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Abnormal lucerne seedlingsKey points• If a germination test shows

more than 15% abnormal seedlings, in most years, the value of the seed lot is immediately reduced and more difficult to market.

• Between 2000 and 2007, more than 10% of seed samples tested by Seed Services Australia contained more than 15% abnormal seedlings.

• In Australia, seed damage during harvest is the most significant cause of the development of abnormal seedlings. Some crops are more predisposed to damage than others.

• Variation of header speed and/or modification to threshing configuration has a direct relationship to mitigating lucerne seed damage.

• A simple in-field test, the Ferric Chloride Test, successfully identified seed damage during harvest.

• Based on the Ferric Chloride Test, the LSD (lucerne seed damage) Kit was developed and released in February 2010, by Alpha Group Consulting.

The issueLucerne seed is sold on the basis of purity and quality, which are assessed according to the rules and guidelines established by the International Seed Testing Association (ISTA), providing uniformity in seed testing around the world.

Seed quality is determined by a germination test. If testing determines that first grade germination is below 85%, the price per tonne for the seed lot will most likely be reduced, in turn, reducing net returns to the grower by up to 50%. The other 15% or more of seeds germinate but are abnormal seedlings, i.e. seedlings that are broken, weak and/or malformed. The majority of these seedlings will not develop into a normal plant under favourable field conditions.

Between 2000 and 2007 more than 10% of seed samples tested by Seed Services Australia contained more than 15% abnormal seedlings.

Research was needed to determine the cause or causes of abnormal seedlings in lucerne under Australian production systems.

The researchAn in-depth literature review on the causes and possible management options of abnormal lucerne seedlings was conducted at the outset of the project. In the production season of 2003–04, field research commenced for a five-year period.

Over 100 lucerne seed crops located in the upper south east of South Australia, near Keith, were included in the research. The results are applicable to all lucerne production areas in Australia.

Abnormal seedlings take many forms but generally are weak, broken and/or malformed.

Seed samples were collected by hand prior to harvest, and samples were taken from the header, field bin and truck. Samples were tested for nutritional status and germination percentage.

The crops selected for the project represented typical production and management systems, and typical handling techniques across a range of header makes and models. The crops sampled also encompassed dryland and irrigated (border check or centre pivot) production systems, desiccated and windrowed crops, low and high biomass production crops, and a diversity of varieties.

In the course of the research, a relatively simple test kit to assess physical damage to legume seed was discovered. To the best knowledge of the researchers, the test may have been used in the 1960s. The test, called the Ferric Chloride Test, was evaluated in the research project during the 2005–06 harvest, to see if the staining percentages produced by the test were closely related to abnormal seedling percentages from seed quality tests. In 2006–07 three seed crops were tested throughout harvest using the Ferric Chloride Test, and the header settings were modified in response.

The Ferric Chloride TestThe Ferric Chloride Test involves placing 100 lucerne seeds in a small dish (a petri dish) and covering the seeds with a solution of 100 mL of 42% ferric chloride (FeCl3) diluted in 400 mL of rain water. Any cracks and chips in the seed coat will be stained black. After 15 minutes the number of stained seeds is counted, and expressed as a percentage of the total number of seeds in the sample. The solution can be strained and reused.

Stained seeds showing damage to the seed coat

Results of seed quality tests from the replicated trial in 2005-06. The data clearly show that the harvest process was related to the incident of abnormal seedlings. The difference in hard seed between hand samples and header samples, reflects the much later testing time of the header samples.

Certain crops were more predisposed to higher levels of harvest damage.

The crops at highest risk of seed damage during harvest are thin and excessively dry crops. However, thin not excessively dry crops and dense dry crops were also at high risk. In thin crops, less plant material feeds into the header concaves and across the thresher. Lucerne pods need a certain force applied to release seed from the pod and often, especially in cool or damp harvest conditions, the concave is typically closed. The seeds of a thin crop were more likely to be damaged passing through the concave and thresher, as there was less buffer than there was with heavier crops, giving the seed more opportunity to bounce around and suffer impact damage. A good flow of crop material through the concave allowed a softer process to break the pods.

The findingsIt became apparent over the first few seasons that many of the potential factors identified by the literature review were not significant contributors to abnormal seedlings.

The process of harvesting lucerne seed presented the most significant threat to seed quality.

The evidence for header use being the major cause of abnormal seedlings was clearly demonstrated by low levels of abnormal seedlings being recorded in hand harvested samples of lucerne seed compared with header samples, for the same crop.

Current operational standards for post-harvest seed handling and cleaning do not affect seed quality significantly.

