In Southeast Louisiana, this is the season where most home vegetable gardens are invaded with nagging summer annual weeds. For home gardeners that use safe environmental practices, cost of natural herbicides to combat large weed infestations can be expensive due to high dosage rates required to achieve control and product size.
However, two good nonchemical options to treat large weed invasions at a lower cost is soil solarization and occultation. Solarization/occultation involves using clear and black plastic over a bare soil area to heat soil allowing weed seeds to germinate from the initial warm moist environment. After a 4-to-8-week period of extreme temperatures and lack of water, the weed vegetation will eventually die promoting a bed that is ready for replanting crops.
This summer I am testing six weed species of broadleaf and grass weeds (Pigweed, Morningglory, Coffeeweed, Crabgrass, Broadleaf Signalgrass, and Johnsongrass) using solarization/occultation to determine which species can be better suppressed with clear or black plastic for home gardeners. This study will evolve from 6-to-8 weeks in our muggy summer heat allowing opportunity for soil temperatures to range between 100 to 130 degrees Fahrenheit adequate for weed control. Initial soil thermometer readings have already shown temperatures at or near 100 degrees but this can also be influenced by rainy days, clouds, humidity, or cooler air temperatures.
As I continue evaluating the data, I am looking forward to provide home gardeners with more feedback to help promote a better understanding of how solarization/occultation can be used as a vital tool to reduce summer weeds.
Integrated Plant Care Gardener
B.S. Landscape Management, LSU
Pursuing M.S. Agriculture Extension Education and Evaluation, LSU