Rainfall Distribution Functions for Irrigation Scheduling: Calculation Procedures Following Site of Olive (<i>Olea europaea</i> L.) Cultivation and Growing Periods

Abstract

In Tunisia (36.5˚N, 10.2˚E, Alt. 10 m), rainfall is the major factor governing olive production. It is characterized by large variability in time and space, making yields of olive trees highly dependent on the amount of water received and timing. Thus, improvement of olive productivity by irrigation is necessary. This study aimed to determine the crop water needs of olive orchards and the rainfall frequencies at which they are covered following age and sites of olive production. For this purpose, the rainfall distribution functions are established for different cities of Tunisia (Tunis, Bizerte, Béja, Nabeul, Sidi Bouzid, Gabes and Sousse). For all sites and growing periods, the reference evapotranspiration (ET0) was computed by using several formulas. Their performance against the Penman Monteith (PM) method was evaluated graphically and statistically in all considered cities in order to evaluate their accuracy for better adapting them to the existing environmental conditions, particularly when data are missing to compute ET0-PM. Results presented herein show that the estimated ET0 values strongly correlate with ET0-PM at all sites and formulas with r values up to 0.88. Particularly, the methods of Turc and Ivanov appropriately predict the ET0-PM in all climatic regions of Tunisia and may constitute an appropriate alternative for ET0 estimation when data are missing to compute ET0-PM. However, although the Turc method performs well with all climatic zones, arid and semi-arid, in western, northern and coastal areas of Tunisia, the Ivanov method appears to be more appropriate to the northern areas (Béja and Bizerte) characterized by semi arid climate and having annual rainfall of up to 450 mm, though a poorer agreement was found when using the Eagleman formula. Estimates of ET0 by using the Hargreave-Samani (HS) formula for the east-southern area (Gabes) characterised by arid climate show satisfactory agreement with ET0-PM estimates, corroborating previous findings reporting

Estimation and comparison of reference evapotranspiration using different methods to determine olive trees irrigation schedule in different bioclimatic stages of Tunisia

“…To calculate ET0, there are a lot of empirical formulas using different climatic parameters (Masmoudi-Charfi and Habaieb, 2014;Bchir, 2015). The use of the different empirical formulas depend on available weather data.…”

“…The Blaney-Criddle (BC) equation also gives similar ET0 values (with a lowestimation) to those recorded by the Penman-Monteith (PM) equation. In the case of lack of climate data, Masmoudi-Charfi and Habaieb (2014) found that the Blaney-Criddle formula is positively correlated with the Penman-Monteith equation in different bioclimatic stages of Tunisia. However, the same authors concluded that, at the phenological scale of the olive tree, this formula is effective only during the vegetative rest, the vegetation development, the beginning of the flowering, the fruit growth, the oil synthesis and ripening of olives.…”

“…From the flower induction (February) to the flowering stage (May), it is possible to use this formula. Masmoudi-Charfi and Habaieb (2014) found that the Blaney-Criddle formula gives estimates of water requirements in the regions of Nabeul and Sousse. In the region of Sidi Bouzid, characterized by a climate similar to that of Gafsa, Masmoudi-Charfi and Habaieb (2014) showed that the formula of Turk, which is based on radiation and temperature was the most adequate.…”

“…A large number of formulas were used, developed and improved to calculate the water consumed in the form of daily or monthly reference evapotranspiration (ET0) (Blaney and Criddle, 1950;Priestley and Taylor, 1972;Hargreaves and Allen, 2003;Bois et al, 2005;Summer and Jacobs, 2005;Temesgen et al, 2005;Alkaeed et al, 2006;Papova et al, 2006;Lovelli et al, 2008;Martinez and Thepadia, 2010;Todorovic et al, 2013;Raziera and Pereira, 2013;Masmoudi-Charfi and Habaieb, 2014;Bchir 2015). The Penman-Monteith equation (ET0-PM), which according to FAO (1998) is considered to be the most rational and reliable approach, requires an important set of climatic parameters.…”

Intelligent Prediction of the Daily Irrigation Water Requirements for Citrus Orchards Using FFNN with Levenberg Marquardt Algorithm

“…36.45°E, E: 0 m) in collaboration with the Technical Centre of Citrus (CTA), which is a governmental centre specialized in the promotion and development of the citrus industry. The region is characterized by a typical Mediterranean climate with five to six rainless months, an average annual precipitation of 460 mm, falling mostly from November to March and a Thornwhite aridity index of 0.29 [6]. The experimented citrus orchard was planted in 1998 at 4x5 m 2 spacing.…”