Mohamed Moncef Masmoudi’s research while affiliated with University of Carthage and other places

Distribution of soil salinity in the root zone of peach trees after six years of deficit irrigation This study concerns soil salinization in the root zone of irrigated peach trees subjected to deficit irrigation during six years with waters having a total dissolved salts of 1.4 g/l. The experiment was carried out in a commercial orchard located in the Mornag region. It is planted with the late producing peach variety "Carnival" and equipped with a drip irrigation system. Two irrigation regimes were used for six years. The farmer's regime, supposed to cover the crop water requirement, is taken as control. The second regime consisted of 33 % less water. During this experiment, August 2001-September 2002, a large number of soil samples have been taken from the top 80 cm layer at different dates for determination of soil moisture and the electric conductivity of the extract of the saturated paste. Spatial distribution of soil water content and soil salinity were derived from point values by Kriging. Average values of salinity and moisture for each stratum of the soil within the 80 cm top layer were calculated. In addition, a salt balance have been established. The average soil salinity varied between 1.1 to 1.74 g.l-1 during this period. Lowest values of soil salinity were observed during spring. With total precipitation of only 330 mm, irrigation during the study period was respectively 1041 and 695 mm for the control and the deficit regime. Reducing water supply by 33 % did not affect natural leaching since both treatments showed similar salinity levels. Total salt added was respectively 12.5 t.ha-1 and 8.3 t.ha-1 for the control and the restricted treatment. However deficit irrigation resulted in a yield decre ase of 15 % while saving 33 % of the irrigation water. RÉSUMÉ-Ce travail concerne la salinisation du sol dans la zone racinaire d'arbres de pêcher soumis à l'irrigation déficitaire pendant six ans. L'expérimentation a eu lieu à Mornag dans un verger irrigué au goutte à goutte avec des eaux titrant 1.4 g/l de sels solubles totaux. Deux régimes d'irrigation sont adoptés pendant six ans. Le premier régime, pris comme témoin, est celui donné par l'agriculteur. Il consiste à satisfaire les besoins en eau du pêcher. Le deuxième régime réduit les quantités d'irrigation de 33 % par rapport au témoin. Des prélèvements de sol ont été effectués à différentes dates du cycle végétatif sur un profil de 80 cm de profondeur sur la ligne des goutteurs, à la perpendiculaire des lignes des arbres et sur la diagonale. La salinité des échantillons de sol a été déterminée par la mesure de la conductivité électrique de l'extrait de pâte saturée et la méthode gravimétrique a été utilisée pour la mesure de l'humidité du sol. Afin de spatialiser les valeurs ponctuelles, la technique d'interpolation optimale par Krigeage a été utilisée. Cette méthode a permis de calculer pour un volume contenant le bulbe d'humectation, des moyennes pondérées de la salinité (g/l) et de l'humidité volumique (%) par couche de sol et pour tout le profil. Un bilan de sels durant la sixième année d'expérimentation a été également établi. Les résultats d'analyses montrent que durant la période août 2001-septembre 2002, la salinité moyenne du sol dans la zone humectée varie entre 1.1 et 1.74 g/l, les valeurs minimales correspondent à la période printanière. En plus, des 330 mm de précipitations, les apports d'eau par irrigation ont été respectivement 1041 et 695 mm pour le témoin et le régime déficitaire. Les quantités de sels correspondantes seraient de l'ordre de 12.5 t/ha et 8.3 t/ha pour le traitement déficitaire. Cependant, la salinité du sol a été maintenue à des niveaux comparables sous les deux régimes. L'irrigation totale ne semble pas en effet provoquer un meilleur lessivage des sels. Tout en permettant d'économiser 33 % de l'eau 2 Non-Conventional Water Resources Practices and Management d'irrigation, la pratique de l'irrigation déficitaire réduit les quantités de sel apportés dans les mêmes proportions, elle ne semble pas défavoriser le lessivage des sels mais provoque une baisse du rendement de 15 %.

