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Nutrient removal – its natural

No matter if you are producing crops, livestock or dairy, the sale of produce from your farm is the removal of nutrients from your soils. No soil has an infinite amount of nutrients, and continued farming will eventually exhaust one or more of the plant-available nutrients in the soil. When this occurs yields and productivity will decline.

In agriculture, an often-quoted principle is Liebigs Law, which states that growth is dictated not by the total resources available, but by the scarcest resource. In practice, it means fertility needs to be evaluated considering all its components and a low level in one key factor will negatively impact overall growth.

It is for this reason that regular soil tests are an important part of planning and implementing improvement. They enable you to make informed decisions on what your soils and crop or pasture require, enabling you to address the limiting factors to production, whether they be chemical, structural or biological, and avoid the potential waste and additional degradation that may be done by simply “spreading super”.

Soil fertility and nutrient levels not only impact yield but also influence the quality or nutritional value. 

In line with Liebigs Law, it is not only macronutrients but also micronutrients and soil chemistry measures (such as pH, Organic Carbon, CEC, PBI and saturations) that influence crop yield and quality.

Importantly when assessing your nutrient program, you need to look forward to the needs of the coming crop or pasture, what is currently in the soil and what needs to be applied to maintain your desired soil nutrient levels. For example, canola has a higher sulphur requirement than cereals, therefore when planning a canola crop additional sulphur needs to be applied.

When developing a nutrition program that accommodates your future crops or pasture there are guidelines on both the nutrients consumed and the efficiency of nutrients applied. It is also known that the same crop can have higher or lower mineral levels based on the growing season and other factors like soil type. Which is one of the key reasons to regularly soil test.

The below is a guide to nutrient removal for some key crops and pasture segments; contact your BioAg Representative to discuss your specific needs.

Beef kg/tonne
Nitrogen
21.0
Phosphorus
8.0
Potassium
1.8
Sulphur
1.5
Calcium
14.0
Milk ke/1000L
Nitrogen
5.7
Phosphorus
0.9
Potassium
1.4
Sulphur
0.3
Calcium
1.2
Live sheep kg/tonne
Nitrogen
34.0
Phosphorus
7.0
Potassium
2.3
Sulphur
4.0
Calcium
14.0
Greasy wool kg/tonne
Nitrogen
17.0
Phosphorus
0.3
Potassium
15.8
Sulphur
28.5
Calcium
1.2
Hay kg/tonne DM
Nitrogen
20.0
Phosphorus
2.0
Potassium
25.0
Sulphur
2.0
Calcium
0.5
Wheat kg/tonne
Nitrogen
23.0
Phosphorus
3.0
Potassium
4.0
Sulphur
1.4
Calcium
0.3

Fertiliser Use Efficiency – Get the most from your nutrition program.

Applying fertilisers or nutrients is not the only component of building fertile soils. Fertile soils not only contain the nutrients required for optimal crop or pasture yields but are also able to supply them to the crop or pasture as they are required.

Too often impediments to the uptake of nutrients from the soil to a crop are overcome through the application of more fertiliser. This leads to overuse of fertiliser, potential environmental issues and if continued for many seasons, breakdown of key soil structures.

By addressing soil structural components and improving overall soil health, more of the fertiliser applied is utilised by your crop; the measure of fertiliser uptake is defined by fertiliser use efficiency.

The key attributes of fertile soils that influence fertiliser use efficiency are nutrient retention, nutrient cycling, pH, organic carbon and levels of antagonists. Each nutrient reacts differently to a change in soil properties as well as factors like fertiliser type, application rates and application timing.

A BioAg Representative will discuss with you how you can improve fertiliser use efficiency.

To read more on nutrient use efficiency, the benefit of BioAg Programs and nutrient removal refer to:

BioAg White Paper – Nutrient use efficiency

GRDC growers notes – Nitrogen Reference Manual for Southern Cropping

GRDC growers notes – for northern farmers