Agronomic Effectiveness of Partially Acidulated Asfordi Phosphate Rock on Canola in two Calcareous and Non-calcareous Soils

Yazd Asfordi phosphate rock (PR) was partially acidulated at five levels (0, 40, 60, 80, 100%) for increasing the Relative Agronomic Effectiveness (RAE) of canola (Brassica Napus L.), var. RGS in two calcareous and non-calcareous soils. The Partially Acidulated Phosphate Rock (PAPR) was compared vs. the standard fertilizer (triple superphosphate) in two levels (50 and 100 mg P/kg). This study was carried out in greenhouse as a factorial experiment in a completely randomized design, and replicated three times. Results indicated that the relative effectiveness of fertilizers as based on dry mater (DM) and phosphorous (P) uptake significantly (p<0.001) increased with an increase in acidity level. In 0% application of acidulated PR, the relative effectiveness based on DM and P uptake was very low (0.8 and 1.8% respectively). In 100% acidulated PR (in match with single superphosphate) the relative DR and P uptake were 75.7 and 67.5% respectively indicating that DR and P uptake amounts were low as against standard fertilizer application but very high against no PR application, the difference being significant. The relative DM yield in calcareous soil (with low free Fe2O3) was significantly higher than that in non-calcareous soil (with high free Fe2O3). Also, the relative DR yield and P uptake at 100 mg P/kg was significantly higher than that in 50 mg P/kg.