Rice

Rice (Oryza sativa L.) is one of the main staple food, which is feeding more than half of the world population. It is cultivating in more than hundred countries, mostly in Asia. Rice supply 21 percentage of energy and 15 percent of protein need of human populations worldwide. It has been estimated that world population increasing about ten billion via the end of current century, thus an enhance in production of rice per unit area is strongly needed (Lal, 2009; Depar, Rajpar, Memon, & Imtiaz, 2011; Rehman et al., 2012; Farooq et al., 2018).
Nowadays, agricultural inputs including pesticides, irrigation, seeds and fertilizers have been put in the field, but sometimes the yield is different across the field at the end of the cultivating season. Soil texture, subsoil characteristics, organic matter, water holding capacity, and salinity alteration are all factors that may effect on the plant performance. Presumably, it may be rather economical to add various amounts of agricultural inputs to parts of the field that have various soil (Chan, Amin, Lee, & Mohammud, 2006). Problem soils consist of essential plant nutrients deficiency or minerals toxicity are widespread worldwide and seriously constraining production of rice. These problem soils embrace a significant proportion of rice production zone, that invariably affiliated with poverty owing to low and unstable productivity (Ismail, Heuer, Thomson, & Wissuwa, 2007). Moreover, balanced providing of micro and macronutrients is essential for filling yield gap. After nitrogen, phosphorus and potassium, prevalent zinc (Zn) deficiency is one of the impactful nutrition on rice yield (Fageria, Baligar, & Clark, 2002; Quijano-Guerta, Kirk, Portugal, Bartolome, & McLaren, 2002). Generally, different factors, consisting intensive of salts toxicity or elements like aluminum, heavy metals, and iron, also deficiency in other essential nutrients, including zinc, iron, and phosphorus has negatively effect on agricultural productivity (Ismail & Thomson, 2011) farmers only adding micronutrients once deficiency symptoms appear, while micronutrient deficiencies reduce yields before the appearance of symptoms (Das, 2014) Micronutrient deficiencies has become a main nutritional problem influencing many people in the developing countries.
Micronutrient does not mean that they are not important to plants than other nutrients. Growing and developing of plant may be delayed if any of these elements are missing in the soil or is not suitable balanced with other nutrients. Two sources of available micronutrients exist in soil: nutrients that are uptake onto soil colloids and salts dissolving form of nutrients in the soil solution. In addition, secondary momentous source of some micronutrients is organic matter. Most micronutrients are held solidly in complex natural mixes and can’t be promptly accessible to plants. In spite of the fact that, they might be pivotal wellspring of micronutrients once they are released to a plant available form as organic matter disintegrate (Das, 2014). Rice is capable to accumulate high levels of metal between the cereal crop, consisting Fe, Al, and Zn. These metals are naturally existed at very low amounts in paddy soils, but acidity or concentration of phytotoxic ion will be increased in long term using of chemical fertilizers (Meng et al., 2017). Multiple abiotic stresses tolerance like P and Zn deficiencies and Fe and Al toxicities includes an overflow of complicated characters, and this multifaceted nature has unfavorably impact on past breeding endeavors for high yielding varieties by satisfactory adaptation to such stress conditions (Ismail et al., 2007). To screen metal tolerance, hydroponic systems is an effective approach because environmental factors are well controlled (Marmiroli et al., 2011). Moreover, leaf color, growth rate, and the expanse of plant injury are measuring to screen the metal sensitivity at the seedling (Audebert ; Fofana, 2009; Meng et al., 2017).
These challenges forced researchers to seek for the novel approaches to make better progress on the adaptively to the deficiencies and toxicities of the rice growing area. Recent improvements in breeding methods such as genomics and molecular marker techniques, likewise powerful phenotyping approaches have made it conceivable to perceive the hereditary determinants of complicated characters related to the stress resistance, fuse these versatile attributes to high yielding rice cultivars. At the same time, maintaining their quality and good agronomic attributes. This review will concentrate on nutritional deficiencies (P and Zn) and toxicities (Al and Fe) as the important problems in rice soils. We will briefly discuss the nutrition management such as application methods and the source of fertilizer, also recent understanding of the genetic bases of tolerance, development, and efforts to cope with the rice soil problems.