NUTRIENT ELEMENTS IN GRASSLAND: SOIL-PLANT-ANIMAL RELATIONSHIPS

By KENNETH MILLER

CONTENTS CONTENTS CONTENTS INTRODUCTION NUTRIENT ELEMENTS ESSENTIAL FOR PLANTS AND ANIMALS TYPES OF GRASSLAND IN TEMPERATE REGIONS THE SIGNIFICANCE OF LEGUME SPECIES NUTRIENT DEFICIENCIES IN TEMPERATE GRASSLAND SYSTEMS NUTRIENT CYCLING IN GRASSLAND SYSTEMS PROBLEMS OF SAMPLING AND ANALYSIS MASS BALANCES OF NUTRIENT ELEMENTS IN GRASSLAND SYSTEMS NUTRIENT ELEMENTS IN SOILS ORIGIN OF MAJOR SOIL CONSTITUENTS INFLUENCE OF PARENT MATERIAL ON NUTRIENT ELEMENTS IN SOILS INPUTS FROM THE ATMOSPHERE INPUTS FROM FERTILIZERS AND LIMING MATERIALS RECYCLING THROUGH THE DECOMPOSITION OF PLANT MATERIAL RECYCLING THROUGH THE EXCRETA OF GRAZING ANIMALS INPUTS FROM THE DISPOSAL OF SEWAGE SLUDGES AVAILABILITY OF NUTRIENT ELEMENTS TO PLANTS IN RELATION TO CHEMICAL FORM AND SOIL PROCESSES INFLUENCE OF CATION EXCHANGE CAPACITY OF THE SOIL ON AVAILABILITY INFLUENCE OF SOIL PH ON AVAILABILITY INFLUENCE OF SOIL ORGANIC MATTER ON AVAILABILITY INFLUENCE OF SOIL REDOX CONDITIONS ON AVAILABILITY ASSESSMENT OF NUTRIENT AVAILABILITY IN SOILS LOSSES OF NUTRIENT ELEMENTS FROM GRASSLAND SOILS UPTAKE AND CONCENTRATIONS OF NUTRIENT ELEMENTS IN GRASSLAND HERBAGE GROWTH AND CHARACTERISTICS OF ROOTS IN GRASSLAND PLANTS CONTACT BETWEEN NUTRIENT IONS AND THE ROOT SURFACE PROCESSES OF NUTRIENT UPTAKE BY PLANT ROOTS THE IMPORTANCE OF THE RHIZOSPHERE AND OF MYCORRHIZAL ASSOCIATIONS UPTAKE OF NUTRIENT ELEMENTS THROUGH LEAVES TRANSPORT AND METABOLISM OF NUTRIENT ELEMENTS IN PLANTS DISTRIBUTION OF NUTRIENT ELEMENTS IN GRASSES AND LEGUMES RANGES OF CONCENTRATION OF NUTRIENT ELEMENTS IN GRASSLAND HERBAGE REMOVAL OF NUTRIENT ELEMENTS IN HARVESTED HERBAGE PLANT : SOIL CONCENTRATION RATIOS THE CONCEPT OF THE CRITICAL CONCENTRATION INFLUENCE OF PLANT SPECIES AND VARIETY ON HERBAGE CONCENTRATIONS OF NUTRIENT ELEMENTS INFLUENCE OF STAGE OF MATURITY ON HERBAGE CONCENTRATIONS OF NUTRIENT ELEMENTS INFLUENCE OF WEATHER AND SEASONAL FACTORS ON HERBAGE CONCENTRATIONS OF NUTRIENT ELEMENTS CHANGES IN THE HERBAGE CONCENTRATIONS OF NUTRIENT ELEMENTS DURING CONVERSION TO HAY OR SILAGE INFLUENCE OF SOIL TYPE ON HERBAGE CONCENTRATIONS OF NUTRIENT ELEMENTS INFLUENCE OF FERTILIZERS, LIME AND SEWAGE SLUDGE ON HERBAGE CONCENTRATIONS OF NUTRIENT ELEMENTS INFLUENCE