There are 16 elements currently considered necessary for plant growth.

Carbon, hydrogen and oxygen are obtained from air and water and through photosynthesis are converted to 90% of a plant’s dry matter.

Then there are six 'macro' nutrients absorbed in large amounts and seven 'micro' nutrients absorbed in small amounts from the soil or a hydroponic solution.

Under intensive production systems, the nutrient elements of which the soil has the smallest reserve in relation to crop requirement, are the first to require replenishment.

The ratio of nutrients available is important as an excess of one nutrient can result in a deficiency of another element.

Optimum plant growth and yield are the goals, thus watering and nutrition are critical. Optimum nutrient solutions begin with good quality and quantity water. Before starting any commercial operation, the water MUST be analysed.

The source water should be fairly neutral pH (5-8) with low salt and heavy metal content. Low or high pH can affect nutrient uptake and salt and metals can affect plant growth.

Optimum plant growth is a function of nutrient concentration in the plant. There is a critical nutrient concentration below which growth is reduced/terminated. The adequate zone is above the critical concentration and provides maximum growth. The toxic zone is above the adequate zone, again resulting in reduced growth or death. THEREFORE, MORE IS NOT ALWAYS BETTER!";

Plants take up more nitrogen than any other nutrient.  It is present in amino acids, enzymes, chlorophyll and genes.  Nitrogen is needed in highest concentrations in plant parts that are actively growing such as young leaves and fruits (flowers) and root tips. Plants can take up nitrogen in both nitrate and ammonium forms. Toxicity can be a problem wither as a result of too high levels of the ammonium ion, by to much soluble manganese being released as the pH is lowered, or by interference with other nutrients.

Deficiencies: (mobile) restricted growth and yellowing (chlorosis) of older leaves.

Agrichem N products

• Clear Liquid Solutions
• Suspension Range

Present in many forms in soils, phosphorous is essential to photosynthesis and the making of protein and new cells. During periods of rapid shoot and root extension it is vital phosphorous is available, otherwise growth will be stunted.  Phosphorous is especially important early in a plant’s life for good root system development and successful establishment.

Deficiencies: (mobile) poor root/plant growth and flowering, 'purplish' under leaves.

Agrichem P products Clear Liquid Solutions

Suspension Range

Starters and Planters

This nutrient is taken up in fairly large amounts by plants.  Being a macro element it is required for good plant growth and development increasing vigour, disease resistance and fruit quality.  Potassium has role in controlling water movement between cells, as a balancing cation for anions and is used various chemical reactions.

Deficiencies: (mobile) poor growth, leaf chlorosis/necrosis (death), slowed gas exchange.

Agrichem K products Clear Liquid Solutions

Suspension Range

Calcium improves the absorption of other nutrients by roots and their translocation within the plant.  It activates a number of plant growth- regulating enzyme systems, helps convert nitrate-nitrogen into forms needed for protein formation, is needed for cell wall formation and normal cell division, and contributes to improved disease resistance.  Calcium, along with magnesium and potassium, helps to neutralize organic acids, which form during cell metabolism in plants. The presence of adequate quantities of calcium aids in the delay of leaf senescence as well as reducing leaf and fruit abscission.

Deficiencies: (not mobile) poor growth of meristems (growing tip), blossom end rot.

Agrichem Ca products Trace Elements   Chelated Micronutrients

Magnesium is an essential component of the chlorophyll molecule, with each molecule containing 6.7 percent magnesium. Magnesium also acts as a phosphorus carrier in plants.  It is necessary for cell division and protein formation.  Phosphorus uptake could not occur without magnesium and vice versa.  So, magnesium is essential for phosphate metabolism, plant respiration and the activation of several enzyme systems.

Deficiencies: (mobile) interveinal chlorosis/necrosis of lower mature leaves.

