Impact of natural zeolite on chemical and biochemical properties of vineyard soils

Sustained tillage and continual applications of phytopharmaceutical and fertilizers using heavy machineries frequently give rise to soil erosion, loss of soil organic matter (SOM) and contamination phenomena in Mediterranean vineyards. Because of their distinctive properties, applying natural zeolites to vineyard soils can conceivably affect the efficient use of fertilizers and reduce nutrient leaching losses. This work assesses the impact of zeolite amendment at differing rates (0, 5 and 10 t/ha) on the chemical and biochemical soil properties of three vineyard soils after 6 months from initial treatments. In particular, chemical properties usually related to soil fertility were evaluated along with more sensitive indicators of soil functionality and indicators of chemical-structural characteristics of SOM. The vineyard soils amended with zeolite showed higher nutrient availability and dehydrogenase activity if compared with the control soils. In addition, even though total organic carbon (TOC) content was unchanged, a decrease in humic substances was observed in the zeolite-treated soils. These results suggested that the stimulation of soil microbial processes by adding zeolite triggered a microbial mineralization process of soil organic carbon stocks. In addition, the modification in the chemical-structural composition of soil organic matter in zeolite-treated soils was shown by the pyrolysis-gas chromatography (Py-GC) results. Py-CG of soil organic matter clearly demonstrated an increase in the labile aliphatic compound furfural and a decline in the more stable aromatic pyrolytic fragments in zeolite-treated soils in contrast with the control soils, thus indicating the higher extent of decomposition of the SOM more stable pool.