed to sun-dry for 10-15 days. After satisfactory drying, threshing and cleaning, grain yield of these five plants was noted and average value of grain weight per plant was recorded for each treatment.

Test weight (g)
A representative seed sample was drawn randomly from the bulk produce of each net plot, 100 seeds were counted from the sample, and their weight in gram was recorded as test weight of each treatment. All the weeds were up rooted from each net plot at the time of harvesting. The weeds were air dried completely till reached to the constant weight and finally dry weight of weeds was recorded for each treatment.

Cost of cultivation (Rs. ha -1 )
The cost of cultivation was calculated on the basis of operating cost incurred for all the agriculture operations from preparatory tillage to harvesting including threshing, cleaning as well as cost of inputs and laboures. ) on the basis of existing market price.

Net return (Rs. ha -1 )
Net return for each weed management practices was computed by deducting the total cost of cultivation including treatment cost from the gross return.

Benefit:Cost ratio
Benefit:Cost ratio (BCR) for each treatment was calculated by dividing net return by cost of cultivation.

Statistical Analysis
The statistical analysis for the various characters studied in the investigation was carried out as per the randomized block design. Significance of variance was tested by F-test [12]. Summary tables for the treatment effects were prepared with standard error of mean (S.Em.±) and critical differences (C.D.) at 5 per cent probability level were given for the treatments, whose effects were found significant. Co-efficient of variance (C.V. %) was calculated and given in the respective tables. ). Among the four herbicides tested in the experiment fluchloralin not found effective against the weeds and T 1 (Fluchloralin + 1 HW +1 IC) recorded dry weight of weeds (275.00 kg ha -1 ). All the four herbicides used in trial have different mode of action and own mechanism to control weeds. Pendimethalin hamper the cell division by combining with tubulin protein which essential for microtubule formation, Imazethapyr inhibit ALS and AHAS enzymes those are responsible for synthesis essential amino acid (leusine, isoleucine and valine), Quizalofop work as ACCase inhibitor and Fluchloralin inhibit cell division through microtubule assembly inhibitor [13].

RESULTS AND DISCUSSION
It was found that application of herbicides with Intercultural operation at 8-10 DAS not effective to control weeds and have no significance in weed biomass reduction over the herbicides alone (Fig. 1). So it is suggested that cowpea grower go for intercultural plus hand weeding at 25 to 40 DAS in combination with suitable pre or post herbicides application to get better weed control. Different treatments significantly affect growth parameter like as plant height, plant spread, number of branches per plant, number of pods per plant, number of seeds per plant and grain weight per plant (Tables 2 and 3). Highest plant height (59.32 cm), plant spread (31.29), number of branches per plant (9.67), number of pods per plant (10.25) number of seeds per plant (11.00), and grain weight per plant (11.71 g) recorded under weed free treatment, which was at par with T 10 (2 HW + 2 IC), T 2 (pendimethalin + 1 HW + 1 IC), T 5 (quizalofop-ethyl + 1 HW + 1 IC) and T 8 (imazethapyr + 1 HW + 1 IC) treatment. These treatment recorded lowest weed biomass accumulation at harvest (Fig. 1). There is no impact on test weight by different weed management practices it is found non significant.  ) and T8 (imazethapyr + 1 HW + 1 IC, 1422.22 kg ha -1 ) respectively (Fig. 2). The maximum stover yield 2096.53 kg ha -1 was recorded by the treatment T 11 (weed free). However, it was found statistically at par with treatments T 10 (Fig. 2). Among the four herbicides tested in the experiment fluchloralin not found effective against the weeds and T 1 (Fluchloralin + 1 HW +1 IC) recorded low grain yield (1262.73 kg ha -1 ).   (Table 4). By adopting appropriate weed management practices farmer can get 3000 to 4000 net increase in return over the other treatment. No doubt that hand weeding along with intercultural practices carried out twice in growing season was found as good as weed free but on the basis of present study it can be suggested that cowpea grower can go for use of suitable pre and post herbicides like as pendimethalin, quizalofop-ethyl and imazethapyr at 20-25 DAS without compromising with output. Results obtained in present study also supported by the findings of [16,17,18].

Effect of different weed management treatments on grain and stover yield
Grain yield (kg/ha) Straw yield (kg/ha)

CONCLUSION
It was found that selection of appropriate herbicides and its application in combination with cultural practices at critical period of weed growth was key factor to get elevated yield in rain fed cowpea. On the basis of present study it can be suggested that cowpea grower in rainfed area, can go for use of suitable pre and post herbicides like as pendimethalin, quizalofop-ethyl and imazethapyr at 20-25 DAS without compromising with output, but it is only one year data so further study required in this research aspect.