Title: Combined effect of organic and inorganic fertilizers on growth of rice plants

Rice is one of the most important staple cereal foods in human nutrition and a major food grain for about 75% of the world’s population. Rice has become a major staple food in Ghana, being the second most important cereal crop after corn. Inorganic, organic and bio fertilizers are the main plant nutrient sources for replenishing agricultural soils. In this study the effect of compost as an organic fertilizer and NPK inorganic fertilizer was evaluated on the growth of rice plants. The experiment was conducted in pots in a greenhouse environment at Gunnarsholt, Iceland, during the 2019 growing season. The major objective was to evaluate the effect of compost as an organic fertilizer and NPK as an inorganic fertilizer used in the growing of rice varieties. The experiment was laid out in a 3 × 4 factorial design with the levels of fertilizers at the full rate of inorganic fertilizer (NPK 90 60 60 kg/ha), compost 12 t/ha, ½ (compost 12 t/ha) + ½ (inorganic fertilizer) and control. The three rice varieties were APO, IR 55419 and UPL R1 7. The full rate of inorganic fertilizer NPK 90 60 60 kg/ha was used as a check for comparison. Results collected at 7 and 9 weeks after planting showed that varieties and fertilizer levels had a positive influence on plant height. The leaf chlorophyll at 9 weeks after planting also responded positively to fertilizer level and varieties, whereas root length was influenced only by varieties. Plant dry biomass did not respond to the fertilizer treatments. A significant difference was obtained between the control, inorganic and organic fertilizers as well as between the APO and IR 55419 varieties. It can be concluded from the findings that use of a quality rice variety and the application of compost, sole or as a complement to chemical fertilizer, has the potential of producing a high yield compared to a full rate of inorganic fertilizer.