The Law Of Minimum

To understand how to balance soil nutrients on a farm we can use Liebig’s law of minimum. This law states.
‘Under equal conditions of temperature and light, the nutrient available in the smallest quantity relative to the requirement by the plant will limit production (1)’

Glossary

• Soil Test: Process of analysing soil for chemical and physical properties.
• Plant Tissue Test: Process of collecting and freezing plant material for nutrient analysis.  

Addressing soil nutrients is a constant balancing act as all nutrients need to be available in sufficient quantities to meet minimum plant health requirements and production targets. A barrel filled with water is used to illustrate this - where each plank in the barrel represents a soil nutrient (Figure 1). The barrel cannot fill up until each limiting nutrient is addressed. If it is not addressed this results in lost productivity. In Figure 1 the limiting nutrient is phosphorus once this is corrected then the limiting nutrient becomes nitrogen and then calcium.

Figure 1: Justus von Liebig's Law of the Minimum (2)

Limiting nutrients are often those required by plants in the largest quantities, such as phosphorus, nitrogen, sulphur, calcium, magnesium and potassium. To understand exactly which nutrient is limiting and how much is needed to correct the deficiency, a soil test needs to be undertaken followed by a plant tissue test.

What To Know More About Soil Nutrients On Your Farm? 

Read a copy of Soil Essentials. This book is a practical guide for farmers and covers common soil issues. Written in a straightforward style, it explains the principles of soil management and the interpretation of soil tests, and how to use this information to address long term soil and enterprise viability. To purchase your copy click on the image below.



Notes
1. Barack, P. 2000 ‘Essential Elements for Plant Growth – Law of the Minimum’, University of Wisconsin , Retrieved 20th February 2008 from www.soils.wisc.edu
2. Law of the Minimum – Liebig’s Law, Avocado Source, Retrieved 15th February 2008 from www.avocadosource.com

Author: Charlton Roberts B.Frm.Mgt (Agronomist).