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Aims: This study was conducted to formulate appropriate fertilization scheme for some rice varieties used at University Income Generating Project (UIGP) sites of Central Mindanao University (CMU), Philippines and to determine the effects of organic and inorganic fertilizers on some soil chemical properties.
Study Design: Split-plot in Randomized Complete Block Design (RCBD) in three replications with 5 levels of inorganic and organic fertilizers as main plot factor and 3 rice varieties as sub-plot factor.
Place and Duration of Study: UIGP area of CMU, Musuan, Bukidnon, the Philippines from November 2015 to May 2016.
Methodology: Plots were laid out following Split-plot in RCBD in 3 replications. The 5 levels of Fertilizers were: no fertilizer (control), 90-60-60 kg NPK/ha, 2t vermicompost/ha, 45-30-30 kg NPK/ha + 2t vermicompost/ha and 90-60-60kg NPK/ha + 2t vermicompost/ha while the three rice varieties were: Matatag 11, NSIC Rc158 and NSIC Rc238. The initial characteristics of the soil served as the basis for the recommended rate of inorganic fertilizer application at 90-60-60 kg NPK/ha.
Results: Analysis of variance showed that interaction between the levels of fertilizers and varieties were not significant for all agronomic and yield parameters except the number of days to 50% flowering implying that the varieties had a similar response to the levels of fertilizers. Results revealed that the levels of fertilizers significantly affected plant height at 30 (P = 0.011) and at 50 days after transplanting, DAT (P = 0.006), productive tiller count (P = 0.002), % filled grains (P = 0.026), and grain yield (P = 0.003) while the varieties significantly differed in plant height at 50 DAT (P = 0.006), number of days to 50% (P = 0.001) and 100% flowering (P = 0.001), % filled grains (P = 0.039), 1,000 grain weight (P = 0.009) and grain yield (P = 0.044). When averaged across varieties, grain yields were increased by fertilizer application with 90-60-60 + 2t vermicompost/ha giving significant increase of 2.14 t/ha (vs control) and 90-60-60 kg NPK/ha, 2t vermicompost/ha, and 45-30-30 + 2t vermicompost/ha giving not significant increases of 1.26, 0.36 and 1.05 t/ha, respectively. NSIC Rc238 had the highest grain yield that was significantly higher than that of NSIC Rc158 but not with that of Matatag 11. Moreover, soil pH, organic matter and extractable phosphorus (P) contents of the experimental plots after harvest were significantly influenced by vermicompost and inorganic fertilizer application (P = 0.01) with plots applied with vermicompost exhibiting significantly higher pH values and organic matter contents compared to those plots with no fertilizer and those applied with inorganic fertilizers alone.
Conclusion: Findings of the study disclosed that vermicompost is an effective organic amendment to improve soil pH, soil organic matter content and rice productivity in Maapag soil and its application at 2t/ha in combination with 90-60-60 kg NPK/ha gave the highest grain yields of Matatag, NSIC Rc158 and NSIC Rc238 at 6.23, 6.10 and 6.75 t/ha, respectively that were higher than their average yields but lower than their maximum yields.