OF LIVESTOCK EXCRETA ON HERBAGE CONCENTRATIONS OF NUTRIENT ELEMENTS CHEMICAL FORMS OF NUTRIENT ELEMENTS IN HERBAGE NUTRIENT ELEMENTS IN RUMINANT ANIMALS OUTLINE OF DIGESTIVE PHYSIOLOGY IN RUMINANT ANIMALS METABOLIC REQUIREMENTS FOR NUTRIENT ELEMENTS HOMEOSTATIC CONTROL OF NUTRIENT ELEMENTS IN ANIMAL TISSUES CONCENTRATIONS OF NUTRIENT ELEMENTS IN ANIMAL TISSUES AND MILK ANIMAL : PLANT CONCENTRATION RATIOS ABSORPTION OF NUTRIENT ELEMENTS FROM THE DIET FACTORS INFLUENCING THE AVAILABILITY OF NUTRIENT ELEMENTS IN THE DIET ASSESSMENT OF THE DIETARY REQUIREMENTS OF NUTRIENT ELEMENTS OCCURRENCE AND DIAGNOSIS OF DEFICIENCIES IN RUMINANT ANIMALS SOIL INGESTION BY RUMINANT ANIMALS NUTRIENT ELEMENTS SUPPLIED BY DRINKING-WATER EXCRETION OF NUTRIENT ELEMENTS PARTITIONING OF INGESTED NUTRIENTS TO ANIMAL PRODUCTS AND EXCRETA NITROGEN NATURAL SOURCES AND AMOUNTS OF N IN SOILS AGRICULTURAL AND ATMOSPHERIC INPUTS OF N RECYCLING OF N THROUGH THE DECOMPOSITION OF ORGANIC RESIDUES FORMS AND AVAILABILITY OF N IN SOILS LOSSES OF N FROM SOILS ASSESSMENT OF PLANT-AVAILABLE N IN SOILS UPTAKE OF N BY HERBAGE PLANTS FUNCTIONS OF N IN PLANTS INFLUENCE OF FERTILIZER N ON HERBAGE YIELD AND ON MILK PRODUCTION DISTRIBUTION OF N WITHIN HERBAGE PLANTS RANGES OF CONCENTRATION AND CRITICAL CONCENTRATIONS OF N IN HERBAGE PLANTS INFLUENCE OF N SUPPLY FROM SOIL AND FERTILIZER ON CONCENTRATIONS OF N IN HERBAGE INFLUENCE OF PLANT SPECIES AND VARIETY ON CONCENTRATIONS OF N IN HERBAGE INFLUENCE OF STAGE OF MATURITY ON CONCENTRATIONS OF N IN HERBAGE INFLUENCE OF SEASON OF THE YEAR AND WEATHER FACTORS ON CONCENTRATIONS OF N IN HERBAGE INFLUENCE OF FERTILIZER P, K AND S AND LIME ON CONCENTRATIONS OF N IN HERBAGE INFLUENCE OF LIVESTOCK EXCRETA ON CONCENTRATIONS OF N IN HERBAGE CHEMICAL FORMS AND AVAILABILITY OF HERBAGE N TO RUMINANT ANIMALS METABOLIC FUNCTIONS OF N IN RUMINANT ANIMALS ABSORPTION OF DIETARY N BY RUMINANT ANIMALS NUTRITIONAL REQUIREMENTS FOR N IN RUMINANT ANIMALS EXCRETION OF N BY RUMINANT ANIMALS TRANSFORMATIONS OF N IN GRASSLAND SYSTEMS QUANTITATIVE BALANCES OF N IN GRASSLAND SYSTEMS PHOSPHORUS NATURAL SOURCES AND CONCENTRATIONS OF P IN SOILS AGRICULTURAL AND ATMOSPHERIC INPUTS OF P TO SOILS RECYCLING OF P THROUGH THE DECOMPOSITION OF ORGANIC RESIDUES FORMS AND AVAILABILITY OF P IN SOILS LOSSES