Interference and estimation of economic threshold level of Alternanthera philoxeroides in maize (Zea mays L.)

Abstract

Knowledge of economic threshold of emerging invasive weed Alternanthera philoxeroides (alligatorweed) is important to implement timely, efficientand economical weed control method for profitable maize production. Two-year field study consisting  fivedensity levels of A. philoxeroides viz. 0, 1, 2, 4 and 8 plants m-2 was conducted  to estimate the maize grain yield losses at different density levels and to determine  economic threshold level (ETL) of A. philoxeroides . Maximum weed dry biomass (44.28 g m-2), N (9.02 kg ha-1), P (7.91-6.86 kg ha-1) and K (7.99 kg ha-1) were observed at 8 plants m-2 A. philoxeroides density. The same weed density caused highest reduction maize plant height, number of grains per cob, 100 grain weight, grain weight per cob and biological yield of maize. Higher A. philoxeroides density also caused up to 62% reduction in maize grain yield and 21% reduction in grain protein contents as compared to weed free. ETL of A. philoxeroides was estimated to be 0.47 plants m-2, if this weed controlled chemically. Based on current finings complete control of this weed using chemical weed control is suggested to tackle yield losses in grain maize