The Macronutrient Elements

Abstract

The term "macronutrient" is recent, having come into popular usage since the general acceptance of the term "micronutrient." Therefore, the term "macronutrient element" suggests· one of the nine elements needed by plants in larger quantity, namely: nitrogen, phosphorus, sulfur, calcium, magnesium, potassium, carbon, hydrogen, and oxygen. However, only the first six which can be supplied conveniently as fertilizers are ordinarily con sidered among the macronutrients. In plant physiology, the understanding associated with "nutrient elements" is distinctively separate from the general sense of energy-containing foods. Thus, in speaking of "nutrient elements," the implications are always of the simple mineral constituents necessary for the growth and development of the living plant.A large and expanding need for the macronutrient elements in contem porary agriculture encourages most of the research effort directed toward them. For the same reason, many other specialists besides plant physiol ogists maintain similar interests in the macronutrients.A continuing live interest in the chemical elements required for plant growth stems, of course, from the activities of agriculture in providing our "daily bread." The time has long since passed when agriculture can supply food to the more advanced countries of the world by the simple methods of tradition. As agriculture accommodates more and more into the methods of industrialization, it depends increasingly upon other industrial activities.Agriculture has now become the most sophisticated of all the arts in adapting things of the natural world to the uses of human society. It calls upon every facet of contemporary science to help in meeting the common problem. It enlists industry to provide the continually increasing require ments for machinery and for additional supplies of water, fertilizers, and toxins to fight the unrelenting war against insects, nematodes, and diseases of plants or animals. Macronutrient elements appear clearly as subjects of ex ceptional importance if for no other reason than their sheer bulk, which has to be moved to suitable geographic regions for economical plant production.It is very rare when the chemical elements needed for maximal plant growth are supplied adequately by soils. Enormous tonnages of calcium, magnesium, potassium, nitrogen, phosphorus, and sulfur are mined, proc-1

Surface application of gypsum in low acidic Oxisol under no-till cropping system

“…The cation exchange capacity of roots is lower in corn than in soybean (Fernandes and Souza, 2006). Roots having a high charge density tend to accumulate bivalent ions in contrast to roots of low charge density differentially absorbing univalent ions (Wallace and Smith 1955 cited by Broyer and Stout, 1959). So, corn plants are less efficient than soybean plants in Ca 2+ uptake from soil solution and an increase in soil exchangeable Ca content followed by decreased level of exchangeable Mg with gypsum addition must have favored the Ca 2+ uptake by corn plants.…”

Use of Gypsum for Crop Grain Production under a Subtropical No‐Till Cropping System

“…Williams and Coleman (1950) found that the CECR was double in soybean as compared with corn. The roots possessing a high charge density tend to accumulate divalent ions in contrast to roots with a low charge density differentially absorbing univalent ions (Broyer and Stout, 1959). Therefore, corn and wheat plants are less efficient than soybean plants in Ca uptake from the soil solution.…”

Role of Mineral Elements with Emphasis on the Univalent Cations

“…Since K+ is required for carbamyl phosphate synthesis in extracts of Rana pipiens liver (Table IV, 29) , it seems logical to postulate that a defi ciency could limit or prevent the biosynthesis of arginine, citrulline, and pyrimidines in organisms where carbamylphosphate synthetase is operative. Potassium has been shown to be required for the enzymatic synthesis of S adenosylmethionine in yeast and animals (Table IV, [36][37][38][39] and, thus, could play a role in the metabolism of methyl transfer. Finally, there are several enzymes involved in the synthesis of vitamins, co factors, and coenzymes (Table IV, 42,21,30,31,43,24,45) that could affect protein synthesis in directly.…”