Novel approach to the evaluation of large area field sampling methods for crop residue coverage measurement

Although many field sampling methods have been used to estimate crop residue coverage in large areas, the widely accepted method is still the line transect method, yet its precision has not been studied thoroughly. In this paper, a novel image processing based approach was used to simulate the line transect sampling, modified line transect sampling, horizontal line sampling, and systematic grid sampling methods for large areas. All methods gave true residue cover if many measurements were made, but with varying precision. The precision was found to be the function of true residue cover and the number of points used in the sampling method. As an example of the simulation results, for 30% corn residue each in a 20 m2 area, an average of five measurements of a 50 foot 100 dot transect line was used to estimate the residue cover, and the percentage error was ±12%. Many more points are required to achieve a higher precision. A more efficient and precise sampling protocol was proposed to estimate residue coverage for large areas.