Allelopathic effect of Pluchea lanceolata (Asteraceae) on characteristics of four soils and tomato and mustard growth

The effect of the leachate of the noxious weed Pluchea lanceolata was explored using mustard and tomato seedling growth bioassays of four soil types (sandy loam, clay loam, silty loam, and sand). The objectives of the present study were: 1) to determine how soil chemistry changes after addition of leachate and leaves of the weed; 2) to determine what level of input to the soil does not cause significant differences from those of weed-associated soils under field conditions; and 3) to determine whether soil texture affects bioassay results. Leaf leachates of the weed were added to four soil types in different dilutions, and soils were analyzed for pH, electrical conductivity, organic matter, Cl, PO4, exchangeable Cu++ , Zn++, Na+, K+, Mg++, and Ca++, and total phenolics. These results indicated that the leachates of the weed altered chemical characteristics of each soil type. Concentration of phenolics in treatment of each soil type was dilution-dependent. Leachates were more inhibitory on sandy loam and clay loam than on silty loam and sand. Present study indicated that in allelopathic bioassays, amended soils that are nonsignificantly different from weed-associated soils should be taken. Further, present investigations confirmed the significance of good control soil with nonsignificantly altered chemical characteristics from those of natural soils, as well as soil texture to establish allelopathy of ecological relevance