Correlation between weeds and crops

Abstract

In order to survey the effects of some crops (allelopathic and non allelopathic) on weed population, an experiment was done with sowing of seven different crops in 2012 at field research of University of Tabriz. Treatments were corn (Zea mays L.), sunflower (Helianthus annus L.), common beans (Phaseolus vulgaris L. var 1 and Phaseolus vulgaris L. var 2), castor bean (Ricinus communis L.), chicken pea (Cicer arientinum L.), and Lallemantia (Lallemantia iberica L.). Sampling of weed density in each plot was done in four times. Canonical correspondence analysis (CCA) showed that crop species can effect on weed species density. So that, the first two CCA axes explained 93.2, 82.5, 88.5, and 81.3 % of the variation in weed species density in sampling times 1, 2, 3, and 4, respectively. For example in the first sampling, the first axis of CCA represents a gradient of Cicer, Ricinus, Helianthus and the second axis represents a gradient of Ricinus, Cicer, Phaseolus 2, Phaseolus 1, and Lallemantia. So that, Lallemantia and Phaseolus 1, also Helianthus and Zea vectors with minimum angle, showed that these crops had maximum correlation each other, but Cicer and Zea vectors with maximum angle, showed they had minimum correlation together. Lamb,s squarters (Chenopodium album L.) and prostrate knotweed (Polygonum aviculare L.) were dominant weed species observed in the beginning and ending of crops life cycle, respectively. In forth sampling, Ricinus plots were weed free, this is may be duo to interference (competition and allelopathy) presented with Ricinus and weeds.