Seed protein content of soybean as affected by spatial variation in field experiments

The Variation of soybean seed protein content has been investigated in performance trials of maturity group 000 to I genotypes at different locations in the eastern part of Austria between 1992 and 1994. In all experiments evaluated, significant portions of spatial Variation were identified which affected seed protein content in the range of -25 to + 30 g/kg. Lattice and neighbour analysis were more efficient than the randomized complete block design in reducing error variance in most experiments. Neighbour analysis was superior to the lattice design when soil trends were changing over short distances or in both longitudinal and latitudinal directions. In most instances, neighbour analysis based on two or three neighbouring plots at each side of a test plot was more efficient than an analysis using only the nearest neighbours. Residuals derived from neighbour analysis were also used to visualize spatial heterogeneity, and clear trends of protein content were identified for particular experimental sites. The ranking of genetic entries was considerably biased by spatial variations, which would have reduced the efficiency of selection for high protein content if genotype performance was not adjusted for field variation.