As we enter the Autumn months and harvest for 2020 is all but over now is the time to start thinking about fertiliser planning for the 2021 harvest. The starting point is knowing what your soil indices are for the major nutrients as well as your soil pH. When did you last test your soils? It is now law to have them tested once every 5 years under the Farming Rules for Water.

NRM Soil Survey 2020 key findings

ADAS and a lot of other companies use NRM for Laboratory Analytical Services. They recently issued a summary of soil samples received in the last 12 months. This showed that a significant number of samples received had indices that were below index 2 for Phosphorus and Potassium.  Between 25% and 41% of the soils used to produce arable crops, vegetables and grassland were below index 2 for phosphate, whilst 27% to 58% of soils were below index 2 for Potassium.

Liebig’s ‘Law of Minimum’

Liebigs barrel
Figure 1: Liebig’s Barrel (Source NRM)

In the current economic climate, it is even more vital to make the most efficient use of all the nutrients and inputs we apply to crops. Liebig introduced his ‘law of minimum’ which describes crop production as being limited by the nutrient of shortest supply. Thus, if a crop has ample supply of say Nitrogen, but phosphorus levels are short then the yield achieved will be limited by the levels of phosphorus.

Obviously, Liebig’s barrel (Figure 1) also has other non-nutrient related factors that can affect the yield, such as light and water supply. We cannot influence all the factors, but where we can we need to do as much as we can to optimise everything.

Liebig’s law shows in order to manage a crops nutrition we must measure and identify the limiting factor.

The nutrition of a crop is a complex system and as well as undersupply of nutrients oversupply can also have a detrimental effect on crops through antagonistic effects on other nutrients.

Nutrient relationships

The Mulder’s chart (Figure 2) below shows the relationships between some of the various nutrients.  High levels of Calcium in the soil can reduce the availability of Boron, Iron and Magnesium, whilst high levels of Nitrogen can reduce the availability of Copper. On the other hand, high levels of Nitrogen will increase the demand for Magnesium.

Mulder Chart
Figure 2: Mulder Chart

It is therefore vital that we get the nutrient balance right and the starting point is checking out the soil analysis. With the cereal harvest over and many fields still in stubbles now is the ideal time to take soils samples and get them sent away for analysis; and once the results are back to start the process of nutrient planning to make the best use of the organic manures, composts and slurries available to the business and to optimise bagged fertiliser purchases, whilst meeting crop requirements.

Nutrient planning services

ADAS provide a soil sampling and nutrient planning service to our clients. If you would like to find out more about how ADAS can help you with Nutrient Planning and help optimise your nutrient inputs, please contact one of the people below: –

North West

Stephen Watson

Tel 07831 145167

Yorkshire Humber and North East

Ian Snowden

Tel 07774 224851

West Midlands

Gillian Preece

Tel 07741 384992

East Midlands

Zoe Morgan

Tel 07771 848359

East and South-East

Mel Holloway

Tel 07785 708545


Tim Martyn

Tel 07741 384442