Testing the ability of vivianite to prevent iron deficiency in pot-grown grapevine

Synthetic vivianite (ferrous phosphate octahydrate) has been reported to reduce the iron (Fe) deficiency symptoms in different crops growing on calcareous soils. We investigated the effectiveness of vivianite in grapevine by means of a 3-year (2002–2004) pot experiment with a Fe chlorosis-susceptible rootstock (‘110 Richter’) grown on a calcareous soil poor in available Fe. There was one treatment in which a suspension of vivianite was injected into the soil at the beginning of the experiment, one treatment with Fe chelate (FeEDDHA) applied yearly, one treatment with one initial application of both vivianite and FeEDDHA, and one control (no Fe fertilizer added) treatment. The concentration of chlorophyll per unit leaf area was estimated with a portable chlorophyll meter (readings in SPAD units). The vines fertilized with vivianite had longer shoots and higher number of leaves, and exhibited higher SPAD values than the control vines. The differences in SPAD value and pruning wood weight between the vines fertilized with Fe and the control were significant through the 3 years. There were no significant differences in SPAD value and pruning wood weight between the vines fertilized with Fe chelate and vivianite. Our results suggest in summary that vivianite is an interesting alternative to other Fe fertilizers used to prevent Fe chlorosis in grapevine judging by its effectiveness and long-term fertilizing effect. Moreover, it is not easily leached from the soil, easy to prepare, and environmentally safe.