Effect of stale seedbed technique and herbicide integration on weed dynamics and yield of rabi Blackgram (Vigna mungo L.)

Introduction

Blackgram is widely grown throughout South and Southeast Asia. In India, it is popularly known as urdbean, whereas in Bangladesh it is referred to as mashkalai addressed by Kaewwongwal et al. (2015) [7] . Due to its significant contribution to vegetarian diets, blackgram is highly valued for its protein content (24-26%) and for being a rich source of essential minerals such as calcium and iron reported by Asaduzzaman et al. (2010) [1] . In Telangana, blackgram occupied an area of 0.30 lakh ha with a production of 0.43 lakh tonnes and an average productivity of 1462 kg ha -1 (Indiastat, 2024-2025) [5] . Despite its nutritional and agronomic importance, blackgram productivity is affected by several constraints, among which weed infestation is one of the most serious, Marimuthu et al. (2024) [9] . Weeds adversely affect crop growth by emerging vigorously and competing with the crop for vital resources such as nutrients, moisture, sunlight and space, particularly during the early stages of crop development reported by Teja et al. (2017) [12] . Significant yield reductions due to unchecked weed growth have been reported in India, with losses reaching up to 79% in Hisar, Sharma et al. (2024) and 42% in coastal Odisha, Dash et al. (2024) [2] . Hence, minimizing crop-weed competition during the critical period of 15-45 DAS is essential for realizing higher crop yields, Reddy et al. (2023) [11] . However, timely manual weeding is often constrained by adverse weather conditions and labour shortages, posing a major challenge to effective weed management in blackgram. Therefore, the integration of the stale seedbed technique with herbicide application has been advocated as an efficient approach for suppressing weeds and maintaining their population below the economic threshold level in blackgram cultivation.

Materials and Methods

A field experiment was conducted during rabi 2025-26 at the Regional Agricultural Research Station, Palem to evaluate the effect of stale seedbed technique and herbicide integration on weed dynamics and yield of rabi blackgram. The present investigation was conducted with 13 weed management treatments (T 1 to T 13 ), T 1 -Normal sowing + pendimethalin 38.7% CS @ 677.25 g a.i. ha -1 (PE), T 2 -Normal sowing + fluazifop-p-butyl 11.1% w/w + fomesafen 11.1% w/w SL @ 250 g a.i. ha -1 (PoE) at 20-25 DAS, T 3 -Normal sowing + propaquizafop 2.5% + imazethapyr 3.75% w/w ME @ 50+75 g a.i. ha -1 (PoE) at 20-25 DAS, T 4 -Stale seedbed (shallow tillage),T 5 -Stale seedbed (paraquat spray @ 500 g a.i. ha -1 before sowing),T 6 -Stale seedbed (shallow tillage) + pendimethalin 38.7% CS @ 677.25 g a.i. ha -1 (PE), T 7 -Stale seedbed (paraquat spray @ 500 g a.i. ha -1 before sowing) + pendimethalin 38.7% CS @ 677.25 g a.i. ha -1 (PE), T 8 -Stale seedbed (shallow tillage) + fluazifop-p-butyl 11.1% w/w + fomesafen 11.1% w/w SL @ 250 g a.i. ha -1 (PoE) at 20-25 DAS, T 9 -Stale seedbed (paraquat spray @ 500 g a.i. ha -1 before sowing) + fluazifop-p-butyl 11.1% w/w + fomesafen 11.1% w/w SL @ 250 g a.i. ha -1 (PoE) at 20-25 DAS, T 10 -Stale seedbed (shallow tillage) + propaquizafop 2.5% + imazethapyr 3.75% w/w ME @ 50+75 g a.i. ha -1 (PoE) at 20-25DAS, T 11 -Stale seedbed (paraquat spray @ 500 g a.i. ha -1 before sowing) + propaquizafop 2.5% + imazethapyr 3.75% w/w ME @ 50+75 g a.i. ha -1 (PoE) at 20-25 DAS, T 12 -Weed free check (Hand Weeding at 20 & 40 DAS), T 13 -Weedy check laid out in a Randomized Block Design (RBD) with three replications. The experimental field comprised well drained sandy loam soil containing 70.0% sand, 16.3% silt and 12.5% clay. The soil was slightly alkaline in reaction with a pH of 7.8, non-saline with an electrical conductivity (EC) of 0.23 dS m -1 and low in organic carbon content (0.35%). Prior to sowing, the soil nutrient status indicated low available nitrogen (220 kg ha -1 ), high available phosphorus (45 kg ha -1 ) and high available potassium (322 kg ha -1 ). During the crop growth period, the mean weekly maximum temperature reached 35.9 °C, while the minimum temperature dropped to 11.9°C. The black gram variety MBG-1070, having a crop duration of 80-85 days was sown at a seed rate of 20-25 kg ha -1 with a spacing of 30 × 10 cm. The stale seedbed was prepared after the layout of the experimental field. Pre-sowing irrigation was applied only to the stale seedbed plots. Two flushes of weeds were allowed to emerge and were removed before sowing. The stale seedbed was maintained for 14 days with an interval of 7 days between successive weed flushes. At sowing, fertilizers were applied at the rate of 20:50:0 kg N:P 2 O 5 :K 2 O ha -1 through urea and single super phosphate. The weed management treatments were imposed according to the treatment schedule. Herbicides were applied using a knapsack sprayer fitted with a flat-fan nozzle, utilizing a spray volume of 500 L water ha -1 . The crop was raised by following the recommended package of practices for black gram cultivation. Weed density of grasses, sedges and broad-leaved weeds was recorded at 15 day intervals up to 60 DAS using a 0.5 × 0.5 m quadrat (0.25 m 2 ) placed randomly within each plot. Data on weed population and weed dry matter were subjected to square root transformation √(X + 0.5) to normalize their distribution before statistical analysis, following the procedure described by Gomez and Gomez (1984) [4] . The weeds collected from the quadrats were oven dried at 65 °C for 24 hours until a constant weight was attained and the dry weight was expressed in g m -2 . Weed control efficiency (WCE) was calculated using the formula proposed by Mani et al. (1973) [8] . WDC-Dry matter production of weeds in control plot (g m -2 ) WDT-Dry matter production of weeds in treated plot (g m -2 )

