Nutrition support in summer cropping

One of the best ways to guide summer crops towards their productive potential is to plan a tissue testing program.

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This requires some careful time management.

High temperatures and rapidly growing summer crops mean that sampling timing is critical to ensure accurate results. Summer conditions also mean there is often only a narrow window for remedial action to be taken.

Plant tissue analysis can be used to monitor nutrient uptake, refine nutrient applications and reveal any hidden hunger in the crop so that no deficiency symptoms occur.

In many cases, by the time a crop is showing nutrient deficiency symptoms, yield potential has already been compromised.

While plant tissue analysis is well known as the best way to assess micronutrient levels, it can also be useful for checking on a range of nutrient levels in summer crops.

For most crops, the critical nutrient concentrations that will produce 90% of maximum yield are known. The nutrient levels are reported as high, optimum or low and can be compared with levels that produce optimum yields.

Get on the front foot this season and suggest plant tissue analysis.

Nine steps for accurate and useful plant tissue analysis

1. Use well defined and identifiable sampling locations (georeferenced or flagged). 
2. Gather all the equipment you will need such as plastic disposable gloves, paper plant sample bags, sunscreen and a hat. Consider an esky to keep samples cool. 
3. Get out in the paddock early in the week and early in the day, before 10am. As well as being the best time for leaf collection from a technical point of view, you will be back in the car in time for the cricket.
4. Collect representative samples of the correct plant part at the correct crop stage. This varies from crop to crop (see table). You could print this page off and put it in the glove box. 
5. Use a reputable and accredited laboratory. Laboratory Services^®Nutrient Advantage is accredited by the National Analytical Testing Authority (NATA^®) and is a member of the Australasian Soil and Plant Analysis Council. 
6. Send the samples off quickly using a courier service that provides rapid delivery. Nutrient Advantage Laboratory Services completes plant tissue analyses within three business days of receiving the sample. 
7. Compare results with critical nutrient concentrations and previous data from soil testing and look for trends. 
8. Interpret the results using either Nutrient Advantage Advice^® or other reputable sources such as Reuter and Robinson’s ‘Plant analysis and interpretation manual’, 2nd edition, 1997, CSIRO Publishing. Most summer crops have interpretation guidelines in NAA. 
9. Refine fertiliser strategies as needed.

Summer crop plant sampling guide

Crop	Growth Stage/ Timing	Plant Part	Number/Qty to sample
Cotton	3 timings 10 days apart at: squaring (~600 day degrees), flowering (~750 day degrees) and early boll fill (~900 day degrees)	Petiole from YML (generally 4th to 5th topmost leaf) (leaf immediately discarded)	minimum of 50
	Suggest 2 to 3 timings at: early squaring peak flowering and boll load and cut-out	Youngest mature leaf (generally 4th to 5th topmost leaf) (petiole immediately discarded)	50
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Cowpea	14-42 DAS (pre-flowering)	YML (petiole discarded)	40
Forage Crops	21-45 DAS (sowing to panicle initiation)	Whole tops	50
Lucerne	Active growth prior to flowering	Whole tops (top 15cm of plant)	50
Maize	3-4 leaf (<30 cm tall)	Whole tops (avoid lateral roots 1-2cm above ground)	50
	Prior to tasselling (>50 cm tall)	Leaf below whorl	30
	At silking	6th leaf from base (leaf below and opposite ear)	30
	Ear leaf at initial silk (prior to silks browning)	Ear leaf	30
Millets/Panicums	21-45 DAS (sowing to panicle initiation)	Whole tops	50
Mungbean	Pre-flowering	YML (petiole discarded)	40
Navy Bean	40 DAS or initial flowering (prior to pod set)	YML and petiole	40
Peanut	Prior to bloom	YML	50
Pigeon Pea	Early flowering	YML (petiole discarded)	50
Rice	40-50 days (Feekes 3-5) or mid-tillering	YMB	50
Sorghum (grain)	<30 cm tall (21-40 DAS)	Whole tops (avoid lateral roots 1-2 cm above ground)	50
	60-90 DAS	YMB (generally 3rd leaf below whorl/apex)	40
Soybean	Early flowering (prior to pod set)	YML (petiole discarded) (generally 3rd to 4th leaf below apex)	40
Sunflower	Approx. 6 weeks post-planting, early budding (growth stage R1)	Lamina of youngest fully expanded leaf	50
	Budding (bud <2 cm in diameter)	3rd and 4th leaf below bud	50

Notes: DAS = Days after sowing   YML = youngest mature leaf   YMB = youngest mature blade Sources: Reuter & Robinson (1997); Incitec Fertilizers (1996)

A comprehensive nutrition program relies on numerous testing methods and sample timings. Tissue sampling sites should be georeferenced or physically marked so soil samples can be taken from the same locations in the future.

Grain testing is complementary to soil and tissue testing. These tests are useful for revealing the grain nutrient content and calculating nutrient removal from the paddock.

For more information, feel free to give me a call on 0417 896 377. If you require plant sampling bags, kits are available by contacting Nutrient Advantage Laboratory Services on 1800 803 453.

Bede O’Mara
Agronomist – subtropical farming systems

Incitec Pivot Fertilisers