# Combined Application of Filter Cake and Macadamia Husk
## 3 Results and Discussions
### Effect of Soil Amendment on Soil Fertility
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c} \hline \hline
**Organatic** & **C** (cm) & **S** & **N** & **Ca** & **Mg** & **K** & **Na** & **Za** & **Ca** & **Mn (mg/kg)** & **Fe (mg/kg)** & **Fe (mg/kg)** & **Al (mg/kg)** & **Moisture** & **CN** \\
**Weites** & C (cm) & **(cm)** & **(cm)** & **(cm)** & **(cm)** & **(cm)** & **(cm)** & **(mg/kg)** & **(mg/kg)** & **Fe (mg/kg)** & **Fe (mg/kg)** & **Fe (cm)** & **Al (mg/kg)** & **Moisture** & **CN** & **Ratio** \\ \hline FC & 6.5 \(\pm\) 0.5\({}^{\circ}\) & 0.08 \(\pm\) 0.02\({}^{\circ}\) & 4.35 \(\pm\) 0.20\({}^{\circ}\) & 2.5 \(\pm\) 0.3\({}^{\circ}\) & 5.0 \(\pm\) 0.04\({}^{\circ}\) & 5.0 \(\pm\) 0.04\({}^{\circ}\) & 5.0 \(\pm\) 0.05\({}^{\circ}\) & 798 \(\pm\) 170 \({}^{\circ}\) & 20.8 \({}^{\circ}\) & 61.2 \(\pm\) 5.9\({}^{\circ}\) & 61.2 \(\pm\) 2.24\({}^{\circ}\) & 0.65 \(\pm\) 0.09\({}^{\circ}\) & 1692 \(\pm\) 160 \({}^{\circ}\) & 63.2 \(\pm\) 1.1\({}^{\circ}\) & 63.3 \({}^{\circ}\) \\ SMC & 51.2 \(\pm\) 0.4\({}^{\circ}\) & 0.04\({}^{\circ}\) & 0.04\({}^{\circ}\) & 0.17 \({}^{\circ}\) & 13.0 \(\pm\) 0.7\({}^{\circ}\) & 13.3 \(\pm\) 0.8\({}^{\circ}\) & 0.17 \(\pm\)From the above results of this study, FC+MHC was undoubtedly the best in terms of enhancing the growth and yield of both cultivars. This is noticeable in the following parameters: the production of more leaves, leaves with larger leaf areas (Table 4), and leaves with higher chlorophyll contents (Figure 1) when compared to the control. The factors that may have contributed to this may be the combined strength of the consortium of nutrients in both FC and MHC. While FC may have mineralized rapidly and provided the needed nutrients such as P and K at the early stages of plant growth, MHC may have mineralized later and supplied some critical minerals such as N and C (which had relatively low concentrations in filter cake) at the later stages of plant growth. Carbon plays a crucial role in photosynthesis as the primary source of energy. It is also a building block for plant nutrients such as starch, protein, and carbohydrate, which are very essential in sweet potato growth [38]. Nitrogen assists in cell division and the development of chlorophyll [38,39]. Earlier studies have suggested that filter cake mineralizes relatively rapidly while macadamia mineralization is very slow [18,20]. The FC+MHC treatment may have also benefited from the combined moisture contents of both filter cake and macadamia husk compost and their ability to hold soil moisture. The positive effect of filter cake on the soil and consequently plant growth has been reported to include increasing total porosity, cation exchange capacity, and water and nutrient retention capacities [40]. Dry matter partitioning is a function of the flow of assimilates from source organs such as leaves through a transport path to the sink organs such as storage roots in sweet potatoes [41, 42, 43]. In this study, the partitioning of dry matter to the storage root was enhanced by the FC+MHC treatment in the 199062.1 cultivar. In Beauregard, in addition to FC+MHC, dry matter partitioning to the root was also favored by all filter cake-related treatments (FC, FC+IF, and FC+MHC). In Beauregard, the root of the plants of the FC+MHC treatments constituted 80.8% of the total biomass; FC and FC+IF had 78.6 and 80.9% of their total biomass partitioned to the root, respectively (Figure 2). Also in 199062.1, partitioning of dry matter to the storage root was significant in FC+MHC and FC+IF treatments, accounting  
Figure 1: Effect of combined application of filter cake, macadamia husk compost, and other treatments on the chlorophyll content in the leaves of Beauregard and 199062.1 cultivars of orange-fleshed sweet potato. Each bar represents the average of the 6 chlorophyll content measurements taken per replicate and for the 3 replicates (\(n=18\)) at 10 weeks after planting. Bars with different letters for each cultivar were significantly (\(p<0.05\)) different. for 85.2 and 84% of the total biomasses, respectively.