Effect of different ready-mix herbicide combinations on growth performance of rice-fallow blackgram (Vigna mungo L.)

Introduction

Blackgram (Vigna mungo L.) is one of the most important pulse crops cultivated in India and plays a significant role in improving soil fertility through biological nitrogen fixation of 20-50 kg ha⁻¹ (Shankar et al., 2025) [13] . In rice-fallow ecosystems, blackgram is commonly grown using residual soil moisture after rice harvest, providing an opportunity to increase cropping intensity and enhance farm income. The growth and development of blackgram under rice-fallow conditions largely depend on efficient utilization of available resources such as nutrients, moisture, light and space (Das et al., 2024) [1] . Weed infestation is one of the major constraints limiting the growth potential of rice-fallow blackgram. During the early stages of crop growth, weeds compete aggressively with the crop for essential resources, resulting in reduced plant height, lower dry matter accumulation, poor branching and restricted leaf area development (Mudalagiriyappa et al., 2022) [10] . Such adverse effects ultimately impair crop vigour and productivity. The critical period of crop-weed competition (20-40 DAS) in blackgram generally occurs during the initial growth phase, when the crop is highly sensitive to weed interference (Manohar et al., 2024) [8] . Effective weed management is therefore essential to ensure vigorous crop growth. Ready-mix herbicides containing two or more active ingredients have emerged as a promising option for broad-spectrum weed control. These formulations help reduce weed competition and create favourable conditions for crop establishment and growth (Maji et al., 2025) [7] . Hence, the present study was undertaken to evaluate the influence of different ready-mix herbicide combinations on the growth parameters of rice-fallow blackgram.

Materials and Methods

A field experiment was conducted during the rabi season of 2025-26 at the Agricultural Research Station, Ragolu, Srikakulam, Andhra Pradesh, India. The experimental site is located at 18.34° N latitude and 83.89° E longitude with an altitude of 27 m above mean sea level in the North Coastal Zone of Andhra Pradesh. The soil of the experimental field was sandy clay loam in texture, neutral in reaction, medium in organic carbon (0.58), available nitrogen (284.1 kg ha⁻¹) and potassium (264.6 kg ha⁻¹) status, while the available phosphorus was high (36.5 kg ha⁻¹). The experimental field received a total rainfall of 14.5 mm in 2 rainy days of the 48 th standard meteorological week. The mean maximum and minimum temperatures ranged from 27.6 to 32.8 °C and 14.4 to 20.6 °C, respectively. The experiment was laid out in a randomized block design (RBD) with ten treatments replicated thrice. The treatments comprised: pre-emergence (PE) application of Pendimethalin 30% + Imazethapyr 2% EC @ 800 g a.i. ha⁻¹ (T₁), post-emergence (PoE) application of Propaquizafop 2.5% + Imazethapyr 3.75% ME @ 125 g a.i. ha⁻¹ (T 2 ), Fomesafen 12.5% + Quizalofop-P-ethyl 4.68% ME @ 174.8 g a.i. ha⁻¹ (T 3 ), Fomesafen 11.1% + Fluazifop-P-butyl 11.1% ME @ 222 g a.i. ha⁻¹ (T 4 ), Fomesafen 16.8% + Propaquizafop 5.2% ME @ 137.5 g a.i. ha⁻¹ (T 5 ), Sodium acifluorfen 16.5% + Clodinafop 8% EC @ 245 g a.i. ha⁻¹ (T 6 ), Quizalofop-ethyl 7.5% + Imazethapyr 15% EC @ 84 g a.i. ha⁻¹ (T 7 ), Imazethapyr 35% + Imazamox 35% WG @ 28 g a.i. ha⁻¹ (T 8 ), Weed-free check (T 9 ) and Weedy check (T 10 ). Blackgram variety "LBG-884" was broadcast on 24.11.2025 and raised under rice-fallow conditions utilising residual soil moisture without any preparatory tillage operations and it was harvested on 19.02.2026. Since there is no recommendation for basal fertilizer application under rice-fallow blackgram, foliar nutrition was provided through spraying of 19:19:19 fertilizer @ 5 g L⁻¹ at flowering stage, followed by 13:0:45 fertilizer @ 1 g L⁻¹ at the pod development stage to enhance pod filling and seed development. Growth parameters such as plant height, number of branches plant⁻¹, number of nodules plant⁻¹ and dry matter production were recorded at 20 and 60 DAS. Plant height was measured from the base of the plant to the tip of the growing point, while the number of branches was counted from five randomly tagged plants in each plot and expressed on a plant basis. Nodulation was assessed through destructive sampling by carefully uprooting five plants from each treatment, washing the roots and counting the nodules manually. Dry matter production was determined by oven-drying the sampled plants at 65°C, using the method proposed by Watson (1952) [18] and until a constant weight was attained and expressed as kg ha⁻¹.

