Maize harvest is well underway and John Burgess of KWS is expecting results to be “variable.” Most forage crops have survived the drought, but yields and starch content will be down on the year and they will require careful management, he says.
The average UK typical fresh weight maize yield is round 40 - 45 tonnes/ha, but few growers will achieve 40 tonnes/ha this year and the figure could fall below 30 tonnes/ha, in the worst-affected areas, says Mr Burgess. Starch content is likely to follow a similar pattern.
“The main issue was the May-June drought, which had a negative effect on pollination and limited flowering, leading to low grain site numbers, small ears and poor grain fill. Therefore, the kernel content of ensiled material will be lower than usual.
“It is difficult to generalise on starch levels, but in a standard year, a range of 28 to 38 per cent would be the norm for maize silage. However 2018 is likely to see a drop by at least 5 per cent.
“Producers with droughted crops will notice a decline in D-values, as plants will have been subject to senescence, especially in the lower leaves. This will have created a more lignified stalk. However, the crop may appear dry, but in fact smaller grain numbers will reduce the overall dry matter, which may not have risen to the optimum 30% at cutting.”
Despite the weather challenges, Mr Burgess predicts that maize silage quality will improve, as winter progresses. For this reason, producers who are fortunate enough to have 2017 stocks should delay the opening of newly-ensiled crops.
“Maize is like a fine wine; it improves with age,” says Mr Burgess. “Opening up a new clamp will not allow enough time for the ensiling process to break down the kernels. The material will lack energy and its rumen degradeability will be compromised. Starch levels peak in maize silage after six months, so it is best to wait until at least three months before feed-out, if possible.
“I consider it a risk to base a whole winter’s ration on one maize silage analysis, because of the changes that occur over the fermentation period. Taking a second set of samples later in the year should show raised starch levels by comparison, and the total ration can be adjusted accordingly.”
Mr Burgess recommends rapid feed-out for maize silage.
“The aim should be to utilise one metre of maize silage a day across the clamp face in winter, with two metres as a general rule throughout the summer.”
Standing crops that are believed to have performed reasonably well can be left to continue their accumulation of starch during October, he adds. At harvest, he advises growers to increase chop length settings on the harvester to roughly 20mm for this year, in order to reduce effluent run-off. This, in turn, will help to minimise the risk of silages becoming acidic.
Faced with a general forage shortage going into the winter, producers may be reluctant to incur the extra expense of an additive at harvest, but he suggests that one should be used on an ‘insurance policy’ basis this season. Increasing the cutting height will boost the starch content of maize silage, although this gain will be offset by a decrease in dry matter yield. It is essential that the new crop goes into a clean clamp, to prevent later spoilage, he stresses.
Another option is to consider a move away from traditional maize silage.
“In extreme cases, some growers harvested their crops in August, as they had little alternative but to cut their losses and look ahead to the next planting season,” he says. “Standing crops that are expected to be below average could be made into corn cob mix (CCM). This is a very high energy product, which is harvested about two weeks after normal dry-down, generally using an additive.
“CCM is a relatively cheap material to make, as it is produced with a single pass operation and without the need for a crimping machine. Once the cobs are fully ripe, they are snapped off the stem and passed through the harvester, where they are chopped and the grains cracked.
“Meanwhile, the stems and leaves are pulled through the header and chopped. The maize header leaves behind a ‘carpet’ of stubble, which can alleviate mud and minimise soil compaction.”
A standard analysis of CCM will show dry matter at about 55%, with starch at 45% and an ME typically at about 13 MJ/Kg. The average pH is similar to maize silage, at 4.3, says Mr Burgess.
“In a low yielding year such as 2018, it is the energy content from starch which will be the highest value in maize silage, to drive over-winter performance at this challenging time,” he concludes.