Comparison of Different Sampling Scales to Estimate Weed Populations in three Soybean Fields

Abstract

A study was conducted to evaluate the accuracy of different weed sampling scales to accurately describe populations in soybean. Three soybean fields were sampled at 8 and 6 weeks after planting in 1998 and 1999, respectively. All weed species were counted on a 10 m grid, using a 0.58-m 2 quadrat. Data were eliminated from the original 10 m grid sample of weeds for each field to develop 40 m, 60 m, and 80 m independent data sets. Distribution and population maps were interpolated using an inverse distance weighted method. Data were extracted from the interpolated maps at known coordinates so that the observed population and the predicted population could be compared. The 10 m grid served as a standard to which all others were compared. No differences in population accuracies between each scale were detected when results were compared on a per weed basis, except when weed populations were very high, generally exceeding 400 plants ha )1 . When the weed density was not at an extreme, the results from these data indicate the ability to describe or account for the weed population fairly accurately, when using coarser grid sizes. These results also suggest that when using a regular grid coordinate system as the sampling structure, an increase from a 10 m scale to an 80 m scale will not cause a significant loss of information when weed populations were not extreme and will provide the necessary information for making suitable weed treatment decisions. However, some small weed patches were not detected with the coarser sampling scales, and the larger sampling scales would not meet their needs if the producerÕs objective is complete control of a species.

The influence of transgenic (Bt) and non-transgenic (non-Bt) cotton mulches on weed dynamics, soil properties and productivity of different winter crops

“…Total weed density was regarded as weed dynamics. The procedures of LaMastus and Shaw [43] and Onen et al [44] were followed to record total weed density. Briefly, l m 2 quadrate was randomly placed at three different locations in each experimental unit and number of weed species present in the quadrate were counted.…”

Investigation of the Role of Pod Abnormality Incidence on Yield and Yield Components of Soybean (A Case Study in Golestan Province, Iran)

“…Five times random sampling was done from each farm. Then, 10 samples (plant) in 3 replications from each experimental farm were randomly selected and the traits mentioned were measured (Lamastus and Shaw, 2005). All pods in the tagged plants were counted and the average number of pods per plant was determined.…”

Multi-Temporal Site-Specific Weed Control of Cirsium arvense (L.) Scop. and Rumex crispus L. in Maize and Sugar Beet Using Unmanned Aerial Vehicle Based Mapping

“…The collected weed scouting data of 0.4 m 2 per grid square was entered directly into a database, along with weed and crop cover and a photograph of the respective counting area. To this end weed species individuals were counted in a 0.1 m 2 counting frame with four repetitions around each grid square centroid, as tested and discussed in the literature [24][25][26]. These counting results were used to get a general overview about the field weed infestation.…”