Potatoes

A guide to applying nutrients with liquid fertilisers in potatoes

• Understanding the growth cycle
• EASY Liquids fertilisers guide
• Fertigation
• Foliar Sprays
• Replacing nutrients removed

Understanding the growth cycle

The potato plant grows from a ‘seed’ tuber that can be planted in spring and/or autumn, depending on location.

Potato growth can be divided into five distinct stages (see Table 1).

Stage 1 is the time taken from planting the seed piece to emergence of young shoots.

Depending on temperature, it usually takes 18 to 21 days for the new shoots to emerge. During emergence and initial growth plant nutrients are supplied from the reserves of the seed piece.

In Stage 2 there is rapid development of the roots, shoots and leaf growth. It is at the latter part of this stage that hooking occurs, although small. Nitrogen, phosphorus and zinc are the most important nutrients in this phase.

Calcium is important during Stage 3, as cell division determines tuber numbers and yield potential.

Stage 4 is largely focused on cell expansion where the tuber is enlarged and consumes large amounts of water and nutrients, primarily nitrogen and potassium.

Stage 5 is the wind down stage for the plant and only maintenance nutrient inputs are required.

The life of the plant from planting to maturity (harvest) is about 100 to 140 days depending on variety, climate and soil type.

Yield is governed by the rate of photosynthesis and respiration, making water and nutrient management crucial to the production of high yielding crops.

 

Table 1: Potato growth cycle

Vegetative growth			10 – 20 mm King tuber	30 – 50 mm King tuber	50 – 75 mm King tuber	75 mm plus King tuber
Planting	Emergence	Hooking	Tuber initiation	Tuber bulking	Late bulking	Harvest
0	20 days	20 – 30 days	30 – 50 days	50 – 60 days	60 – 100 days	100+ days
Stage 1		Stage 2	Stage 3	Stage 4		Stage 5

 

Source: Incitec Pivot Limited, 2011.

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EASY Liquids fertilisers guide

				Nutrients applied (kg/ha)
Growth stage	Fertiliser	Product rate	Application method	N	P	K	S	Ca		Other
(Stage 1)	Plant with granular NPK fertilisers as required, based on soil test results.
Emergence and hooking (Stages 1 and 2)	EASY N EASY NPK 27™ Topfoliar®	75 L/ha 100 L/ha Up to 2 L with up to 400 L/ha of water	Fertigation Fertigation Foliar spray	32 8 0.2	14 0.1	5 0.1				0.7 Zn trace
Assess tuber number per plant to determine yield potential.
Tuber initiation (Stage 3)	EASY Cal® EASY KS® Zincsol® or Topfoliar	160 L/ha 100 L/ha Up to 1 L with up to 400 L/ha of water Up to 2 L with up to 400 L/ha of water	Fertigation Fertigation Foliar spray Foliar spray	20   0.2	0.1	30 0.1	25 0.1		29		0.7 Zn trace
Tuber bulking (Stage 4)	EASY N EASY KS	120 L/ha 200 L/ha	Fertigation Fertigation	51		60	50
If yield potential is high and disease pressure under control, consider additional applications as below.
Late bulking to harvest (Stage 5)	EASY N EASY KS	50 L/ha 100 L/ha	Fertigation Fertigation	21 30 25

 

Source: Incitec Pivot Fertilisers, 2011

Notes:

1. These are only general recommendations. Crop variety, vigour, yield expectations and soil and leaf tissue tests should be used to refine the actual requirements of the crop. Required rates will vary depending on the end use of the crop, such as seed, fresh, crisping or french fry potatoes.

2. Additional nutrients, such as magnesium and boron, may need to be considered in the program.

3. Product application rates are the total for the growth stage. The applications may be split into smaller applications on a weekly or daily basis.

4. Check compatibility of fertilisers before applying two products in the same fertigation application. Refer to the EASY Liquids Compatibility guide.

Figure 1: Daily nitrogen uptake

Nitrogen requirement 100 day potato crop

Source: Greenwood DJ, Plant and Soil, 1985

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Fertigation

EASY Liquids® fertilisers can be applied with irrigation water using fixed sprinklers, drip/trickle or travelling irrigation systems.

EASY N and EASY NPK 27™ fertilisers can be applied several weeks after emergence and in regular applications up to flowering. Nitrogen should not be applied during the peak of flowering. Apply regular inputs of EASY N and EASY KS® fertilisers during tuber bulking.

