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Grain Storage – Cool It!

09 November 2011

AUSTRALIA - Aeration cooling for on-farm grain storages can improve grain quality in so many ways it's surprising to discover many grain farmers are yet to embrace this technology.

The Grains Research and Development Corporation (GRDC) is concerned that growers are either unaware of its full scope of benefits, or confused about some of its uses.

GRDC is continuing its efforts to encourage best practice for grain growers storing grain on-farm, and is working with grain storage expert Peter Botta.

Mr Botta says aeration cooling is about maintaining quality and controlling insect pests during harvest and storage, but growers often get aeration cooling confused with aeration drying.

“Aeration drying is a totally different process whereby you enable harvesting at higher moisture content by having drying capacity in your storages. This takes significantly greater airflow and power compared to aeration cooling,” he said.

Aeration cooling requires low airflow rates of only two - four litres per second per tonne of grain (L/s/t). However to reliably dry grain with aeration, airflow rates should ideally be no less than 15 L/sec/tonne and preferably greater than 20 L/sec/tonne.

“Aeration cooling is a simpler task, which aims to create cool, uniform moisture conditions, in the grain bulk. Reducing the temperature of the grain helps reduce the numbers of breeding storage pests and maintains many grain quality attributes. Seed colour, germination and vigour, oil and flour quality – it’s all better with aeration cooling as a tool.

“The GRDC and industry experts are very keen to see all farmers storing grain establish aeration cooling systems. It would be such a boon to national grain quality,” he said.

Low flow-rate aeration fans either fitted or retro-fitted to grain storages are a relatively low-cost way to maintain grain quality in storage for longer. Low flow rates of two to four L/s/t will cool grain and suppress moulds and insects.

Without aeration, grain is an effective insulator and will maintain its warm harvest temperature (often around 30ºC) for a long time.

“By rapidly reducing temperature after harvest you can limit chances for grain pest problems. While adult pests may survive, most young storage pests stop developing at temperatures below 18 - 20°C.

“So while aeration cooling may not eliminate the need for chemical pest control, it will dramatically slow insect development.”

Grain temperatures below 20°C will also reduce mould development, and protect seed viability.

“Controlling aeration is a three step process at harvest time. You need to run fans continually for the first few days, then run fans for the coolest 9 – 12 hours each day for the following few days and finally, the maintenance mode, fan run times of approximately 100 hours per month,” he said.

“The easiest way to do this is to have an automatic grain aeration controller installed, which selects the optimum fan run times to give you a great result,” he said.

But it’s not a set and forget system, with Peter Botta emphasising regular testing, maintenance and check- ups are very important.

“Most controllers will have hour meters fitted so run times can be checked to ensure they’re within in the total average hours per month that you would expect.

“Check that fans are connected and functioning properly, and also that you can feel suction in, and air flows out when the fans are running.

“If possible you should also check the grain temperature at the bottom and top of the stack regularly. While keeping it at the right temperature and moisture levels will decrease the likelihood of pest infestations, you should still check your grain often.”

TheCropSite News Desk



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