## 2 Materials and Methods
### Effects of Different Amounts of Chicken Litter Biochar and Phosphorus on Plant Nutrient Uptake  
Maize plant leaves, stems, and roots P uptake in T1 (soil only) were statistically lower than other treatments (Figure 4A-C) because one of the most common problems associated with highly weathered mineral acid soils is Al\({}^{3+}\) toxicity [33] because Al\({}^{3+}\) toxicity reduces plant growth and development increases. Additionally, highly weathered mineral acid soils are low in P because of P fixation by Fe, Al, and Mn. These factors contribute to severe reduction of soil P availability and P uptake [33]. Leaf P uptake with only chemical fertilization (T2) was statistically higher than with CLB (Figure 4A). Phosphorus uptake in stems was higher in T4, T7, T10, and T11 than those of T1, T2, T5, T6, T9, and T12 (Figure 4B) whereas P uptake in the maize plant roots of T3, T8, and T9 were not statistically different but higher than those of T1, T2, T4, T5, T6, T7, T10, T11, and T12 (Figure 4C). This was because most of the P taken up in T2 were not translated into dry matter production compared with the treatments with CLB where most of the nutrients taken up were converted into dry matter yield [34]. Generally, total P uptake in T2 was similar to those of T4, T7, and T11 but significantly lower than that of T10 (Figure 4D). Treatment 10 showed the highest total P uptake because this treatment had the highest amounts of CLB and TSP. This suggests that T10 (combination of CLB and TSP) is the most suitable treatment that can improve maize plants growth and development on tropical acid soils. Figure 3: Effects of treatments on maize plants’ root at tasseling stage. (Note: T represents treatment and R represents replication). Figure 2: Effects of treatments on maize plants at tasseling stage. Iron uptake in leaves, stems, and roots of T1 were statistically lower than in other treatments due to the poor growth and development of maize plants (Figure 5A-C). Iron uptake in leaf and root of T2 was lower than those of T3, T4, T5, T7, T8, and T10 (Figure 5A,C). However, in stem, Fe uptake in T2 was statistically higher than the rest of the treatments (Figure 5B) and this was due to the higher  
Figure 4: Effects of treatments on P uptake of (**A**) leaves; (**B**) stems; (**C**) roots; and (**D**) total P uptake of maize at tasseling stage. Different letters indicate significant difference between means using [PERSON]’s HSD (Honestly Significant Difference) test at \(p\leq 0.05\). The error bars are the \(\pm\) standard error of triplicates. concentration of Fe in the maize plant biomass of T2 compared with the treatments with CLB. Generally, the total Fe uptake in T2 was not statistically different from those of T3 and T10 but higher than those of T1, T4, T5, T6, T7, T8, T9, T11, and T12 (Figure 5D). These results further confirm the liming effect of CLB and its ability to reduce concentrations of Fe and Al in the soil solution of tropical acid soils [35]. Figure 5: Effects of treatments on iron uptake of (**A**) leaves; (**B**) stems; (**C**) roots; and (**D**) total iron uptake of maize at tasseling stage. Different letters indicate significant difference between means using [PERSON]’s HSD (Honestly Significant Difference) test at \(p\leq 0.05\). The error bars are the \(\pm\) standard error of triplicates. With T1, the N, K, Ca, Na, and Mg taken up by the maize plants' leaves, stems, and roots were statistically lower than those of T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, and T12 (Tables 5-9) because of the inherent low fertility of Bekenu series [36; 37]. Amending tropical acid soils with biochar increases soil P and K availability [38; 39; 40]. In addition, biochar is not only able to reduce P fixation, but it also increases mineralization of nutrients such as N, release of K, and availability of Ca, Na, and Mg by complexing with organic radicals [41].