Broad nutrition resources are outlined in the Agronomists Toolkit. Specific nutrient categories are listed below:

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Nitrogen

Constraint - Nitrogen 

Plant use

  • Nitrogen is a macronutrient

  • Nitrogen is an essential component of amino acids, and is needed for all growth processes and is integral to the correct functioning of all cells

  • Nitrogen deficiency is the most common nutrient deficiency in canola especially during cold, wet conditions and in sandy soils in high rainfall areas

Symptoms 

  • Symptoms are worse in wetter seasons and on lighter soil areas 

  • Mildly deficient plants are smaller with paler green, narrower and more erect leaves

  • Deficient seedlings have reddened cotyledons

  • Oldest leaves develop whitish-purple veins and mild purple pigmentation that starts at the end of the leaf and progresses to the base on both sides of the leaf

  • The whole leaf then turns yellow or pinkish-purple

  • Established plants that become nitrogen deficient develop yellowing on leaf margins that spreads in toward the midrib between the veins. The midrib becomes discoloured then the leaf dies

  • From stem elongation, the main stem is thinner and branching is restricted

  • Flowering time and pod numbers are reduced

Damage

  • Yield penalty can be severe

Management

A soil test or a plant tissue test should be used to confirm nitrogen deficiency. Nitrogenous fertilisers and foliar sprays can be applied before stem elongation. Late application of nitrogen can reduce oil content. Maintaining soil pH above 5.5 will increase the amount of soil N available for plant use. 

Links and Resources

AOF - Canola nutrition. Nitrogen

Pages 2 and 3 of 8. Introduction, fertiliser rates, fertilising methods, benefits of added nitrogen, soil testing, and effects on yield and oil content.

AOF - Oilseeds WA Nitrogen

Sections 5.3 and 5.4. General information on nitrogen, fertiliser strategies, avoiding excessive amounts of N, best time of application, placement and timing, and application options. Published 2006.

DAFWA - Crop updates Nitrogen and Canola

How much nitrogen is required, the reliability of the recommendation, other factors to take into consideration, and timing of application. Published 2001.

DAFWA - Diagnosing Nitrogen deficiency

Introduction, what to look for in paddock and plant, what else it could be, where does it occur, monitoring, and management strategies. Page last updated 2014.

DEPI VIC - What nutrients do plants require? Nitrogen

Section 6.3.1 Plant uses for nitrogen, deficiency symptoms, and the nitrogen cycle. Page last updated 2013.

GRDC - Best Practice Management Guide. Nitrogen

Page 30- 32 of 92. Information on adequate nutrition and care to take when applying N at sowing, plant uses, and deficiency symptoms. Published 2009.

IPNI - Canola 4R Guide. Nitrogen

Pages 7-10 of 21. General introductory information, rates, timing, and source of N. Published 2013.