Amal GHANNEM, Imed BEN AISSA, Mahmut ÇETİN, Rajouene MAJDOUB

Assessing salt accumulation in the root zone of tomato plant through using ordinary kriging interpolation technique under deficit irrigation regime

Aims: Deficit irrigation might be a remedy to increase water use efficiency in water scarce areas albeit it may cause to: a) increase salt accumulation in the root-zone, b) decrease crop yield. Therefore, monitoring and assessment of salt accumulation in the root-zone is necessary in deficit irrigation practices. Primary objectives of this work were to: a) assess salt accumulation in the root-zone of tomato crop irrigated with conventional deficit irrigation (DI-50) through using ordinary kriging interpolation technique, and b) compare it with full irrigation (FI) treatment. Methods and Results: To this end, soil electrical conductivity (EC in dS m1) measurements were conducted under emitters, between emitters and plant, and under plant on right and left side of root-zone by using an EC probe. In order to assess spatial and temporal changes of salt accumulation in the root-zone of tomato crop, EC lectures were done: a) at the beginning crop growth stage, b) in the middle, and c) at the end of growing season. In order to generate salinity maps in the root-zone, geostatistical interpolation techniques have been utilized. Geostatistical analysis has been realized by using “Jeostat-2017” software. Geostatistical analysis results indicated that the most suitable theoretical semivariogram model to the experimental semivariogram was Gaussian and/or Spherical model. Cross validation analysis revealed that kriging interpolation errors were fitted to the normal distribution, indicating that theoretical semivariogram model and its parameters as well as kriging search parameters are representative for the study site. Kriging errors helped us to evaluate efficiency of sampling design for salinity assessment. Conclusions: In this regard, results showed that salt accumulation was concentrated in the root-zone just beneath the plant. This finding can be explained by the heavy texture of soil, which obstructs the leaching operation also by the high root density of tomato under this profile. Soil salinity maps reveal that salt accumulation in the root-zone gets more and more as the growing stage progress. Significance and Impact of the Study: Deficit irrigation treatment reduce the amount of total salt accumulated in the root zone compared with the full irrigation treatment due to the fact that the amount of water applied with deficit irrigation is half of the full treatment, hence salt accumulation.

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