Habitat and utility assessment of Singapore daisy (Sphagneticola trilobata L.)

Abstract

In order to understand the habitat affinity and utilisation potential of Singapore daisy (an invasive weed of Kerala), study was conducted at three different locations which are thickly infested with the weed in the Kasaragod district viz., Kalichampothi, Nileshwaram and Azhithala to assess the habitat conditions, weed seed bank dynamics, allelopathic effect and utility. Correlation analysis between plant and soil samples revealed that plant height and density had a positive correlation with available nitrogen and soil moisture. Available potassium also had a positive correlation with plant height. Plant height, dry weight and leaf area per plant had a negative correlation with soil pH. Weed seed bank analysis revealed that germination of native weed seeds were adversely affected in the soils collected from the invaded sites in all the three seasons. This was confirmed by the fact that there was more than 95 percentage reduction in the light availability at ground level in the invaded sites compared to the uninvaded sites attributing to the reduced density of associated weed flora. Higher concentrations of shoot extracts of Singapore daisy (1:5 w/v of fresh shoot extract) inhibited the root and shoot growth of all the test plants (cowpea, rice and weedy rice) indicating that allelopathic effect of the aqueous extract of Singapore daisy depended on the concentration of the extract and the plant part used for extract preparation. Singapore daisy has the potential to be used in phytoremediation of cadmium, chromium, lead and arsenic in contaminated soil, with an average biomass production of 12.92 tonnes ha-1. The values of proximate principles of Singapore daisy revealed its potential to be used as a fodder crop as the nutritive values were comparable with common fodder crops of Kerala. The K/(Ca+Mg) ratio was 1.19, which is regarded safe for animal feed. However, the presence of antinutritional factors (tannin and saponin) and phytoremediation potential indicate further studies to justify its use as fodder. Singapore daisy has high ecological flexibility as it was able to establish well under different soil nutrient and moisture conditions. Weed seed bank analysis warns the necessity to control the spread of the weed as it has the capacity to reduce the density of native weed flora with its lush growth; allelopathic potential of the aqueous extract to inhibit seedling growth could also be attributed for the reduction of native weed flora. Singapore daisy has the potential to be used as a phytoremediator, fodder, compost and bioherbicide.