Tanzania Journal of Agricultural Sciences 2000, Vol. 3(2): 157 - 164
A Stll(~Vli'as underiaken fo find out the cause'o/poorper/ormance o/maize in some parts o/l\Iorogoro
DistriCt, Tmizania,.Rain/all (R) and Refori?l1ce crop evapotranspiration.(ETo) data were organized on
1 O-daybasis/ara periodo/20yearsfrom1974 to 1993. Correspondingvalueso/the two parametersJor
each I O-dayperiod were thenl1latchedandllsed to determine the duration 0/ rain seasons; ,apprqpria(e
plantini'dates and to detect the occurrence o/dr.Y spells. Findings indicate that, long rains are marked by
a period o/illoistllre sUfficiency (R> ETo) lasting 60 days beginning Afarch 12''' . .The average long-term
raiiifaltamount during long rains 'is 360mm, which.is inadequate for optimum yields for late maturi[1g
eilltivfirs a/maize, Storage a/surplus moisture in the profile lVould extend the period o//l~OistlireSl![ficienc,
v by 20 da:vs during long rains, However, this is unlike~v because soils are coarse textured and low in
organic matter. Further lilOre, pooragronomic practices encourage the loss o/up 30% o/rainwater as
runoff. Short rains 'are characterized by a period 0/ general increase in the suppZv o/moisture beginning
Novemberj 71
" reaching a peak in December. During the entire short rain season, rains do not aUaina
level o/sufficiency (RiETo 1) in any o/theten da:vperiods. Thus, moisture supp~v for the crop is sufficienl
during long rains bllton~v to short maturing maize cultimr Kilo/Katumani., There is a deficit in the suppZv
o/moisture throughout the short rains ruling Qilt a sliccess/ul production 0/ a maize crop. The current
study has however failed-to detect the freql1ent~v experienced dry spells (during long rains) which adverseZv'dffoct
the maize crop. On the strength 0/ the results obtained, the /ollowing can be concluded.
During short rains: neither short (Kilo/Karuman;) nor long maturing (Staha/]Ionga Composite) mai;e
cuTtivars'can He successJulZv grown. Short maturing Kito; Katumani is recommended/or planting during
long1ailis instead o/Stahalllonga:Composite as is current~v practiced. Dry planting should be done be!
ore-lUarch, .] (J" so as to make /ull use o/the first rains.