Phosphorus Availability and Balance with Long-Term Sewage Sludge and Nitrogen Fertilization in Chernozem Soil under...

A continuous long-term field experiment with maize monoculture was conducted to evaluate the P availability and balance, DM yield, P uptake, and P sorption parameters in chernozem soil after 27 years. A total of 2 doses of nitrogen (120 and 240 kg ha^-1) were applied as mineral nitrogen (N₁₂₀ and N₂₄₀) and sewage sludge (SS₁₂₀ and SS₂₄₀) and compared with unfertilized control (Con). The aboveground biomass (DM) yields significantly increased in the order of Con < SS₁₂₀ < SS₂₄₀ < N₁₂₀ < N₂₄₀ treatments and the maximum P uptake was recorded for both N₂₄₀ and SS₂₄₀ (25.1 kg P ha^-1) according to the nutrient application gradient. The N₁₂₀ and N₂₄₀ treatments positively influenced the DM yield but negatively influenced the P balance (-648 and -678 kg P ha^-1 27 years^-1), gradually bringing a risk of P deficiency in the soil. On the other hand, applications of SS₁₂₀ and SS₂₄₀ positively influenced the P availability and pseudototal (P_AR) content in the soil, which resulted in a buildup of legacy P or an increase in P saturation greater than the environmental threshold value. Aluminum was found to be a major controlling sorption factor for P in our chernozem soil.