Abstract
Emex australis and E. spinosa are significant weed species in wheat and other crops. Information on the extent of competition of the Emex species will be helpful to access yield losses in wheat. Field experiments were conducted to quantify the interference of tested weed densities each as single or mixture of both at 1:1 on their growth and yield, wheat yield components and wheat grain yield losses in two consecutive years. Dry weight of both weed species increased from 3-6 g m-2 with every additional plant of weed, whereas seed number and weight per plant decreased with increasing density of either weed. Both weed species caused considerable decrease in yield components like spike bearing tillers, number of grains per spike, 1000-grain weight of wheat with increasing density population of the weeds. Based on non-linear hyperbolic regression model equation, maximum yield loss at asymptotic weed density was estimated to be 44 and 62% with E. australis, 56 and 70% with E. spinosa and 63 and 72% with mixture of both species at 1:1 during both year of study, respectively. It was concluded that E. spinosa has more competition effects on wheat crop as compared to E. australis.
Highlights
Bio-economic weed management decisions are essential for precision agriculture
These decisions are based on estimates of weed population size, and the crop yield loss to be caused by that population and the most effective weed control practices to regain potential yield loss (Deines et al, 2004)
Seeds of E. australis and E. spinosa were planted as a single weed species or in combination with both species in a higher number than the required densities
Summary
Bio-economic weed management decisions are essential for precision agriculture. These decisions are based on estimates of weed population size, and the crop yield loss to be caused by that population and the most effective weed control practices to regain potential yield loss (Deines et al, 2004). Extensive herbicide use is one of the major tools for managing weed population and maintaining economical food supply in developed agriculture-based countries. Increasing herbicide resistance in certain weeds, and higher input expenses and environmental hazards (Sanyal & Shrestha, 2009) induce greater pressure on food producers to reduce herbicide use. Integrated weed management practices are being developed to limit herbicides application in the environment (Sanyal & Shrestha, 2009). Weed threshold is one of the key components of an integrated weed management system that helps farmers to determine the need for herbicide application (Fleck et al, 2002)
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