This, with alluvial or enriched soil, enables substantial yield grain farming in areas with good soil. Rivers have been successfully dammed particularly flowing from relief precipitation areas (high emininences) and those from the edge of the Great Rift Valley, such as the Zambezi, well within the Tropics. In most of this belt of southern Africa, a minimum of seasonal rainfall is reliable and farming is possible, though yields struggle to compete with for example the Mississippi basin, even against like-to-like soil fertilisers. During the December solstice (Southern Hemisphere summer), there are 13 hours, 35 minutes of daylight. There are approximately 10 hours, 41 minutes of daylight during the June solstice (Southern Hemisphere winter). See under circles of latitude for information.
Therefore, distance between Arctic Circle and Tropic of Capricorn is essentially constant moving in tandem. This wobble means that the Tropic of Capricorn is currently drifting northward at a rate of almost half an arcsecond (0.468″) of latitude, or 15 metres, per year (it was at exactly 23° 27′S in 1917 and will be at 23° 26'S in 2045). Earth's axial tilt varies over a 41,000 year period from 22.1 to 24.5 degrees and currently resides at about 23.4 degrees. The Tropic of Capricorn's position is not fixed, but constantly changes because of a slight wobble in the Earth's longitudinal alignment relative to its orbit around the Sun. The Northern Hemisphere equivalent of the Tropic of Capricorn is the Tropic of Cancer. The Tropic of Capricorn is the dividing line between the Southern Temperate Zone to the south and the tropics to the north. (Due to the precession of the equinoxes the Sun currently appears in Sagittarius at this solstice.) This is the date each year when the Sun reaches zenith at this latitude, the southernmost latitude it reaches for the year.
When this line of latitude was named in the last centuries BC, the Sun was in the constellation Capricornus at the December solstice.
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