科研之友
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摘要
Conventional wisdom suggests that soil water lost through transpiration by weeds can intensify crop drought stress, and that this is an important mechanism by which weed competition decreases yields and crop water productivity (CWP). To assess the impact of weed competition on soil water uptake and crop drought stress, a 3-year field experiment was conducted with maize (Zea mays L) grown in monoculture and in combination with high-density stands of three troublesome weed species (Setaria faberi Herrm., Abutilon theophrasti Medic., and Amaranthus retroflexus L). Independent of weed species type, when canopy light interception was largely unchanged by the presence of weeds, maize-weed mixtures did not deplete more soil water than maize grown in monoculture. Conversely, when early weed growth was vigorous, maize-weed mixtures intercepted more light early in the growing season and this resulted in higher initial rates of water depletion and drier soils. In both cases, measurements of stomatal conductance suggested that the internal water status of the maize was not significantly impacted by the presence of weeds as the soil dried. CWP was influenced by weed competition and in the most extreme case declined by almost 50% relative to monoculture maize (2.6 kg m(-3) vs. 5.0 kg m(-3)). However, the impact of weeds on CWP was not uniform. Under low yield loss scenarios (ca. 10%), weeds had little impact on the soil water balance and CWP did not markedly decline relative to monoculture maize. Our results suggest that if weeds do not increase canopy light interception and are subordinate to lower parts of the canopy, high-density infestations can be retained in the field without increasing the probability of drought or substantially reducing CWP.
- 出版日期2010-12
