Liverwort (Marchantia polymorpha) is one of the problematic weeds in ornamental crop production that deteriorates the quality and aesthetic value of ornamentals. To study the effectiveness of allelopathic properties of organic mulch extracts, six different organic mulch materials including rice hull (RH), cocoa hull (CH), pine bark (PB), maple leaf (ML), shredded cypress (SC) and red hardwood (HW) were used for obtaining mulch extracts. The extracts were prepared by following the modified EPA 1312 synthetic precipitation procedure. In the lab experiment, the mulch extracts obtained were used to impregnate agar media at an increasing dose at either 1x (2ml), 2x (4ml), 3x (6ml), and 4x (8ml) rates. Ten gemmae were transferred to the culture medium in each petri dish and all petri dishes containing gemmae were maintained inside the growth chamber. Data was recorded for number of gemmae germinating in each petri dish and at the end of experiment, the length and width of the thallus derived from each gemmae were measured. For greenhouse experiment, the mulch extracts were applied to nursery containers filled with standard substrate and amended with controlled-release fertilizer for assessing the postemergent liverwort control in nursery containers. Either RH, HW, CH, ML, SC or PB mulch extracts were applied to each of the container uniformly at either 1X (15ml), 2X (30ml), 3X (45ml), and 4X (60ml) rates, at the beginning of experiment and bi-weekly until 10 weeks. Control set without any mulch extract was included as well. Percent of substrate surface covered by liverwort thalli was visually estimated bi-weekly until 10 weeks after first treatment. Fresh biomass of the thalli and number of gemmae cups in each pot were also recorded at the end of the experiment. Both lab and greenhouse experiments had four replications per treatment and were arranged in a randomized complete block design. After 1 week in the growth chamber, ML followed by SC, PB and RH extracts showed maximum suppression of liverwort gemmae germination. At 2 weeks, all rates of ML provided complete inhibition of liverwort. In the greenhouse, all the mulch extracts were able to provide complete liverwort control for the first two weeks. PB and HW mulches showed excellent liverwort control and minimum biomass of liverwort after 10 weeks as compared to other mulches. Hence, the allelopathic potential of the organic mulches can be a promising option for biopesticidal control of liverwort, and a component of integrated liverwort management.
