Action: Add mulch and fertilizer to soil (alongside planting/seeding)
- A randomized, controlled study in the USA found that adding mulch and fertilizer, followed by sowing of seeds increased the abundance of seedlings for a minority of shrub species. The same study found that adding mulch and fertilizer, followed by sowing seeds had no significant effect on grass cover.
Adding mulch to soil may help to increase the amount of moisture it contains, while adding fertilizer may help to promote the growth and survival of introduced plants.
Supporting evidence from individual studies
A randomized, controlled study in 1997–1999 in a sagebrush scrub shrubland that had been invaded by grass and burnt by wildfires in California, USA (Cione et al. 2002) found that adding mulch, followed by addition of nitrogen fertilizer, and seeding with shrub seeds increased the seedling abundance of two of seven shrub species but did not reduce grass cover after one year. Areas where mulch, fertilizer and shrub seeds were added had more shrub seedlings for two of seven species (1–2 seedlings/m2) than areas where mulch, fertilizer and seed were not added (0 seedlings/m2). There was no difference in grass cover between areas where mulch, fertilizer and seed had been added (84%) and areas where mulch, fertilizer and seed were not added (84%). In 1997 mulch and fertilizer were added to five randomly located 5 m x 5 m plots which were subsequently sown with seeds from native shrubs, while in five other plots no mulch or fertilizer were added. In spring 1997 plots were surveyed for grasses using two 0.25 m x 0.5 m quadrats/plot and two 0.5 m x 1 m quadrats/plot for shrubs.