Raising ducks in paddy fields promoted phosphorus absorption by changing soil phosphorus forms in the Yangtze River Delta of eastern China

Abstract

Abstract Aims The rice-duck system was widely promoted to attaining the sustainable development of agricultural ecosystem was due to its potential eco-friendly characteristics. Soil phosphorus (P) forms are closely related to crop P uptake and soil environmental quality. Nevertheless, the effects of rice-duck system combined with different fertilizer on crop P uptake, the change of soil P forms, phosphorus use efficiency (PUE) and interrelation remain unclear. Methods A field experiment of ducks were put into the four fertilizer treatments: chemical fertilizer (RDF and RMF), a mixture of 70% chemical and 30% organic fertilizers (RDFO and RMFO), organic fertilizer (RDO and RMO) and no fertilizer (RD and RM) were carried out in rice tiller and maturity period and ensure consistent P, nitrogen (N) and potassium input. Results Results showed that the RDO and RDFO had higher readily available inorganic P pool (Resin P + NaHCO3-Pi), extractable organic P fractions (NaHCO3-Po + NaOH-Po), and Fe-P and Al-P (NaOH-Pi) than the corresponding rice monoculture. RDF decreased the extractable organic P fractions (NaHCO3-Po + NaOH-Po) and Fe-P and Al-P (NaOH-Pi) compared with RMF; RDO increased the accumulation of Residual-P while RDF and RDFO decreased the accumulation of Residual-P compared with RMO, RMF, and RMFO. pH was the dominant factor affecting P forms of soil. RDF and RDFO had higher P content of grain and straw that mainly affected by soil NaHCO3-Pi and NaOH-Pi than other treatments. Simultaneously, rice–duck system can increase PUE, especially RDF significantly increased by 171.63% and 22.63% than RDO and RDFO, respectively. Conclusions Rice–duck system can promote rice grain and straw to absorb soil P by changing the soil pH to stimulate soil surplus P into active P and improve PUE.