Download Plant Competition: Weeds vs. Crops for Water, Nutrients, and Light - Prof. Andrew R. Kniss and more Study notes Agricultural engineering in PDF only on Docsity! Weed Ecology: Part 3 Competition PLNT 4070/5070 September 22, 2008 Andrew Kniss Plant Competition Competition is why we study weed science Plants compete for – Water – Nutrients – Light Plants will compete for limited resources Plant Competition Rice yield at 3 different N rates 0 kg/ha N 60 kg/ha N 120 kg/ha N Rice only 4.5 Rice + barnyardgrass Rice + barnyardgrass + Monochoria From: Moody, 1981 Plant Competition Rice yield at 3 different N rates 0 kg/ha N 60 kg/ha N 120 kg/ha N Rice only 4.5 4.4 Rice + barnyardgrass Rice + barnyardgrass + Monochoria From: Moody, 1981 Plant Competition Rice yield at 3 different N rates 0 kg/ha N 60 kg/ha N 120 kg/ha N Rice only 4.5 4.4 4.1 Rice + barnyardgrass Rice + barnyardgrass + Monochoria From: Moody, 1981 Plant Competition Rice yield at 3 different N rates 0 kg/ha N 60 kg/ha N 120 kg/ha N Rice only 4.5 5.3 4.4 4.0 4.1 3.1 Rice + barnyardgrass Rice + barnyardgrass + Monochoria From: Moody, 1981 Plant Competition Rice yield at 3 different N rates 0 kg/ha N 60 kg/ha N 120 kg/ha N Rice only 4.5 5.3 6.6 4.4 4.0 5.5 4.1 3.1 3.5 Rice + barnyardgrass Rice + barnyardgrass + Monochoria From: Moody, 1981 Plant Competition Wild oat density Wheat yield at 3 different N rates (plants/sq. m) 0 kg/ha N 60 kg/ha N 120 kg/ha N 0 6,990 7,520 7,650 4 6,430 6,660 6,640 8 6,460 6,100 6,140 16 5,940 5,200 5,470 32 5,400 4,120 3,450 From: Carlson and Hill, 1981 Plant Competition Degree of competition controlled by: – Species – Density – Distribution – Duration Modified by: – Edaphic conditions – Climatic conditions Plant Competition Nutrients – N, P, K most important – Weeds usually require similar amounts of the same nutrients at the same time as the crop – Weeds are often more successful at obtaining these nutrients – N becomes limiting first – Competition for P, K usually occurs after plants are mature, and have overlapping root systems Plant Competition Water – Most critical, but least reliable of all resources for plant growth – Water use efficiency is usually similar between weeds and the crops with which they compete – Weeds reduce water availability for the crop (or other desirable vegetation), and contribute to water stress Plant Competition Light – Most reliable resource for plant growth – Cannot be stored, either utilized when available, or lost (unlike water and nutrients) – Light regulates many plant processes • Flowering • Germination Plant Competition Light – Leaves intercept light, and may: • Reflect • Absorb • Convert to photosynthetic products • Convert to heat • Transmit – If transmitted, the light is filtered (dimmer and of different quality) Plant Competition Light – If one leaf is shaded by another, competition for light occurs – Competition for light increases under high fertility and moisture conditions • Plants can grow vigorously • Leaf area increases – If out-competed for light, reduced growth, and less competitive for water and nutrients Plant Competition Interactions between light, nutrients, and water exist, but are more difficult to quantify Plant Competition Factors for which plants DO NOT compete – Space • Competition is for resources within the space – Carbon dioxide • Although crop yields can be increased by supplemental CO2, concentrations are nearly always higher than the compensation point – Heat • Theoretically possible, but never documented
