The effect of planting date and irrigation on the establishment of an herbaceous community in an arid, post-agricultural system

Background/Question/Methods

Restoration of agriculturally-degraded arid and semiarid land is a problem faced by all major continents. Erratic precipitation in these lands makes restoration of a species-rich community difficult. Application of supplemental irrigation has been suggested as a restoration technique to overcome limitations in natural precipitation. However, studies that investigate irrigation in arid and semiarid systems have had variable success. In a full-factorial design, we tested the effects and the interactions of irrigation and seeding date on the ground cover of intended species and unintended exotic species in a post-agricultural restoration experiment in southern Colorado, USA.

Results/Conclusions

Plots seeded in April and November were dominated by exotic species regardless of the irrigation treatment. We found the greatest ground cover of intended species and lowest ground cover of unintended species when seeds were sown in May and had higher levels of supplemental irrigation. Our results suggest that the timing of sowing is important in arid post-agricultural restoration as well as the amount of irrigation applied. Supplemental water addition did not always result in native species establishment and suggests that there are other barriers to restoration in these systems.