AGA142_PART1 CHAPTER5

• Plant nutrition


  The study of the chemical elements and compounds necessary for plant growth and reproduction, plant metabolism and their external supply. In its absence the plant is unable to complete a normal life cycle, or that the element is part of some essential plant constituent or metabolite

  
• Plants


  • Can absorb nutrients and water through their root system, as well as carbon dioxide from the atmosphere
  • Soil quality and climate are the major determinants of plant distribution and growth
  • The combination of soil nutrients, water, and carbon dioxide, along with sunlight, allows plants to grow

  
• Essential nutrients

  • Light
  • Water
  • 20 elements
• Secondary macronutrients

  • Nitrogen (N)
  • Phosphorus (P)
  • Potassium (K)
  • Calcium (Ca)
  • Magnesium (Mg)
  • Sulfur (S)
• Micronutrients

  • Chlorine (Cl)
  • Cobalt (Co)
  • Copper (Cu)
  • Iron (Fe)
  • Manganese (Mn)
  • Molybdenum (Mo)
  • Nickel (Ni)
  • Zinc (Zn)
• Primary macronutrients

  • Carbon (C)
  • Hydrogen (H)
  • Oxygen (O)
• Cation Exchange Capacity (CEC)


  The total amount of cations that a soil can retain<|>The higher the soil CEC the greater ability it has to store plant nutrients<|>Soil CEC increases as the amount of clay increases, the amount of organic matter increases, and the soil pH increases

  
• Forms of nutrients taken up by plants

  • CO2
  • H2O, H+
  • CO2, H2O, O2
  • NO3-, NH4+
  • H2PO4-, HPO4+
  • K+
  • Ca2+
  • Mg2+
  • SO4+
  • Fe2+, Fe3+
  • Mn2+
  • H3BO3
  • Cu2+
  • Zn2+
  • Cl-
  • Ni2+
  • Co2+

  
• Functions of elements in plants

  • C, H, O - All plant organic components, sugars, cellulose, starch, lipids
  • N & S - Component of Amino Acid, constituents of protein, nucleic acid (DNA, RNA), chlorophyll
  • N & P - Nucleotides, energy transfer (ATP), electron transfer (NADP), genetic information (DNA & RNA)
  • P - Carries chemical energy in ATP, synthesis of ATP, sugar-phosphates, component of DNA & RNA, component of phospholipids in membranes
  • K - K ions, enzyme activator, osmotic regulator especially in stomatal opening/closing
  • Ca - Regulator of cell process
  • Mg - Complexed as chlorophyll, photosynthesis
  • Fe - Complexed with ATP, energy transfer
  • Mo - Complexed as cytochromes, electron transfer
  • Ca, Mg, Mn, Cu, Zn - Component of enzymes, N2 fixation & nitrate reduction, associated with enzymes, activators
• Nutrients

  • Taken up by the fine root hairs, not by the big roots
  • The larger roots are used for supporting the tree and for storage of water and other plant food
  • The root hairs can also excrete liquids that affect the acidity of the soil (pH)
  • When the pH changes, the amount of nutrients available may also change

  
• Types of nutrients

  • Macronutrients - required in large quantities
  • Micronutrients - required in small quantities
• Essential nutrients

  • Nitrogen (N)
  • Phosphorus (P)
  • Potassium (K)
  • Calcium (Ca)
  • Magnesium (Mg)
  • Sulfur (S)
  • Chlorine (Cl)
  • Cobalt (Co)
  • Copper (Cu)
  • Iron (Fe)
  • Manganese (Mn)
  • Molybdenum (Mo)
  • Nickel (Ni)
  • Zinc (Zn)
• Nitrogen


  An integral component of many essential plant compounds<|>Major roles: part of amino acids, enzymes, nucleic acids, chlorophyll, use of carbohydrates, stimulates root growth and development, uptake of other nutrients, imparts deep green colour, increases plumpness of cereal grains, protein content, succulence of crops, stimulates plant productivity
• Nitrogen deficiency causes plants to have a pale yellowish green color, stunted appearance, develop thin, spindly stems, low protein content, high sugar content

  
• Excessive nitrogen causes enlarged but weak plant cells, prone to lodging, delayed maturity, more susceptible to disease and insect pests, poor crop quality

  
• Phosphorus


  Essential component of ATP, DNA, RNA, phospholipids<|>Enhances photosynthesis, nitrogen fixation, maturation, flowering, fruiting, seed production, root growth, structural tissues, crop quality