Agrichem Mg products Trace Elements Chelated Micronutrients

Sulphur is absorbed primarily in the sulfate form (SO4-2) by plants.  It may also enter the leaves of plants from the air as sulfur dioxide gas. It is part of every living cell and required for synthesis of certain amino acids (cysteine and methionine) and proteins.  Sulphur is also important in photosynthesis and crop winter hardiness. Leguminous plants need sulphur for efficient nitrogen fixation. Sulphur is also important in the nitrate- reductase process where nitrate- nitrogen is converted to amino acids.

Deficiencies: (slightly mobile) reduced growth in mid/young leaves, thin brittle stems.

Agrichem S products Trace Elements

Micronutrients are elements which are essential for plant growth, but are required in much smaller amounts than those of the primary nutrients.

Iron is involved in the production of chlorophyll, and iron chlorosis is easily recognised on iron- sensitive crops growing on calcareous soils.  Iron also is a component of many enzymes associated with energy transfer, nitrogen reduction and fixation, and lignin formation. Iron is associated with sulphur in plants to form compounds that catalyse other reactions

Deficiencies: Iron deficiencies are mainly manifested by yellow leaves due to low levels of chlorophyll.  Leaf yellowing first appears on the younger upper leaves in interveinal tissues.  Severe iron deficiencies cause leaves to turn completely yellow or almost white, and then brown as leaves die.  Iron deficiencies are found mainly on calcareous (high pH) soils, although some acid, sandy soils low in organic matter also may be iron-deficient. Cool, wet weather enhances iron deficiencies, especially on soils with marginal levels of available iron.  Poorly aerated or compacted soils also reduce iron uptake by plants. Uptake of iron decreases with increased soil pH, and is adversely affected by high levels of available phosphorus, manganese and zinc in soils.

Agrichem Fe products Trace Elements

Chelated Micronutrients

Involved in enzyme activation during carbohydrate reduction, chlorophyll and RNA/DNA synthesis and other reactions.  Manganese deficiencies mainly occur on organic soils, high-pH soils, sandy soils low in organic matter, and on over-limed soils. Soil manganese may be less available in dry, well-aerated soils, but can become more available under wet soil conditions when manganese is reduced to the plant-available form.  Conversely, manganese toxicity can result in some acidic, high-manganese soils. Uptake of manganese decreases with increased soil pH and is adversely affected by high levels of available iron in soils.

Deficiencies: In very severe manganese deficiencies, brown necrotic spots appear on leaves, resulting in premature leaf drop.  Delayed maturity is another deficiency symptom in some species.  Whitish-gray spots on leaves of some cereal crops and shortened internodes in cotton are other manganese- deficiency symptoms

Agrichem Mn products Trace Elements

Chelated Micronutrients

A primary function of boron is related to cell wall formation, so boron-deficient plants may be stunted.  Sugar transport in plants, flower retention and pollen formation and germination also are affected by boron.  Seed and grain production are reduced with low boron supply.

Deficiencies: Boron deficiencies are mainly found in acid, sandy soils in regions of high rainfall, and those with low soil organic matter. Borate ions are mobile in soil and can be leached from the root zone. Boron deficiencies are more pronounced during drought periods when root activity is restricted.  Boron-deficiency symptoms first appear at the growing points.  This results in a stunted appearance (rosetting), barren ears due to poor pollination, hollow stems and fruit (hollow heart) and brittle, discoloured leaves and loss of fruiting bodies.

Agrichem B products Trace Elements

Acts as an enzyme activator in protein, hormone (i.e., IAA) and RNA/DNA synthesis and metabolism; aids in ribosome complex stability.  Zinc uptake by plants decreases with increased soil pH. Zinc uptake by plants decreases with increased soil pH.  Uptake of zinc also is adversely affected by high levels of available phosphorus and iron in soils.

