Phytotoxic effect of Parthenium residues on the selected soil properties and growth of chickpea and radish

The present study investigates the effect of residues of noxious weed Parthenium hysterophorus in soil as well as under laboratory conditions. Soils were infested with different amounts of Parthenium residues to determine the changes in soil chemistry, phenolic content and the phytotoxic effects on crops like chickpea ( Cicer arietinum ) and radish ( Raphanus sativus ). The modified soils and unmodified (control) soil were analyzed for pH, conductivity, organic carbon, organic matter, available nitrogen, phosphorus, potassium and micronutrients such as sodium, iron, manganese and zinc. The pH of all the modified soils decreased whereas the conductivity, organic carbon and organic matter increased. Further, the amount of sodium and potassium increased, whereas that of zinc decreased. In the soil infested with 4 g of Parthenium residue, the amount of available nitrogen decreased. The presence of significantly high amounts of phenolics in all modified soils indicated their possible interactions with soil chemical properties. This was also indicated by the correlation analysis between phenolics and various soil properties. The growth studies carried out in the modified soils indicated their phytotoxic nature, as seedling growth of both chickpea and radish was significantly decreased compared with seedlings grown in unmodified soils. The extracts prepared from Parthenium residues were also found to be phytotoxic to both the test crops and were also rich in phenolics. The presence of phenolics in Parthenium residues and their interference with soil chemistry upon release may be responsible for a decrease in the growth of radish and chickpea.