## 1 Introduction  
Asian countries grow rice (_Oryza sativa_ L.) in a huge accage, where the production and consumption is the highest. Rice is cultivated in different diverse ecosystems, and irrigated lowland rice is the most important rice ecosystem in Malaysia [1]. Rice production in Malaysia is the highest at the irrigated lowland rice system because it is more economical and reliable. Although rice growers prefer irrigated lowland system for rice production, there are many arising problems in rice fields, such as increased fertilizer application rate due to volatilization or leaching of nitrogen (N), which leads to poor rice crop growth [2, 3]. Plants need N the most during the vegetative stage for proper growth and cell division, but the volatilization of N from applied urea fertilizer reduces the availability of N in the soil. To overcome the deficiency of N in the soil, rice growers tend to add excessive and unreasonable amounts of inorganic fertilizer, which adversely affect the quality of the environment [4]. These practices do not only waste the fertilizer and degrade nature, but are also costly. Major N loss from applied urea in irrigated lowland rice systems is due to the adoption of the surface applied method [5]. Due to surface application, immediately upon contact with water, urea hydrolyses and is lost through ammonia (NH3) volatilization [6]. It also agreed that a main pathway of applied N loss in cropping systems is through NH3 volatilization [7]. The urea-N volatilization process needs to be minimized in the agricultural field in order to increase the rice plant N uptake and yield. Agricultural waste can be used since it is cost effective, renewable, and abundant [8]. Rice residues such as rice straw and rice husk are one of the agricultural wastes that can be found in abundance and are being burnt to avoid excessive accumulation. One promising management approach is to convert the agricultural wastes into biochar. Recently, there has been much renewed interest in using biochar in the agricultural field as a soil ameliorant [9]. Turning rice residues to biochar can reduce the wastage problem and environmental pollution. Biochar as an organic amendment offers a wide variety of benefits to the soil environment. It is a carbon-rich product obtained from wood, paper, manure, or wheat straw burned in a pyrolyzed condition [10]. [PERSON] et al. [11] stated that biochar enhances soil nutrient retention, which overall reduces the total fertilizer requirements in agricultural soil. Further, a study by [PERSON] et al. [12] concluded that biochar has a large surface area and numerous pores which aids in ions' adsorption capacity. These properties of biochar might increase the retention of ammonium (NH4+) and nitrate (NO3-) in soil [13]. Retention of NH4+ and nitrate NO3- in soil is crucial for plant uptake and utilization. Further, biochar has a higher cation exchange capacity (CEC) value which further aids in more nutrient retention and increases its potential to be an adsorptive agent [14]. Biochar application reduces NH3 volatilization successfully and retains more nutrients in soil. Previously, rice husk biochar had been used for C sequestration and to minimize greenhouse gas emission in rice fields [15]. Rice fields are known as a major source of atmospheric greenhouse emission. [PERSON] et al. [16] stated that rice straw and rice husk conversion into biochar and its application reduced methane gas emission in the rice cultivation area. Much research has been conducted in rice fields by using biochar for C sequestration and climate mitigation, but there is little research on soil amendments. Hence, there is a need to know the efficacy of rice straw and rice husk biochar on soil quality improvements. There is also a scarcity of information and research in amending rice straw and rice husk biochars with the soil to minimize NH3 loss in the agricultural field.