Use of pre and post emergent herbicides for better weed control, higher seed yield and economics of chickpea (Cicer arietinum L.)

Introduction

Chickpea (Cicer arietinum L.) is one of the most prominent pulse crops not only in India but also in the world. It is called by different synonyms such as gram or bengalgram and is popularly referred to as chana in several places of the country. Chickpea is a cool season longday legume crop belongs to the family fabaceae and subfamily faboideae. It is valued for its rich nutritive seed with enormous source of protein (23%), carbohydrate (63%), fat (5%), crude fiber (6%), ash (3%) and also rich in calcium, magnesium, iron and niacin (Ratnam et al.,2011) [16] . Hence, it is increasingly consumed as a substitute for animal protein. It is predominantly consumed in the form of whole grain or dhal, sprouted grain, green or matured dry seeds and is used in the preparation of variety of snacks, sweets and condiments. Due to its high nutritional value, it has become an integral part of the daily dietary system for over millions of people. In India chickpea is grown on an area of 10.74 m ha, with a production of 13.54 m t and a productivity of 1261 kg ha -1 (Anon, 2024) [1] . In Karnataka, chickpea occupies an area of 0.73 million hectares having 0.47 m. tones of production with an average productivity of 689 kg ha -1 (Anon., 2024a) [2] . In Karnataka, Kalaburagi occupies the first position with respect to chickpea area (1.24 lakh ha), production (8.63 lakh tonnes) and productivity (733 kg ha -1 ) (Anon, 2024b) [3] Chickpea is grown during rabi under residual moisture conditions and marginal lands which are low in fertility status and facing various biotic and abiotic stresses.

The overall productivity of chickpea in India is comparatively low as compared to other countries. The lower productivity of chickpea is mainly because of several biotic and abiotic factors. Among the biotic factors, heavy weed infestation is the major factor responsible for poor yield of chickpea. Heavy weed infestation is recognized as a major bottleneck in realizing the potential yield of chickpea. The crop has to compete for light, water, nutrient, and space with weeds during initial growth phases. The report suggested that 30-50% losses in chickpea yield have been estimated due to weed infestation. Weeds pose a serious threat in chickpea and cause up to 50-60 per cent yield losses as indicated by Ratnam et al., 2011 [15] . Since the crop is grown in rabi season, if it is infested by a large number of weeds which have quick growth habit the growth and yield will be severely affected. The first 20-30 days after sowing are most critical period of competition between crop and weed for resources (nutrients, moisture, light and space). During this period, as the crop is having slow growth and weeds grow fast. They smother the crop and offer great completion for moisture, nutrients, light and space. They take most of the native and applied nutrients. The problem is further aggravated under the conditions of water stress where, weeds utilize the available moisture in the root zone quickly as they have quick growth habit as established by Kamble et al,.2014 [8] . Therefore, research methodologies need to be reoriented to evolve appropriate weed management practices for their better control and improving the productivity of chickpea. Thus, keeping theses points in view, an experiment to study the effect pre and post emergent herbicides on weed control, growth, yield and economics of chickpea was planned and implemented.

