Allelopathy is an ecological phenomenon that recently attracted researchers' attention as a new approach in weed control. Pot and field experiments were conducted to study the allelopathic effect of Casuarina equisetifolia L. leaf litter, one of three most common Casuarina species in Egypt. The influence was studied during two successive seasons (2012-2014) on wheat and associated weeds through foliar application of the aqueous extract and incorporating Casuarina leaf litter in the soil. In pot experiment, the results showed remarkable improvement in the growth of wheat under screen house conditions at the different rates of incorporation (15, 30 and 45 g dry L/kg soil). On the contrary, associated weed (that is, canary grass) was adversely affected and recorded up to 62% inhibition over the control. Germination was less affected both for crop and weed. Slight increases in macro (N, P, K, Ca and Mg) and micro (Fe, Mn, Zn and Cu) elements were recorded in the shoots of wheat, 21 days after sowing, compared to the control. Good response otherwise was noted in increasing soil content of the different nutrients. Under field conditions, the incorporation of dry leaf litter at a rate of 1 ton/fed (fed = 0.42 ha) caused increases in wheat biomass (65 days after sowing) by up to 27.5% in comparison with the untreated control. On the other hand, weed biomass was significantly reduced by up to 27%. Foliar application (twice) of water extract was most effective. Wheat biomass increased by up to 42.9% versus 51.2% reduction in weed biomass compared to the untreated control. Hand pulling treatment for weeds was the best regarding the increase of wheat yield (up to 66.9%) and its components (from 24.4% to >100%) followed by foliar application of the extract and then incorporation of leaf litter in the soil. From these results it can be concluded that spraying water extract of Casuarina leaf litter (comparing to incorporation the litter in the soil) has a high degree of effectiveness which ensures safe use in controlling weeds in wheat fields.
Key words: Allelopathy, cannary grass, casuarina leaf litter, nutrients, weed, wheat.
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