Iron chlorosis

The iron chlorosis is iron deficiency in the plant, which affects its metabolism and chlorophyll synthesis and is manifested by yellowing of the leaves. It is highly dependent on pH in the soil. Plant-assimilable iron is reduced to its lowest levels when the Soil pH is between 7.5 and 8. Therefore calcareous soils will be prone to this chlorosis. Excessive VWC  will lead to oxygen deficiencies and also assimilable iron.

Calcareous soils are prone to chlorosis.

Symptoms of high deficiencies are whitish turf, and limp leaf tissue.

The application of iron sulphate or ferric ammonium sulphate will solve the problem within a couple of days.

Analytical results of 10-15 ppm iron are generally considered adequate for most turfgrasses.

Most arid climates have iron chlorosis in the varieties of poa pratensis, perennial ryegrassand fescue, and agrostis (less frequent). Chlorosis induced by the arrival of high summer temperatures is frequent, while this problem is less frequent in the cooler periods of spring and autumn. The hypothesis of David Devette (Iowa State University, Horticulture Dept.) is that high temperatures can cause the roots (especially those of poa pratensis) cannot absorb all the necessary iron. Iron deficiency symptoms can confuse itself with those of nitrogen or sulphur, and can also lead to fungal diseases. In addition, the interaction of iron with other nutrients complicates the situation. For example, high copper contents can cause a blockage in iron absorption and lead to iron deficiency for this reason. This situation can also occur when there is an imbalance with other micronutrients such as Manganese, Zinc and Molybdenum.

Both foliar and granular applications are recommended, with ferrous sulphate being the most widely used fertiliser in both applications. Application of nitrogen in the form of nitrates can lead to the development of iron deficiency. Potassium and Zinc deficiencies can also reduce the rate of translocation of iron within the plant, causing physiological deficiency symptoms, even when there are normal levels of iron in the soil. Excessive levels of Phosphorus can also lead to deficiencies due to the formation of ferric phosphate precipitates.

All the above factors, together with others related to pH, organic matter and soil oxygen level, make iron chlorosis one of the most difficult deficiencies to correct. In general, soil applications with iron-containing compounds do not solve the problem, as it is quite possible that insoluble compounds are formed which are not available to the plant. Prevention, with balanced fertilisation, taking care that pH, organic matter and drainage are adequate, is the best way to keep iron chlorosis at bay.