Phosphorus Movement in Long-Term Experimental Plots.

Phosphorus (P) is an essential macronutrient that is frequently applied to soil for optimum plant growth. Many short-term studies have elucidated on P movement in the soil. But relatively few studies have investigated the impact of long-term applications of different P rates on P movement in soil profile under continuous farming practices. Our objective was to determine P movement in soil profile in the long-term experimental plots of the Old Rotation (circa 1896), Cullars Rotation (circa 1911), Two-year Rotations (1928) and the N-P-K Tests (1954). The first two are located on the campus of Auburn University, Alabama (USA) while the last two are located at Experiment Station plots across the State representing different soil areas. We determined extractable P at 0-15, 15-30, 30-60, 60-90 and 90-120 cm depths on composite soil sample cores. In general, our results indicated that extractable P decreased with soil depth and the rates of P decrease in the soil profiles were related to P application rates. In addition, highly significant amount of P was accumulated in the 0-15 cm depth. We will present P movement and accumulation in these Long-term Experimental plots with continuous P applications and agronomic production for the past 60-120 years.