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A major cash crop in the Bighorn Basin of Wyoming (WY) and the Yellowstone River valley of eastern Montana (MT) is Sugarbeet (Beta vulgaris L.). This growing area is characterized by alkaline/calcareous soil conditions that inhibit phosphorus (P) availability. Phosphorus, however, is reported to increase root growth in sugarbeet. This study evaluated the effects of two P fertilizer sources and rates on sugarbeet productivity in Sidney, MT and Powell, WY. The P fertilizer sources were liquid ammonium polyphosphate (APP) and dry monoammonium phosphate (MAP) applied with or without a P availability enhancer (Avail®). A fifth fertilizer treatment consisting of APP + Avail® + starter fertilizer was tested. The APP was banded at 5 cm beside and below the seeds, the starter fertilizer was seed-placed and the MAP was broadcast-incorporated to 5-cm depth. Five P application rates (0, 34, 67, 134, and 201 kg P2O5 ha−1) were tested in Montana, and seven rates (0, 34, 67, 134, 201, 269, and 336 kg P2O5 ha−1) in Wyoming. Results showed significant effects of P fertilizer products and application rates on sugarbeet productivity and quality. The starter fertilizer increased plant stands in Wyoming, which was due to lower temperature (3–6 °C) condition at planting. Avail® increased root yield when APP was applied in Powell, WY, but had no effects when MAP was applied. There was no benefit from treatment with Avail® in Sidney, MT, regardless of fertilizer source. Phosphorus application rates had significant effects on root and sugar yields at both locations. The relationship between P application rate and root and sugar yield was linearly positive and failed to reach a plateau, despite the high P rates tested in this study. Such high P rates however, are not recommended in Wyoming and Montana because of the high economic and environmental cost associated with such rates. |
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