Revegetation in semiarid zones: Influence of terracing and organic refuse on microbial activity

Revegetation of areas under semiarid conditions is difficult due to both the water shortage and the poor quality of the soils of semiarid areas; Two techniques of soil management (manually and mechanically built terraces), as well as soil amendment with organic materials were used for revegetation in a semiarid area. In this work the effect of such techniques on the microbial activity of a soil revegetated with Aleppo pine (Pinus halepensis Miller) was studied. The content of the different labile C fractions studied (water-soluble C, water-soluble carbohydrates, and polyphenol compounds) substantially increased in soils with mechanically built terraces and with addition of organic refuse. The highest values of these labile C fractions were found in soil samples collected in spring (rainy season) while those collected in January (dry season) showed the lowest values. The activity of oxidoreductases such as dehydrogenases as well as that of hydrolases involved in the biogeochemical cycles of important nutrients (ureases, proteases, phosphatases, and beta-glucosidases) were stimulated by the addition of organic matter to the soil. The lowest values of microbial biomass and enzyme activities were detected when revegetation was carried out on mechanical terraces without addition of organic materials. The simultaneous use of both soil management techniques, mechanical terracing and amendment with organic refuse, clearly improved soil microbial activity and hence soil biological quality. Plant growth was also improved with these techniques.