OF P FROM SOILS ASSESSMENT OF PLANT-AVAILABLE P IN SOILS UPTAKE OF P BY HERBAGE PLANTS FUNCTIONS OF P IN HERBAGE PLANTS INFLUENCE OF FERTILIZER P ON YIELDS OF GRASSLAND HERBAGE DISTRIBUTION OF P WITHIN HERBAGE PLANTS RANGE OF CONCENTRATIONS AND CRITICAL CONCENTRATIONS OF P IN HERBAGE PLANTS INFLUENCE OF PLANT SPECIES AND VARIETY ON CONCENTRATIONS OF P IN HERBAGE INFLUENCE OF STAGE OF MATURITY ON CONCENTRATIONS OF P IN HERBAGE INFLUENCE OF SEASON OF THE YEAR AND WEATHER FACTORS ON CONCENTRATIONS OF P IN HERBAGE INFLUENCE OF FERTILIZER N ON CONCENTRATIONS OF P IN HERBAGE INFLUENCE OF FERTILIZER P AND K AND OF LIME ON CONCENTRATIONS OF P IN HERBAGE INFLUENCE OF LIVESTOCK EXCRETA ON CONCENTRATIONS OF P IN HERBAGE CHEMICAL FORMS OF HERBAGE P OCCURRENCE AND METABOLIC FUNCTIONS OF P IN RUMINANT ANIMALS ABSORPTION OF DIETARY P BY RUMINANT ANIMALS NUTRITIONAL REQUIREMENTS FOR P IN RUMINANT ANIMALS EFFECTS OF P DEFICIENCY ON RUMINANT ANIMALS EXCRETION OF P BY RUMINANT ANIMALS TRANSFORMATIONS OF P IN GRASSLAND SYSTEMS QUANTITATIVE BALANCES OF P IN GRASSLAND SYSTEMS SULPHUR NATURAL SOURCES AND CONCENTRATIONS OF S IN SOILS ATMOSPHERIC AND AGRICULTURAL INPUTS OF S TO SOILS RECYCLING OF S THROUGH THE DECOMPOSITION OF ORGANIC RESIDUES FORMS AND AVAILABILITY OF S IN SOILS LOSSES OF S FROM SOILS ASSESSMENT OF PLANT-AVAILABLE S IN SOILS UPTAKE OF S BY HERBAGE PLANTS FUNCTIONS OF S IN HERBAGE PLANTS INFLUENCE OF FERTILIZER S ON YIELDS OF GRASSLAND HERBAGE DISTRIBUTION OF S WITHIN HERBAGE PLANTS RANGE OF CONCENTRATIONS AND CRITICAL CONCENTRATIONS OF S IN HERBAGE PLANTS INFLUENCE OF PLANT SPECIES AND VARIETY ON CONCENTRATIONS OF S IN HERBAGE INFLUENCE OF STAGE OF MATURITY ON CONCENTRATIONS OF S IN HERBAGE INFLUENCE OF SEASON OF THE YEAR AND WEATHER FACTORS ON CONCENTRATIONS OF S IN HERBAGE INFLUENCE OF FERTILIZER N ON CONCENTRATIONS OF S IN HERBAGE INFLUENCE OF FERTILIZER P, K AND S ON CONCENTRATIONS OF S IN HERBAGE INFLUENCE OF LIVESTOCK EXCRETA ON CONCENTRATIONS OF S IN HERBAGE CHEMICAL FORMS OF HERBAGE S OCCURRENCE AND METABOLIC FUNCTIONS OF S IN RUMINANT ANIMALS ABSORPTION OF DIETARY S BY RUMINANT ANIMALS NUTRITIONAL REQUIREMENTS FOR S IN RUMINANT ANIMALS EFFECTS OF S DEFICIENCY AND EXCESS ON RUMINANT ANIMALS EXCRETION OF S BY RUMINANT ANIMALS TRANSFORMATIONS OF S IN GRASSLAND SYSTEMS