Influence of sequential application of weedicides on weed management and yield of black gram (Vigna mungo L.)

Introduction

Black gram (Vigna mungo L. Hepper) is popularly known as "Urd", is one of the important pulse crop cultivated worldwide in tropical and subtropical regions of the world. The crop is resistant to adverse climatic conditions and improves the soil fertility by fixing atmospheric nitrogen in the soil. It has wide adaptability and can be grown through round the year in different agro-ecological regions of the country. It contains 48.0 per cent carbohydrates, 22.3 per cent protein, 154 mg calcium, 9.1 mg iron, 1.4 g fat, 0.37 g riboflavin and 0.42 mg thiamine in per 100 g (Asaduzzaman et al., 2010) [1] . It is consumed in the form of "dal" (whole or split, husked and un-husked) and in a variety of ways across from North to South India. In India are prepared of different regular and popular dishes like vada, idle, dosa, halwa and imarti in combination with other food grains. Hand weeding is effective against most of the weeds that becomes difficult due to dependence on labour. Hence, the use of pre-emergence or early post emergence weedicides along with their combinations with other weedicides are to be studied for wide spectrum of weed control in black gram. Recently, weedicides used for weed control include pre-emergence application of pendimethalin and post emergence application of most of these weedicides provide only a narrow spectrum of weed control. Therefore, there is need to have alternate weedicides having broad spectrum weed control to prevent weed shift as well as possible development of weedicides resistance. Identification of alternate strategy such as new weedicides and weedicide combinations with different mode of action like fomesafen + fluazifop-p-butyl, propaquizafop + imazethapyr and sodium-acifluorfen + clodinafop-propargyl may be need of the hour to tackle the problem of weed infestation in black gram. If farmers fail to apply pre-emergence weedicides after sowing of urd bean due to any reason, the use of post-emergence weedicides becomes the only viable weed management option. In recent years, a combination of fluazifop-p-butyl and fomesafen has been found effective in managing both annual and perennial grasses as well as broad-leaved weeds in various pulse and oilseed crops. Fluazifop-p-butyl, an acetyl-CoA carboxylase (ACCase) enzyme inhibitor, specifically targets grassy weeds, whereas fomesafen, a protoporphyrinogen oxidase (PPO or PROTOX) inhibitor, is effective against annual broad-leaved weed species (Silva et al., 2007) [10] . Use of propaquizafop + imazethapyr combination found effective in pulses. Imazethapyr is a systemic, post emergence weedicide, absorbed by the roots and foliage with translocation in the xylem and phloem and accumulate in the meristematic regions. The use of this weedicide controlled major annual and perennial grasses and broad-leaved weeds in leguminous crops (Dixit and Varshney, 2007) [2] . Propaquizafop is a selective post emergence weedicide used to control wide range of annual and perennial grasses in broad-leaved crops. After foliar application of the weedicide, it is absorbed by the leaves and translocated from the foliage via the phloem to the growing points of the leaves and roots of the weeds. Treated plant ceases growth within 3-4 days, show chlorosis on the younger plant tissues followed by a progressive collapse of the entire plant after 10-20 days later. Sodium-acifluorfen controls many annual broad-leaved weeds and several grasses. Clodinafop-propargyl is a broad spectrum graminicide with activity on many annual and perennial grass weed species under different climatic conditions. The combined application of sodium-acifluorfen + clodinafop-propargyl results in broad spectrum weed control (Rao, 2018) [7] . Current literature on weed management in black gram has examined various weedicide options; however, there is a significant research gap concerning weedicide mixture strategies specifically tailored for effective weed management in black gram fields. Utilizing weedicides and their ready-mix combination could offer a viable alternative for managing weeds (Marimuthu et al., 2024) [6] .

Materials and Methods

The experiment was carried out at the Krishi Vigyan Kendra, Pratapgarh MPUAT, Udaipur during kharif, 2025. The soil of the experimental field was clay-loam in texture, moderately alkaline in reaction with low level of available nitrogen, medium level of available phosphorus and high level of available potassium. The experiment was laid out in randomized block design comprising of 12 treatments replicated thrice. The treatments evaluated were: weedy check (T 1 ), weed free (T 2 ), hand weeding at 20 and 40 DAS (T 3 ), pendimethalin @ 1000 g ha -1 (T 4 ), diclosulam @ 20 g ha -1 (T 5 ), imazethapyr @ 75 g ha -1 at 20 DAS (T 6 ), fomesafen @ 250 g ha -1 at 20 DAS (T 7 ), fluzifop p-butyl @ @ 250 g ha -1 at 20 DAS (T 8 ), fomesafen + propaquizafop @ 252+78 g ha -1 at 20 DAS (T 9 ), propaquizafop + imazethapyr @ 50 + 75 g ha -1 at 20 DAS (T 10 ), sodium-acifluorfen + clodinafop-propargy @ 140 + 70 g ha -1 at 20 DAS (T 11 ) and fomesafen + fluzifop p-butyl g ha -1 20 DAS (T 12 ). As a test crop black gram variety kota urd-4 was shown during the last week of June, 2025 with crop geometry 30 cm x 10 cm. Spraying of pre-emergence weedicides viz., pendimethalin and diclosulam was done two days after the sowing of crop. Grassy, sedges and broad-leaved weed count was taken at 60 DAS from two randomly selected spot in each plot by using a quadrate of 0.5 m x 0.5 m and then expressed as number m -2 . Weeds were removed from 0.5 m x 0.5 m area inside the quadrate at 60 DAS and then dried under shades for 24 hours followed by oven drying at 65 ºC to obtain a constant weight and was expressed in g m -2 . Weed data were subjected to square root transformation (√𝑋 + 0.5) to normalize their distribution. Weed control efficiency (%) was computed on the basis of total dry weight. The crop was harvested manually during the last of September.

