Response of Blackgram (Phaseolus mungo L.) Varieties to Weed Competition and to Pre and Post Emergence Herbicide Application during Rabi

Blackgram (Phaseolus mungo L.), a major pulse crop of Andhra Pradesh grown in an area of 3.52 lakh ha with a production of 2.93 lakh tons during rabi season (Anonymous, 2019). One of the major characteristics for selection of blackgram varieties for rabi season under conditions of receding soil moisture in black soils is their early vigour and good weed smothering capability. Early varieties due to their early growth habit can cover the land and thus can smother weeds better than late maturing varieties. Further some variations are observed to be more tolerant to post emergence herbicide application. Hence, there is need to evaluate the promising blackgram varieties for their weed competitiveness and tolerance to pre and post emergence herbicidal application. A field experiment was carried out at Regional Agricultural Research Station, Lam, Guntur, Andhra Pradesh, with an objective to find out the competitive ability of blackgram varieties to smother weeds during rabi season of 2015–16 and 2016–17 under upland conditions. The experiment was laid out in split plot design with three replications. The treatments consisted of five methods of weed control as main plots, viz., pendimethalin 1.0 kg ha⁻¹ PE, imazethapyr 50 g ha⁻¹ PoE, pendimethalin 1.0 kg ha⁻¹ PE fb imazethapyr 50 g ha⁻¹, PoE, manual weeding at 20 and 40 days after sowing (DAS) along with inter cultivation at 30 DAS and unweeded; four blackgram varieties, viz., GBG 1, PU 31, LBG 787, LBG 752, as sub treatments which were replicated thrice. Weed dry matter recorded at 45 days was lower and weed control efficiency (WCE) was higher with pendimethalin 1.0 kg ha⁻¹ PE fb imazethapyr 50 g ha⁻¹ PoE and was on par with manual weeding with inter cultivation. All the varieties were comparable and equally effective in controlling weed dry matter. Yield of variety GBG 1 was higher due to higher yield attributes viz., no. of pods per plant and 100 seed weight. Among the weed control methods manual weeding treatment with inter cultivation recorded significantly higher yield followed by a combination of pendimethalin 1.0 kg ha⁻¹ PE fb imazethapyr 50 g ha⁻¹ PoE. Further, varieties GBG 1 and PU 31 performed better in manual weeding treatment with intercultivation and without any herbicide use.