20 September 1996

Advice on DMassessments

WHERE there has been no frost, maize should be harvested at 28-30% dry matter.

"There is little difference in feed quality between these dry matter levels. However, careful monitoring of dry matter as harvest approaches is vital," says the MGAs Simon Draper. Dry matter increases by 2% a week once the crop exceeds 22% DM. Cobs should be about 55% DM to ensure that when the crop is clamped the plant and cob together average 30% DM.

He advises monitoring the crop more frequently as harvest approaches and to assess DM by a combination of the thumbnail, milkline or oven test.

"The oven test is the most accurate assessment because it measures dry matter in the whole plant, and as the crop is later this year accuracy could be critical."

Three whole plants should be taken randomly across the field then chopped and mixed. A 1kg sample should then be dried in an open tin in an oven overnight.

"Reweigh the sample and divide the weight by 10. This figure equates to the dry matter level in the crop," explains Mr Draper.

"Where accuracy is less critical the thumbnail test provides a estimation of dry matter. When grains are cheesy ripe – soft cheese consistency at the top and hard cheese at the bottom- the cob is about 50% DM.

"The middle grains should just hold an imprint of a thumbnail, and to back up the thumbnail test the milkline test should be used."

This test is carried out by breaking a cob in half and examining the kernel for a cream coloured line. When this line extends two-thirds of the way down the kernel the plant is at least 30% DM.

MGAs Simon Draper:"Monitor frequently as harvest approaches and assess DMusing the thumbnail, milkline or oven test."