Effect of phosphorus application on soil available phosphorus and maize phosphorus uptake and yield

To simultaneously enhance maize yield and phosphorus fertilizer efficiency, the effects of phosphorus application on maize phosphorus uptake and utilization, yield, and the dynamic changes of rhizosphere phosphorus were studied in a field experiment. The study was conducted in low soil phosphorus (Olsen-P 4.9 mg·kg^-1) condition at Henan Province with two maize varieties - "Ludan 9002" (LD9002) and "Xianyu 335" (XY335). The application rates of the P fertilizers were 0 (T₀), 50 kg(P₂O₅)·hm^-2 (T₁) ,100 kg(P₂O₅)·hm^-2 (T₂), 200 kg(P₂O₅)·hm^-2 (T₃) and 1 000 kg(P₂O₅)·hm^-2 (T₄), respectively. The results showed that the order of available phosphorus contents in rhizosphere and non-rhizosphere soils of the two maize varieties at different growth stages was T₁ < T₂ < T₃ < T₄. The highest phosphorus transformation rate from non-rhizosphere to rhizosphere soils was at 61 d after maize planting under 200 kg(P₂O₅)·hm^-2 (T₃). Also treatment T₃ had the highest biomass, grain yield and phosphorus transformation rate. Under 1 000 kg(P₂O₅)·hm^-2 phosphorus fertilizer application (T₄), no significant increase was noted in biomass and grain yield compared to intermediate phosphorus level. However, maize phosphorus uptake was much higher under treatment T. Phosphorus transformation rate of XY335 after flowering was lower than that of LD9002, suggesting higher phosphorus use efficiency by LD9002. Correlation analysis showed significant relationships among available phosphorus contents of rhizosphere and non-rhizosphere soils and phosphorus accumulation in stems and leaves of LD9002, especially at 79 d after planting. Also significant relationships were noted among available phosphorus content of rhizosphere and non-rhizosphere soils and those of stems and leaves of XY335, especially at 47 d after planting. This suggested that 79 d and 47 d after planting were key phosphorus demand periods after planting in LD9002 and XY335, respectively. Available phosphorus content of rhizosphere and non-rhizosphere soils reflected the capacity of the soils to release phosphorus. Suitable phosphorus concentration of rhizosphere and non-rhizosphere soils for the highest phosphorus uptake were respectively 54.95 mg·kg^-1 and 32.99 mg·kg^-1 at 79 d after planting LD9002. The corresponding values for XY335 were respectively 51.24 mg·kg^-1 and 35.35 mg·kg^-1 at 47 d after planting. When phosphorus application rate increased to 1 000 kg(P₂O₅)·hm ^-2, no significant difference existed in terms of yield, biomass and phosphorus uptake compared with those under phosphorus application rate of 100~200 kg(P₂O₅)·hm^-2.