Harvest with higher moisture? The Reward and Risks

Farm Infrastructure

We could be harvesting grain at much higher moisture levels. There are risks involved but they can be more than compensated for by bigger yields and better-quality grain.

Modern storage and handling techniques would allow successfully storing wheat on farm at 15 per cent moisture content without damage, and harvesting pulses at higher moisture levels results in some truly spectacular yield increases. These findings come from work at the CSIRO Stored Grain Research Laboratory and at the Wagga Agricultural Research Institute.

Growers should be aware, however, that the current Australian delivery standard for cereals remains 12.5 per cent moisture and growers who harvest at higher moisture levels have to dry their crop to conform to these standards. The same would be true for pulse delivery standards.

Australian findings are seconded by experience overseas. Cristoph Reichmuth, Director of the Institute for Stored Product Protection in Berlin, says that cereal crops in Europe are routinely harvested with a moisture content as high as 20 per cent, and that wheat is sold with a moisture content of 15 per cent.

"We regularly out-turn wheat at 15 per cent moisture that has been successfully stored for two years," he says. "You can certainly store cereals at higher moisture levels than the 12.5 per cent accepted as the standard in Australia."

Harvesting grain at higher moisture contents obviously means we'd be selling more water with the crop but that's not the main advantage. (Grain is paid for on weight, and higher moisture content makes for a heavier crop.)

Jonathan Banks at the CSIRO's Stored Grain Research Laboratory says that the longer grain is left in the head after maturity the more risk there is of loss from machine damage and shattering, and that protein levels also suffer. The potential losses are considerable.

"Grain is mature when there are no green heads in the sample," he says. "Once you pass that point you're losing half a per cent of your crop per day and about 0.1 per cent protein with each week that passes." Add up those losses and, particularly if they just tip you out of a premium grade, they amount to a lot of money. (Dr Banks said it's so far unknown why the protein drops.)

"Getting higher moisture content at harvest could increase yield by as much as 10 per cent," says Dr Banks. "That's the equivalent of 10 years progress on the plant-breeding front."

Pulses could be even better

In the case of pulses the potential gains are even more spectacular. In trials conducted at the Wagga

Agricultural Research Institute, Bohatyr field peas harvested at 15 per cent moisture content showed a 30 per cent yield increase over peas harvested at the standard 12 per cent, and there was a marked improvement in quality.

Dr Banks recommends harvesting wheat at 17 per cent moisture "if you have a header that can do it and if you have modern storage infrastructure".

Beware of moulds

You can't let the grain stay at 17 per cent moisture, he warns, and that means that you must have both the modern storage infrastructure necessary to handle the grain and the skills to manage the risks involved.

"You might simply blend the grain or you might operate a storage system capable of pumping large volumes of air through the grain. Either way, taking into account the costs associated with drying you'll make money on the deal."

Safe storage conditions

Harvesting at higher moisture content needs time and good management of stored grain. Good storage hygiene is critical, as is the ability to control the temperature and the moisture content of the stack.

Be prepared to cool and dry the grain. Failure means losing all the yield and quality advantages achieved from the early harvest. (See box this page.)

Even at 12-13 per cent moisture content, insect damage can occur and moisture will move from hot to cool spots in the stack, and that risks mould growth.

"The very least we should be doing is delivering cereals at as close to the permissible 12.5 per cent moisture as possible, rather than treating that as an upper limit," said Dr Banks.

Contact: Dr Jonathan Banks 02 6246 4214