THE COST OF COUNTING AND IDENTIFYING WEED SEEDS AND SEEDLINGS.

Authors: Wiles, Lori; SCHWEIZER, E. - ARS-RETIRED

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/27/1999
Publication Date: N/A
Citation: Wiles, L., Schweizer, E.E. 1999. The cost of counting and identifying weed seeds and seedlings.. Weed Science.

Interpretive Summary: Bioeconomic weed management models are an IPM tool to help growers protect water quality by managing weeds with less herbicide. These models help growers select the best management for the weed population in a field, however growers lack cost-effective methods to estimate how many and what types of weeds are in a field. Counting and identifying seeds and seedlings sis the most time-consuming and costly process of sampling weed populations How long it takes to count and identify was investigated and modeled as a first step in developing sampling plans for growers using WEEDCAM, a weed management model for corn in Colorado. The time required to count and identify seeds or seedlings was recorded for 9405 soil cores (5 cm diameter and 10 cm deep) and 9726 quadrats (18-cm band over 1.52 m of crop row) collected or examined in eight commercial corn fields. The time required to count and identify seeds increased with the number of seeds and species, and the amount of sand in the core. For seedlings, time increased with the number of seedlings and species. The cost of counting and identifying the in this study was $2.71 per core for seeds and $0.08 per quadrat for seedlings. Models of the time required to count and identify seeds and seedlings were developed and will be used to estimate the cost of sampling and to identify cost-effective sampling plans for growers using WEEDCAM and other bioeconomic weed management models.

Technical Abstract: Bioeconomic weed management models are a tool to help growers manage weeds with less herbicide by matching management to the weed population in a field. Growers, however, will not use these models unless cost-effective methods to sample weed populations are identified. Counting and identifying seeds and seedlings is the most time-consuming and costly process of sampling weed populations. The time required for this process was investigated and modeled as a first step in developing sampling plans for growers using WEEDCAM, a weed management model for corn in Colorado. The time required to count and identify seeds or seedlings was recorded for 9405 soil cores (5 cm diameter and 10 cm deep) and 9726 quadrats (18-cm band over 1.52 m of crop row) collected or examined in eight commercial corn fields. The time required to count and identify seeds was best described using a log-linear regression with time increasing with the number of seeds and species, and the amount of sand in the core. The time required for seedlings was best described using a log-linear regression with time increasing with the number of seedlings and species. The average cost of counting and identifying the observed weed populations was $2.71 per core for the seed bank and $0.08 per quadrat for seedlings.