Results and Discussion

Plant height

Plant height of rice-fallow blackgram was not significantly influenced by the herbicide treatments at 20 DAS. However, the weed-free check (T 9 ) recorded a numerically higher plant height (14.50 cm), followed by pre-emergence application of Pendimethalin 30% + Imazethapyr 2% EC (T₁) (12.80 cm). The non-significant differences at this stage could be attributed to the absence of post-emergence herbicide application and relatively lower crop-weed competition during the early growth period. At 60 DAS, significant differences in plant height were observed among the herbicidal ready-mix treatments. The weed-free check (T 9 ) registered the highest plant height (37.51 cm), while among the herbicide ready-mix combinations, fomesafen 16.8% + propaquizafop 5.2% ME (T 5 ) recorded superior plant height (33.42 cm), which was followed by fomesafen 12.5% + quizalofop-P-ethyl 4.68% ME (T 3 ) and fomesafen 11.1% + fluazifop-P-butyl 11.1% ME (T 4 ). The enhanced plant growth under these treatments could be attributed to effective weed suppression, which reduced competition for nutrients, moisture and light, thereby promoting better crop vigour and growth (Kumar et al., 2025 and Harisha et al., 2021) [5,3] . The lowest plant height was recorded under the weedy check (T 10 ) due to severe weed competition throughout the crop growth period (Shashidhar et al., 2020) [14] .

No. of branches (no. plant -1 )

At 20 DAS, the herbicide treatments had no significant effect on the number of branches plant⁻¹. This may be due to, no postemergence herbicide ready-mix application, but the weed-free check (T 9 ) showed a comparatively larger number of branches than all other treatments. The treatments differed significantly at 60 DAS. Among herbicide ready-mix combinations, fomesafen 16.8% + propaquizafop 5.2% ME (T 5 ) showed better branching, followed by fomesafen 12.5% + quizalofop-P-ethyl 4.68% ME (T 3 ) and fomesafen 11.1% + fluazifop-P-butyl 11.1% ME (T 4 ), which are statistically on par with each other. The weed-free check(T 9 ), on the other hand, produced the most branches plant⁻¹ (Jain et al., 2025) [4] . This could be because weeds were effectively controlled during the critical crop growth phase, which may have improved branching under these treatments by increasing the availability of nutrients, moisture and light, which promoted strong vegetative growth (Singh et al., 2022) [16] . The weedy check (T 10 ) indicated the fewest branches plant⁻¹ because of continuous weed competition during the crop growth period.

No. of nodules (no. plant -1 )

The herbicide ready-mix treatments did not exert a significant effect on the number of nodules plant⁻¹ at 20 DAS, though minor numerical variations were noticed among the treatments. The weed-free check (T 9 ) registered a relatively higher number of nodules may be due to favourable environment. In contrast, significant differences in nodulation were observed at 60 DAS. The weed-free check (T 9 ) produced the maximum number of nodules plant⁻¹ and was comparable with fomesafen 16.8% + propaquizafop 5.2% ME (T 5 ), fomesafen 12.5% + quizalofop-Pethyl 4.68% ME (T 3 ), imazethapyr 35% + imazamox 35% WG (T 8 ) and fomesafen 11.1% + fluazifop-P-butyl 11.1% ME (T 4 ). The improved nodulation under these treatments could be attributed to effective weed suppression, which minimized cropweed competition and promoted better root development, nutrient uptake and Rhizobium activity, resulting in enhanced biological nitrogen fixation (Maji et al., 2025 and Susmitha et al., 2019) [7,17] .

