IKR Knowledge Bank

The importance of the Liebig minimum-law in nutrient feed back

The description of the so-called minimum-law is related to JUSTUS VON LIEBIG German scientist who realized the importance of the basic factors determining the yield already in the second part of the 1800's that are the following:

• water
• nutrients
• light
• temperature

This discovery was the basis of the modern aspect of fertilization. The discipline of the yield and its determining factors are demonstrated best by the widely-known, so called 'barrel-theory': at the different height staves of the barrel the water or the crop flows out where the shortest stave is.

The nutrients and the environmental factors are the staves of the barrel. The height of the staves are different dependant on the supply. The water poured into the barrel symbolizes the yield (yield level). The yield is always determined by the smallest factor.

The yield loss causes deficit because of the non-recovering investments.

Minimum-law:

The factor (nutrient, water, light, temperature) in (relative) minimum limits yield. This is continued until another factor goes to minimum.

The relative minimum-law can be expanded to other production factors, as well.

The yield reduction caused by the factor in minimum or significant loss appears in the recovery of the expenses of the production so it causes deficit, as well.

Phosphor in the soil

• only a small amount of the complete phosphor content of the soil (organic + inorganic) can be utilized directly.
• even the phosphor content of the phosphor fertilizers - if not utilized by the plants - relatively quickly transforms into more hardly soluble phosphor compounds - it becomes combined
• regarding solubility the application of the phosphor is the best in the slightly acidic and ph neutral soils
• the phosphor application ability is effected by the expansion of the roots of the plants, so the fabaceae highly surpass the cereals
• the phosphor application of the plants is significantly effected by the moisture content and the compaction of the soil
• the Mg and P content mutually-synergently (strengthening each other) influences the application and utilization of these two elements from the soil
• the phosphor utilized from the soil by the plants in H₂PO₄^- and HPO₄^2- form
• the most of the phosphor content of the plants is concentrated in the generative organs - the crops
• the phosphor has an indispensable role in the energy transfer of the plants (ATP, ADP..), so in case of phosphor absence the protein and carbohydrate synthesis is depressed, the crop quality is reduced (gluten, sugar, starch content)
• due to its role the plants continuously need phosphor from the beginning of their vegetation, the absence of the phosphor in the early stage of the vegetation can not be restores with later phosphor supply
• concerning cereals the volume of the maximum yield is determined until the end of the bushing / the beginning of spearing - supposing optimal environmental conditions for the rest of the vegetation - however the spikelet is developed by this time
• in the phases of the development of the plant when it uses especially high amount of energy (generative period) spreading easily adoptable, well water-soluble phosphor fertilizer is favourable

Calcium in the soil

• present mainly in insoluble form, calcite and dolomite Ca²⁺ content can be mobilized
• its solubility is significantly influenced by the carbonic acid generated during the disintegration of the organic materials in the soil by the action of CO₂ and root acids
• the leaching losses of the water soluble calcium can be significant
• the plants adopt it in Ca²⁺ form from the soil
• has important role in the development of the vegetative parts of the plants and the cell level transportation of the nutrients
• its presence is continuously necessary in the soil for the undisturbed growth of the vegetation
• in case of application of acidic fertilizers on carbonate-free soils it would be reasonable to apply lime fertilizers

Sulphur in the soil

• present in organic and inorganic combination
• the organic sulphur content of the soil is in positive correlation with the mould content
• the plants adopt it in SO₄^2- form from the soil
• the sulphur entering the soil with the precipitation has been a significant resource that reduced because of the strict emission regulations
• with the reduction of the application of super phosphate-based fertilizers the volume of sulphur spread during super phosphate application has significantly reduced, as well
• its physiological role is to build the amino acids, enzymes and proteins containing sulphur
• to produce quality agricultural products it is necessary to have the proper volume of sulphur in the soil, protein quality of the wheat and the oil quantity and quality of the oil plants depend on the sulphur supply