Journal of Research in Weed Science

Abstract Field experiments were conducted to identify the effective tank-mix combinations of HPPD (p-hydroxyphenylpyruvate dioxygenase) herbicides (Mesotrione, tembotrione and topramezone) with atrazine for post-emergence grass and broadleaf weeds control in maize crop during the three kharif seasons of 2013 to 2015. The dominant weeds infested the experimental plots were crow footgrass{Dactyloctenium aegyptium (L.) Willd.}; large crabgrass, Digitaria sanguinalis (L.) Scop; barnyard grass, Echinochloa crus-galli (L.) Beauv.; Digera arvensis Forsk. and Horse purslane(Trianthema portulacastrum L.). All the three HPPD herbicides showed good crop safety and among them, for grass weed control, mesotrione 120 g ha^-1 applied alone was inferior to topramezone 50 g ha^-1 and tembotrione 120 g ha^-1 applications. However, reduced doses of the HPPD herbicide (mesotrione 90 g or topramezone 37.5 g or tembotrione 90 g ha^-1) with atrazine 900 g ha^-1 as post-emergent tank-mixture gave better weed control and maize yield than their solo applications. The uncontrolled weed competition reduced the maize yields by 31.5 to 68.5%. Overall, topramezone + atrazine provided comparable or superior control of annual grass and broad-leaf weeds than mesotrione + atrazine or tembotrione + atrazine. Post applied (15-18 days after sowing) atrazine 1000 g ha^-1 was better to pre-emergence atrazine in weed control and producing maize yield. In another field study, replacement of maize with puddle rice completely reduced the Johnsongrass {Sorghum halepense (L.) Pers.} density and therefore, in areas having its infestation, rice can be an alternative to contain its problem. The synergistic interactions between HPPD-inhibiting herbicides, and atrazine, were also observed against three grass weeds in pot experimentation as higher weed control achieved than what was expected from Colby’s equation. The results show that tank-mixture of topramezone or tembotrione with atrazine can be effectively used for diverse weed flora control in maize.

Abstract An experiment was conducted in IAAS, Lamjung research field in 2017 in spring Maize with split plot design to evaluate the effect of weed management practice and tillage system on productivity of spring maize. In tillage system, no-till and conventional tillage were kept as main factor whereas seven weed management practices (viz. sequential application of atrazine at 0.75 kg a.i. ha-1 and 2,4-D at 1.5 kg ha-1; pre-emergence tank mix application of atrazine at 0.75 kg ha-1 and glyphosate at 2.5ml lit-1 of water; pre-emergence tank mix application of atrazine at 0.75 kg ha-1 and pendimethalin at 2ml lit-1 of water; cowpea co-culture; black polythene mulch with control treatment weed free and weedy check as sub-plot. Tillage method had not significant effect on the weed dry matter accumulation in different stages. However, weed dry matter accumulation was varied with different weed management practices. The weed check plot was of highest dry matter accumulation (273.38g m-2, 361.95 g m-2 and 235.95 g m-2 in three different stages (30, 60 and 90 DAS respectively). The highest grain, straw yield and yield attributes was found in plastic mulch plot and no-till system with less severe to weed infestation and index which is statically at par with intercropping with cowpea. Though none of weed management practices completely eliminated weeds, black polythene mulching resulted in best grain yield. Besides the environmental protection, cowpea co-culture treatments yielded almost similar grain yield as compared with common herbicidal weed management practices.