Secondary nutrients magnesium

The secondary nutrients, Calcium (Ca), Magnesium (Mg), and Sulfur (S), should be supplied in the hydroponic ingredients in the proper percentages required by plants. Always be attentive to the use of each different formula as the nutrients are mixed... 

Macro Nutrients - the secondary nutrients calcium, magnesium, and sulfur... 

Secondary nutrients Elements required by plants in moderate amounts (calcium, magnesium, sulfur)... 

Secondary nutrients and micronutrients usually are expressed on an elemental basis althou calcium and magnesium sometimes are ejq ressed in the oxide form. However, several countries express all plant nutrients on an elemental basis. Plante actually use neither tile pure element nor the pure oxide form, so the difference is largely academic. Conveireion factors for those plant nutrients that may be expressed in the elemental or oxide form, depending on the country, are shown in Table 1.2. 

Calcium, magnesium, and sulfur are designafi as secondary nutrients. Plants require these nutrients in fairiy... 

The International Fertilizer Development Center conducts an annual survey of NPK granulation plants in the United States. By 1995 the number of operating plants decreased to only 25, from about 200 in 1965. No estimate has been made of the number of NPK granulation plants worldwide, but aImost-all-of-these-plants,-pIus-all nitrophosphate plants, incorporate secondary nutrients, primarily calcium and/or sulfur, in their products as the preferred, least expensive raw materials. Magnesium is different and is usually incorporated as a special additive. 

Plants need other nutrients as well-such as the secondary nutrients (calcium, magnesium, and sulfur) and the micronutrients (boron, chlorine, copper, iron, manganese, molybdenum, sodium, vanadium, and zinc)-but these are needed in smaller quantities and rarely need replenishment in soils. 

In Table 11.1, the elements calcium, magnesium, and sulfur are shown under their usual designation as secondary nutrients. These elements are required by plants in moderate amounts, but in most agricultural situations are not found to be deficient in the soil. There are exceptions, however. Areas of sulfur deficiency are well recognized in Australia, some U.S. locations, and elsewhere. Correction usually is made by application of fertilizers that are naturally high in sulfur content, such as normal superphosphate and ammonium sulfate, or by special application of gypsum or elemental sulfur. A very considerable amount of sulfur enters many soils dissolved in rainwater. The origin of this sulfur... 

There are thirteen mineral nutrients that plants obtain from the soil, and these are divided into the categories of macronutrients and micronutrients. The primary macronutrients include nitrogen, phosphorus, and potassium. Plants require these primary macronutrients in relatively large quantities and deplete them from the soil more rapidly than others. The secondary macronutrients include calcium, magnesium, and sulfur. Micronutrients are required in smaller quantities than the macronutrients, and these include boron, copper, iron, chloride, molybdenum, manganese, and zinc. 

Limestone is homogeneous in chemical composition, mainly containing calcium carbonate, with varying amounts of magnesium (dolomites) and clay (Marschner, 1995 Lugo et al., 2001). On limestone bedrock a variety of calcium-rich soils develop, particularly the rendzinas. Climatic differences determine variations in ion accumulations in the upper soil layers. In drier climates, rapid evaporation causes water-soluble salts to accumulate at the surface. In more hmnid regions, rainfall leaches out both nutrients and calcium carbonate leading to a secondary acidification . 

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