Understanding the Role of Secondary Elements and Micronutrients in Sportsturf Management
The secondary elements include magnesium, sulphur and calcium
Magnesium
Magnesium is critical for photosynthesis because each chlorophyll molecule, which makes grass green, has a single atom of Mg at its core. It also plays a role in energy transfer, nutrient uptake and transfer. Magnesium is a cation and exists in the soil as a positively charged element, Mg+
. The higher the cation
exchange capacity (CEC) of the soil, the less likely it is that a Mg deficiency will occur. Magnesium availability in the soil is governed by two factors, the amount in the soil and the proportion compared to calcium and potassium. Heavy applications of either calcium or potassium can increase the leaching of Mg by displacing it from cation exchange sites so that the amount in the root zone is reduced. Magnesium is second to calcium as the most abundant nutrient absorbed on exchange sites. It is susceptible to leaching in sandy soils, however, losses are not as rapid as calcium. Turf established on sandy rootzones (such as is often used on golf course greens) is likely to develop Mg deficiency symptoms. Magnesium deficiency symptoms include general chlorosis, leading to interveinal chlorosis, which may be followed by blotchy red margins and necrosis. The sources of magnesium most commonly used on golf courses are Kieserite (MgS04 (MgS04
.H2 .7H2 0) and Epsom salts 0), which contain 16% and
10% magnesium respectively. Calcium
Calcium plays an important role in wall formation, cell division and growth and is a component or cofactor in several enzymes. Calcium occurs in the soil as exchangeable ions (Ca2+
), carbonates,
silicates and as a constituent of organic matter. Because many calcium minerals are soluble, adequate moisture favours continual solubilisation and leaching. Calcium ions also exert a strong influence on the absorption of other ions by the turfgrass plant. Calcium deficiencies are rare except in very sandy
soils or where strong acidity has resulted from intensive leaching. The sand type used to construct or topdress greens will influence the need for calcium. Silica sands are chemically inert, and usually contain little if any calcium. Calcareous sands may contain up to or more than 20% calcium carbonate (limestone), the limestone actually being a component of the sand-fraction. Calcium deficiency symptoms are usually a reddish-brown discolouration along leaf margins which develops to light red. Common sources of calcium include calcium carbonate (agricultural limestone) and gypsum.
Sulphur
Sulphur is a part of several plant vitamins and is a constituent of some amino acids required for protein synthesis. Most soil sulphur is contained within the organic fraction, and its availability to plants is a function of organic-matter decomposition. Sulphur deficiencies in soils are rare,
but responses to sulphur may be possible on sand-based greens, especially in areas of high precipitation. Young greens in particular may benefit from occasional applications of sulphur. As organic matter accumulates in the soil, however, the need for supplemental sulphur should become minimal. When used, sulphate-containing fertilisers usually supply adequate amounts of sulphur for turfgrass growth. Deficiency symptoms include yellowing older leaves, slowed growth and delayed maturity. An addition of sulphur to bentgrass greens has been reported to reduce the incidence of fusarium patch and black algae.
Micronutrients
The seven micronutrients or trace elements required by turfgrasses are iron, manganese, zinc, copper, molybdenum, boron and chlorine. These microelements are needed only in minute amounts and rarely need to be supplied to turfgrasses growing in mineral soils. However, when turfgrasses are grown in high-sand-content soils or high-pH soils, micronutrient application may be beneficial and is often practised. The importance of micronutrients lies primarily in their role as catalysts in enzymatic reactions. Iron is the micronutrient most often
found to be deficient in turf. One of its primary functions in the plant is its involvement in the formation of chlorophyll. Iron is not a part of the chlorophyll molecule, but chlorophyll will not be formed if iron is not there in sufficient quantities. Iron deficiency in individual plants is characterised by an interveinal chlorosis of turfgrass leaves and the eventual thinning of the turf. Iron deficiency may occur because of excessive levels of zinc, copper or manganese.
Manganese is involved in the formation of chlorophyll and plays a role in photosynthesis. Deficiency symptoms on grass include chlorosis and slow growth. The exact roles of chlorine and boron within plants are still uncertain, although boron is known to be involved in cell wall synthesis. Chlorine is thought to be involved in the regulation of osmotic pressure and cation balance within plant cells. Turfgrass colour is sometimes poorer when a boron deficiency occurs.
Copper is highly toxic to plants except when it occurs in very dilute soil concentrations. Copper functions as a component of several enzyme systems and in the synthesis of certain growth promoting substances. Zinc is essential to plants but only in minute quantities. Zinc plays important roles in enzyme activation, membrane function and auxin stability. Of all the mineral nutrients known to be essential for plants, molybdenum is required in the least amount. Its primary function in plants is as a cofactor to the enzyme system involved in nitrate reduction.
About the author: Dr. Tim Butler is a Sportsturf Science Agronomist and Independent Expert on all aspects of Golf Course, Sports Pitch and Race Track construction, renovation, drainage, agronomy and environmental management. Contact Tim at
tim@irishpitchdoctor.ie or log on to
www.irishpitchdoctor.ie
SECONDARY ELEMENTS
Understanding their role in sportsturf management Sulphur Crystals © Würzburg Mineralogical Museum
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111