Deficiencies: Zinc deficiencies are mainly found on sandy soils low in organic matter and on organic soils.  Zinc deficiencies occur more often during cold, wet spring weather and are related to reduced root growth and activity as well as lower microbial activity decreases zinc release from soil organic matter. Delayed maturity is a symptom of zinc-deficient plants.  Loss of lower bolls of cotton and narrow, yellow leaves in the new growth of citrus have been diagnosed as zinc deficiencies.

Agrichem Zn products Trace Elements \rChelated Micronutrients

Broadacre Seed Dressings and Foliars

Copper is necessary for carbohydrate and nitrogen metabolism, so inadequate copper results in stunting of plants.  Copper also is required for lignin synthesis which is needed for cell wall strength and prevention of wilting. Copper uptake decreases as soil pH increases. Increased phosphorus and iron availability in soils decreases copper uptake by plants.

Deficiencies: (immobile) stunting, tip death, new leaf twist, blue-green leaves, necrosis, loss of turgor.  Copper deficiencies are mainly reported on organic soils (peats and mucks), and on sandy soils which are low in organic matter.

Agrichem Cu products Trace Elements

Chelated Micronutrients

Molybdenum is involved in enzyme systems relating to nitrogen fixation by bacteria growing symbiotically with legumes. Nitrogen metabolism, protein synthesis and sulfur metabolism are also affected by molybdenum. Molybdenum has a significant effect on pollen formation, so fruit and grain formation are affected in molybdenum-deficient plants.  Molybdenum uptake by plants increases with increased soil pH, which is opposite that of the other micronutrients.

Deficiencies: Because molybdenum requirements are so low, most plant species do not exhibit molybdenum-deficiency symptoms.  These deficiency symptoms in legumes are mainly exhibited as nitrogen-deficiency symptoms because of the primary role of molybdenum in nitrogen fixation.  Unlike the other micronutrients, molybdenum deficiency symptoms are not confined mainly to the youngest leaves because molybdenum is mobile in plants.

Agrichem Mo products Trace Elements

Chelated Micronutrients

Because chloride is a mobile anion in plants, most of its functions relate to salt effects (stomatal opening) and electrical charge balance in physiological functions in plants.  Chloride also indirectly affects plant growth by stomatal regulation of water loss.  Wilting and restricted, highly branched root systems are the main chloride-deficiency symptoms, which are found mainly in cereal crops.  Most soils contain sufficient levels of chloride for adequate plant nutrition. However, reported chloride deficiencies have been reported on sandy soils in high rainfall areas or those derived from low-chloride parent materials.

Deficiencies: (mobile) older leaves chlorotic then necrotic; wilt; overall stunting.

Other Elements

A number of other elements have been found in plant tissue and are most likely required by some plants including sodium, silicon, cobalt, vanadium, iodine, bromine, fluorine, aluminium and nickel.

A fertile soil is one that contains an adequate supply of all the nutrients required for the successful production of plant life. This is important because the full potential of crops is never realised if a shortage of nutrients occur at any time during the growth cycle. This is true even though plants are capable of remarkable recovery from short periods of starvation. A fertile soil is not necessarily a productive one. The second major requirement is that the soil must provide a satisfactory environment for plant growth. The environmental factors include: texture, structure, soil water supply, pH, temperature, and aeration.

Soil organic matter represents an accumulation of partially decayed and partially resynthesised plant and animal residues.  Such material is in an active state of decay, being subject to attack by soil micro- organisms.  Consequently, it is a rather transitory soil constituent and must be renewed constantly by the addition of plant residues.  The organic matter content of a soil is small — only about 3 to 5 percent by weight in most topsoils.  However, it may actually be less than 0.5 percent in the very sandy soils.  Organic matter serves as a 'granulator' of the mineral particles, being largely responsible for the loose, friable condition of productive soils.  Also, organic matter is a major source of two important mineral elements, phosphorus and sulfur, and essentially the sole source of inherent soil nitrogen.