The sustainability of agricultural productivity is closely related to the optimal exploitation of natural resources, namely the efficient water resources management. The evaluation of the effectiveness of the adopted strategies and the applied practices and systems relies on a number of criteria and parameters of which water productivity indices represent the most relevant criteria. In this context, the present study aims to assess the water productivity for date palm cultivation in Tunisia based on an accurate literature review of the previously published scientific papers and reports related to the different studies carried out in these agro-oases regions of the country for the evaluation of the different indices of water productivity. This review represents the main baseline document highlighting in an exhaustive way the challenging features related to water productivity for date palm agro-systems. The outcome of this review indicates that (i) the cultivated date surface is expanding, covering more than 58.000 ha with a total production of 355.000 tons in 2021(ii) the distribution of irrigation water is variable and irregular. iii) The reported water supply for date palm range from 20,000 to 30,000 m 3 /ha while a number of scientific-based calculations estimate the crop water requirements for regular date palm production is between 10,000 and 18,000 m 3 /ha (iv) the efficiency of water conservation techniques is related to numerous in farm factors related to the old traditional surface irrigation systems, to the soil salinization, alkalization and permeability loss and to the overexploitation issues of water resources that reaching is growing and may impact the productivity of date palms and sustainability of the production system (v) the estimation of the biophysical water productivity based on the reported data reaching barely 0.66kg/m 3. This overview highlights the need for an accurate evaluation of the ecological efficiency of the used management measures to a clear appreciation of the new strategies and policies to face the current constraints with regard to all different driving forces influencing water productivity both at the macro and micro scale.

The sustainability of agricultural productivity is closely related to the optimal exploitation of natural resources, namely the efficient water resources management. The evaluation of the effectiveness of the adopted strategies and the applied practices and systems relies on a number of criteria and parameters of which water productivity indices represent the most relevant criteria. In this context, the present study aims to assess the water productivity for date palm cultivation in Tunisia based on an accurate literature review of the previously published scientific papers and reports related to the different studies carried out in these agro-oases regions of the country for the evaluation of the different indices of water productivity. This review represents the main baseline document highlighting in an exhaustive way the challenging features related to water productivity for date palm agro-systems. The outcome of this review indicates that (i) the cultivated date surface is expanding, covering more than 58.000 ha with a total production of 355.000 tons in 2021(ii) the distribution of irrigation water is variable and irregular. iii) The reported water supply for date palm range from 20,000 to 30,000 m3/ha while a number of scientific-based calculations estimate the crop water requirements for regular date palm production is between 10,000 and 18,000 m3/ha (iv) the efficiency of water conservation techniques is related to numerous in farm factors related to the old traditional surface irrigation systems, to the soil salinization, alkalization and permeability loss and to the overexploitation issues of water resources that reaching is growing and may impact the productivity of date palms and sustainability of the production system (v) the estimation of the biophysical water productivity based on the reported data reaching barely 0.66kg/m3. This overview highlights the need for an accurate evaluation of the ecological efficiency of the used management measures to a clear appreciation of the new strategies and policies to face the current constraints with regard to all different driving forces influencing water productivity both at the macro and micro scale.

In this work estimation of effective precipitation (Pe) is performed using different methods with an assessment of their performance for different time steps. Experimental work was carried out on wheat at the INAT-Mornag experimental station over four years having different distributions of monthly precipitation. Soil moisture was monitored at monthly interval using neutron probe and gravimetric methods. Rainfall and weather factors used for evapotranspiration estimations were collected daily at the experimental site. Pe was estimated using four models: 1) method considering Pe as a fraction of total rainfall, 2) method based on linearized sectors of FAO, 3) method using linearized sectors (USDA-1) and 4) the more elaborated method which integrates soil water holding capacity and evapotranspiration (USDA-2). Crop evapotranspiration (ETc) and the different estimates of Pe were used to simulate soil water content at different time steps. Analysis of the deviations between predicted and observed values of soil water content shows that RMSE varies in the range 40-60 mm for periods of one, two and three months and over 60-130 mm for periods of six months. Using actual evapotranspiration (ETa) estimated by the FAO AquaCrop model, instead of ETc, resulted in reducing errors associated to the estimation of crop evapotarnspiration within the water balance model and therefore better appreciation of the error related to the Pe calculation model. Results show also that simulation errors were reduced on the overall, with an RMSE of 40-110 mm for the six month period. Differences between observed and predicted values calculated over sequences of two months seem to show more dispersion for the decemberjanuary and february-march periods than for april-may. Keywords : effective rainfall, evapotranspiration, water balance, wheat, AquaCrop