QUANTITATIVE BALANCES OF S IN GRASSLAND SYSTEMS MACRONUTRIENT CATIONS: POTASSIUM, SODIUM, CALCIUM AND MAGNESIUM SOURCES AND CONCENTRATIONS OF K, NA, CA AND MG IN SOILS AGRICULTURAL AND ATMOSPHERIC INPUTS OF K, NA, CA AND MG RECYCLING OF K, NA, CA AND MG THROUGH THE DECOMPOSITION OF ORGANIC RESIDUES LOSSES OF K, NA, CA AND MG FROM SOILS FORMS AND AVAILABILITY OF K, NA, CA AND MG IN SOILS ASSESSMENT OF PLANT-AVAILABLE K, NA, CA AND MG IN SOILS UPTAKE OF K, NA, CA AND MG BY HERBAGE PLANTS FUNCTIONS OF K, NA, CA AND MG IN HERBAGE PLANTS DISTRIBUTION OF K, NA, CA AND MG IN HERBAGE PLANTS RANGES OF CONCENTRATION AND CRITICAL CONCENTRATIONS OF K, NA, CA AND MG IN HERBAGE PLANTS INFLUENCE OF FERTILIZATION WITH K, NA, CA AND MG ON YIELDS OF GRASSLAND HERBAGE INFLUENCE OF SPECIES AND VARIETY ON CONCENTRATIONS OF K, NA, CA AND MG IN HERBAGE INFLUENCE OF STAGE OF MATURITY ON CONCENTRATIONS OF K, NA, CA AND MG IN HERBAGE INFLUENCE OF SEASON OF THE YEAR AND WEATHER FACTORS ON CONCENTRATIONS OF K, NA, CA AND MG IN HERBAGE INFLUENCE OF SOIL TYPE ON CONCENTRATIONS OF K, NA, CA AND MG IN HERBAGE INFLUENCE OF FERTILIZER N ON CONCENTRATIONS OF K, NA, CA AND MG IN HERBAGE INFLUENCE OF FERTILIZER P ON CONCENTRATIONS OF K, NA, CA AND MG IN HERBAGE INFLUENCE OF FERTILIZER K ON CONCENTRATIONS OF K, NA, CA AND MG IN HERBAGE INFLUENCE OF THE APPLICATION OF NA, MG AND LIME ON CONCENTRATIONS OF K, NA, CA AND MG IN HERBAGE INFLUENCE OF LIVESTOCK EXCRETA ON CONCENTRATIONS OF K, NA, CA AND MG IN HERBAGE CHEMICAL FORMS AND AVAILABILITY OF K, NA, CA AND MG IN HERBAGE OCCURRENCE AND METABOLIC FUNCTIONS OF K, NA, CA AND MG IN RUMINANT ANIMALS ABSORPTION OF DIETARY K, NA, CA AND MG BY RUMINANT ANIMALS NUTRITIONAL REQUIREMENTS FOR K, NA, CA AND MG IN RUMINANT ANIMALS EFFECTS OF DEFICIENCIES OF K, NA, CA AND MG ON RUMINANT ANIMALS EXCRETION OF K, NA, CA AND MG BY RUMINANT ANIMALS TRANSFORMATIONS OF K, NA, CA AND MG IN GRASSLAND SYSTEMS QUANTITATIVE BALANCES OF K, NA, CA AND MG IN GRASSLAND SYSTEMS MICRONUTRIENT CATIONS: IRON, MANGANESE, ZINC, COPPER AND COBALT SOURCES AND CONCENTRATIONS OF FE, MN, ZN, CU AND CO IN SOILS AGRICULTURAL AND ATMOSPHERIC INPUTS OF FE, MN, ZN, CU AND CO TO SOILS RECYCLING OF FE, MN, ZN, CU AND CO THROUGH THE DECOMPOSITION OF ORGANIC RESIDUES FORMS AND AVAILABILITY OF FE, MN, ZN, CU AND