The dynamic chemical and physical properties of soils are controlled largely by clay and humus.  They act as centres of activity around which chemical reactions and nutrient exchanges occur.  Furthermore, by attracting ions to their surfaces, they temporarily protect essential nutrients from leaching and then release them slowly for plant use. Because of their surface charges they are also thought to act as 'contact bridges' between larger particles, thus helping to maintain stable granular structure so desirable in a soil that is easily tilled. The best agricultural soils contain a good balance of these two important soil constituents.

The ability of soil colloids to attract and hold positively charged ions is referred to as cation exchange capacity.  Knowledge of this phenomenon is basic to understanding how much and how frequently lime and fertilisers should be applied for optimum crop production.  Soils differ in their capacity to attract and hold positively charged fertiliser elements against the force of leaching.  This capacity is governed by the type of clay and amount of organic colloids present in the soil.  Soils containing a high percentage of organic matter also tend to have high cation exchange capacities.  Sandy soils containing a low percentage of clay and organic matter have low exchange capacities.  This explains why coarse textured soils require more frequent applications of lime and fertiliser than soils containing more clay and organic matter.

As fertilisers represent a substantial annual expenditure for growers, applying the optimal fertiliser rate at the right time is critical to profitable farming. Optimisation is preferable to reducing fertiliser applications, which can lead to reduced productivity and profitability. Using too much is costly, wasteful and has potential environmental effects. Using too little makes the yield less productive and consequently less profitable.

The productive capacity and the soils on farms and individual paddocks on a farm can vary widely.  Thus, there are no solutions that can be applied across all farms, or even all paddocks.  In order to manage this complicated system, growers need to make use of some or all the diagnostic tools that are available:

• Soil tests to verify phosphorus is adequately supplied
• Plant tissue tests to detect trace element deficiencies
• Sap nitrate tests and NIR tests to manage nitrogen status - a nutrient required in large amounts and which is subject to a complicated cycle in the plant and its environment.

To achieve maximum yield, crops require adequate supply of essential plant nutrients. This supply needs to account for deficiencies, inefficiencies in nutrient availability to the plant (due to soil and environmental factors) and nutrient removal in produce.

The decision on how much fertiliser to apply is complex, as many factors are outside the farmer's control. Decisions on application rates can be made using the following:

• Assessment of nutrient availability from the soil (using soil tests).
• Calculating the nutrients removed in produce (based on target yield of crop to be grown)
• Gathering local trial data and experience to determine a fertiliser application rate (kg/ha).

Computer models that can accept this information are used to generate the optimal application rate.

Once the correct rate has been established, placement and timing of application must be considered.

The uptake of nutrients by plants is determined by:

• the availability of nutrients held on soil particles
• the supply of nutrients to the plant’s root surfaces
• the nutrient absorption rate at the root surface

As roots grow through the soil medium, the root hairs penetrate and come into contact with the soil colloids and those nutrients held by these colloids. This is termed root interception.

The soil solution consists of some nutrients dissolved in solution and as the plant absorbs water, these soluble nutrients move to the root surface by mass flow.  As the root hairs absorb nutrients, a concentration gradient occurs in this root zone. Hence, ions diffuse towards the root surfaces in response to this gradient.

Nutrients enter plant roots as ions that are dissolved in the soil solution.  As ions are removed from this water by the plant they may be replaced from colloid surfaces, decomposition of organic matter, decomposition of minerals (weathering) and addition of fertilisers.  Nutrient absorption involves passive and active transport into the plant.

Both external factors and inherent plant factors will have an influence on the rate of active nutrient absorption.

External factors include temperature (metabolic rate), light (respiratory substrate), oxygen (metabolic rate), carbon dioxide concentration, pH of soil, concentration of solutes in soil solution and interactions between ions.

Plant factors involve the actual surface volume of the absorbing surface (i.e. mass of root hairs), the internal solute concentrations, internal sugar concentration (source of energy), growth and genetic (inherent) aspects.