Materials and Methods

A field experiment was conducted during rabi season, 2022-23 and 2023-24 at Zonal Agricultural Research Station, Kalaburagi (Karnataka) to assess the 'use of pre and post emergent herbicides for better weed control, higher yield and economics of chickpea'. The soil of experimental site was medium black clay in texture having alkaline pH of 8.4, bulk density 1.33 g/cc and with organic carbon content 5.2 g kg -1 . The soil was medium in nitrogen (178 kg ha -1 ), low in phosphorus (22 kg ha -1 ) and medium in potassium (328 kg ha -1 ) at the time of initiation of the experiment. The climate of the area was subtropical, received annual average rainfall of 720 mm and mean maximum and minimum temperature were 38.77 o C and 17.76 o C, respectively. The experiment was laid out in Randomized complete block design (RCBD) with three replications. The experiment consisted of 13 treatments as T1: Oxyfluorfen @ 150 g a.i. ha -1 (PRE), T2: Oxyfluorfen @ 250 g a.i. ha -1 (PRE), T3: Quizalofop-P-Ethyl @ 100 g a.i. ha -1 at 15-20 DAS, T4: Propaquizafop @ 100 g a.i. ha -1 at 15-20 DAS, T5: Topromezone @ 20.6 g a.i. ha -1 at 14 DAS, T6: Topromezone @ 20.6 g a.i. ha -1 at 21 DAS, T7: Topromezone @ 25.7 g a.i. ha -1 at 21 DAS, T8: Oxyfluorfen 150 g fb Quizalofop-p-ethyl @ 100 g a.i. ha -1 at 15-20 DAS, T9: Oxyfluorfen 150 g fb Propaquizafop @ 100 ga.i. ha -1 at 15-20 DAS, T10: Oxyfluorfen 150 g fb Topramezone @ 20.6 g a.i. ha -1 at 14-21 DAS, T11: Pendimethalin @ 750 g a.i. ha -1 , T12: Weedy check and T13: Weed free check. The sowing of the experiment was done during 2 nd fortnight of October in both the years of experimentation. The certified seeds of chickpea variety JG-11 were used for sowing. The recommended dose of fertilizer (25: 50 N:P kg ha -1 ) was applied at the time of sowing. The crop was sown by hand dibbling and maintaining spacing of 30 cm between rows and 10 cm between plants. A knapsack sprayer fitted with flat fan nozzle was used to apply the pre-emergent weedicide on the first day after sowing and post-emergent weedicide was sprayed as per the treatment with a spray volume of 750 l ha -1 . In different plots weed management operation was done as per the treatments. Observations on weed population were recorded at 30 and 45 DAS. Weeds were counted randomly at selected places in each plot using 0.5 × 0.5 m quadrant (0.25 m 2 ). Weed count was expressed as number per m -2 and subjected to square-root transformation (x+0.5) 1/2 to normalize their distribution. Total weed density was obtained by adding all the grasses, sedges and broad leaf weeds. The weeds removed from the selected areas were dried at 70 o C for 72 hours to obtain constant weight and the dry weight was expressed in g m -2 . Weed control efficiency (WCE) was calculated by using suitable formula given by Lal et al., 1990 [13] .

Where, WCC = Dry weight of weeds in unweeded control plot (g) WCT = Dry weight of weeds in treated plot (g) Weed index represents actual measure of weeds present and was calculated by following suitable formula (Lal et al., 1990) [13].

Where, X = Seed yield in weed free check plot (kg ha -1 ) Y= Seed yield in treated plot (kg ha -1 ) Suitable plant protection measures were followed during the cropping season. Five plants were randomly selected in each net plot area for taking observations on growth and yield and quality attributing parameters as per the schedule. The crop in each net plot was harvested separately as per treatment and the values were converted into hectare basis and expressed in kilograms per hectare. The data recorded during the investigation were compiled and analyzed for statistical significance as per the analysis of variance for the split plot design. Fisher's method of analysis of variance (ANOVA) adopted for the purpose. Standard error of mean and coefficient of variability have been worked out for a set of observations under each character at P=0.05 to interpret the significance as given by Panse VG and Sukhatme, 1978 [14] .

