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Fig. 1. Annual alfalfa hay yield increases in a curvilinear fashion to rate of fluid and granular P fertilizer applied in December of the previous year. The P fertilizers used were fluid ammonium polyphosphate (APP, 10–34–0) applied in the flood irrigation water and granular monoammonium phosphate (MAP, 11–52–0) topdressed and incorporated with flood irrigation. Yields were higher with the granular MAP than fluid APP fertilizer in 1997, but were similar in 1998 and 1999 for both fertilizers. The symbols ns, +, *, ** indicate that the coefficient of determination (r2) of the fitted equation (y = b0 + b1/x) is not significant at P = 0.10, or is significant at P = 0.10, 0.05, or 0.01, respectively.
