Effects of land use and irrigation practices on Ca, Mg, K, Na loads in rice-based agricultural systems

Irrigation planning and management is essential in order to preserve agricultural production without affecting the ecosystem functioning by inducing salinity problems. The objective of the study is to assess the mass balance of the major cations (Ca2+, Mg2+, K+, Na+) SAR and ECw values during the growing season (May–October) in a lowland irrigated agricultural area. The selected area (150 ha) contained agricultural fields with rice, maize, cotton and fodder crops and is located in the Axios River delta, Thessaloniki plain, Greece. Monitoring was performed for two years (2006–2007) in the irrigation and drainage network of the study area. Higher concentrations of cations and higher values of SAR and ECw were observed in the drainage water compared to the irrigation water, due to leaching and evapo-concentration processes in the fields. Cations mass balance in both seasons was estimated and it was found negative in the study region, due to plant uptake and especially due to salt removal through leaching for approximately 50% irrigation efficiency. Cluster analysis was used to group the sampling sites in the drainage network according to their salinity quality characteristics. According to the cluster analysis results, rice cultivation is the primary influence on drainage water quality in the agricultural land of Axios River Delta.