Access to small amounts of irrigation water is recognized as a major mean of improving overall productivity of rainfed agriculture. Within a context of increasing water scarcity, supplemental irrigation (SI) has been adopted by many arid countries and incorporated in their respective national development programs. Presently, SI is shaping the way agricultural water is being managed. For instance, in Tunisia large investments have been devoted to the development of irrigation practices on short lived water courses. A typical example is the construction of many hundred of small earth dams. However, it has been observed that water collected by these newly implemented waterworks is used with variable efficiency, depending on various local physical and social conditions. This paper is concerned with the identification of criteria that influence the suitability for the implementation of such small irrigation schemes. The objective is to produce a methodology whereby the potential of using runoff water for supplemental irrigation could be evaluated and regional suitability for this practice could be mapped using commonly available spatial information such as DEM and Satellite images. To this end, an appropriate land rating system was used for deriving soil suitability for irrigation. On the other hand, relevant information on existing reservoirs in the pilot site were used in a bottom up approach to map regional suitability for runoff water harvesting and storage. Basically quantitative data on rainfall distribution, slope, watersheds size and soil types have been integrated to satellite information in order to develop the methodology. Up-scaling allowed to produce spatial information on soil suitability for SI and to delineate potential areas for water collection in northern Tunisia with a reasonable accuracy.

FAO’s Aquacrop is one of the most suited models to water limited and saline conditions. It can help to assess management practices and allows developing better informed decisions concerning management and environmental factors that affect crop production. In this study, Aquacrop was used to determine the acceptable threshold of initial soil salinity and the suited period for sowing barley. Three initial soil salinity levels (3, 6 and 8 dS m-1) were evaluated under different initial soil water content for full (FI) and deficit irrigated barley and two contrasting seasons. Barley yield was predicted also for 8 consecutive sowing dates including the sowing dates used by famers. The model simulations were evaluated using statistical indicators (Root Mean Square Error (RMSE), Mean Bias Error (MBE), Mean Absolute Error (MAE) and the coefficient of determination (r2) and the three season’s experimental data. Results show that grain yield and final biomass decrease with delay of sowing date and these reductions were accentuated with high initial soil salinity and the variability of rainfall events. The most suitable period for sowing barley ranging between end of November and the beginning of December. Initial conditions affect yield while the yield reduction started to be considerable (30%) only with the relatively higher level of soil salinity (8 dS m-1) and for dry season and deficit treatment. The comparison between measured and simulated yield and biomass under varied sowing dates and initial soil salinity shows good agreement with RMSE ranging between 0.36 and 1.6 t ha-1, MAE ranging between 0.29 and 1.48 t ha-1, r² about 0.77 and 0.81 for yield and final biomass, respectively. Aquacrop could be a useful tool to determine the optimum barley yield for different restricted factors. Key words: Barley, irrigation, Aquacrop, saline water, sowing date, management practices, arid environment.

A 2‐year study was conducted to assess the effects of irrigation regimes using saline water on soil salinization, yield, water productivity, and net income of faba bean ( Vicia faba L.) under actual farming conditions in arid regions of Tunisia. Faba bean (cvs. Luz de Otono and local) was grown on a sandy soil and drip‐irrigated with water having an electrical conductivity of 6 dS m ⁻¹ . Two deficit irrigation (DI70 and DI40) and one full irrigation (FI) strategy consisting of applications of 40%, 70%, and 100% of crop evapotranspiration (ETc), respectively, were compared to the traditional farmers' irrigation method (FM) in which 16 mm irrigation were applied every 5 days from planting till harvest. Results showed that the lowest soil salinity values at harvest were observed under FI treatment, while the highest were obtained with DI40 and the FM. The maximum values of faba bean yields were obtained under FI and the lowest with the FM. No significant reduction in yields was observed with the DI70 treatment compared to FI, while DI40 and the FM significantly decreased the fresh pod yields. Using 12%–20% more irrigation water than FI treatment, the FM did not improve soil salinity but resulted in a significant yield reduction compared to FI. Total water productivity values varied between 4.9 (FM) and 14 kg m ⁻³ (DI40) across different years and treatments. Compared to the FM, which applies fixed amounts with the same frequency, the FI strategy, which adapts the irrigation amounts to the actual crop water requirements, was more productive and provided a significant advantage in terms of yield and net income. Under limited availability of irrigation water, adoption of the DI70 treatment was found to be a good alternative as it allowed 30% water saving and was subject to limited negative effects on soil salinity, yield, and net income.