  
• Phosphorus deficiency causes plants to be stunted, thin-stemmed, spindly, dark green foliage, delayed maturity, sparse flowering, poor seed quality

  
• Potassium


  Activates enzymes responsible for energy metabolism, starch synthesis, nitrate reduction, photosynthesis<|>Excess salinity can cause brown, necrotic leaf margins, affects newer leaves
• Potassic fertilizers

  • Muriate of potash (KCl) - 50% or 60% K2O
  • Sulphate of potash (K2SO4) - 48% K2O
• Nutrient deficiency symptoms

  • Nitrogen - Chlorosis, yellowing of lower leaves first, stunting
  • Phosphorus - Low photosynthesis rate, leaves & stems turn purple, stunting, low yield
  • Potassium - Leaves turn light green, burning of leave margins & tips, less roots development, weak stems, susceptible to disease
  • Calcium - Young leaves crinkled, twisted & short
  • Magnesium - Chlorosis of lower leaves
  • Sulfur - Yellowing of young leaves & stunting
  • Iron - Interveinal chlorosis of young leaves
  • Zinc - Chlorosis of veins especially of young leaves

  
• Sufficiency


  When do you know if your plant has enough of a nutrient?

  
• Toxicity


  When do you know when there's too much of a nutrient?
• Muriate of potash (KCI)


  Contains either 50% or 60% K2O
• Sulphate of potash (K2SO4)


  Contains about 48% K2O
• Plant nutrient deficiency symptoms

  • Nitrogen: Chlorosis, yellowing of lower leaves first, stunting
  • Phosphorus: Low photosynthesis rate, leaves & stems turn purple, stunting, low yield
  • Potassium: Leaves turn light green, burning of leave margins & tips, less roots development, weak stems, susceptible to disease
  • Calcium: Young leaves crinkled, twisted & short
  • Magnesium: Chlorosis of lower leaves
  • Sulfur: Yellowing of young leaves & stunting
  • Iron: Interveinal chlorosis of young leaves
  • Zinc: Chlorosis of veins especially of young leaves

  
• Toxicity


  When do you know when there's too much of that nutrient?
• Deficiency


  How can you know that there's not enough of that nutrient?
• One nutrient can cause malnutrition when it prevents your plants from absorbing other important nutrients
• Nutrition deficiency: When one nutrient is lacking, a plant may not germinate. It may fail to develop roots, stems, and leaves. Or the plant may not flower or create seeds. In many cases, plants simply die due to nutrition starvation
• Nutrition toxicity: Too much nutrition can cause problems. For instance, too much nitrogen creates too many leaves and no fruits; overfeeding with manganese turns leaves yellow/ and too much boron kills plants
• Agricultural crops use the nutrients that are held in the soil. As crops are harvested and removed from the land, nutrients are removed with the plant tissues

  
• To maintain high yields, nutrients must be added to the soil

  
• Fertilizer


  An organic or inorganic material applied to soils or water, which provide nutrients that increase plant growth, yield, and nutritional quality

  
• Organic fertilizer


  Organic material that releases or supplies useful amounts of a plant nutrient when added to a soil

  
• Examples of organic fertilizers

  • Dried and pulverized manures
  • Bone meal
  • Slaughterhouse tankage
  • Blood meal
  • Dried and ground sewage sludge
  • Cottonseed meal
  • Soybean meal
• Characteristics of organic fertilizers

  • Nitrogen is usually the predominating nutrient with lesser quantities of phosphorus and potassium
  • Nutrients are only made available to plants as the material decays in the soil, so they are slow acting and long lasting
  • Organic materials alone are not balanced sources of plant nutrients, and their analysis in terms of the three major nutrients is generally low
  • The material is bulky and the exact amount of fertilizer applied is difficult to measure

  
• Inorganic fertilizer


  Those from a non-living source, and included various mineral salts, which contain plant nutrients in combination with other elements

  
• Characteristics of inorganic fertilizers

  • Nutrients are in a soluble form and are quickly available for plant use
  • The soluble nutrients make them caustic to growing plants and can cause injury
  • Analysis of chemical fertilizer is relatively high in terms of the nutrients they contain

  
• Types of fertilizer

  • Organic
  • Non-Organic (Straight/Incomplete, Compound/Complete, Mixed)
• Organic fertilizers

  • Animal wastes such as cow dung, chicken dung, bat dung (also known as guano), blood and fish bones processed to make them safer to use
  • Plant parts recycled as 'green' fertilizers or processed into commercial organic fertilizers