Allelopathic interference of Parthenium hysterophorus residues in soil

Abstract

A study was conducted to explore the allelopathic potential of ragweed parthenium (Parthenium hysterophorus L.; Asteraceae) residue and to determine its possible interactions with soil nutrient status. The extracts prepared from 1, 2 and 4-weeks old Parthenium residues significantly inhibited the seedling growth (length and dry weight) of two test crops - radish and mustard. Soils were amended with varying amounts and ages of residue and their effect on radish and mustard growth and soil nutrients was determined. The growth of both crops was significantly inhibited in the amended soil as compared to unamended soil. A decrease in phytotoxicity was observed with increasing age of residue. The amount of N, P, K, and micronutrients increased significantly in the amended soil compared to unamended soils, thereby ruling out any possibility of their direct involvement in observed growth inhibitions. However, in the older residues, the amount of all the nutrients (except N) decreased compared to younger residue, though it was more than that of unamended soils. The residue extracts and amended soils were observed to be rich in phenolics -known allelochemicals. Based on the results, it is concluded that Parthenium residues affect the growth of test species by releasing phenolics rather than decreasing the available nutrient status in the soil.