Factors affecting spatial variation in two crop rotations
van Kessel, C.
An experiment was initiated at two 4-ha sites with hummocky to undulating terrain, to examine the spatial variation rotation benefits of wheat grown after pea compared to wheat grown after wheat. In the second year of the rotations, N and non-N effects related to rotational differences - soil water content, root and leaf disease, weed density, growing season N availability - were used to assess spatial variation of wheat seed yield in the two crop rotations. ANOVA and state-space modeling and landform complex approaches were used to quantify spatial variation. Yield was 10% greater in the footslopes of both rotations at St. Louis, and 10% lower in the footslopes of only the wheat-wheat rotation at Birch Hills, when compared with yield in the shoulders. The lower yield in the footslopes of the wheatwheat rotation at Birch Hills partly was associated with higher weed density. The landform effect at St. Louis could not be explained with ANOVA. State-space analysis showed that the factors responsible for the spatial variation of seed yield differed between sites. Furthermore, local variation for soil water and N availability in the pea-wheat rotation, and lower leaf disease severity, mainly explained wheat yield at given locations in space at St. Louis. At Birch Hills, local variation for common root rot incidence in both rotations explained wheat yield at given locations in space. Preliminary results from this study reflect the spatial variation can be rotation specific, depending on the site.
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