Effect of Different Types of Fertilizer Application on the Soil Fertility of Oil Palm Reclamation Soil under Polyculture System

To evaluate the effect of different fertilizer application on soil fertility under polyculture cropping system (okra, water spinach and yard long bean), a field experiment was conducted in the oil palm reclamation soil at the research farm in ICA UTM-Pagoh. There were five treatments involved which were: (T1) no fertilizer, (T2) organic fertilizer, (T3) inorganic fertilizer, (T4) organic inorganic compound fertilizer and (T5) organic + inorganic fertilizer.  The initial and final soil samples were collected to study the effect of different types of commercial fertilizer application on soil pH, electrical conductivity (EC), moisture content, soil organic carbon (SOC), total nitrogen (TN), C/N ratio, soil organic matter (SOM), bulk density and nutrients (P and K) contents in the soil surface layer (0–15 cm) of the experimented site for 14 weeks. Results showed that the soil pH was the lowest with an average of 6.05 units in T5 and was significantly higher in T1 (8.23 units). The EC value in T5 is the highest with 172.4 ds/m and lowest in T1 with an average of 25.5 ds/m. T5 showed the highest soil moisture and soil organic matter with 15.81% and 4.01% respectively. The combine application of organic and inorganic fertilizers has increased SOC and TN values compared with the T1 (control) specifically, which resulted in 3.7% and 0.33% of SOC and TN concentrations, respectively (). Bulk density showed no significant different among all the treatment with the highest value was in T4 (1.22g/cm3) and lowest in T3(1.05g/cm3). The average amounts of C/N ratio ranged from 11.11 to 13.60 between all treatments with the highest ratio in T4 (13.6). The average P and K contents were highest in T5 (1564.7 mg/kg and 1056.2 mg/kg). Thus, it showed that the application with the mixture of organic and inorganic fertilizer (T5) improved the soil condition.