Low phytic acid (LPA) barley (Hordeum vulgare L.) cultivars partition phosphorus (P) in seed tissue differently than conventional wild-type (WT) barley cultivars. A reduction in seed phytic acid (myo-inositol-1,2,3,4,5,6-hexkisphosphate) is coupled with an increase in inorganic phosphorus (Pi). The response of the LPA characteristic to phosphate fertilization has not been previously investigated; therefore the effect of phosphate fertility on barley seed yield, and concentrations of seed total P, seed Pi, and flag leaf P was investigated at four locations over two years. The LPA cultivars were hypothesized to behave similarly to WT cultivars, therefore two WT cultivars, Baronesse and Colter, were compared to one LPA cultivar, Herald (lpa1–1 mutation), and one LPA advanced breeding line, 01ID451H (mutation 640). At three locations, phosphate fertilizer (P2O5) was applied in the form of triple superphosphate (0–45–0) at rates of 0, 56, 112, and 168 kg ha–1. Increased P fertilization was associated with increased flag leaf P concentration, but no changes were observed for other measured characteristics. At a fourth location, differential soil P fertility was provided via previously established plots varying from very low to adequate P fertility. Inadequate levels of P were associated with delayed maturity, and reductions in yield, test weight, height, and total seed P concentration. The responses of LPA and WT barleys were similar, indicating the LPA traits in barley originating from the lpa1-1 and 640 mutations are stable under a wide range of soil P fertility.