The largest agricultural areas in the world are in North America, Euro-Asia, and Central South America. However, agriculture in tropical and temperate climates is very different, mainly because of the environmental conditions. Unlike in temperate climates, there are not four seasons in the tropics. The tropics have only two seasons, rainy and dry, with plants flowering all year round because air temperatures are not too low in the winter, and crops can grow during this season; thus, some crops may have three cycles per year in the tropics. In most temperate climates, there is only one crop cycle per year due to low winter temperatures, but the yield can be the highest. The low temperatures of a temperate climate, below 0°C, allow soils to be shallow, with high organic matter content and fertility because soil microbial activity and lixiviation are arrested at such temperatures, and organic matter is less degraded than in tropical soils where soil microorganisms and lixiviation continue throughout the year. As a result, yields of major crops in temperate climates are the highest in the world, confirming the efficiency of temperate agriculture, even with only one crop cycle per year. On the other hand, in tropical climates, yields are lower, but crops can be grown several times a year, thus increasing the annual production.