2 Abnormal lucerne seedlings

The research eliminated the following factors as significant causes of abnormal lucerne seedling in Australian lucerne seed production:• growing conditions• environmental conditions• variety• desiccation and windrowing• time of harvest in season• seed moisture• handling techniques• header type• nutritional analysis.

A simple test can be used to identify and manage seed damage during harvest.

For the same seed sample, the results obtained by the Ferric Chloride Test (percentage stained seed) were very similar to the results of a seed germination test (percentage abnormal seedlings). This result led the researchers to recommend that a user-friendly kit for the Ferric Chloride Test be developed, for use by header operators.

The great value of the Ferric Chloride Test is that it can be conducted during the harvest operation. If a test reveals an unacceptable level of seed damage (greater than 15%), changes can be made to header operation to reduce further damage.

Value of field testingThe lucerne stand at one of the research sites in 2006-07 was an old stand, with a sufficient but variable plant population. Using the Ferric Chloride Test, the header sample had 20% more damaged seed than the hand sample. This indicated that the seed was being damaged during harvest – which concurs with the findings of the literature review that more seed damage was likely when there is less plant material.

Considering the seed damage, the header’s speed was increased from 7 km/h to 12 km/h with no changes to other settings. The increase in speed reduced the damaged seed from 23% to 9%. The final sample, after cleaning, had an abnormal seedling count of 7%.

The 15-minute seed test meant that the highest market price was made possible.

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Implications for seed producersLucerne seed is a living organism and how it is treated has lasting effects on how it grows.

The harvesting process of lucerne seed presents the most significant threat to lucerne seed quality. Other factors such as genetics and environment have minimal influence on the likelihood of abnormal seedlings.

The findings of the research enable producers to identify high risk crops.

The risk of header damage is highest in thin crops, whether or not they are dry prior to desiccation or windrowing. Thin good crops and dry dense crops are also at high risk. The header operator should be aware of these risks and the header should be set up and operated accordingly.

The header needs to be configured and operated to suit the crop.

In certain lucerne seed crops, the standard operational settings for the header may not be appropriate. The speed of the header should be managed so that the intake of plant material into the header concaves and across the thresher is balanced with the ability of the separation mechanisms to separate seed from sticks and pods, without damaging the seed.

Growing conditions and variety were eliminated as causes of abnormal seedling development in lucerne seed.

Abnormal lucerne seedlings

Increasing header speed in thin areas of crop will increase the flow of material into the header and reduce the risk of damaging impact of the mechanisms to the seed. However, if the plant material is passing through the separation mechanisms too quickly, lucerne seed will fall out the back of the header with the offal rather than separating into the header box. Consequently there is a compromise to accept between ground speed of the header and seed wastage.

Seed testing with ferric chloride during harvest provides an opportunity to manage seed damage.

Frequent seed inspections and use of the Ferric Chloride Test to assess seed damage and fine tune header operations, are the best options to mitigate seed damage and resulting abnormal seedlings. Alpha Group Consulting developed, and released in 2010, a field test kit based on the Ferric Chloride Test (the LSD Kit) for use by header operators during harvest.

The findings of this research can be applied to all lucerne seed crops, grown anywhere in Australia, and anywhere in the world.

Research detailsRIRDC project: DEB-4A — Understanding and managing the causes of abnormal seedlings in lucerneResearcher: James De Barro, Alpha Group Consulting P/L Contact: telephone 08 8755 1502 – mobile 0417 946 053 – email james@thealphagroup.com.auThis research has been funded by De Barro Consulting, Waite Analytical Services and Seed Services Australia; along with grower levies that have been matched by funds from the Australian Government.

Publication details Understanding and managing the causes of abnormal seedlings in lucerne (RIRDC publication no. 08/023) Download the publication for free from the RIRDC website at https://rirdc.infoservices.com.au/items/08-023 Hardcopies can be purchased for $35 from the website or from the RIRDC bookshop on telephone 1300 634 313

© Rural Industries Research & Development Corporation, 2011. This publication is copyright. No part may be reproduced by any process except in accordance with the provisions of the Copyright Act 1968. RIRDC publication no. 11/114

Disclaimer The information contained in this fact sheet is intended for general use to assist public knowledge and discussion. You must not rely on any of this information without taking specialist advice relevant to your particular circumstances. While reasonable care has been taken in ensuring that this information is true and correct, the Commonwealth of Australia gives no assurance as to the accuracy of any this information.

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Damage to seed during harvest can be reduced by modifying header operation according to the crop conditions.

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Abnormal lucerne seedlings