While making my rounds at various nurseries around the
county I am finding more and more managers are utilizing parboiled rice hulls
as a source of mulch for early weed control in container woody ornamental plantings.
The question is, "Do rice hulls prove to be
both an economical and effective solution for weed control?"
When asking this question, I have a lot of anecdotal
evidence of weed suppression during the early growth stage of container plant
production, but I have very few facts to back up whether there is an economic
benefit when comparing the cost of materials, labor costs and the difference
between traditional weeding and a preemergent herbicide.
There is good evidence that rice hulls can reduce
bittercress and liverwort when applied at depths of ½” to one inch thick on the
surface of container soil (Atland, 2019). Mulches play
a crucial role in inhibiting weed growth by creating an unfavorable environment
for seed germination. By covering the substrate surface, mulches restrict the
access of small weed seeds to essential resources, such as stored energy and
nutrients. However, most mulches eventually decompose and become conducive to
weed germination, limiting their long-term effectiveness.
Effective mulches for container crops should possess
specific characteristics, including low nutrient content, quick drying
properties, and resistance to decomposition. Rice hulls exhibit these desirable
qualities, making them a potentially good choice for preventing the
establishment of some weeds.
I have seen sawdust or shredded wood being used at nurseries
but when I tested the cost and effectiveness in an experiment, there were no
economical and no practical benefits compared to hand-weeding and preemergent
herbicides.
Dr. Chris Marble (UF Weed Scientist) and I did a mulch study and published the results. We found that large pine bark nuggets did well restricting weeds but when
compared to thin plastic (the kind used for strawberry or vegetable fields); plastic mulch wins
hands down (Marble et al, 2019).
In another study of plastic mulch for weed control, I
demonstrated that plastic mulch almost eliminated weeds, reduced water loss,
reduced the need for irrigation, and reduced the leaching of fertilizer (Steed et al, 2018). I did find that plants grew slower in plastic
mulch, but I speculate that it was due to the lack of leaching irrigation and a
dramatic increase in EC and decrease in pH over the growth time.
Soon we will be experimenting with rice hulls and let you
know whether it is a good idea to use them as a weed control method or not.
References:
Atland, James.
2019. USDA tests PBH rice hulls
for weed control in container crops.
Nursery Management Magazine.
Marble, S. C., Steed, S. T., Saha, D., & Khamare, Y. 2019.
On-farm Evaluations of Wood-derived, Waste Paper, and Plastic Mulch Materials
for Weed Control in Florida Container Nurseries, HortTechnology hortte, 29(6),
866-873.
Steed, S.T., Bechtloff, A., Koeser, A. & Yeager, T. 2018.
Response of Japanese privet to plastic mulch applied over nonspaced containers
HortTechnology 28 58-65
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