Edge and neighbour effects in cereal yield trials

Summary In two field experiments with winter wheat varieties, the grain yields per unit area calculated from entire plots 4·2 × 1·18 m were 25% greater than the yields of the centre row. This occurred mainly because the outer rows in the plots yielded 62% more than the centre row. When the yields were calculated on the basis of a plot width of 1·53 m (the distance from path centre to path centre across the long axis of a plot), it was estimated that they were 4% less than the yields of the centre rows. In the most extreme case when a short variety in a plot of this size was bordered by neighbours 70 cm taller, its yield, relative to that of the tall variety, was underestimated by 10–12%. A separate experiment showed that the greater yield from plants at the edges of plots was associated mainly with more ears.