Inject EASY Liquids into micro and fixed sprinkler irrigation systems toward the end of the irrigation shift. For example, irrigate for a number of hours and then inject EASY Liquids for 30 to 45 minutes and then flush for a similar time to finish.

For travelling irrigators, injection needs to be continuous. It is best to inject low concentrations of EASY Liquids fertiliser over a number of irrigations.

Do not fertigate when rain is forecast, because the nutrients applied, especially nitrate nitrogen, may be readily leached.

EASY Liquids should be injected on a regular basis during the growing season to ensure even growth and desired cropping and quality parameters.

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Foliar sprays

Foliar sprays of EASY Liquids can be beneficial in a number of situations.

1. Periods of rapid nutrient use

The nutrient requirements of a rapidly growing potato crop are not uniform and exhibit peaks in demand.

EASY Liquids can be used to ‘top up’ the crop’s nutrient supply when its overall daily nutrient uptake is increasing.

The leaves can rapidly absorb up to 60% per cent of the applied nitrogen.

2. Periods of stress

Plant growth can be retarded or limited by low temperatures, moisture stress, waterlogging, hail damage, pest and disease infestations or combinations of these issues.

Not all stress conditions can be helped by applications of EASY Liquids. For example, applying these products to a potato crop with a stress condition caused by low temperatures and low moisture may lead to greater harm than good.

However, in periods of stress caused by low nutrient supply, applications of foliar fertilisers can often assist.

Potato crops suffering physical damage (hail, insect attack) will generally respond to a post stress application of EASY Liquids.

A pre-stress application is the most reliable and effective way to limit the damage caused by waterlogged crops.

Waterlogging may be predicted in fields with low grades, where there are known low areas or on particular soil types.

It is best to apply EASY Liquids to crops that are at risk of waterlogging at least 24 hours prior to the event.

EASY Liquids may also be applied when the crop starts to show signs of growth after a waterlogging event, but results are not as consistent as pre-stress applications.

To avoid leaf burn, do not apply EASY Liquids while crop growth has stopped and/or the soil is still waterlogged.

Allow a minimum of 48 hours of direct sunlight after waterlogging and prior to application. Multiple applications of EASY Liquids may be required if extended waterlogging occurs.

Trace elements, such as iron or zinc, may also be required during extended waterlogging events.

Waterlogging for greater than 16 hours may significantly reduce yield potential, regardless of preventative or post-stress actions.

3. Appearance of deficiency symptoms

Once a nutrient deficiency has been diagnosed, a foliar application of EASY Liquids may limit yield loss.

However, it should be recognised that yield reduction can occur prior to the deficiency symptoms becoming evident.

Preventative treatments are preferred if the likelihood of a nutrient deficiency can be predicted. Leaf tissue tests are useful to monitor crop nutrient requirements and avoid deficiencies.

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Replacing nutrients removed

Removal of nutrients will vary with yield, soil type and management techniques such as water scheduling, pest and disease control, so can only be a rough guide to a crop’s nutrient requirements.

The removal data in this table does not take into account nutrients located in the plant tops and roots, nor for fixation of phosphorus or potassium in soils.

Nutrient removal from potato crops

Nutrient		Removal for a 10 t/ha yield	Whole plant uptake
Nitrogen	kg	30 – 40	50
Phosphorus	kg	6	9
Potassium	kg	40 – 65	95
Magnesium	kg	3.5	10
Calcium	kg	1	20
Manganese	g	15	65
Boron	g	34	136
Copper	g	30	42
Zinc	g	17	45

 

Source: Haifa, 2003.

 

For further information, contact your local Incitec Pivot Fertilisers’ Distributor or freecall 1800 009 832.

www.incitecpivot.com.au

This is a guide only, which we hope you find helpful as a general tool. While Incitec Pivot Fertilisers has taken all reasonable care in the preparation of this guide, it should not be relied on as a substitute for tailored professional advice and Incitec Pivot Fertilisers accepts no liability in connection with this guide. Talk to your local Incitec Pivot Fertilisers Distributor Agronomist about soil testing and arranging a specific fertiliser recommendation that best suits your needs.

® EASY Liquids, EASY N, EASY KS and EASY Cal are registered trademarks of Incitec Pivot Limited. ™ EASY NPK 27 is a trademark of Incitec Pivot Limited. ® Zincsol and Topfoliar are registered trademarks of Top Australia Limited.

Incitec Pivot Fertilisers is a business of Incitec Pivot Limited, ABN 42 004 080 264.

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