Nutrient Fuel Gauges

With a fuel gauge installed, in-season nutrients can be monitored and measured with ease by our Area Mangers. The information they provide will allow you to make better decisions regarding your in-season fertilizer applications, with the aim of maximizing yield and profit.

All of our services are carried out by our network of full trained Area Managers

A fuel gauge is a strip placed in the paddock (typically 2m x 100m) containing a non-limiting rate of a specific nutrient. Fuel gauges can be carried out across a wide range of crops as a way to monitor in-season nutrients. They also allow Area Managers to measure nutrient response against farmer practice.

How do they work?

A strip of non-limiting nitrogen has been applied in-season, to measure the potential benefit to the crop.

Once the nutrient rich strip has been applied, they are read throughout the growing season with a GreenSeeker®. NDVI readings are taken on and off the strip and and inputted into the nitrogen calculator, along with other information such as the paddock sowing date. The software then predicts the response to nitrogen and calculates the rate required to achive optimum yield and returns.

Summit has carried out extensive field research trials under Western Austrialan conditions to test the validity and accuracy of fuel gauge recommendations.

Types of fuel gauges

The majority of fuel gauges are nitrogen, as remedial action can be carried out within the season. Potassium, phosphorus and other nutrient fuel gauges can also be carried out, with responses actioned for the following season.

If you’re interested in setting up a fuel gauge on your farm, or would like to learn more, get in contact with your local Area Manager.

Nutrient
Symbol
Units Used
Adequate Range Expected
Comments
Phosphorus

P

ppm (mg/kg)

15 - 45

Dependent on crop/pasture type and soil type.
Potassium

K

ppm (mg/kg)

40 - 120

Lupins and Canola are less sensitive to K deficiency. Clover and Medic require higher soil levels.
Sulphur

S

ppm (mg/kg)

5 - 15

Dependent on soil type.
Nitrate

NO3

ppm (mg/kg)

up to 30

Very mobile in the soil. May be lost to leaching.
Ammonium

NH4

ppm (mg/kg)

up to 20

Stable in the soil as it is a cation, but converts to Nitrate readily.

Copper

Cu

ppm (mg/kg)

> 0.3

Soil tests for Copper are a guide only.
Zinc

Zn

ppm (mg/kg)

0.12-0.5

Dependent on soil pH. The more alkaline the soil (higher pH) the higher the soil Zinc level needs to be.
Organic Carbon

O.C.

%

1.0 - 3.0

Dependent on soil type and rainfall.
Electrical Conductivity

EC (1:5)

dS/m

< 0.25

A measure of 'salinity'. Highly dependent on soil type with heavier soils having some buffering capability, but generally EC (1:5) values <0.2 are non-saline and >0.7 is of concern and possibly accumulating salt.

A variable conversion factor can be applied so values will fit one scale across all soil types. This is called 'estimated EC' or ECe. In this case ECe threshold of >8 represents highly saline soil.
pH

(CaCl2)

>5.0

Economic responses to applying lime to increase pH above 5.0 are doubtful. If subsoil pH is low, it may be necessary to increase topsoil pH >5.5 (CaCl2)
Aluminium

Al

ppm (mg/kg)

<5.0

As pH declines (becomes more acidic) aluminium can increase in soil solution. Aluminium is toxic to roots. When roots don't grow, plants cannot explore the soil to access nutrients and soil moisture. Levels above 5 mg/kg strongly impact wheat. Other crops such as barley are more sensitive (Read the article on soil pH here)

PBI

PBI (Phosphorus Buffering Index) is a function of soil type. Generally where soil particles contain more iron, aluminium and calcium such as forest gravels, plus some soils with considerable clay and organic matter, the PBI will be higher and decrease plant-available P  (See article)

Nutrient
Symbol
Units Used
Nitrogen
N
%
Phosphorus
P
%
Potassium
K
%
Sulphur
S
%
Calcium
Ca
%
Magnesium
Mg
%
Copper
Cu
ppm
Zinc
Zn
ppm
Manganese
Mn
ppm
Boron
B
ppm
Sodium
Na
ppm
Iron
Fe
ppm
Nitrate
NO3
ppm
Chloride
Cl
%
Options
Molybdenum
Mo
ppm