Phytotoxicity of sunflower (Helianthus annuus L.) and its allelopathic potentiality on growth and yield attributes of Parthenium hysterophorus

Abstract

Recent developments in the weed science and allied aspects have involved several interdisciplinary approaches. In this context, indiscriminate use of herbicides for weed control has become a questionable subject, that besides controlling the weeds, the chemical herbicides are harmful in many ways to the soil, crops, other plants and the environment as a whole. To this end, pot and field experiments were conducted to test whether sunflower rhizosphere soil (SRSS) in pot and sunflower green manuring (SGM) in field experiments at various stages; 75, 90,105 and 120 days after sowing (DAS) can reduce Parthenium hysterophorus. Sunflower cv. Myhco was screened at various stages viz. 75, 90,105 and 120 days after sowing (DAS) through green manuring for field experiments and rhizosphere soil for pot experiments. Two cover crops, green gram (Vigna radiata) and pearl millet (Pennisetum glaucum) were used. In pot experiment, SRSS at various stages was compared with non sunflower rhizosphere soil (NSRSS). Growth and yield attributes of P. hysterophorus was compared between SGM and SGM along with cover crops and control in field experiments. Field experiments revealed that all growth and yield attributes of P. hysterophorus were inhibited maximum at 75 DAS of SGM with treatment SGM + pearl millet (PM) and the inhibitory effect decreased with increase of sunflower stage growing in the field. Pot experiments showed that SRSS at 75 DAS proved maximum inhibition to growth and yield attributes of P. hysterophorus as compared to higher stages. Allelochemicals were identified from sunflower through paper chromatography and subjected to spectroscopic analysis viz. ultraviolet, intra-red, nuclear  magnetic resonance and mass spectra etc., for confirmation. These results suggest that sunflower green manuring and its rhizosphere soil has herbicidal potential and may be utilized as biological control of weeds for sustainable agriculture and environmental safeguard.

Key words: Green manuring, rhizosphere soil, allelochemicals, cover crops.