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EFFECT OF SOIL PROPERTIES ON THE DIVERSITY AND DISTRIBUTION OF WEEDS IN CITRUS FARMS IN ARID REGION

The weed diversity and distribution in agroecosystems can be controlled by environmental variables. In this study, soil physical and chemical variables were investigated in three citrus farms located in the northern part of Saudi Arabia. A total of 12 soil physical and chemical variables were measured. Among the studied variables, only organic matter (OM), pH, phosphorus (P), calcium (Ca), bicarbonate (HCO3) and sulphate (SO4) were significantly different (one-way ANOVA at P < 0.05) among the three studied citrus farms. The regression model (Adj-R = 0.416, P=0.024) showed that the organic matter (OM), calcium (Ca) and carbonate (CO3) significantly affect the species richness of weeds. The multivariate model of CCA explained 68.64% of the variation of the taxonomic composition of weeds in citrus farms. It also revealed strong effect of soil texture (sand %), carbonate (CO3), pH and sulphate (SO4) on weed diversity and distribution. It was concluded that the soil physical and chemical properties are strong explanatory variables of the distribution of weeds in agroecosystems.