THE EFFECT OF QUADRAT SHAPE AND PLACEMENT ON THE ACCURACY OF YIELD AND DENSITY ESTIMATES FOR CROPS SEEDED IN NARROW ROWS

Small quadrats (commonly 1-m(2) or less) have been used extensively as the sampling unit in studies examining crops seeded in narrow rows. T he effects of sampling unit shape and orientation on yield and plant d ensity estimates was examined. When small quadrats are required for sa mpling crops seeded in narrow rows, sampling would best be done using rectangular quadrats with sides parallel to crop rows and having some multiple of row width. In seventy seven published papers from 1988 to 1994, the quadrat shape used in sampling plant populations was appropr iate in only fourteen instances. Inappropriately shaped quadrats could result in errors of up to 25% in estimates of crop related variables, such as yield.