Results and Discussion

Weed Density

The experimental site was heavily infested with mixed flora of grasses, sedges and broad-leaved weeds chiefly consisted of Echinochloa colona, Cynodon dactylon, Cyperus rotundus, Amaranthus viridis, Parthenium hysterophorus, Phyllanthus niruri, Convolvulus arvensis, Echinochloa crus-galli, and Digera arvensis, where the dominancy of grassy weeds was observed. The sum of grassy, sedges and broad-leaved weeds was included in total weed density. Data presented in Table 1 indicate that different weed management practices resulted in significantly lower density of grassy weeds in comparison to weedy check. The maximum reduction of grassy weed density was observed under the application of fomesafen + fluzifop p-butyl @ 220 + 220 g ha -1 at 20 DAS (T 12 ) which was statistically at par with the application of propaquizafop + imazethapyr @ 50 + 75 g ha -1 at 20 DAS (T 10 ). The decline of total grasses under sodium acifluorfen + clodinafop-propargyl @ 140 + 70 g ha -1 at 20 DAS (T 11 ) was 73.35 per cent over weedy check (9.27 m -2 ). In case of sedges, application of diclosulam @ 20 g ha -1 resulted in the minimum density (3.35 m -2 ) which was statistically at par with T 6 and T 10 . This might be because sedges propagated by rhizomes and disruption by hand weeding encouraged increased growth of below-ground rhizomes. Since weeds continuously emerge during the crop growth period, post-emergence weedicides help in eliminating weeds at later stages. Due to of weedicides effectiveness, crop experiences less competition from weeds, which favours the crop in efficient utilization of nutrients, moisture, light and space. Consequently, a substantial improvement in growth and yield attributes occur, which is ultimately reflected in higher yield of the crop This is in conformity with the findings of Reddy et al. (2021) [9] . The maximum reduction of broad-leaved weed was noticed under the application of fomesafen + fluzifop p-butyl @ 220 + 220 g ha -1 at 20 DAS (T 12 ) which was statistically at par with T 10 and T 11 , accounting for 74.38, 73.69 and 73.69 per cent lower weed count, respectively over weedy check (8.59 m -2 ). Data show that application of propaquizafop + imazethapyr @ 50 + 75 g ha -1 at 20 DAS (T 10 ) recorded the least count of total weed with 66.12 per cent reduction over weedy check (14.08 m -2 ). However, its outcome was statistically at par with diclosulam @ 20 g ha -1 and fomesafen + fluzifop p-butyl @ 220 + 220 g ha -1 at 20 DAS (T 12 ) and superior over rest of the treatments. Application of diclosulam @ 20 g ha -1 and fomesafen + fluzifop p-butyl @ 220 + 220 g ha -1 at 20 DAS (T 12 ) recorded 65.83 per cent reduction of total weed population in comparison to weedy check. This might be due to the effectively suppressed weed density because the prevalent weed flora was highly susceptible to these pre-mix weedicide combinations. These weedicides inhibit protoporphyrinogen oxidase (PPO) and acetyl-CoA carboxylase (ACCase) enzyme activity, leading to chlorosis, bronzing, desiccation, and necrosis in susceptible weeds species. The present findings are in conformity with those of Elankavi et al. (2019) [5] , Singh et al. (2019) [9] Dhayal et al. (2022) [3] and Dhakad et al. (2023) [4] .

