|Morrison Jr, John|
Submitted to: American Society of Agronomy
Publication Type: Abstract Only
Publication Acceptance Date: 11/3/1996
Publication Date: N/A
Technical Abstract: Linear transects with evenly spaced points are used to measure per cent cover by crop residue or crop canopy. When used on uniformly distributed residue, relatively precise measures of cover can be found with as few as five, 100 point counts. Conversely, if evenly spaced points are used to measure cover that lies in regularly spaced parallel rows, estimates can be highly variable (std dev. may exceed mean). The problem is most pronounced when evenly spaced stripes with >50% cover parallel alternate with stripes with <20% percent cover. Precise means can be obtained in such situations with equally spaced point transects if both point spacing and transect angle relative to tillage rows are custom selected. No equal point spacing will provide precise cover estimates at all planter and tillage row spacings. Cover estimates from randomly spaced point transects are not dependent upon transect angle or row spacing and will have a std dev. between 5 and 10 percentage points. A sinewave-like point spacing also produces cover estimates that are not dependent upon transect angle or row spacing. The advantages of this pattern are: it is unique in contrast to the large number of possible random spacings, it can be used on any row spacing, and it usually provides a small variance.