Take it to the bank: Weed seed, that is

If we could take weeds to the bank, we’d all be millionaires. Because an important component of managing weeds is preventing the seeds released by weeds each autumn from becoming new plants, researchers set up what might be termed weed seed banks. Nature assists in the loss of weed seed through predation, decay and loss of viability. Based on work at two locations in Arkansas, researchers found that integrated weed management strategies that facilitate these processes can lead to high levels of weed seed loss.

The October-December 2013 journal Weed Science Vol. 61, No. 4, presents results of field experiments conducted between November 2010 and October 2011. Researchers studied post-dispersal seed loss of five of the most problematic weeds in the midsouthern United States: barnyardgrass, johnsongrass, pitted morning glory, Palmer amaranth and red rice.

Although the work was targeted at field crops, it should be valid for turfgrasses, too. Weed seeds left on the ground are vulnerable, and biological interventions can keep them from becoming seedlings and the next season’s weeds. The seeds provide food for ants, rodents and birds. Pathogenic microorganisms attack seeds, causing decay. In addition, physiological aging can affect the longevity and viability of seeds.

The authors of the study estimated total seed loss through predation, decay, germination and loss of viability, and they examined the influence of residue level and seed burial depth, both near the surface and at a 5 centimeter depth. All five species in both locations showed a reduction in the percentage of the active seed bank present between the spring, five months after dispersal and the next fall, a year after dispersal.

The study appears to indicate that practices to increase soil temperature, organic matter and moisture content could help promote microbial activity and therefore seed decay.

Biological seed bank management is a tool of sustainable weed management. Incorporating this as one of many diverse strategies is important for achieving sustainable weed management, particularly with the spread of herbicide-resistant weeds.