STUDIES INTO BIO-ECOLOGICAL INTERFERENCE OF SPINY EMEX (Emex australis Steinh.) IN WHEAT (Triticum aestivum L.)

Abstract

Emex australis interference in wheat was investigated in three different experiments (Laboratory, Pot and Field experiments) at the Agronomic Research Area, Department of Agronomy, University of Agriculture, Faisalabad, Pakistan during the year 2005/06 and 2006/07. The First experiment was aimed to study the “Allelopathic effects of E. australis on germination and early seedling growth of wheat at different temperatures”. In pot and field experiments “Influence of spiny emex (Emex australis Steinh.) density on the growth and yield of wheat (Triticum aestivum L.) sown at different times” was studied. Interactive effect of E. australis residual soil and temperature significantly reduced the root/shoot length, dry weights and seedling biomass. Interaction of temperature with different aqueous extracts of E. australis significantly reduced the root/shoot length, dry weight and seedling biomass of wheat with pronounced inhibitory effects with leaf and stem extract as compared with distilled water (control). Interactive effect of temperature with wheat seed soaked in stem aqueous extract of E. australis caused highest significant effect on germination, mean germination time and germination index of wheat seeds. Interactive effect of temperature with continuously applied stem aqueous extract of E. australis caused highest significant effect on germination, mean germination time and germination index of wheat seeds. Aqueous leaf extract showed the highest inhibitory effect on wheat seed germination (48.7% inhibition) followed by butanol fraction (40% inhibition) and hexane fraction (26.2% inhibition). Hexane fraction from ethonolic extract of E. australis leaf extract significantly reduced root/shoot length, their dry weights and seedling dry biomass more that the aqueous ethanolic extract and other fractions. Result of pot experiment showed that E. australis plant height, number of seeds per plant, seed weight per plant, fresh and dry weight per plant and NPK uptake and concentration of E. australis was significantly affected by sowing dates and different levels of E. australis density in uniformly seeded wheat. The wheat growth and yield parameters like number of spike bearing tillers, non-spike bearing tillers, plant height, spike length, grains per spike, 1000-grain weight, grain yield, biological yield, harvest index and NPK concentration were significantly affected by different E. australis density levels. The delayed sowing of 24 th November resulted in lowest grain yield mainly due to less number of spike bearing tillers and grains per spike. Results of field experiment showed that E. australis plant height, number of seeds per plant, seed weight per plant, fresh and dry weight per plant and NPK uptake and concentration of E. australis was significantly affected by sowing dates and different levels of E. australis density in uniformly seeded wheat during both years of study. Wheat growth and yield parameters like number of spike bearing tillers, non-spike bearing tillers, plant height, spike length, grains per spike, 1000-grain weight, grain yield, biological yield, harvest index and NPK concentration were significantly affected by different E. australis density levels. The maximum grain yield was obtained from weed free wheat, mainly due to more spike bearing tillers, number of grains per spike and 1000-grain weight. The delayed sowing of 23 rd November resulted in lowest grain yield mainly due to less number of spike bearing tillers and grains per spike. E. australis demonstrated allelopathic prospective against wheat seed germination and seedling growth which suggests that soil incorporated plant residues of E. australis may have broader ecological implications on the growth of succeeding crop. Sowing of wheat on 7 th Nov. proved to be helpful in reducing wheat grain yield loss from E. australis infestation.