Grapevine agronomic responses to different water regimes south of Tunisia

Abstract

Water scarcity is a limiting factor for agricultural development. Accordingly, the improvement of its efficiency is indispensable through the application of adequate irrigation strategies including deficit irrigation. In this context this work was undertaken. A field experiment have been carried out in Beni Khdache, south of Tunisia on grapevines to evaluate the agronomic responses, in terms of crop development, yield, yield quality and water productivity, under different water regimes. The first treatment (T100) consisted in delivering to the crop 100% of the ETc. The other two treatments (T75 and T50) consisted in delivering only 75 and 50% of the total real needs of the crop respectively. The fourth treatment (T0) was irrigated according to the farmer's recommendations. The results show a significant effect of the deficit irrigation on the vegetative growth of the grapevines in terms of berry weight. This difference had later a significant impact on the final yield. The highest yield (14t/ha) was found with full irrigation (T100). The farmer's method led to a significant drop in yield (40%) compared to the full irrigation treatment. Trees under water deficit (T75, T50) responded with an accumulation of sugars (17.3 °Brix and 16.8° Brix respectively) and a slight decrease in fruit acidity (3.9 and 3.8 respectively) compared to the T100 treatment (15°Brix,4) .  The difference in irrigation water productivity of the grapevines obtained with the deficit irrigation treatments (T75, T50) is not significant compared to that of T100.  The low water productivity was observed for the T0 and T75 treatments (1.9kg/m3 and 2.4 kg/ m3 respectively), while the highest values were obtained with the T50 and T100 treatments (2.8 kg/m3 and 2.6 kg/m3). These results indicate that full irrigation (T100) seems to be an adequate irrigation strategy for grapevine production under Tunisian arid conditions. Under water scarcity conditions, deficit irrigation with a 25% reduction in inputs (T75) is recommended for grapevine management. The T75 deficit irrigation treatment allows to save large amounts of irrigation water (25%) and to improve water productivity but accepting a certain yield drop.Keywords: Full irrigation, deficit irrigation, grapevine, yield, water productivity, arid environment, farmer's practices