*2.1. Field Experiment*

A field experiment was carried out in 2016 in Bałcyny (Poland, 53◦60 N, 19◦85 E). The experimental plant was spring wheat (*Triticum aestivum* ssp. *vulgare*) cv. Monsun sown on 21 April at 450 plants m<sup>−</sup>2, at a depth of 3–4 cm, at a row spacing of 15 cm.

The experimental factor was phosphorus fertilization (Table 1). Granular recycled phosphorus fertilizer (Rec) and biofertilizer (Bio) were compared with commercial superphosphate (SP; Gda ´nskie Zakłady Nawozów Fosforowych Fosfory Sp. z o.o., Gda ´nsk, Poland). Phosphorus fertilizers were applied before sowing at 40, 60, and 80 kg P2O5 per ha. The fertilizers from recyclables (Rec and Bio) were produced by the New Chemical Syntheses Institute in Puławy based on the formula developed by the Department of Advanced Material Technologies of the Wrocław University of Science and Technology. Sewage sludge ash was obtained from the Łyna Municipal Wastewater Treatment Plant in Olsztyn, and dried animal blood was obtained from the meat industry. The bacterial strain of *B. megaterium* was obtained from the Polish Collection of Microorganisms of the Institute of Immunology and Experimental Therapy of the Polish Academy of Sciences in Wrocław (Poland). The procedure of obtaining fertilizer formulations was described by Rolewicz et al. [32].


**Table 1.** Elemental composition of phosphorus fertilizers.

<sup>1</sup> according to the information provided on the label, <sup>2</sup> according to the Department of Advanced Material Technologies of the Wrocław University of Science and Technology, LD—level of detection.

The field experiment had a randomized block design with four replications. The experimental plots had an area of 20 m<sup>2</sup> each. Winter oilseed rape was the preceding crop. In addition to phosphorus fertilization, wheat in all plots was fertilized with nitrogen at 130 kg N ha−<sup>1</sup> (34% ammonium nitrate, Grupa Azoty Puławy, Poland) and potassium at 100 kg K2O ha−<sup>1</sup> (60% potash salt, Luvena, Lubo ´n, Poland). Potassium was applied at a single rate before sowing, and nitrogen was split into three applications: 60 kg before sowing, 50 kg in the stem elongation stage (BBCH 30) [33], and 20 kg in the heading stage (BBCH 55).

Wheat was protected against diseases, weeds, and pests (Table 2) and was harvested with a plot harvester on August 12.


**Table 2.** Plant protection treatments applied in the field experiment.

<sup>1</sup> Warsaw, Poland.

## *2.2. Soil and Meteorological Conditions*

Wheat was grown on luvisol [34] formed from sandy clay loam. The arable layer was slightly acidic (average pH of 6.28 in 1 M KCl). At the beginning of the experiment in 2016, soil contained 8.53 g kg−<sup>1</sup> C, 1.42 g kg−<sup>1</sup> N, 2975 mg kg−<sup>1</sup> K, and 607 mg kg−<sup>1</sup> P (total content). Soil phosphorus content after spring wheat harvest is presented in Table 3.

**Table 3.** Total P content of soil after spring wheat harvest (mean ± standard error).


Abbreviations are explained in Table 1.

Mean annual precipitation was 62.5 mm, with 66.3 mm in June, 138.6 mm in July, 71.9 mm in August, and 17.1 mm in September. Mean annual temperature was 8.8 ◦C, and the mean monthly temperature ranged from −3.8 ◦C in January to 18.5 ◦C in July.
