Inorganic phosphorus fractionation and its translocation dynamics in a low-P soil

The translocation of different inorganic phosphorus (Pi) forms in a low-P soil (Langfang experimental station, Hebei province, China) over time was investigated using P fractionation extraction and a 32P tracer technique. The L-value and P availability of the soil was assessed using 5 different maize genotype (Zea mays L.) cultivars. The results showed that the different Pi fractions in the soil increased in the order of H2SO4-extractable P (Ca10–P) > Na3C6H5O7–Na2S2O4-extractable P (O–P) > NH4Ac-extractable P (Ca8–P) > NaHCO3-extractable P (Ca2–P), NH4F-extractable P (Al–P), NaOH–Na2CO3-extractable P (Fe–P), and the content of plant-unavailable P (Ca10–P + O–P) was high, up to 79.1%，which might be an important reason for P deficiency in this low-P soil. The 32P tracer results showed that after the addition of 32P-Pi to the soil with no P fertilizer applied for 25 d, 29.0% of 32P was quickly transformed into Ca2–P (rapidly available P), and 66.1% of 32P was transformed into Al–P, Fe–P and Ca8–P (slowly available P). Only 5.0% of 32P was transformed into O–P and Ca10–P (plant-unavailable P). Moreover, in the soil with P fertilizer applied, 32P transformation into Ca2–P increased, and the transformation into Ca8–P + Fe–P + AL–P and O–P, Ca10–P significantly decreased compared to the soil with no P fertilizer applied (p < 0.05). This result suggested a higher rate for water-soluble P transformation to slowly available and plant-unavailable P in P deficient soil than in soil with sufficient P. The results of maize L-value determination showed that different genotype maize cultivars had different soil P-use efficiency and low-P tolerance mechanisms. Low-P tolerant cultivar DSY-32 regulated soil P-use efficiency and plant P content according to exogenous P fertilizer application. However, another low-P tolerant cultivar, DSY-2, used soil P more efficiently, regardless of the application of exogenous P.

► Translocation inorganic phosphorus over time investigated using P fractionation and 32P tracer.
► L-value and P availability assessed using 5 maize genotype.
► Observed higher rate of P transformation to unavailable P in deficient soil than in sufficient.
► Different genotypes had different soil P-use efficiency and low-P tolerance mechanisms.