UNRAVELLING CROP WATER PRODUCTIVITY OF TEF (ERAGROSTIS TEF (ZUCC.) TROTTER) THROUGH AQUACROP IN NORTHERN ETHIOPIA

Abstract

At various locations in North Ethiopia (Tigray), field experiments were conducted from 2006 to 2009 to assess the crop response to water stress of tef (Eragrostis tef (Zucc.) Trotter) under rainfed, fully irrigated and deficit irrigation conditions. Observed soil water content (SWC), canopy cover (CC), biomass production (B) and final grain yield (Y) were used to calibrate and validate AquaCrop for tef. Data from an experiment in a controlled environment in 2008 were also considered in the calibration process. Simulations of SWC, CC, B and Y were evaluated by determining the index of agreement, the root mean square error, the coefficient of determination and the Nash-Sutcliffe efficiency. The statistical parameters showed an adequate fit between observations and simulations. The model was able to simulate for tef growing under rainfed condition the observed fast drop in SWC and CC when the rains ceased. The overall goodness of fit between the observed and simulated CC and SWC indicated that the thresholds for root zone depletion at which water stress (i) affects canopy development, (ii) induces stomata closure and (iii) triggers early canopy senescence were well selected. The normalised biomass water productivity (WP * ) for tef was 14 g m −2 for the local variety and 21 g m −2 for the improved variety, which is a lot smaller than the WP * expected for C 4 plants (30-35 g m −2 ). The results revealed an increase of 27% in reference harvest index (HIo) of tef in response to mild water stress during the yield formation of up to 33%. However, severe water stress causing stomata closure had a negative effect on HIo. Once it is properly calibrated, AquaCrop can provide room to improve the water productivity of tef by developing guidelines for good agricultural management strategies.

Performance of Tef [Eragrostis tef (Zucc.) Trotter] Genotypes for Yield and Yield Components Under Drought‐Stressed and Non‐Stressed Conditions

“…Wide genetic diversity for different traits in tef has been reported previously (Assefa et al, 1999(Assefa et al, , 2001Ayalew et al, 2011;Plaza-Wuthrich et al, 2013), in assessments conducted under optimal conditions. However, some tef growing areas of Ethiopia, especially in the northern regions, frequently experience drought stress during the grain-filling periods of tef, that is, in September to November, which leads to significant reductions in tef yields (Tsegay et al, 2012). They also pointed out that the late maturing and tall tef varieties develop deeper root systems, making them more drought tolerant.…”

“…They also pointed out that the late maturing and tall tef varieties develop deeper root systems, making them more drought tolerant. However, some tef growing areas of Ethiopia, especially in the northern regions, frequently experience drought stress during the grain-filling periods of tef, that is, in September to November, which leads to significant reductions in tef yields (Tsegay et al, 2012). Their studies only evaluated a limited number of genotypes, and under greenhouse conditions.…”

A Crop Simulation Model for Tef (Eragrostis tef (Zucc.) Trotter)

“…The DSSAT-Tef model's grain yield RMSE was comparable to the two existing tef models, but the model overestimated biomass production more than the other two models [12,13,17,18]. The FAO-AEZ tef model was applied at 13 locations [12].…”

“…The FAO-AEZ grain yield RMSE was 402 kg/ha (rRMSE 29.1%). The FAO-AquaCrop tef model has been tested at multiple locations in multiple papers [13,17,18]. The AquaCrop final biomass RMSE ranged from 466 kg/ha to 720 kg/ha (rRMSE 23.6%) [13,18].…”

“…This limits its application in Ethiopia, where soil degradation [15] and low levels of fertilizer use [16] cause nutrient limited growing conditions. In addition, the AquaCrop tef model was not developed to take differences in daylength into account [1,13,[17][18][19], limiting its application to low latitudes.…”