The experimental data were statistically analyzed using Fisher's analysis of variance (ANOVA) technique. Treatment effects were tested for significance using the F-test at the 5% probability level. Analysis of variance was carried out on all the observations recorded during the course of the investigation.

Results and Discussion

Weed flora

The predominant weed flora observed in the experimental field comprised Echinochloa colona, Digitaria sanguinalis and Dactyloctenium aegyptium among grasses, Cyperus rotundus among sedges and Parthenium hysterophorus, Amaranthus viridis, Euphorbia hirta, Phyllanthus niruri, Digera arvensis, Trianthema portulacastrum and Mollugo verticillata among broad-leaved weeds. Among the different weed groups, broadleaved weeds were dominant followed by sedges and grasses.

Different weed management practices significantly influenced weed count, weed biomass and weed control efficiency, as presented in Tables 1 and2. Among all the treatments, T 12 recorded the lowest weed count 1.05 (0.67) No. m -2 and weed biomass 1.00 (0.53) g m -2 , along with the highest weed control efficiency (99.6%) and was statistically on par with T 8 and T 9 .The superior performance of T 12 may be attributed to the weed free conditions maintained during the critical period of crop-weed competition through hand weeding at 20 and 40 DAS. In the case of T 8 and T 9 , the effective control of weeds could be due to the combined effect of the stale seedbed technique and herbicide application. The stale seedbed practice reduced the initial flush of germinating weeds through shallow cultivation in T 8 and through the application of paraquat, a nonselective contact herbicide, in T 9 . Similar findings were reported by Johnson and Mullinix (1995) [6] , observed that the stale seedbed technique was effective in reducing weed density in peanut cultivation. This was followed by the post-emergence application of the ready-mix herbicide fluazifop-p-butyl + fomesafen, which provided broad-spectrum weed control. Fluazifop-p-butyl effectively controlled grassy weeds by inhibiting the ACCase enzyme, whereas fomesafen controlled sedges and broad-leaved weeds through inhibition of the PPO enzyme. Similar findings were recorded by Pallerla et al. (2024) [10]. Among all the treatments weedy check recorded the highest weed count 14.14 (199.67) No. m -2 , weed biomass 11.82 (139.55) g m -2 and lowest weed control efficiency (0.00%).

