Submitted to: Weed Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/17/2006
Publication Date: 5/1/2006
Citation: Westerman, P., Liebman, M., Heggenstaller, A., Forcella, F. 2006. Integrating measurements of seed availability and removal to estimate weed seed losses due to predation. Weed Science. 54:566-574. Interpretive Summary: The weeds that plague crops each year typically arise from seeds that were produced in the previous one or two years. While these seeds are being stored in the soil or on the soil surface, they are subject to consumption by various animals. Seed-eating animals are called granivores, and common granivores include mice and beetles. To better understand granivory and as a first step in the search for good ways to increase weed seed losses in crops, we developed a conceptual model that combines seed dispersal, seed burial and seed demand, which are the three processes that describe the dynamics of summer annual weed seeds on the soil surface in late summer and autumn. We used experimental data to develop a simulation model for various combinations of crops and weeds. For giant foxtail in corn and soybean, we found that factors related to seed availability are more important to overall granivory than those related to seed demand. Granivory increased the longer a seed remained on the ground. Thus, delaying harvest dates of crops to allow more time for weed seeds to shed increased granivory and seed losses. Also, destroying unshed weed seeds collected by combines at harvest was a promising strategy to reduce new seed additions to the seed bank. Estimates of overall seed losses due to granivory based on model simulations in various crops and cropping systems indicate that granivory can serve as an important tool in the ecological management of weeds. The results of this study are useful primarily to scientists and researchers involved with weed population dynamics and growers and crop advisors interested in low-input crop management.
Technical Abstract: To fully understand seed predation and as a first step in the search for effective ways to enhance weed seed losses in arable fields, we developed a conceptual model that integrates seed dispersal, seed burial and seed demand, the three processes that describe the dynamics of summer annual weed seeds on the soil surface in late summer and autumn. Published and unpublished experimental data were used to parameterize a simulation model for a number of crop-weed combinations. Sensitivity analyses for models for giant foxtail in corn and soybean indicate that factors related to seed availability are more important to overall seed losses due to predation than those related to seed demand. Delaying harvest date and destroying unshed weed seeds collected at harvest emerged as promising strategies to reduce seed input into the seed bank. The role of plant debris in hiding weed seed from predators was not unambiguous and requires further investigation. Estimates of overall seed losses due to predation based on model simulations in various crops and cropping systems indicate that weed seed predation can serve as an important tool in ecological weed management.