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To improve crop yields start with best practice seed management

8 April 2013

With the start of 2013 planting under way, Simon Alexander of SA Consulting notes the importance of good seed management this season.

It’s vital to be ready for seed deliveries, and when they do arrive, check the delivery and know what’s in there. “Bags should be labelled and carry the appropriate seal from the certifying authority. Inspect the seed and where necessary wash a sample to ensure its fit for purpose,” said Simon.
 
The first job is to make sure your delivery is what you’re expecting and that the seed on the lorry matches the paperwork. Making sure the seed producer number, size and tonnage split all corresponds to your order.  
 
Seed arrivals in either bags or boxes should have been closed with an official seal to ensure traceability of stock and to minimise the risk of cross contamination. This will have been issued by FERA for English or Welsh material, and by SASA for Scottish seed, or NAK if it is of Dutch origin. 
 
Before you carry out an inspection it’s important to know the acceptable disease levels. English and Scottish seed may have different tolerances, and this would be reflected in the seed grade such as Super Elite (SE) and Elite (E). 
 
The tolerances for English seed can be found in The Seed Potatoes (England) Regulations 2006.  
 
The Scottish tolerances can be found in the Scottish Seed Potato Classification Scheme document.
 
Recording the variety, certification grade, producer number, size grade, tonnes per size grade, date of closing and date of delivery is necessary and will be vital information should problems arise in the growing crop.  
 
Initially, opening a bag of each size fraction will give an overall impression of seed quality. But only break the seals on as few as possible to retain identity of the bags and then assess a 10-20kg sample.  
 
Tolerances on seed are calculated by expressing the defect as a percentage by weight of the sample.  If you have concerns over quality, do not open any more bags until the seed supplier has been notified.
 
“If all is well with the first check, it’s worth undertaking a detailed tuber count and disease loading inspection by taking at least three bags from each size grade, as quality can vary with size,” explained Simon.  “Wash at least 100 tubers selected from a number of bags. This will give a picture of skin disease levels such as Black scurf, Black dot and Silver scurf and will help with the justification for applying any seed treatment.” 
 
The tolerance for Black scurf under The Seed Potatoes (England) Regulations 2006 stipulates that the tuber must have ‘at least two eyes at the rose end that are wholly unaffected and less than one-quarter of whose surface area has been affected in respect of class A and class CC and one-eighth unaffected in respect of all other classes shall be deemed to be unaffected by the disease’. 
 
The picture provided by SA Consulting below shows washed seed tubers showing significant Black scurf.  “Although the percentage by weight was not high enough to lodge a seed complaint it is justification for seed treatment for the disease,” added Simon.
 
“If you do find a disease that is within certification tolerance, the more bags you open the better the understanding of how widespread an issue there may be. It’s important that you keep an accurate record of where the stock is planted in the field.”  
 
Seed should be fit for purpose, any issue not covered by Plant Health regulations but which can be a cause of problems should be reported back to the seed supplier immediately. Severe sprout growth in the bag, evidence of damaged sprouts on seed tubers or levels of dehydrated tubers due to Silver scurf are all examples that may have a detrimental effect on seed health or vigour. 
 
“Notify your seed supplier if quality issues exist but ensure this is within the timespan of the terms and conditions governing the sale under either BPTA or RUICIP rules,” adds Simon.  
 
Attention to quality is also important when decanting seed either into boxes or the planter. If the quality of seed is worse than that assessed from the top of the bag, it is important to stop and reassess. 
 
On-farm seed handling will depend on the window between delivery and planting. For seed that is going to be planted over the next few days, it is acceptable to leave the seed in bags, but the stack needs to have a 15 – 30cm gap around each bag. This will provide air circulation by natural breeze and will help if you are using roof fan assistance.
 
When a seed delivery arrives that will not be planted for one or two weeks, ideally it will be decanted into boxes. But leaving the seed in bags is acceptable if being managed properly and with due care and attention.
 
“It is important to ensure adequate airflow around either the bags or boxes to ensure the seed is free of condensation,” says Simon. “The biggest concern with leaving seed in bags is the poor airflow through the bag and the condensation build up in the middle, which is out of sight and therefore not obvious.”
 
When there is a window of over three weeks until planting, bags should be decanted into boxes and the seed should be cured and ideally placed in a seed store and cooled down to approximately 3°C.  
 
It is vital seed is only stored in buildings or boxes that have not been treated directly with CIPC or contaminated by leakage from a connected store. It is also important that all ware potato handling equipment, such as graders or box fillers, are thoroughly cleaned and if necessary disinfected before being used for seed handling.
 
Retaining traceability is also imperative, so seed should be stored together in the load in which it was delivered, with size grade, producer numbers or different stocks identified. 
 
If the seed is decanted, label each box so that it clearly identifies the variety, producer number and date of delivery, as a minimum.  The easiest method is to transfer the certifying label across from the bag and fix it to the box.
 
Where a seed store is not available, in order to minimise the risk of condensation and sprouting, the construction of a temporary plenum chamber using a portable fan and boarding or canvas to cover the plenum gap is possible.  The team at Sutton Bridge Crop Storage Research can advise on this and growers and store managers can call the free Storage Advice Line on 0800 02 82 111 for further information.
 
“During storage seed should be inspected regularly,” noted Simon. “If there are signs of sprouting and planting is not imminent, the seed should be transferred to a cold store to retain integrity and quality”.
 
Seed transferred into a cold store will need to be cured and pulled down to holding temperature, ensuring adequate air is used to help minimise condensation.
 
The temperature of the cold store depends on what period the seed is to be held at, the longer the period the lower the holding temperature (down to 3°C).  If seed is to be stored for three to five weeks it might not be necessary to bring it down to 3°C and holding at 4-5°C might be adequate.
 
“When the seed is taken out of cold store, warm it up with good ventilation to ensure condensation is not present in the box,” explained Simon. “This will reduce the risk of blackleg and a dry seed surface will ensure that powder seed treatments are applied evenly.”
 
 
 
 
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