Chapter 16

Vineyard Nutrient Management

Macronutrients and Micronutrients

Iron

Role and Deficiency Symptoms

Iron plays an important role in chlorophyll formation, in photosynthesis and respiration, and cell strengthening.

Iron deficiency occurs on the apical leaves early in the season resulting in general yellowing (chlorosis) of young leaves and new growth.

Assessing the Need for Iron Fertilizer

As with most micronutrients, tissue sampling can be used to determine the vines’ iron status.

Time of Application

Foliar applications around bloom time have been able to correct moderate deficiency problems.

Application Methods

Direct Soil Surface Application: Generally, direct soil applications of inorganic iron sources are not effective in supplying iron to grapevines.

Fertigation: Iron applied to vineyards with the drip system is effective and feasible. Drip irrigation is effective since nutrients are placed where roots are highly concentrated, and uptake is supported by continuous high soil moisture beneath emitters.

Foliar Application: A foliar application of iron chelates can be sprayed on for immediate effect, but several applications may be necessary to correct sever deficiencies.

Soil Factors Affecting Availability

Iron deficiencies are found mainly on calcareous (high pH) soils, a condition known as lime-induced iron chlorosis.

Iron Toxicity

Iron toxicity is primarily pH related and occurs where the soil pH has dropped sufficiently to create an excess of available iron.

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