| To facilitate irrigation in central Washington, land is leveled or smoothed on a broad scale. As a result, the calcareous and extremely infertile subsoils are exposed and used directly as a medium for plant growth. Phosphorus fertilizer requirements of exposed subsoils were determined by measuring crop yield and P uptake on plots that were fertilized in the current and one, two or three preceding seasons. Annual crops used as indicators of P availability at three sites were field beans, Sudangrass and sugar beets. A supplementary experiment involved fertilization of a previously established alfalfa crop. Crop growth and P uptake results were correlated with sodium bicarbonate soil testing |