Weed Dry Matter Accumulation

It is evident from data (Table 2) that fomesafen + fluazifop pbutyl @ 220 + 220 g ha -1 at 20 DAS (T 12 ) recorded the lowest dry matter accumulation of grassy weed which was statistically at par with T 10 , T 11 and T 9 showing 62.85, 47.32, 45.87 and 44.41 per cent reduction over weedy check (11.08 g m -2 ), respectively. Application of diclosulam @ 20 g ha -1 (T 5 ) provided significantly lower dry matter accumulation of sedge i.e., Cyperus rotundus (1.96 g m -2 ) over weedy check ((3.56 g m -2 ). But its effect was found to be statistically at par with T 6, T 10 and T 12 . Like weed density, treatments comprising of hand weeding also recorded statistically higher dry matter accumulation of sedges as compared to weedy check. In reducing the dry matter accumulation of broad-leaved weed, fomesafen + fluazifop pbutyl @ 220 + 220 g ha -1 at 20 DAS (T 12 ) showed the superior results with 50.70 per cent reduction over weedy check (10.00 g m -2 ). However, the effect was statistically at par with propaquizafop + imazethapyr @ 50 + 75 g ha -1 at 20 DAS (T 10 ) and sodium acifluorfen + clodinafop-propargyl @ 140 + 70 g ha - 1 at 20 DAS (T 11 ) showing 49.10 and 47.70 per cent lower value than weedy check. The maximum reduction of total weed dry matter accumulation was noticed under fomesafen + fluazifop p-butyl @ 220 + 220 g ha -1 (T 12 ). The next best weedicides treatment was propaquizafop + imazethapyr @ 50 + 75 g ha -1 at 20 DAS (7.92 g m -2 ), which stood statistically at par with sodium acifluorfen + clodinafoppropargyl @ 140 + 70 g ha -1 at 20 DAS (8.14 g m -2 ) and fomesafen + propaquizafop @ 252 + 78 g ha -1 at 20 DAS (8.34 g m -2 ).

Weed Control Efficiency (WCE)

The results (Table 2) reveal that all the weed control treatments provided significantly higher WCE over weedy check. Weed free treatment (T 2 ) throughout the crop growing period registered 100 per cent WCE. Among weedicide treatments, the maximum weed control efficiency (80.94%) was achieved by the application of fomesafen + fluazifop p-butyl @ 220 + 220 g ha -1 (T 12 ). However, its effect was found to be statistically at par with Propaquizafop + Imazethapyr @ 50 + 75 g ha -1 at 20 DAS and Sodium-acifluorfen + Clodinafop-propargy @ 140 + 70 g ha -1 at 20 DAS providing weed control efficiency of 73.09 and 71.52 per cent.

Yield

Seed and haulm yield of black gram were significantly enhanced by different weed control treatments over weedy check (Table 3). Data distinctly indicate that the maximum seed yield (1595 kg ha - 1 ) and haulm yield (2354 kg ha -1 ) was recorded under weed free treatment (T 2 ). This was attributed to weed free atmosphere up to harvest with least competition for growth resources. It is well established fact that least crop weed competition during critical phases of crop growth exerts an important regulation function on complex process of yield formation due to better availability of water, space and nutrients to the crop plant (Patel et al. 2026) [6] . Among weedicide treatments, fomesafen + fluazifop p-butyl @ 220 + 220 g ha -1 (T 12 ) registered the superior seed yield (1441 kg ha -1 ) and haulm yield (2259 kg ha -1 ). However, its effect was statistically at par with propaquizafop + imazethapyr @ 50 + 75 g ha -1 at 20 DAS (T 10 ) and sodium acifluorfen + clodinafoppropargyl @ 140 + 70 g ha -1 at 20 DAS (T 11 ) in seed yield and haulm yield. This might be due to the fact that least crop-weed competition during critical phase of crop growth exerts an important regulatory function on complex process of yield formation due to better availability of water, space and nutrients to the crop plant. It also helps in improving aeration and nutrient uptake by plant resulting in higher metabolic activity Singh et al. (2022) [11] and Sreekanth et al. (2024) [12] . 883 1578 T5: Diclosulam @ 20g ha -1 (PE) 955 1624 T6: Imazethapyr @ 75g ha -1 at 20 DAS 905 1535 T7: Fomesafen @ 250 g ha -1 at 20 DAS 753 1446 T8: Fluzifop p-butyl @ 250 g ha -1 at 20 DAS 792 1415 T9: Fomesafen + Propaquizafop @ 252 + 78 g ha -1 at 20 DAS (Ready mix) 1024 1678 T10: Propaquizafop + Imazethapyr @ 50 + 75 g ha -1 at 20 DAS (Ready mix) 1398 2185 T11: Sodium-acifluorfen + Clodinafop-propargy @ 140 + 70 g ha -1 at 20 DAS (Ready mix) 1338 2162 T12: Fomesafen + Fluzifop p-butyl @ 220 + 220 g ha -

Conclusion

From the findings of the experiment, it was observed that sequential application of fomesafen + fluazifop p-butyl @ 220 + 220 g ha -1 (T 12 ) fomesafen + fluazifop p-butyl @ 220 + 220 g ha - 1 (T 12 ) as PoE provided the maximum weed control efficiency as well as the highest seed and haulm yield of black gram among various weedicide treatments. Hence, it may be concluded that under the scenario of labour shortage and high labour cost, weedicide sequence fomesafen + fluazifop p-butyl will effectively control weed leading to higher yield of black gram.

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