Secondary nutrients

Increased knowledge about secondary nutrients and micronutrients, including plant requirements, nutrient sources, and methods of application, has resulted in th increased use. Improvements In soil testing and plant analyses have provided more knowledge about plant needs and the unde variations in plant responses to these nutrients. Higher crop yields and the use of h h-analysis NPK fertilizers also have resulted in increased needs for these nutrients. 

The secoixlary nutrients are calcium, magnesium, and sulfur. Concentrations of these nutrients in plant tissues generally are lower than those of the primary nutrients (nitrogen, phosphorus, and potassium) but are higher than those of the micronutrients. The seven micronutri-ents are boron, chlorine, copper, iron, manganese, molybdenum, and zinc, Because chlorine deficiencies rarely occur in nature, most discussions on supplying micronutrient fertilizers are confined to the other six micronutrients. 

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

Calcium is relative abundant in soils, and calcium rarely limits crop production per se. Low levels of exchangeable calcium in soils result in increased soil acidity, which usually results in reduced growth of most crops. Using lime applications to correct soil acidity to recommended soil pH levels will provide sufficient calcium for crops because liming materials contain calcium (Table 17.1). 

Magnesium deficiencies are found mainly on acid, sandy soils and on organic soils containing free calcium carbonate. Magnesium deficiencies also can be accentuated by high levels of available potassium or on soils that have been limed for many years with calcitic limestone, which is very low in magnesium. 

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Sulfur-Coated Fertilizers. Sulfur-coated urea technology (SCU) was developed in the 1960s and 1970s by the Tennessee Valley Authority, now called the National Fertilizer and Environmental Research Center. A commercial-scale demonstration plant (9.1 t/h) was put in operation by TVA in late 1978. Sulfur was chosen as the principle coating material because of its low cost and its value as a secondary nutrient. 

Primary nutrients or elements Secondary nutrients or elements... 

Because there is no growth during the stationary phase, it is clear that Equation (7-112) caimotbe used to account for substrate consumption, nor can the rate of product formation be related to the growth rate [e.g.. Equation (7-113)], Many antibiotics, such as peniciUin, are produced in the st onary phase. In this phase, the nutrient consumed for growth has tecome vulually exhausted and a different nutrient, called the secondary nutrients, is used for cell maintenance and to produce the desired product. Usually, the rate law for product formation during the stationary phase is similar in form to the Monad equation, that is,... 

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... 

An attempt was made to calculate the total worldwide annual removal by crops of the three major and three secondary nutrients (Table 9.15). These crude estimates indicate that nearly 70 Tg of plant nutrients are cycled annually through the world s cultivated crops, which approaches the total world fertilizer consumption of N, P2OS, and K2O in 1975, calculated to be about 82 Tg (Table 9.5). This does not suggest that there is a high... 

Ammonium Sulfate. Before 1950, ammonium sulfate [(NH SO, ] was the most common nitrogen fertilizer. However, the low nitrogen content (21.2%) and lack of value in the secondary nutrient sulfur (24.3%) have reduced the demand. Today, this accounts for only 4% of the nitrogen fertilizer used in the United States. 

The substrate in this case is usually a secondary nutrient, which wc discuss in more detail later. 

The net rate of secondary nutrient consumption during the stationary phase... 

Because ihc desired product can be produced when there is no cell growth, it is always best to relate the product concentration to the change in secondary nutrient concentration. For a batch system the concentration of product. C,. formed after a time f in the staiionaiy phase can be related to the substrate concentration. C. at that time. 

The assumption here in using the p-parameter is that the secondary nutrient is... 

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