Leaf area index was not significantly affected by the herbicide ready-mix treatments at 20 DAS, although the weed-free check (T 9 ) registered comparatively higher LAI values. The nonsignificant response at the initial growth stage could be due to lower weed pressure. However, significant differences were observed at 60 DAS. The weed-free check (T 9 ) recorded the highest LAI and remained comparable with fomesafen 12.5% + quizalofop-P-ethyl 4.68% ME (T 3 ), fomesafen 11.1% + fluazifop-P-butyl 11.1% ME(T 4 ), imazethapyr 35% + imazamox 35% WG (T 8 ) and fomesafen 16.8% + propaquizafop 5.2% ME (T 5 ). The higher LAI under these treatments may be attributed to effective weed control, which ensured better availability of nutrients, moisture and light, thereby promoting greater leaf expansion and canopy growth (Dhayal et al., 2022) [2] . In contrast, the weedy check (T 10 ) recorded the lowest LAI owing to prolonged cropweed competition that adversely affected crop growth and canopy development. Similar findings on the beneficial effect of efficient weed management on canopy development and LAI were reported by Kumar et al. (2022) [6] and Reddy et al. (2023) [12] .

Drymatter production was not significantly affected by the herbicide ready-mix treatments at 20 DAS, although the weedfree check (T 9 ) showed comparatively greater biomass accumulation. The lack of significant differences during the initial growth stage may be due to lower weed pressure and the fact that post-emergence ready-mix herbicides had not yet applied. In contrast, significant differences in dry matter production were evident at 60 DAS. The highest dry matter accumulation was recorded under the weed-free check (T 9 ), while among the herbicide treatments, fomesafen 16.8% + propaquizafop 5.2% ME produced the greatest biomass. This was subsequently followed by post-emergence applications of fomesafen 12.5% + quizalofop-P-ethyl 4.68% ME (T₃), fomesafen 11.1% + fluazifop-P-butyl 11.1% ME (T₄), imazethapyr 35% + imazamox 35% WG (T₈) and quizalofop-ethyl 7.5% + imazethapyr 15% EC (T₇), which were statistically comparable with each other in descending order. The higher dry matter production under these treatments may be attributed to efficient weed control, which reduced competition for growth resources and enabled better crop growth, resulting in greater biomass accumulation (Shashidhar et al., 2020 and Ramesh et al., 2020) [15,11] . The weedy check (T 10 ) recorded the lowest dry matter production, indicating the adverse effect of unchecked weed growth on crop development (Meena et al., 2020) [9] .

Conclusion

The study revealed that the herbicide ready-mix treatments did not markedly influence the growth parameters of rice-fallow blackgram during the initial stage of crop growth (20 DAS). However, clear treatment effects became evident at 60 DAS, where significant improvements in plant height, branching, nodulation, leaf area index and dry matter production were observed under effective weed management practices. Among the herbicide ready-mix treatments, post-emergence application of fomesafen 16.8% + propaquizafop 5.2% ME (T₅) consistently exhibited better growth performance and this was followed by the application of fomesafen 12.5% + quizalofop-P-ethyl 4.68% ME (T₃), fomesafen 11.1% + fluazifop-P-butyl 11.1% ME (T₄). The favourable response under these treatments may be attributed to effective weed suppression, which minimized crop-weed competition and ensured better utilization of available resources such as nutrients, moisture and light. While the weed-free check (T 9 ), recorded the highest values for all growth parameters, fomesafen 16.8% + propaquizafop 5.2% ME (T 5 ), proved to be the most promising herbicide ready-mix among the tested treatments for improving crop growth and biomass production. However, the weedy check recorded the poor growth performance owing to its continuous weed interference throughout the crop growth period.

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