CO IN SOILS LOSSES OF FE, MN, ZN, CU AND CO FROM SOILS ASSESSMENT OF PLANT-AVAILABLE FE, MN, ZN, CU AND CO IN SOILS UPTAKE OF FE, MN, ZN, CU AND CO BY HERBAGE PLANTS FUNCTIONS OF FE, MN, ZN, CU AND CO IN HERBAGE PLANTS DISTRIBUTION OF FE, MN, ZN, CU AND CO WITHIN HERBAGE PLANTS RANGES OF CONCENTRATION AND CRITICAL CONCENTRATIONS OF FE, MN, ZN, CU AND CO IN HERBAGE PLANTS TOXIC CONCENTRATIONS OF MN, ZN AND CU IN HERBAGE PLANTS INFLUENCE OF PLANT SPECIES AND VARIETY ON CONCENTRATIONS OF FE, MN, ZN, CU AND CO IN HERBAGE INFLUENCE OF STAGE OF MATURITY ON FE, MN, ZN, CU AND CO IN HERBAGE INFLUENCE OF SEASON OF THE YEAR AND WEATHER FACTORS ON CONCENTRATIONS OF FE, MN, ZN, CU AND CO IN HERBAGE INFLUENCE OF SOIL TYPE ON CONCENTRATIONS OF FE, MN, ZN, CU AND CO IN HERBAGE INFLUENCE OF FERTILIZER N ON CONCENTRATIONS OF FE, MN, ZN, CU AND CO IN HERBAGE INFLUENCE OF FERTILIZER P AND K AND LIME ON CONCENTRATIONS OF FE, MN, ZN, CU AND CO IN HERBAGE INFLUENCE OF LIVESTOCK EXCRETA ON CONCENTRATIONS OF FE, MN, ZN, CU AND CO IN HERBAGE INFLUENCE OF THE ADDITION OF FE, MN, ZN, CU OR CO ON THE CONCENTRATIONS OF THESE ELEMENTS IN HERBAGE CHEMICAL FORMS OF FE, MN, ZN, CU AND CO IN HERBAGE OCCURRENCE AND METABOLIC FUNCTIONS OF FE, MN, ZN, CU AND CO IN RUMINANT ANIMALS ABSORPTION OF DIETARY FE, MN, ZN, CU AND CO BY RUMINANT ANIMALS NUTRITIONAL REQUIREMENTS FOR FE, MN, ZN, CU AND CO IN RUMINANT ANIMALS EFFECTS OF DEFICIENCIES OF FE, MN, ZN, CU AND CO ON RUMINANT ANIMALS EXCRETION OF FE, MN, ZN, CU AND CO BY RUMINANT ANIMALS TRANSFORMATIONS OF FE, MN, ZN, CU AND CO IN GRASSLAND SYSTEMS QUANTITATIVE BALANCES OF FE, MN, ZN, CU AND CO IN GRASSLAND SYSTEMS THE NUTRIENT HALOGENS: CHLORINE AND IODINE SOURCES AND CONCENTRATIONS OF CL AND I IN SOILS ATMOSPHERIC AND AGRICULTURAL INPUTS OF CL AND I TO SOILS RECYCLING OF CL AND I THROUGH THE DECOMPOSITION OF ORGANIC RESIDUES FORMS AND AVAILABILITY OF CL AND I IN SOILS LOSSES OF CL AND I FROM SOILS UPTAKE OF CL AND I BY HERBAGE PLANTS FUNCTIONS OF CL AND I IN HERBAGE PLANTS DISTRIBUTION OF CL AND I IN HERBAGE PLANTS RANGES OF CONCENTRATION OF CL AND I AND CRITICAL CONCENTRATIONS OF CL IN HERBAGE PLANTS INFLUENCE OF PLANT SPECIES AND VARIETY ON CONCENTRATIONS OF CL AND I IN HERBAGE INFLUENCE OF STAGE OF MATURITY ON CONCENTRATIONS OF CL AND I IN HERBAGE