A comparison of four methods for determining pasture botanical composition

Background

Grassland researchers use many different methods to assess pasture botanical composition, but direct comparison between methods has been limited. The objective of this study was to determine an accurate and efficient method to monitor botanical composition for researchers and/or practitioners.

Methods

Six cattle farms with two pastures each were monitored across the state of Kentucky. Sampling was three times per year from fall 2020 through fall 2022. The evaluation methods included step point, visual estimation, occupancy grid, and point quadrat. The point quadrat method was designated as the reference method for accuracy comparison.

Results

The occupancy grid method had the highest statistical similarity to the reference method. The occupancy grid method was less likely to provide over- or underestimations and had the highest correlation coefficient using Pearson's method, ranging from 0.87 to 0.99 across all species. Correlations between visual estimation and the reference method ranged from 0.75 to 0.98 and the step point method had the lowest correlations, ranging from 0.40 to 0.90 due to high variability in recording certain species.

Conclusions

Analysis of variance results showed that the occupancy grid method did not differ from the point quadrat method. Overall, the occupancy grid method was the most similar to the reference method and was the most efficient method for botanical composition analysis.