Agricultural practice in the semi-arid region of Brazil is highly dependant on irrigation. As access to water is limited in the region, there is a need to guarantee its
efficient use, especially in small-scale farming schemes.
Models adequately calibrated for semi-arid conditions and
for typical crops are useful tools for analysis of on-farm
strategies to improve water use efficiency. A physically
based agrohydrological model, SALTMED, is calibrated
and validated for carrots (Daucus carota L., Brası´lia variety)and cabbage (Brassica oleracea var. capitata), two of the main crops in small-scale irrigated agriculture in the northeast of Brazil. SALTMED is also calibrated for castor beans (Ricinus communis L.) under rainfed conditions. The results demonstrated the suitability of the SALTMED model for simulating soil water dynamics and crop yield in the area. Predicted time series of soil water content and matric potential of root zone showed good agreement with observed values, as shown graphically and statistically.
Using the calibrated and validated model, management
scenarios were analysed in terms of applied irrigation
water, irrigation frequency, soil and crop types. Impact of
climate change on the irrigation water requirements was
also briefly analysed for possible changes in annual temperature using two different emission scenarios. Analysis
of possible impact of climate change on temperature
related to two emission scenarios on the area showed an
increase around 11% of the crop water requirement for
carrots and cabbage, for the low emission scenario, and
around 17% for the high emission scenario. The analysis of
management scenarios indicated possible over-irrigation in
the area. The simulation showed that the deficit irrigation
was a useful water-saving strategy for the region. The
simulations also indicated that irrigation frequency affected crop water use and differed according to the soil type
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