INFLUENCE OF SEASON OF THE YEAR AND WEATHER FACTORS ON CONCENTRATIONS OF CL AND I IN HERBAGE INFLUENCE OF SOIL TYPE ON CONCENTRATIONS OF CL AND I IN HERBAGE INFLUENCE OF FERTILIZER N ON CONCENTRATIONS OF CL AND I IN HERBAGE INFLUENCE OF FERTILIZER P AND K, OF LIME AND OF KI ON CONCENTRATIONS OF CL AND I IN HERBAGE INFLUENCE OF LIVESTOCK EXCRETA ON CONCENTRATIONS OF CL IN HERBAGE CHEMICAL FORMS OF CL AND I IN HERBAGE OCCURRENCE AND METABOLIC FUNCTIONS OF CL AND I IN RUMINANT ANIMALS ABSORPTION OF DIETARY CL AND I BY RUMINANT ANIMALS NUTRITIONAL REQUIREMENTS FOR CL AND I IN RUMINANT ANIMALS EFFECTS OF DEFICIENCIES OF CL AND I, AND TOXICITY OF I, ON RUMINANT ANIMALS EXCRETION OF CL AND I BY RUMINANT ANIMALS TRANSFORMATIONS OF CL AND I IN GRASSLAND SYSTEMS QUANTITATIVE BALANCES OF CL AND I IN GRASSLAND SYSTEMS BORON, MOLYBDENUM AND SELENIUM SOURCES AND CONCENTRATIONS OF B, MO AND SE IN SOILS AGRICULTURAL AND ATMOSPHERIC INPUTS OF B, MO AND SE TO SOILS FORMS AND AVAILABILITY OF B, MO AND SE IN SOILS LOSSES OF B, MO AND SE FROM SOILS ASSESSMENT OF PLANT-AVAILABLE B, MO AND SE IN SOILS UPTAKE OF B, MO AND SE BY HERBAGE PLANTS FUNCTIONS OF B, MO AND SE IN HERBAGE PLANTS DISTRIBUTION OF B, MO AND SE WITHIN HERBAGE PLANTS RANGES OF CONCENTRATION AND CRITICAL CONCENTRATIONS OF B, MO AND SE IN HERBAGE PLANTS INFLUENCE OF PLANT SPECIES AND VARIETY ON CONCENTRATIONS OF B, MO AND SE IN HERBAGE INFLUENCE OF STAGE OF MATURITY ON CONCENTRATIONS OF B, MO AND SE IN HERBAGE INFLUENCE OF SEASON OF THE YEAR AND WEATHER FACTORS ON CONCENTRATIONS OF B, MO AND SE IN HERBAGE INFLUENCE OF SOIL TYPE ON CONCENTRATIONS OF B, MO AND SE IN HERBAGE INFLUENCE OF FERTILIZERS AND LIME ON CONCENTRATIONS OF B, MO AND SE IN HERBAGE INFLUENCE OF THE ADDITION OF B, MO AND SE ON CONCENTRATIONS OF THESE ELEMENTS IN HERBAGE INFLUENCE OF LIVESTOCK EXCRETA ON CONCENTRATIONS OF B, MO AND SE IN HERBAGE CHEMICAL FORMS AND AVAILABILITY OF B, MO AND SE IN HERBAGE OCCURRENCE AND METABOLIC FUNCTIONS OF B, MO AND SE IN RUMINANT ANIMALS ABSORPTION OF DIETARY B, MO AND SE BY RUMINANT ANIMALS NUTRITIONAL REQUIREMENTS FOR MO AND SE IN RUMINANT ANIMALS EFFECTS OF DEFICIENCIES AND TOXICITIES OF B, MO AND SE ON RUMINANT ANIMALS EXCRETION OF B, MO AND SE BY RUMINANT ANIMALS TRANSFORMATIONS OF B, MO AND SE IN GRASSLAND SYSTEMS QUANTITATIVE