Response of Tomato on Calcareous Soils to Different Seedbed Phosphorus Application Rates

摘要

Field experiments were conducted with five rates (0, 75, 150, 225, and 450 kg P_2O_5 ha~(-1)) of seedbed P fertilizer application to investigate the yield of tomato in response to fertilizer P rate on calcareous soils with widely different levels of Olsen P (13-142 mg kg~(-1)) at 15 sites in some suburban counties of Beijing in 1999. Under the condition of no P fertilizer application, tomato yield generally increased with an increase in soil test P levels, and the agronomic level for soil testing P measured with Olsen method was 50 or 82 mg kg~(-1) soil to achieve 85% or 95% of maximum tomato yield, respectively. With regard to marketable yield, in the fields where Olsen-P levels were < 50 mg kg~(-1), noticeable responses to applied P were observed. On the basis of a linear plateau regression, the optimum seedbed P application rate in the P-insufficient fields was 125 kg P_2O_5 ha~(-1) or about 1.5-2 times the P removal from harvested tomato plants. In contrast, in fields with moderate (50 < Olsen P < 90 mg kg~(-1)) or high (Olsen P > 90 mg kg~(-1)) available P, there was no marked effect on tomato fruit yield. Field survey data indicated that in most fields with conventional P management, a P surplus typically occurred. Thus, once the soil test P level reached the optimum for crop yield, it was recommended that P fertilizer application be restricted or eliminated to minimize negative environmental effects.