Knowledge, science, and practice in ecological weed management: farmer–extensionist–scientist interactions - Ecological Management of Agricultural Weeds - page 123

Figure 3.5 Data sheet used by farmers to record weeds in annual crops in
Nicaragua.Farmers observe both total cover and the presence ofmajor types of
weeds by phenological stage in 50 circular quadrats.This example was taken in a
maize field 25 days after planting and before the first weeding.
Berti et al ., 1992; Forcella, 1993; Gold, Bay & Wilkerson, 1996; Johnson et al .,
1996). The primary objective is the one-time determination of whether the
mean weed population density in a field is below or above a threshold that
triggers application of a post-emergent herbicide.
In the context of farmer decision-making and a weed working group
routine, additional reasons can be identified for documenting weed abun-
dance, weed floristic composition, and weed patterns at the field and land-
scape levels. These include analysis of the timeliness of practices in farmer
fields and researcher experiments, the evaluation of field-scale trials, and the
comparison of weed dynamics among experiments and fields, and across
years. For example, the format in Figure 3.5 was designed for use with small-
holder maize and bean producers in Nicaragua. In a 15-30 minute walk
through their fields (0.5-2.0 ha), farmers determine total weed cover and the
presence and reproductive status of different weeds in 50 circular quadrats
25-30 cm in diameter. In a later group discussion, farmers compare problem
weeds in different fields, total weed cover and crop stage, variability within
each field, and the likelihood that the floristic composition will change based
on current weed control practices. This method does not generate a spatial
map, but it does provide information to analyze decisions on field-wide weed
control and particular practices directed at specific weeds or patches.
The development of simple methods for on-farm use that combine