Climate and Growing Season Precipitation


Like temperature, precipitation in the Rufiji Basin closely correlates with elevation. The higher elevation areas receive over 1,000 mm per growing (rainy) season from December to May, whereas the lower elevation areas can receive less than 500 mm per season.

Rice is demanding of water, requiring substantially more than other grain crops grown in Tanzania. Although it does not require continuously saturated soil, it grows poorly if water stressed particularly during the transplanting and reproductive stages. Much of the rice grown in the Rufiji Basin is under rainfed conditions with minimal irrigation, so precipitation amounts and timing are important. Depending on the variety, it can require between 450 and 700 mm during its growing season, or between 900 to 2,250 mm/day.

Water requirements for maize vary greatly depending on variety, soil type and temperature, but generally it does best between 500 to 800 mm/growing season. However, yields are very sensitive to water deficits during the flowering period. Severe water deficits during silking and pollination may lead to little or no yield. Farmers have noticed an increase in the length and frequency of dry spells in the season, and this could threaten yields. Other changes in precipitation, particularly in growing season onset and length, are also affecting successful planting, growth and yield.


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