Evaluation of the Use of Parboiled Rice Hull Mulch for Weed Control in Outdoor Ornamental-Plant Production Environments.

Parboiled rice hull mulch is becoming a widely used non-chemical weed control method in container nurseries, but research is lacking on the performance of rice hulls in outdoor production nursery environments. Two separate experiments were conducted to assess the effect of rice hull mulch on the emergence and growth of several common nursery weed species in an outdoor container nursery environment and to determine how well rice hulls performed over time. In a 12-week container experiment, rice hulls provided significantly better control of common container nursery weed species when seeds were placed on top of rice hull mulch applied at depths of 1.3 or 2.5 cm. In contrast, there was little difference in control when seeds were placed below the mulch layer regardless of mulch depth. In a long-term evaluation over 12 months, rice hulls applied at depths of 1.3, 2.5 or 5.0 cm provided control similar to pre-emergence herbicides through 6 months, but herbicides provided better control thereafter. Overall, rice hulls proved to be a suitable alternative to commercial herbicides and would be recommended in cases where pre-emergence herbicides cannot be used due to crop safety or grower preferences.