BALANCES OF B, MO AND SE IN GRASSLAND SYSTEMS INTRODUCTION CHAPTER CHAPTER INTRODUCTION NUTRIENT ELEMENTS ESSENTIAL FOR PLANTS AND ANIMALS PLANTS AND ANIMALS ARE COMPOSED PRIMARILY OF CARBON (C), HYDROGEN (H) AND OXYGEN (O), BUT A NUMBER OF OTHER ELEMENTS, THE NUTRIENT ELEMENTS, ARE NECESSARY AS COMPONENTS OF THEIR STRUCTURAL TISSUES OR AS PARTICIPANTS IN BIO- CHEMICAL REACTIONS THE NUTRIENT ELEMENTS KNOWN TO BE ESSENTIAL FOR PLANTS ARE NITROGEN (N), PHOSPHORUS (P), SULPHUR (S), POTASSIUM (K), CALCIUM (CA), MAGNESIUM (MG), CHLORINE (CL), IRON (FE), MANGANESE (MN), ZINC (ZN), COPPER (CU), BORON (B) AND MOLYBDENUM (MO) PLANTS, SUCH AS LEGUMES, THAT RELY DIRECTLY ON N2 FIXATION FOR THEIR N SUPPLY ALSO REQUIRE COBALT (CO) AS A NUTRIENT FOR THEIR RHIZOBIAL BACTERIA IN ADDITION, NICKEL (NI) HAS BEEN SHOWN TO BE ESSENTIAL FOR SOME PLANT SPECIES (MARSCHNER, 1995); AND SODIUM (NA), SELENIUM (SE) AND SILICON (SI) HAVE BEEN SHOWN TO BE BENEFICIAL IN SOME SITUATIONS, WITHOUT SATISFYING THE CRITERIA FOR ESSENTIALITY AN ELEMENT IS REGARDED AS ESSENTIAL FOR PLANTS IF: (I) A DEFICIENCY MAKES IT IMPOSSIBLE FOR THE PLANT TO COMPLETE THE VEGETATIVE OR REPRODUCTIVE STAGE OF ITS LIFE CYCLE; (II) THE DEFICIENCY IS SPECIFIC TO THE ELEMENT IN QUESTION AND CAN BE PREVENTED OR CORRECTED ONLY BY SUPPLYING THIS ELEMENT; AND (III) THE ELEMENT IS DIRECTLY INVOLVED IN THE NUTRITION OF THE PLANT AND IS NOT SIMPLY CORRECTING SOME UNFAVOURABLE CONDITION OF THE SOIL OR CULTURE MEDIUM (WILD AND JONES, 1988) ALL THE ELEMENTS ESSENTIAL FOR PLANTS, WITH THE POSSIBLE EXCEPTION OF B, ARE ESSENTIAL FOR ANIMALS AND, IN ADDITION, ANIMALS REQUIRE IODINE (I), NA, SE, CHROMIUM (CR) AND NI A FEW OTHER ELEMENTS, INCLUDING FLUORINE (F) AND SI, HAVE ALSO BEEN SHOWN TO BE BENEFICIAL WHEN ADDED IN MINUTE AMOUNTS TO PURIFIED DIETS UNDER RIGOROUSLY CONTROLLED LABORATORY CONDITIONS (UNDER- WOOD AND MERTZ, 1987; MILLS, 1992; UNDERWOOD AND SUTTLE, 1999) HOWEVER, THERE IS NO EVIDENCE OF CR, NI, F OR SI BEING DEFICIENT IN AGRICULTURAL PRACTICE OR IN NATURAL ECOSYSTEMS, AND THEY ARE NOT DISCUSSED FURTHER IN THIS BOOK THE QUANTITY OF A NUTRIENT ELEMENT REQUIRED BY EITHER PLANTS OR ANIMALS DEPENDS ON ITS METABOLIC FUNCTIONS AND VARIES WIDELY FROM ELEMENT TO ELEMENT THERE IS A MARKED CONTRAST IN PLANTS, FOR EXAMPLE, BETWEEN N AND