• Interpretation of the phosphorous soil test for Alaska agricultural soils

      Michaelson, Gary J.; Ping, Chien Lu (School of Agriculture and Land Resources Management, Agricultural and Forestry Experiment Station, 1989-04)
      Phosphorus (P) along with nitrogen (N) and potassium (K) comprise the three macronutrients most frequently added as fertilizer for growing plants. In Alaska soils, P is often the second most limiting nutrient after N. A proper supply of plant-available P is important for root development and plant growth. To supply P to growing crops, the soil not only must contain enough P, but it must be in a form which is available for utilization by the plant. The status of P in the soil has an important influence on fertilization practices. Agricultural soils of Alaska vary considerably, not only in their total content of P and its distribution (form it occurs in), but also in the characteristics for sorption or fixation of P (Ping and Michaelson, 1986). Forms of P in the soil will affect its availability. The P-sorption character of soils will affect P fertilizer reactions in the soil and thus influence the amount of P fertilizer necessary and carry-over effects of applied P. It is essential that P soil tests and their interpretation be tailored for soils with similar P reactions. A useful P soil test must be based on both correlation of test values to plant growth and to field calibration of soil test values with yield.