Significantly higher seed yield (1415 kg ha -1 ) and haulm yield (2731 kg ha -1 ) were recorded with T 12 (weed free check maintained by hand weeding twice at 20 and 40 DAS) represented in Table 3. This could be attributed to the lower weed count, reduced weed biomass and higher weed control efficiency maintained throughout the crop growth period under weed-free conditions, which minimized crop-weed competition. The yields (seed yield and haulm yield) recorded under T 12 were statistically comparable with those obtained under T 8 (1395 and 2668 kg ha -1 , respectively) and T 9 (1349 and 2655 kg ha -1 , respectively). Higher harvest index reported with weed free check (hand weeding at 20 and 40 DAS) which was stastically on par with T 8 and T 9 . This may be attributed to the stale seedbed technique, which effectively reduced the initial flush of emerging weeds through shallow tillage in T 8 and paraquat application before sowing in T 9 . The subsequent post-emergence application of fluazifop-p-butyl + fomesafen provided broad-spectrum and season long weed control. Effective weed suppression during the critical stages of crop growth minimized competition for light, water and nutrients, creating favourable conditions for crop development and assimilate translocation, which ultimately resulted in higher seed yield. These results are in accordance with those reported by Yadav et al. (2022) [13] . T11 SSB (paraquat spray @ 500 g a.i. ha -1 before sowing) + propaquizafop 2.5% + imazethapyr 3.75% w/w ME @ 50+75 g a.i. ha

Conclusion

Among the different weed management practices, T 12 (hand weeding at 20 and 40 DAS) was found to be superior, recording the lowest weed count and weed biomass, along with the highest weed control efficiency, yield and harvest index. However, its performance was statistically comparable with T 8 , SSB (shallow tillage) + fluazifop-p-butyl 11.1% w/w + fomesafen 11.1% w/w SL @ 250 g a.i. ha -1 (PoE) at 20-25 DAS and T 9, SSB (paraquat spray @ 500 g a.i. ha -1 before sowing) + fluazifop-p-butyl 11.1% w/w + fomesafen 11.1% w/w SL @ 250 g a.i. ha -1 (PoE) at 20-25 DAS.

Acknowledgement

I take immense pleasure in expressing my sincere gratitude to the Department of Agronomy, College of Agriculture, Rajendranagar, Hyderabad, Professor Jayashankar Telangana Agricultural University (PJTAU), Telangana, India.

References

1. T3 Normal sowing + propaquizafop 2.5% + imazethapyr 3.75% w/w ME @ 50+75 g a.i. ha -1 (Ready mix) (PoE) at 20-25 DAS 817 1974 29.3 T4 SSB (shallow tillage) 901 2103 30.0 T5 SSB (paraquat spray @ 500 g a.i. ha -1 before sowing) 865 2082 29.6 T6 SSB (shallow tillage) + pendimethalin 38.7% CS @ 677.25 g a.i. ha -1 (PE) 1039 2306 30.9 T7 SSB (paraquat spray @ 500 g a.i. ha -1 before sowing) + pendimethalin 38.7% CS @ 677.25 g a.i. ha -1 (PE) 969 2234 30.2 T8 SSB (shallow tillage) + fluazifop-p-butyl 11.1% w/w + fomesafen 11.1% w/w SL @ 250 g a.i. ha -1 (PoE) at 20-25 DAS 1395 2668 34.3 T9 SSB (paraquat spray @ 500 g a.i. ha -1 before sowing) + fluazifop-p-butyl 11.1% w/w + fomesafen 11.1% w/w SL @ 250 g a.i. ha -1 (PoE) at 20-25 DAS 1349 2655 33.7 T10 SSB (shallow tillage) + propaquizafop 2.5% + imazethapyr 3.75% w/w ME @ 50+75 g a.i. ha -1 (PoE) at 20-25 DAS 1228 2491 32.9 T11 SSB (paraquat spray @ 500 g a.i. ha -1 before sowing) + propaquizafop 2.5% + imazethapyr 3.75% w/w ME @ 50+75 g a.i. ha -1 (PoE) at 20-25 DAS 1203 2463 32.7 T12 Weed free check (Hand Weeding at 20 & 40 DAS) 1415 2731 34.0 T13 Weedy check 401 1345 23.1 SEm± 77 95 1.7 CD (P=0.05) 224 279 5.0 Note: SSB-Stale seedbed, a.i.-Active ingredient, CS-capsule suspension, ME-Micro emulsion, SL-soluble liquid, PE-pre-emergence, PoE-Post-emergence References
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