Asia has the largest percentage of rice on good soils (47%) whereas rice production on good soils is much less common in the Americas (28%) and accounts for only 18% in Africa. The most common soil chemical problems in rice fields are very low inherent nutrient status (35.8 million ha), very low pH (27.1 million ha), and high P fixation (8.1 million ha); widespread soil physical problems especially severe in rainfed environments are very shallow soils and low water-holding capacity.