An experiment on the interaction between cultivated rice and barnyard grass at different planting densities

Abstract

To examine the relation between the effects of density and interaction between species, a rice and a barnyard grass strain were tested in pure and mixed (1 : 1) plantings at five different densities. In pure stands, the data for dry weight per plant and other characters gave a good fit to the logarithmic regression equation on plant density (derived from WN a = K). For the mixed plantings, a parameter showing neighbor effect was added to the equation, and its values were estimated. Rice and barnyard grass had different signs for this parameter. The trend of competition effect to increase with density was not observed. Both species tended to reduce reproductive effort at high densities, but at different rates. Rice showed logarithmically linear density responses in both size and number of stems, while barnyard grass showed it only in stem number.