Correct clamp DM depends on close check on growing crop
ACHIEVING a clamp of maize at 30% dry matter means checking the crop twice a week in the run up to harvest and liasing closely with the contractor.
Oxon milk producer and MGA chairman, David Christensen, says that when maize reaches 35% DM it is more difficult to clamp well and is at risk from aerobic spoilage. This makes monitoring the crop closely in the three weeks before harvest vital.
When he checks crops in the field at Kingston Hill Farm, Abingdon, he examines grain in the cob to see how the crop is moving forward and assess its starch content. "Ideally, we would do an oven test, but that takes time."
Maize is sown at the same time each year and harvested in the third or fourth week of September, so he relies on previous experience of assessing maize grain, which has resulted in a 30% DM crop.
To ensure all maize is ready for harvest at the same time, he grows all mid-late maturing varieties, although different varieties are chosen to suit different fields. "When the contractor leaves the farm, it is much more difficult to get them back when other fields are ready: You go to the back of the queue," he says.
But be wary of cutting too early. "Although there may be little bulk to gain by waiting, wet crops have less starch and will produce effluent. The ideal crop is 28-32% DM."
Mr Christensen believes that when clamping conditions are right and crops are taken out quickly enough, an additive is unnecessary. "It is more important to consolidate the clamp well.
"We pay our contractor to have a second tractor and driver on the clamp for the whole time. It is no good me doing it and trying to do other jobs at the same time: In just half an hour 100t of maize can come into the clamp," he says.
Ensuring a short chop length also helps consolidate the crop well. "Too short a chop, reducing the crops fibre content, is only really a concern when feeding 100% maize diets. But it is still crucial that the kernels are cracked, or the crops value is lowered."
He also sheets the clamp each night during harvest, providing the wind allows it. However, he advises against rolling clamped maize the next day, as it sucks air in rather than squeezing it out. *
• Correct DM% critical.
• Check twice a week.
• Spoilage when too dry.