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Phosphorus effects on competitive interactions of smooth pigweed (Amaranthus hybridus) and common purslane (Portulaca oleracea) with lettuce (Lactuca sativa)

Published online by Cambridge University Press:  12 June 2017

Joan A. Dusky
Affiliation:
Everglades Research and Education Center, University of Florida, Belle Glade, FL 33430
William M. Stall
Affiliation:
Horticultural Science Department, University of Florida, Gainesville, FL 32611
Donn G. Shilling
Affiliation:
Agronomy Department, University of Florida, Gainesville, FL 32611
Thomas A. Bewick
Affiliation:
University of Florida. Current address: Cranberry Experimental Station, P.O. Box 569, East Wareham, MA 02538

Abstract

Replacement series studies were conducted under controlled conditions to determine the effect of phosphorus (P) rates and population densities on the competitiveness of smooth pigweed and common purslane with lettuce. Densities were 2, 4, and 8 plants per 113 cm2, whereas P rates were 0, 0.4, and 0.8 g PL−1 soil. A P-deficient Histosol (0.3 mg water-extractable P L−1 soil) was used. High P fertility enhanced the competitive ability of lettuce in smooth pigweed-lettuce mixtures. Smooth pigweed was not responsive to P rates. However, luxurious P consumption by smooth pigweed occurred, reducing the amount of the nutrient available for lettuce absorption. In common purslane-lettuce mixtures, the weed was responsive to P rates, increasing its competitive ability, whereas no increase in lettuce competitive ability was observed. Both weed species were more competitive than lettuce. Competition for P appears to be the main mechanism of common purslane interference on lettuce grown in low-P organic soils. Alternative fertilization strategies (i.e., banded applications) may reduce the effect of smooth pigweed on lettuce.

Type
Weed Biology and Ecology
Copyright
Copyright © 1998 by the Weed Science Society of America 

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