Fig. 4 Box plots of the yields of soft white spring wheat on the Palouse Conservation Field Station, Pullman, in plots fumigated just prior to direct-seeding, one year earlier, or not fumigated and planted in rows spaced uniformly (U) at 30 cm apart or in pairs (P) spaced 18 cm apart with 42 cm between the paired rows. White bars are the yield means and brackets are the yield extremes

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