A refresher as your turf starts to wake-up for a new season or for at any point throughout! This micronutrient is an important one and so this post a little longer. Feel free to comment, offer additional insights or information.
The mineral composition of soil, pH, and the availability of ions principally depends on the nature of the underlying rock (Larcher 2003). Iron (Fe) makes up an average of 5% of the earth’s crust (Carrow 2001). It can be found everywhere and is generally not found to be deficient in native soils and associated native plants. Typically, Fe is found affixed to an organic chelates created from microbial activity and root exudates that occur naturally in the soil. Factors affecting the availability of Fe for active uptake by the turfgrass plant are, pH, aeration and soil moisture, soil temperature, organic matter, and the interaction between Fe and other nutrients in the profile. Fe plays a vital role in plant physiology by allowing the plant to capture and store the suns energy during the process of photosynthesis. Fe is also an important component of plant enzymes and proteins involved in respiration, and nitrogen metabolism. There can be challenges with the plants ability to uptake this mineral.
Fe is usually present in soil in fair amounts, and deficiencies often result from soil conditions (especially high pH) that restrict Fe uptake by the plant (Grounds Maintenance 1997). Fe is readily available in more acidic soils where pH is less than 6. In highly acidic conditions (pH <5) Fe levels can reach toxic conditions for the plant if the conditions are right; Ie: saturated, compacted soils. It is not uncommon, however, to find a pH greater than 6 when looking at the environment created to host a golf course putting green and the more common turfgrass plants such as Poa Annua and Agrostis stolonifera. As the pH increases >6 Fe becomes less available and is virtually unavailable when it is in excess of 7, this can seen in highly calcareous soils.
When soils are highly saturated, and compacted, Fe3 converts to Fe2 rendering it readily available for plant uptake. This can present toxic conditions for the plant as it negatively affects microbial activity, while contributing to the development of black layer. Proper drainage and aeration is important for Fe metabolism into the turfgrass plant. In the rhizosphere, iron concentration in the soil solution is even lower because of its uptake by aerobic organisms (plants and microorganisms), leading to a high level of competition for Fe3 (A. Robin 2008).
Soil temperature can influence Fe chlorosis through effects on plant activity and soil Fe availability (Carrow 2001). In low soil temperatures root growth is reduced causing spring die back due to the plants inability to uptake Fe. In high soil temperatures a similar response is seen especially in cool season grasses in the heat of the summer stress.
Fe is essential in the plant’s production of chlorophyll. Deficiencies can be seen by the yellowing of the turfgrass plant in the oldest shoots resulting in irons immobility within the plant. The plants ability to create chlorophyll and absorb the energy from the sun necessary for the photosynthetic process is vital to the success and health of any turfgrass plant. Iron (Fe) is the most important micronutrient for turfgrass growth and maintenance (Bell 2011).
The need for Fe by the plant is vital, while the ability to access it in the soil solution is affected by many factors. A common solution to Fe deficiencies are the application of chelated-iron fertilizers, EDTA being the most common. Iron applications can also sprayed directly to the turfgrass plant and is often incorporated in most liquid fertility plans where Fe availability in the soil is reduced. Because of the ability for Fe to influence chlorophyll function and size it is considered an important mineral and it must be properly managed.
A. Robin, (., G. Vansuyt, (., P. Hinsinger, (., J.M. Meyer, (., J.F. Briat, (., & P. Lemanceau, (. (2008). Chapter 4 Iron Dynamics in the Rhizosphere. Consequences for Plant Health and Nutrition. Advances In Agronomy, 99183-225. doi:10.1016/S0065-2113(08)00404-5
Bell, G. E. (2011). Turfgrass physiology and ecology : advanced management principles / Gregory E. Bell. Wallingford, Oxfordshire ; Cambridge, MA : CABI, c2011.
Carrow, R. N., Waddington, D. V., & Rieke, P. E. (2001). Turfgrass soil fertility and chemical problems : assessment andmanagement / R.N. Carrow, D.V. Waddington, P.E. Rieke. Chelsea, MI : Ann Arbor Press, c2001.
Fertility. (1997). Grounds Maintenance, 3266.
Larcher, W. W. (2003). Physiological plant ecology : ecophysiology and stress physiology offunctional groups / Walter Larcher. New York : Springer, 2003