Efficacy of Combined Herbicides on Weed Dynamics, Crop Quality, Nutrient Content and Uptake and Post-harvest Soil Nutrient Status in Summer Black Gram (Vigna mungo L.)
Abstract
Weed infestation is a major constraint to summer black gram production because the crop exhibits relatively slow initial growth and limited early canopy development, allowing weeds to compete strongly for nutrients, moisture, light and space. Effective weed management is therefore important for reducing crop–weed competition and improving crop quality, nutrient uptake and post-harvest soil nutrient status. A field experiment was conducted during the summer season of 2019 at the Hill Millet Research Station, Rajendrapur farm, N. A. U., Waghai, to study the “Efficacy of combined herbicides in summer black gram (Vigna mungo L.)”. The study area was characterised by clayey soils low in available nitrogen, medium in available phosphorus and fairly rich in available potassium. The study comprised ten weed-management treatments, viz., T1: Pendimethalin 900 g ha-1 as pre-emergence + 1 HW at 30 DAS, T2: Sodium acifluorfen + clodinafop-propargyl (RM) 250 g ha-1 as post-emergence at 20 DAS, T3: Imazethapyr + pendimethalin (RM) 750 g ha-1 as pre-emergence, T4: Imazethapyr + imazamox (RM) 70 g ha-1 as pre-emergence, T5: Imazethapyr + propaquizafop (RM) 125 g ha-1 as post-emergence at 20 DAS, T6: Quizalofop-p-ethyl 100 g ha-1 post-emergence at 20 DAS, T7: Fenoxaprop-p-ethyl 100 g ha-1 post-emergence at 20 DAS, T8: 2 HW at 20 and 40 DAS, T9: Unweeded control, T10: Weed-free. The treatments were evaluated on black gram cv. GU-1 and arranged in a randomised block design (RBD) with three replications. The results indicated that the highest protein content (24.17%) and protein yield (261.92 kg ha⁻¹) were recorded under the weed-free treatment (T₁₀), followed by treatments T₁, T₂ and T₈. The lowest weed population and weed dry weight at harvest (326.67 kg ha⁻¹) were recorded with two hand weedings at 20 and 40 DAS (T₈). The maximum weed control efficiency (83.20%) and the lowest weed index (7.98%) were also observed under the same treatment. The residual N, P₂O₅ and K₂O contents in the soil after crop harvest were significantly higher under the weed-free treatment, T₁₀ (277.67, 61.33 and 423.00 kg ha⁻¹, respectively), and were statistically at par with those recorded under treatments T₁, T₂ and T₈. Significantly higher N (3.87 and 1.12 %), P2O5 (0.49 and 0.29 %) and K2O (2.03 and 1.03 %) contents were registered under the weed-free condition (T10) in seed and haulm, respectively. The highest N, P2O5 and K2O uptake by seed (41.91, 5.30 and 21.94 kg ha-1, respectively) and haulm (27.53, 7.22 and 25.19 kg ha-1 respectively) were registered under treatment T10, in which the plot was kept weed-free.