Slow and Controlled Release Nitrogen Fertilizers: Options for Improving Rice Productivity: A Review

Rice (Oryza sativa L.) is the most important food crop not only in Asia but also in the entire world. Over the past several decades, conventional fertilizer application for rice has caused the loss of nutrients, which could lead to a series of environmental problems such as eutrophication and greenhouse effects. The emergence of slow and controlled-release fertilizers provides a new option for more efficient fertilization of rice. International Fertilizer Association (IFA) included controlled release fertilizers (CRFs), slow release fertilizers (SRFs), sulphur coated urea (SCU), stabilized nitrogen fertilizers (SNFs), WSFs, liquid NPKs, and chelated micronutrients and boron in their assessment study of the global market for special products. In India, the specialty fertilizers are categorized broadly as water soluble fertilizers, neem coated urea, fortified fertilizers, customized fertilizers (CFs), micronutrient fertilizers, and liquid fertilizers. Controlled-release fertilizers, such as sulphur and/or resin coated urea, can reduce N losses (e.g. nitrogen leaching, ammonia volatilization), while increasing N availability in plant and enhance rice grain yield upto 22.1% in rice. These, slow release controlled fertilizer increase crop yields by maintaining soil health over time.