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Fig. 2. Grain yield of winter wheat (WW) after summer fallow (one crop every 2 yr) compared with continuous annual no-till hard red spring wheat (HRSW) during 6 yr in the Horse Heaven Hills, Washington. 
= WW yield in 1997 is the average from several neighboring fields, not from replicated plots, and thus statistical analysis is not possible in 1997. 
= HRSW grain yield is from replicated plots during all 6 yr. 
= statistical comparison of average grain yield is for 5 yr (1998 to 2002). Grain yield of WW after summer fallow was significantly (P < 0.05) greater than grain yield of annual HRSW each year and when averaged over the 5 yr.
