Effect of pre and post-emergence herbicides and irrigation levels on yield, weed flora, and weed index on drip irrigated paired row maize

A field experiment was conducted at College of Agriculture, Vishweshwaraiah Canal Farm, Mandya during kharif 2018 to study the effect of chemical weed management and drip irrigation levels on paired row maize. The experiment consists 10 treatments and replicated thrice in factrorial- RCBD design. Pre-emergence (PE) application of atrazine at 1.25 kg a.i. ha-1 at 3 DAS resulted in no adverse effects on maize compared to the unweeded control. Additionally, this treatment achieved complete control of both dicot and monocot weeds at 10 and 20 DAS, leading to superior visual weed control ratings (9.3-10 and 9.0-9.1, respectively). PE application of pendimethalin at 0.45 kg a.i. ha^-1 at 3 DAS also showed no maize toxicity but provided less effective weed control compared to atrazine (7.3-8.3 and 6.8-7.8 visual weed control ratings at 10 and 20 DAS, respectively). Post-emergence (PoE) application of halosulfuron methyl at 90 g a.i. ha^-1 combined with atrazine at 625 g a.i ha^-1 at 20 DAS provided moderate control of sedges, grasses and broad-leaved weeds, resulting in average visual weed control ratings of 6.1-6.2 and 5.2-5.7 at 10 and 20 DASP (30 and 40 DAS), respectively. Further, Irrigation at 80% CPE recorded significantly lower total weed population (70.67 and 367.70 No.m-2), weed dry weight (55.31 and 72.45 g m-2) at 60 DAS and at harvest respectively as compared to 100% CPE. Among weed control methods, pre-emergence application of atrazine @ 1.25 kg a.i. ha^-1 at 3 DAS recorded higher kernel yield (8,310 kg h^-1), lower WI (-4.61%) total weed population (70.67 and 201,83 No.m-2) and weed dry weight (21.57 and 21.57 g m^-2) at 60 DAS and at harvest respectively and were comparable with hand weeding twice at 30 and 45 DAS or rest of the chemical weed control practices.