Results and Discussion

Weed flora observed Many different types of weeds were observed in the experimental plot of chickpea. The most important grassy weeds observed in the experimental plot were Cynodon dactylon, Panicum repens, Dactyloctenium aegyptium, Digitaria marginata and Erogrostis gangetica. While common broadleaved weeds observed were Commelina benghalensis, Phyllanthus niruri, Tribulus terrestris, Abutilon indicum, Euphorbia hirta, Trichodesma spp., Portulaca oleracea, Tridax procumbens, Amaranthus viridis, Digeria arvensis and Leucus aspera and the common sedge observed was Cyperus rotundus (Kalyani and Srinivasulu, 2011) [7,12] Effect on weed density weed dry weight The weed density and weed dry weight in all the treatments at 30 and 45 DAS were significantly reduced with the use of weedicide compared to weedy check (Table 1 &2). Among the herbicide treatments, the pooled data indicated that significantly lower weed density (4.37 and 5.07 at 30 and 45 DAS respectively) was recorded with use of oxyfluorfen 150 g fb quizalofop-p-ethyl @ 100 g a.i. ha -1 at 15-20 DAS and weed dry weight also followed the similar trend (3.70 and 4.60 g m -2 at 30 and 45 DAS respectively). these results are in conformity with findings of Kumar et al, 2014 [11]. This was mainly due to combination of both pre and post emergent herbicide which were efficient in killing the most of the weeds compared to other treatments. Oxyflorofen primarily acts by inhibiting the enzyme protoporphyrinogen oxidase (PPO), which is crucial for chlorophyll synthesis. This inhibition causes a buildup of toxic prophyrins, damaging cell membranes and leading to rapid desiccation and death of weeds. Quizalofop-P-ethyl's acts by inhibiting the Acetyl-CoA carboxylase (ACCase) enzyme, which is crucial for lipid and fatty acid synthesis (Kachhadiya et al, 2009) [6]. Among all the treatments, weedy check recorded significantly higher weed density (7.44 and 8.18 at 30 and 45 DAS respectively) and weed dry weight (6.53 and 7.47 g m -2 at 30 and 45 DAS respectively) due to presence of more number of weeds. Whereas, weed free check recorded significantly lower weed density (2.62 and 2.97) and weed dry weight (2.21 and 2.90 g m -2 ) when compared to all other treatments. This was mainly due to less density of weeds contributing less dry weight in weed free check. Similar results are obtained by Lal, 1990 [13] .

Effect on weed control efficiency and weed index

Among the herbicide treatments, the pooled data (Table 3) indicated that application of oxyfluorfen 150 g fb quizalofop-pethyl @ 100 g a.i. ha -1 at 15-20 DAS recorded significantly higher weed control efficiency (68.61% and 59.97% at 30 and 45 DAS respectively) compared to other treatments. This was mainly due to efficient killing of weeds due to combination of pre and post emergent herbicides. Among the herbicides, lower weed control efficiency (48.49% and 40.83% at 30 and 45 DAS respectively) was observed with the use of oxyfluorfen @ 150 g a.i. ha -1 as pre emergent spray (48.49% and 40.83% at 30 and 45DAS respectively). similar observations are made by Buttar, et al., 2008 [4] . With regard to weed index, application of oxyfluorfen 150 g fb quizalofop-p-ethyl @ 100 g a.i. ha -1 at 15-20 DAS recorded significantly lower weed index (5.57) owing to effective death of weeds by the herbicides as compared to other herbicidal treatments whereas, weedy check recorded significantly higher weed index (22.84) due to more number of weeds compared to all other treatments. Similar results are obtained by Poonia TC and Pithia (2013) [15] and Sanket et al., 2021 [18] .

Effect on growth parameters

Growth of the plant was severely affected due to the presence of weeds as they competed with crop for growth resources. It is clear from the pooled data (Table 4) that among all the treatments, significantly lower plant height, number of branches and dry matter production were obtained with weedy check (28 cm, 3.05 and 8.98 g plant -1 respectively). This was mainly due to the presence of more number of weeds in the treatment and the intense competition by the weeds for the growth resources which they utilized and suppressed the crop. Whereas, weed free check recorded significantly higher values (37.67, 5.34 and 19.88 gm - 2 cm plant height, number of branches and dry matter production respectively) due to less competition by the weeds in the treatment (Sanket et al., 2021) [18] . Among the herbicides, application of oxyfluorfen 150 g fb quizalofop-p-ethyl @ 100 g a.i. ha -1 at 15-20 DAS recorded significantly higher plant height, number of branches and dry matter production per plant (35.21, 4.68 and 17.36 g respectively) as the combination of pre and post emergent herbicide was more effective in controlling the weeds there by avoiding the competition by the weeds in the treatment as compared to other herbicidal treatments. Similar results are obtained by Dubey et al., 2018 [5] and Rupareliya et al., 2017 [17] .

