Question

Conclude your report by commenting which methods is more suitable to sample out-door plant density.

Answer 1

Three experiments were conducted in 2014 resulting in 14 plots across varied sowing density, cultivars and environmental conditions. The co ordinates of the plants along the row were measured over RGB high resolution images taken from the ground level. Results show that the spacing between consecutive plants along the row direction are independent and follow a gamma distribution under the varried conditions experienced. A gamma count model was then derived to define the optimal sample size required to estimate plant density for a given precision.

Results suggest that measuring the length of segments containg 90 plants will achieve a precision better than 10%, independently from the plant density. This approach appears more efficient than the usual method based on fixed length segments where the number of plants are counted. The optimal length for a given precision on the density estimation will depend on the actual plant density. The gamma count model parameters may also be used to quantity the heterogeneity of plant spacing along the row by exploiting the variability between replicated samples. Results show that to achieve a 10% precision on the estimates of the 2 parameters of the gamma model , 200 elementary samples corresponding to the spacing between 2 consecutive plants should be measured.

This method provides an optimal sampling strategy to estimate the plant density and quantity the plant spacing heterogeneity along the row.