Response of soil phosphorus to P balance under long-term rotation and fertilization in brown soil

Objectives The study aimed to explore characteristics of P balance and response of soil phosphorus to P balance under a long-term rotation and fertilization, in attempt to provide theoretical bases for scientific application of phosphorus fertilizer in brown soil.

Methods The long-term fertilization and maize-maize-soybean rotation experiment in brown soil was started since 1979, in Shenyang, Liaoning Province. The selected seven treatments included CK (without applying P fertilizer), NP, NPK, low manure plus NP (M1NP) and NPK (M1NPK), and high manure plus NP (M2NP) and NPK (M2NPK). In 2015, soil samples were collected to analysis the contents of Olsen-P and total P, and the relationships between soil Olsen-P, total P and P balance were studied.

Results The soil P was in deficit for the CK, with annual deficit of soil P 9.0 kg/hm². While the soil P in the phosphorus fertilizer treatments (NP and NPK) and chemical P plus manure applied (M1NP, M1NPK, M2NP and M2NPK) remained in surplus status, and M2NP and M2NPK accumulated higher soil P than others. The Olsen-P was highly and significantly correlated with P balance (P < 0.01). For every mean deficit of P 100 kg/hm² in brown soil, Olsen-P of the CK would be correspondingly decreased by 0.84 mg/kg. For every mean surplus of P 100 kg/hm² in the soil, Olsen P of the treatments would be correspondingly increased by 1.97−7.23 mg/kg. There was significant positive correlation between total P and P balance under the long-term different fertilization except for the CK treatment (P < 0.01). For every mean surplus of P 100 kg/hm² in the soil, total P of the chemical P fertilizer, and chemical P fertilizer plus manure would be correspondingly increased by 0.03−0.04 g/kg.

Conclusions Input of phosphorus fertilizers affects soil total P and Olsen-P significantly. The P in brown soil is remained deficit under the long-term rotation and without P input. The P is remained surplus with the annual input of chemical P₂O₅ 70 kg/hm², and more P is surplus with the total input of chemical plus annual P₂O₅ 126−182 kg/hm². The combination of chemical phosphorus fertilizer and manure performs better in the increase rate of Olsen-P content than chemical P along does in brown soil.