Effect on yield and yield parameters

Different treatments had significant effect on yield and yield parameters of chickpea (Table 5 &6). The pooled data indicated that, weedy check recorded significantly lower seed yield (1448 kg ha -1 ) compared to all the treatments that was due to production of significantly lower number of pods per plant, seed weight per plant, 100 seed weight, haulm yield and harvest index (18, 5.85, 17.98, 2891 kg ha -1 and 32.85% respectively) compared to all the treatments. The high density of weeds caused stiff competition with crop for growth resources leading to poor growth and consequently lesser yield in this treatment. These results confirm the findings of Srikanth et al., 2021 [19] . Whereas, weed free check recorded significantly higher seed yield (1881 kg ha -1 ) compared to all other treatments. This was mainly due to production of significantly higher yield attributes such as number of pods plant -1 , seed weight per plant -1 , 100 seed weight, haulm yield and harvest index (31.02, 10.66 g, 21.49 g, 3417 kg ha -1 and 35.50 respectively) as there was less competition by weeds with crop (Khope et al., 2011) [10] . Among the herbicide treatments, application of oxyfluorfen 150 g fb quizalofop-p-ethyl @ 100 g a.i. ha -1 at 15-20 DAS recorded significantly higher number of pods plant -1 , seed weight per plant -1 , 100 seed weight, haulm yield and harvest index (28.01, 9.79 g, 21.19 g, 3271 kg ha -1 , 35.18% respectively). The application of herbicide provided best weed free condition in this treatment leading to better growth and yield parameters. These findings are in conformity with Yadav et al., 2019 [20] . All these parameters contributed for the production of significantly higher seed yield (1775 kg ha -1 ) over other herbicide treatments.

Effect on economics

The economics of chickpea cultivation was significantly influenced by different weed management treatments. The pooled data (Table 7) indicated that weed free check recorded significantly higher gross returns, net returns and B:C ratio (₹. 96570, ₹. 70803 and 3.83 respectively) compared to all the treatments owing to higher yield in that treatment because of lesser weed competition. Whereas, weedy check recorded significantly lower gross returns, net returns and B:C ratio (₹. 74194, ₹. 52405 and 3.83 respectively) due to poor yield that was caused by heavy weed infestation leading to poor growth and yield parameters. Among the herbicide treatments, application of oxyfluorfen 150 g fb quizalofop-p-ethyl @ 100 g a.i. ha -1 at 15-20 DAS recorded significantly higher gross returns, net returns and B:C ratio (₹.91032, ₹. 66567 and 3.72 respectively) compared to other herbicide treatments, as the combination of pre and post emergent herbicide that eliminated majority of the weeds and created good condition for plant growth leading to higher yield. This coupled with higher market price lead to significantly higher gross and net returns and hence better B:C ratio in the treatment. Similar results are noticed by Kashyap et al., 2022 [9] .

Conclusion

Performance of chickpea productivity is very much influenced by weed infestation. The weed free check recorded significantly higher growth and yield parameters while weedy check recorded significantly lower growth and yield attributes. Among the herbicides, application of oxyfluorfen 150 g fb quizalofop-pethyl @ 100 g a.i. ha -1 at 15-20 DAS recorded significantly higher growth and yield parameters, suppressing the weeds, effective utilization of growth resources, attaining the higher gross returns, net returns and B:C ratio compared to other herbicide treatments. This treatment can be recommended to farming community for wide spread adoption for getting higher productivity and profitability.

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