Land suitability evaluation for the production of the major crops in the southwestern part of the Uluguru Mountains, Morogoro rural district, Tanzania

Abstract

Land evaluation study was conducted on the southwestern slopes of the Uluguru Mountains in Morogoro Rural District, Tanzania to assess the potentials and constraints of the various land units for the production of low input rainfed cabbage, round potato and arabica coffee. The study area is located between latitudes 7 o 0000 and 7 o 1123.5S and longitudes 37 o 3000 and 37 o 3836.6E covering the villages of Kibaoni, Langali, Bunduki, Bumu, Kikeo, Luale, Mwarazi, Nyandira, Kibuko and Tchenzema. The areal extent is 419.64 km 2 (41,964 ha) with an average elevation ranging between 900 - 2700 m a.s.l. The mean annual rainfall in the study area ranges from 1065 mm to 2450 mm. The rainfall distribution pattern is monomodal with the rainy season starting from December to May. The peak rainfall occurs in April in most places of the study area. The high altitude areas receive more rainfall than the lower areas. In some areas rainfall distribution tends more to be bimodal with two peaks occurring in October and in April. There is considerable temperature variability in the study area with the mean monthly temperature ranging from 17.4 o C (July) to 22.4 o C (December). At high elevations temperatures are much cooler. The shortest reference length of growing period is 180 days while the longest is 270 days. The geology of the study area consists of a mixture of banded pyroxene granulites with occasional biotite-rich bands, foliated mica gneisses, hornblende gneisses and granulites and some iron-rich meta-anorthositic rocks, all belonging to the Usagaran system. In some places alluvial deposits and kaolinitic clays of Neogene age are found. The study area consists of strongly dissected mountains with very steep plateau and ridge slopes of about 30-60% and narrow valleys and incisions. Lukwangule plateau is the highest peak in the study area reaching an altitude of 2,623 m a.s.l. The Lukwangule plateau is only slightly dissected and the surface forms quite a mature relief. Two distinct drainage patterns exist in the study area. A sub-radial pattern which is related to the horse-shoe of high mountains from Mkumbaku through Lukwangule and Magari to Lupanga, which is currently represented by some of the larger rivers such as Mngazi, Mbakana and, in part, the Mgeta. A rectilinear pattern is exhibited where secondary streams and many main rivers show adjustment to geological structure and rock type. The pattern of the minor rivers follows the geological structure more closely and has resulted in river capture, reversed drainage and wind gaps. The edge of the meta-anorthosite is marked by the Mgeta, Mfunesi and Lukangazi river valleys for about two-thirds of its circumference, and this weakness is presumably the cause of the spiral course of the Mgeta River as it cuts back along the junction of rocks, capturing successively all the radial drainage from the north and west of the high level plateaux.