Deficit Irrigation Using Saline Water of Fruit Trees under Water Scarcity Conditions of Southern Tunisia

Fathia El Mokh,Mohamed Moncef Masmoudi,Netij Ben Mechlia,Giorgio Ghiglieri,Kamel Nagaz

doi:10.3390/atmos12070864

Fathia El Mokh, Mohamed Moncef Masmoudi + Show 3 more

Open Access

https://doi.org/10.3390/atmos12070864

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Abstract

Both water scarcity and salinity are major obstacles for crop production in arid parts of Tunisia and require adoption of strategies aimed at improving water-use efficiency. Field experiments on deficit irrigation (DI) of table olive, orange trees, and grapevines with saline water (2 dS·m−1) were conducted in the arid region of Médenine, Tunisia. Three irrigation treatments were compared with the farmer’s method (FM) over two years (2013–2014): deficit irrigation (DI75) and (DI50), which received 75% and 50% less water than full irrigation (FI), respectively, and full compensation of the crop evapotranspiration (FI). Measurements included seasonal changes in soil water content, soil salinity, yield, fruit quality, and economic return. Results showed that in-season water limitations, roughly between 700–250 mm, caused significant reductions in yield and fruit weight, but improved the total soluble solids of fruits. Under FI, DI75, DI50, and FM, average yields were 26.6, 20.1, 14.7, and 21.2 t·ha−1 for orange, 4.5, 4.0, 3.1, and 3.5 t·ha−1 for table olive, and 3.8, 3.4, 3.1, and 3.5 t·ha−1 for grapevine, respectively. Soil salinity build up increased linearly with decreasing irrigation water. Irrigation water productivity (IWP), although lowest for FM, was relatively high (3.30–4.30 kg·m−3 for orange, 0.65–1.20 kg·m−3 for table olive, and 0.74–1.30 kg·m−3 for grapevine). Economic evaluation showed that the FI strategy generated the greatest net income (1800–6630 USD·ha−1), followed by DI75 (1350–3940 USD·ha−1), FM (844–4340 USD·ha−1), and DI50 (600–2400 USD·ha−1). The results show an important potential for reasonably sustaining farmer’s income under increased water scarcity.

Highlights

Water scarcity is the main factor limiting agricultural production in arid regions
An irrigation of 80 mm was applied each year in April and February to orange and table olive trees in order to refill the root zone and start with a soil at field capacity in the root zone, and irrigation continued until the end of December with amounts estimated by the FAO-56 method and delivered on a weekly basis
This study showed that irrigation water quantity applied by farmers in orange, table olive, and grapevines orchards using empirical knowledge and fixed amounts and frequency was lower than needed according to the FAO-56 method

Summary

Introduction

Water scarcity is the main factor limiting agricultural production in arid regions. In this context, adaptation strategies to increasing water scarcity must be developed and adopted by farmers in order to optimize the use of limited water resources [1]. Deficit irrigation (DI) scheduling, considered as an interesting and sustainable production practice for arid regions [2,3], reduces tree water consumption without a harmful impact on crop productivity [4] and allows improvement of water productivity for higher yields per unit of evapotranspired (ET) or applied irrigation water [2,4,5,6,7]. DI of fruit trees seems to be a relevant choice in Mediterranean semi-arid agro-systems for currently cultivated fruit crops with higher water requirements [9]

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