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.

Field studies on saline water use (6 dS/m) for carrot, lettuce and pepper production in smallholder's farms were conducted in the arid region of Medenine-Tunisia. The irrigation regimes were full (FI) and deficit (DI-80, DI-60, FI-DI60) irrigated with levels of 100, 80 and 60% of ETc when 40% of total available water in the root zone in the FI treatment was depleted, and farmer method (Farmers). Results show that the greatest values of soil salinity were observed under Farmers (FM) and DI-60 treatments. Relatively low ECe values were also recorded under FI-DI60 and DI-80 treatments. The highest mean yields of carrot (26.8-28.7-29.5 t/ha), lettuce (42.6-45.8 t/ha) and pepper (22.3-24.4 t/ha) were recorded for the FI treatment, that is not significantly different from the FI-DI60 and DI-80 treatments. Compared with FI, significant reductions in carrot, lettuce and pepper yields were observed under the DI60 and Farmers treatments, resulting from a reduction in yield components. The Farmers's method increased soil salinity and resulted in an increase of water use of 43-57% for carrot, 26-29% for lettuce and 11.5-16% for pepper. Water productivity (WP) values reflected the differences in yields and varied between 3.4 (Farmers) and 9.7 kg/m 3 (DI-80) for carrot, 7.5 and 19.1 kg/m 3 for lettuce and 2.4 and 5.5 kg/m 3 for pepper across different years and treatments. The soil water balance-based irrigation method (FI) generated the greatest net income compared to the Farmers treatment in carrot, lettuce and pepper productions under arid environment and the lowest soil salinization. FI scheduling technique is suggested for optimizing saline water use for vegetable crops. Under water scarcity, the adoption of the FI-DI60 and DI-80 strategies results in 4.5 to 20% water savings as compared to FI with small impact on salinity in the root zone and yield and net income reductions.

Crop models are useful in evaluating management strategies and exploration of new practices, particularly in studies related to climate change and productivity assessment of agricultural systems. At field level, biophysical crop models are generally suitable in homogeneous environments when accurate input data and calibration parameters are available. However, their use at watershed level is limited, especially in hilly areas with great variability of soils, slope, and land use. Systematic method considering all terrain variabilities is time consuming since it requires high-resolution data and parameterization effort while geospatial models like SWAT, using simplified crop modules do not reflect the complexity of the simulated processes. In this work, an alternative methodology is proposed and tested in the hilly Mediterranean watershed of Kamech located in the Cap Bon Peninsula, Tunisia (N 36.88°, E 10.88°); it uses the FAO AquaCrop biophysical model to estimate production in selected fields and scale up the results to the watershed level. Maps of soil, slope, and land use are combined by a GIS tool to obtain a database of averaged field properties and occupations. Three categories of texture, depths, and slopes were considered to classify the 313 fields of the watershed into 27 soil classes and determine their respective area-weighting factor. The systematic method considering all fields and the proposed method considering the 27 representative fields were used to estimate the watershed production for dominant crops: wheat, barley, and faba bean. Results show a good correlation between both methods with values of relative RMSD in the range of 0.5–2% for biomass and 2–5% for grain yield. Decile-decile analysis showed that the proposed methodology simulated almost all the observed spatial variability of yield within the watershed suggesting its suitability for productivity assessment and prediction in hilly fragmented agricultural landscape.