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Research
Trends of
Productivity of Water in Rainfed Agriculture - Historical Perspective
by Henry E. Igbadun, Henry F. Mahoo, Andrew K.P.R. Tarimo
In Sub-Sahara Africa, rain-fed
agriculture is the dominant source of food production. It is likely
going to remain so for the next foreseeable future. However, yields
from rain-fed agriculture are often very low. But there is an enormous
opportunity to raise crop yield of rain-fed agriculture especially by
focusing on the aspect of increasing productivity of water. In order
to formulate and adopt appropriate and adequate options for increasing
productivity of water in rain-fed agriculture, there is a need to have
an historical hindsight to the trend of productivity of water in
rain-fed agriculture. In this paper, a historical analysis of the
trend of productivity of water (PW) for five crops cultivated under
rain-fed condition in Mbarali District, Mbeya Region, Tanzania, was
carried out using secondary data. The crops include: maize, sorghum,
beans, potato, and groundnut. The PW (rainfall) for maize, sorghum,
potato, beans, and groundnut had peak values of 0.49kg/m3 in 1993/94,
0.47 kg/m3 in 1994/5, 3.06kg/m3 in 1993/94, 0.33kg/m3 in 1996/97, and
0.20kg/m3 in 1994/95 cropping seasons, respectively.
Evapotranspiration deficit occasioned by either mid cropping-season
dry spell or early cessation of rainfall and low rainfall utilization
efficiency are the primary drivers of PW in rainfed agriculture in the
area. Other factors that are usually put forward by agricultural
stakeholders in the region, which include poor soil nutrient and lack
of proper crop management, are secondary and could be considered as
spill over effects from these primary drivers of PW.
Key Words: Productivity of water,
crop yield, crop water requirement, evapo-transpiration deficit
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