Parthenium hysterophorus Weed Fecundity and Seed Survival at Different Soil pH and Burial Conditions

Abstract

Parthenium hysterophorus L. is regarded as one of the most invasive weed species. This study evaluated the effect of soil pH on P. hyterophorus weed growth and fecundity, as well as the effect of burial depths on P. hyterophorus seed survival and emergence. The first study evaluated five soil pH levels (acidic, sub-acidic, neutral, sub-basic, and basic) in a randomised complete block design. Seed germinability and subsequent seedling growth (height, leaf area, biomass, and seed number/plant) were evaluated. This study showed that P. hysterophorus seeds have a similar germination capacity under varying soil pH conditions. However, acidic soil indicated accelerated growth (25% higher biomass with 15.2% more leaf area) and fecundity (13.4% faster to enter the flowering stage at 74 days after sowing). In the second study, two factors were tested; burial depths (0.5, 5, 10, and 20 cm) being nested into seven burial durations (0, 2, 4, 6, 8, 10, and 12 months). Seed viability (final germination percentage and germination rate index), electrical conductance, and emergence percentage were assessed with the burial conditions. The results showed that only seed buried at 0.5 cm depth indicated emergence (81.3% of cumulative emergence). Forty per cent of the seeds remained viable after exhumation at 0.5–5 cm depth, while only 19–27% survived as the burial depth increased beyond 10 cm depth within 12 months. The seed remained viable for more than 12 months as a seed bank, despite faster deterioration at increasing soil depth.