Testing the effects of seed pellet composition to aid in semiarid restoration seeding

Abstract

Restoring and revegetating semiarid regions with native perennial grasses is an extremely difficult task, often unsuccessful due to harsh abiotic conditions. We conducted studies evaluating the use of seed pellets to improve restoration seeding success in controlled and field environments. In a controlled setting, we evaluated the impacts of clay volume, pellet size, and watering rate on seedling establishment and pellet disintegration. The amount of clay, size of pellets, and watering rate were varied in a full factorial design. Seedlings emerged from 40% of the pellets. Clay content did not impact seedling emergence, but larger pellets (2.5 cm) were more likely to produce seedlings. However, when smaller pellets (1.5 cm) produced seedlings, a higher proportion emerged (15 vs. 9%). In the field, we compared seedling establishment monthly, overall summer recruitment, and disintegration of seed pellets made with 10% and 55% clay to broadcast seed and a non-seeded control using a randomized design. Seedling emergence was higher for both the 10% (1.4 seedlings) and 55% clay pellets (1.0 seedling) than the control treatments (0.5 seedlings), and also higher for the 10% clay pellets than broadcast treatments (0.8 seedlings). Additionally, we found that seedling establishment and recruitment were unaffected by pellet disintegration. End-of-season recruitment was higher in 10% clay pellets (2.6 seedlings) than in 55% clay pellets (1.2 seedlings) and control treatments (1.0 seedling). We also found that 2.5 cm pellets had slightly higher recruitment, indicating that larger pellets may be more suited to seedling survival in semiarid environments.