A Sahli

Charts for guiding irrigation in real time

In order to adjust correctly the irrigationcalendar to actual weather and waterlimiting conditions, farmers requireguidelines to help them in their day to daydecisions. In this paper a procedure isoutlined to present such guidelines in theform of a single chart. On the chartinformation concerning the irrigationinterval and irrigation duration ispresented. Tables guide the user (i) toadjust the irrigation interval to theactual weather conditions throughout thegrowing season and (ii) to select theduration of the water application as afunction of the characteristics of theirrigation system. In case of watershortage during a particular period,additional data informs the user on thesensitivity of the crop to water stress. Anexample is presented for drip irrigatedtomatoes in the region of Tunis on afluvisol.

Comparative performance of δ13 C, ion accumulation and agronomic parameters for phenotyping durum wheat genotypes under various irrigation water salinities: Triticum durum, salinity, stable carbon isotope, nitrogen concentration

The use of efficient selection traits for screening under contrasting irrigation water salinity is a challenge for breeders. To identify patterns, grain yield (GY) and yield components (kernels m⁻², thousand kernels weight), growth traits (plant height, biomass), flag leaf ion accumulation (Na⁺ and K⁺), carbon isotope composition (δ¹³Cgᵣₐᵢₙ) and nitrogen concentration (Ngᵣₐᵢₙ) of grains were assessed on 25 durum wheat genotypes (G) in two consecutive growing seasons (2010 and 2011), in three semi‐arid locations in Tunisia. Each location differed in their irrigation water salinity as measured by electrical conductivity: Echbika (S1, 6 dS m⁻¹), Barrouta (S2, 12 dS m⁻¹) and Sidi Bouzid (S3, 18 dS m⁻¹). GY was shown to be negatively correlated to Ngᵣₐᵢₙ as well as to δ¹³Cgᵣₐᵢₙ. This is confirmed by a multiple linear regression analysis that showed that both δ¹³Cgᵣₐᵢₙ and Ngᵣₐᵢₙ were the major determinant components for GY variability under S3. A high genotypic variability was observed and the improved genotype Maali exhibited the most stable GY under the three irrigation water salinities and the two cropping seasons. Maali showed the lowest δ¹³Cgᵣₐᵢₙ. This indicates that tolerance in durum wheat is likely to be correlated to the ability of maintaining a high stomatal conductance. According to our data suggests δ¹³Cgᵣₐᵢₙ can be used for an efficient screening of salt tolerant durum wheat. Under our experimental conditions, Ngᵣₐᵢₙ was shown to be highly correlated to δ¹³Cgᵣₐᵢₙ and can therefore be easier‐to‐use trait to assess the tolerance to salinity.