## 3 Results and Discussion
### P Content and Accumulation in Plant Biomass
#### 3.2.1 Wheat Grain and Straw
Plants fed with A\({}_{8}Bm\) accumulated the same P amount in grains as plants treated with SP, and more than those under PR, A + H\({}_{2}\)O and B\({}_{8}Bm\). In turn, B\({}_{8}Bm\) resulted in a higher P accumulation in grain than PR. In experiments II-V, waste-fertilisers and traditional fertilisers did not differ in their effect on the P accumulation in grain. In experiment II, +PP against -PP contributed to an increase in P accumulation in grain, which was both a function of a higher yield and a higher grain P content (Table 11). The interaction between plant protection and P-fertilisation treatments was not noted. No significant impact of fertiliser and plant protection treatments on P accumulation in straw was found in any experiment. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Wheat Grain** & **Wheat Straw** & **Weeds** & **Post-Harvest Residues** \\ \hline \(-0.631\)\({}^{1}\) & \(-0.152\) & \(-0.429\) & \(-0.402\) \\ \hline \multicolumn{4}{c}{\({}^{1}\) values significant at \(p=0.05\).} \\ \end{tabular}
\end{table} 
Table 10: Relationship between P content and biomass volume of plant biomass parts—simple correlation coefficients. \begin{table}
\begin{tabular}{c c c} \hline \hline
**In** & **P Content** & **Biomass Volume** \\ \hline Wheat grain & \(0.350\)\({}^{1}\) & \(0.502\) \\ Wheat straw & \(0.931\) & \(0.206\) \\ Weed biomass & \(-0.396\) & \(0.969\) \\ Post-harvest residues & \(0.599\) & \(0.467\) \\ \hline \multicolumn{4}{c}{\({}^{1}\) values significant at \(p=0.05\).} \\ \end{tabular}
\end{table} 
Table 11: Dependence of P accumulation on P content and biomass volumes of plant biomass parts—simple correlation coefficients. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**In** & **Wheat Grain** & **Wheat Straw** & **Weeds** \\ \hline \multicolumn{4}{c}{**Content**} \\ \hline Wheat straw & \(0.747\)\({}^{1}\) & - & - \\ Weed & \(-0.133\) & ns & - \\ Post-harvest residues & \(0.423\) & \(0.191\) & \(-0.395\) \\ \hline \multicolumn{4}{c}{**Accumulation**} \\ \hline Wheat straw & \(0.543\) & - & - \\ Weeds & \(-0.632\) & \(-0.266\) & - \\ Post-harvest residues & ns & \(0.134\) & ns \\ \hline \multicolumn{4}{c}{\({}^{1}\) values significant at \(p=0.05\); ns—no significance at \(p<0.05\).} \\ \end{tabular}
\end{table} 
Table 9: Relationship between P content of individual plant biomass parts and between P accumulation in these parts—simple correlation coefficients. To date, there have been few studies on the effect of waste-fertilisers on the P content of arable crops. The issue of P uptake/accumulation is more often addressed. It was proven recently in pot experiments by [PERSON] et al. [63] (with barley) and [PERSON] et al. [64] (with wheat) that SSA caused the lower P content in cereal shoots (measured 6 weeks after sowing) than TSP applied at the same P dose (50 or 60 mg/kg soil, respectively). These results of pot research differ from the findings of our field experiments. However, in another field experiment by [PERSON] and [PERSON] [65], the P content in maize grain and straw did not differ when 21.8 kg P/ha was applied in the form of SSA or SP. The authors also noted that the P content in grain and straw increased when SSA was applied at 65.4 kg P/ha, but no SP at the same P dose was applied to compare, so this result is inconclusive. Other field studies on recycling P products, such as ashes made of wood and cereal straw, also showed results similar to ours, with no effect on P content in wheat grain [66] or the same effect on P content in barley grain and straw as the SP applied at the same P dose performed [67]. Previous studies, mostly based on pot experiments, demonstrate mainly the lower P uptake/accumulation in plant biomass when fertilised with recycled fertilisers, as compared with SP or other fertilisers of easily available P compounds [21; 30; 68]. The low bioavailability of P from secondary raw materials has been suggested as the reason for this [23].