Conservation agriculture Tanzania_casestudy.pdf - Sokoine ...

in private ownership still cultivate the cash crop on the hills and valleys outside oftown.ClimateRainfallRainfall in the district is bimodal; the short rains fall between October andDecember and the long rains (‘masika’) between March and June (KDC 2001)(table 1). Rainfall may range from less than 400 mm in the Eyasi Basin to over 1000mm in the highlands with rain zones classified as semi-arid (300–700 mm/year) andsubhumid (700–1200 mm/year) respectively. The wettest month is April. Rainfallvaries considerably between years, especially in the semi-arid region, where thecoefficient of variation of annual rainfall is 30–40% (Meindertsman and Kessler1997). Duration and intensity of individual storms are unpredictable. Rainfallintensity can be very high, causing erosion, particularly at the onset of the rainyseason when soils are bare.Humidity and evapotraspirationRelative air humidity increases during the rainy months from about 55% inOctober to about 75% in April/May (Meindertsman and Kessler 1997). Potentialevapotranspiration measured at Karatu is about 1440 mm per year (average 120mm per month). Evapotranspiration generally increases during the dry season,reaching a maximum in November just before the rains start. It is lowest at the endof the rainy season in May.Table 1. Rainfall data (mm) 2000–2005MonthYear2000 2001 2002 2003 2040 2005January — 149.3 124.6 18.7 65.9 37.5February 25 48.8 126.3 14.2 26.3 48.4March 90.6 148.9 115.5 104 54.7 67.2April 94.4 180.6 222.5 20.9 124 38.8May 4.0 30.1 89.3 137 3.9 27.7June — 4.4 — 1.1 2.5 1.1July — 3.5 — 1.0 — 1.5August — — 9.1 — — 1.5September — — 18.5 — — —October — 6.4 62.5 14.2 53.6 40.7November 31.5 67.9 24.4 61.7 68.0 22.4December 10.5 171.2 15.3 42.7 198.5 3.9Total 256.0 811.1 808.0 415.5 597.4 320.7Karatu District 61