Spate irrigation slightly ameliorates an arid soil's quality, but tree planting enhances its characteristics

Spate irrigation (SI) is an appropriate technology to utilize the harvested floodwater, which besides providing the required water for plant consumption ameliorates the soil quality in arid and semi-arid areas. The long-term effects of SI on the soil quality, especially enzymatic and biological activities of rangelands and farm fields, remain virtually unknown. A desertification control project through floodwater spreading was initiated in the Gareh Bygone Plain (GBP) in the Province of Fars, Iran in 1983 with aims of augmenting groundwater, stabilizing the moving sand, and particularly improving the rangeland yield through SI. We have investigated the physicochemical, biological and biochemical qualities of the soil in the spate-irrigated fields planted to river red gum (Eucalyptus camaldulensis Dehnh.), cooba (Acacia salicina Lindl.), and quail bush [Atriplex lentiformis (Torr.) (Wats.)], and a native rangeland and compared them with the same fields without SI. The loamy sand texture has changed to silt loam, which has improved water availability. Improvements have also occurred in the soil pH, organic carbon content, nutrients, enzymatic activities, and microbial respiration; however, the magnitude of these improvements varied among the different vegetative covers. Furthermore, the impacts of SI on soil functions enhanced by tree planting. The soil's higher fertility indicators, increased enzymatic activities and microbial respiration were attributed to the Eucalyptus plantation under SI by the principal component analysis (PCA). We recommend simultaneous implementation SI and tree planting in the arid and semi-arid regions for the enhancement of soil productivity.