Determining the Optimum Level of Soil Olsen Phosphorus and Phosphorus Fertilizer Application for High Phosphorus-Use Efficiency in Zea mays L. in Black Soil

Phosphorus is an essential macronutrient, both as a component of several important plant structural compounds and as a catalyst in the conversion of numerous important biochemical reactions in plants. The soil Olsen P (OP) level is an important factor affecting crop production and P-use efficiency (PUE). We tested the effect of six OP levels and P doses on maize yield, where the P doses were 0, 22, 44, 59, 73, and 117 kg P 2 O 5 ha −1 , with three replications, from 2017 to 2019. The response of crop yield to the OP level can be divided into two parts, below 28 mg kg −1 and above 28 mg kg −1 . The change point between the two parts was determined as the agronomic critical level for maize crops in the study area. The PUE (%) increased with soil OP levels and decreased with P fertilizer application rates. In addition, results for the low P application rate (P2), 22 kg P 2 O 5 ha −1 , showed that PUE significantly increased with an increase in the soil OP level compared with PUE at a low OP level (OP1), 0 kg P 2 O 5 ha −1 . The PUE value increased by 49.5%, 40.1%, and 32.4% at a high OP level (OP6) in 2017, 2018, and 2019, respectively, compared to that at a low OP level (OP1). At the same OP levels, in all three years, the PUE at a high P application rate (P6) decreased significantly, in the range of 62.8% to 78.7%, compared to that at a low P application rate (P2). Under an average deficit of 100 kg ha −1 P, the OP level of the soil in all three years decreased by 3.9 mg kg −1 in the treatment without P addition (P1) and increased by 2.4–3.5 mg kg −1 in the P treatments for each 100 kg ha −1 P surplus. A phosphorus application rate of 44 kg P 2 O 5 ha −1 and an OP level of 28 mg kg −1 are sufficient to obtain an optimum yield, increase the PUE, and reduce environmental hazards in the study area in northeastern China.